This document discusses several medically important bacteria, including Neisseria gonorrhoeae, Neisseria meningitidis, Haemophilus influenzae, and Bordetella pertussis. It describes their characteristics, diseases caused, pathogenesis, diagnosis, treatment and prevention. Key differences between N. gonorrhoeae and N. meningitidis include that N. gonorrhoeae causes gonorrhea through infection of mucosal surfaces while N. meningitidis causes meningitis and has a polysaccharide capsule allowing it to evade phagocytes.

1. Medical
Dr. Khalil Abujheisha
PhD, Medical Microbiology
1

2. Chapter 3
Medically important Bacteria
Chapter 3
Medically important Bacteria
”
Gram Negative
“
2

3. Pathogenic Neisseriae
• Neisseriae: Gram-negative cocci.
• Neisseriae contain endotoxin in their outer
membrane.
** Note that the endotoxin of Neisseriae consist
of lipooligosaccharide (LOS), in contrast to the
lipopolysaccharide (LPS) found in enteric gram-
negative rods.
• N. gonorrhoeae infections (Gonorrhea) have
High prevalence and Low mortality.
• N. meningitidis infections (Meningitis) have Low
prevalence and High mortality.
3

4. • The growth of both bacteria is inhibited by
toxic trace metals and fatty acids found in
certain culture media (blood agar).
• They are cultured on “chocolate” agar
containing blood heated to 80°C, which
inactivates the inhibitors.
• Neisseriae are oxidase-positive (they possess
the enzyme cytochrome C ).
• It is the terminal enzyme of the respiratory chains,
catalyzes electron transfer from cytochrome c to
molecular oxygen, reducing the latter to water.
• Note: All bacteria that are oxidase positive are aerobic
and can use oxygen as a terminal electron acceptor in
respiration.
4

5. N. Gonorrhoeae
• First described by A. Neisser in 1879.
• Gram-negative cocci in pairs with adjacent
flattened sides.
5

6. • Gonococcus.
• Never Normal flora.
• Fragile organism: susceptible to temperature
changes, drying, UV light, and other conditions.
• Fastidious: media containing hemoglobin.
• Cultures:35-36C + 3-10% CO2.
• No growth less than 25 or more than 38.5.
Virulence Factors
• Has no capsule but has multiple serotypes based
on the antigenicity of its pilus protein.
• Attachment by pili.
• Nonpiliated strains are avirulent.
6

7. • Protein P.II: invasion of epithelial cells.
• The outer membrane porin/ P.I: to Survive
inside of Phagocytes.
• The lipooligosaccharide (LOS) of the outer
membrane responsible for symptoms.
• The organism’s IgA protease can hydrolyze
secretory IgA.
Disease
• Gonococci cause both localized infections,
usually in the genital tract, and disseminated
infections with seeding of various organs.
• Gonococci reach these organs via the
bloodstream (gonococcal bacteremia).
7

8. Pathogenic mechanism
• Attachment to Non-Ciliated epithelial cells
via pili and production of LOS endotoxin.
• Gonococci infect primarily the mucosal
surfaces (urethra and vagina) resulting in
Purulent discharge/ Pus like (Foul smelling).
• Symptoms: inflammation, redness, swelling,
Dysuria and Burning sensation during
urination.
8

9. • Neonatal Conjunctivitis.
• Infection in females can result in Pelvic
inflammatory disease. If untreated may lead
to Infertility.
9
Gonococcal ophthalmia neonatorum develop in
28% of infants born to women with gonorrhea.

10. • The most frequent complication in women is an
ascending infection of the uterine tubes, which
can result in sterility or ectopic pregnancy.
• The incidence of gonococcal ophthalmia has
declined greatly in recent years because of
the widespread use of prophylactic
erythromycin eye ointment (or silver nitrate)
applied shortly after birth.
• Syphilis and non-gonococcal urethritis caused
by Chlamydia trachomatis) can coexist with
gonorrhea; therefore, appropriate diagnostic
and therapeutic measures must be taken.
10

11. Diagnosis
• Signs and symptoms: Purulent (Pus like)
discharge.
• In men, finding of gram-negative diplococci
within PMNs in urethral discharge specimen is
sufficient for diagnosis.
• In women, use of Gram stain alone can be
difficult to interpret; therefore, cultures should
be done.
• Gram stains on cervical specimens can be falsely
positive because of the presence of gram-
negative diplococci in the normal flora.
11

12. • It can be also falsely negative because of the
inability to see small numbers of gonococci
when using the oil immersion lens.
Culture
Chocolate agar and Thayer-Martin Agar
• TMA: 3 antibiotics and nutrients.
• Vancomycin: inhibit gram positive.
• Polymyxin: Inhibit gram negative bacilli.
• Nystatin, which can kill most fungi.
12

13. Oxidase +ve.
Ferment glucose
only/ No gas.
13

14. Treatment and Prevention
• Ceftriaxone is the treatment of choice in
uncomplicated gonococcal infections.
• Because mixed infections with C. trachomatis
are common, azithromycin or doxycycline should
be prescribed also.
• A major problem is the detection of
asymptomatic carriers.
• Gonococcal conjunctivitis in new-born is
prevented most often using erythromycin
ointment.
• No vaccine is available.
14

15. Neisseria meningitidis
• Meningococcus
• Identical in staining and morphologicaly to N.
gonorrhoeae.
• Has antiphagocytic polysaccharide Capsule.
• Cultivation in moist chamber containing 5-10%
CO2.
• All media must be warmed to 37C prior to
inoculation as the organism is Susceptible to
above or below 37C.
15

16. Meningitis
• Inflammation meninges of brain or spinal cord.
• Meninges: 3 membranes that envelope brain and spinal
cord.
• Meningitis: caused by bacteria and viruses.
• N. meningitidis, Haemophilus influenzae,
E. coli, S. pneumoniae, S. pyogenes, S. aureus.
16

17. Pathogenesis
• Humans are the only natural hosts for
meningococci.
• The organisms are transmitted by airborne
droplets; they colonize the membranes of the
nasopharynx.
• Carriers (5%) are usually asymptomatic.
• From the nasopharynx, the organism can enter
the bloodstream and spread to specific sites,
such as the meninges or joints, or be
disseminated throughout the body
(meningococcemia).
17

18. Clinical Findings
• The two most important manifestations of
disease are meningococcemia and meningitis.
• The most severe form of meningococcemia is
the life-threatening Waterhouse–Friderichsen
syndrome, which is characterized by high
fever, shock, widespread purpura,
disseminated intravascular coagulation and
thrombocytopenia.
• Petechiae (minute hemorrhagic spots in skin)
or Purpura (hemorrhages into skin) in 30-60%
of patients with meningococcal disease.
18

19. • Bacteremia can result in the seeding of many
organs, especially the meninges.
• The symptoms of meningococcal meningitis are
those of a typical bacterial meningitis,
(Headache, Fever, Stiff neck, Confusion,
difficulty in wake) and an increased level of
PMNs in spinal fluid.
19

20. Virulence Factors
• Fimbriae for attachment.
• Polysaccharide capsule: enables the organism
to resist phagocytosis by polymorphonuclear
leukocytes (PMNs).
• Endotoxin: lipooligosaccharide (LOS) and its
mechanism is endotoxic which causes fever,
shock, and other pathophysiologic changes.
• Immunoglobulin A (IgA) protease helps the
bacteria attach to the membranes of the upper
respiratory tract by cleaving secretory IgA.
20

21. Diagnosis
• Sample: Cerebrospinal fluid (CSF).
• A presumptive diagnosis of meningococcal
meningitis can be made if gram-negative cocci
are seen in a smear of spinal fluid.
21

22. • Culture on Chocolate agar and TMA.
The organism grows best on chocolate agar
incubated at 37°C in 5% CO2.
• Oxidase (all Neisseria positive).
• N. meningitidis utilize glucose and maltose.
• Tests for serum antibodies are not useful for
clinical diagnosis.
• Rapid diagnosis of meningococcal meningitis is
done by “latex agglutination test”, which
detects capsular polysaccharide in the spinal
fluid.
22

23. CSF findings in different forms of meningitis
Type of
meningitis
Glucose Protein
Acute bacterial Low High
Acute viral Normal Normal or high
23

24. Normal CSF !!!!
Normal CSF !!!!
 Appearance:
 WBCs count:
 RBCs:
 Bacteria:
 Protein and Glucose:
24

25. Treatment and Prevention
• Penicillin G is the treatment of choice for
meningococcal infections.
• A third-generation cephalosporin such as
ceftriaxone can also be used.
• Ciprofloxacin can be used for prophylaxis in
people who have had close contact with the
index case.
• Menomune, unconjugated vaccine, contains only
the four polysaccharides (not conjugated to a
carrier protein).
25

26. What are the difference between
N. gonorrhoeae and N. meningitidis
What are the difference between
N. gonorrhoeae and N. meningitidis
????????????
26

27. Haemophilus influenzae
• Small gram-negative rod (coccobacillus) with a
polysaccharide capsule.
• It is one of the three important encapsulated
pyogens, along with the pneumococcus and the
meningococcus.
• Serologic typing is based on the antigenicity of
the capsular polysaccharide.
• Of the 6 serotypes, type b causes most of the
severe, invasive diseases, such as meningitis
and sepsis.
27

28. • Unencapsulated strains can also cause disease,
especially of the upper respiratory tract such
as sinusitis and otitis media, but usually non-
invasive.
• Growth of the organism on laboratory media
requires the addition of two components, heme
(factor X) and NAD (factor V), for adequate
energy production.
Diseases
• H. influenzae used to be the leading cause of
meningitis in young children, but the use of the
highly effective “conjugate” vaccine has greatly
reduced the incidence of meningitis.
28

29. • It is still an important cause of upper
respiratory tract infections (otitis media,
sinusitis) and sepsis in children.
• It also causes pneumonia in adults, particularly
in those with chronic obstructive lung disease.
Pathogenesis
• H. influenzae infects only humans; there is no
animal reservoir.
• It enters the body by airborne droplets into
the respiratory tract, resulting in either
asymptomatic colonization or infections such as
otitis media, sinusitis, or pneumonia.
29

30. • The organism produces IgA protease that
degrades secretory IgA, thus facilitating
attachment to the respiratory mucosa.
• After becoming established in the upper
respiratory tract, the organism can enter the
bloodstream (bacteremia) and spread to the
meninges.
Clinical Findings
• Meningitis caused by H. influenzae cannot be
distinguished on clinical grounds from that
caused by pneumococci or meningococci).
• The rapid onset of fever, headache, and stiff
neck, along with drowsiness, is typical.
30

31. • Sinusitis and otitis media cause pain in the
affected area.
• Other serious infections include septic arthritis,
cellulitis, and sepsis.
• A swollen “cherry-red” epiglottis is seen.
Laboratory Diagnosis
• It depends on the isolation of the organism on
heated-blood (“chocolate”) agar enriched with
two growth factors required for bacterial
respiration (factor X ( heme compound) and
factor V (NAD)).
31

32. • The blood used in chocolate agar is heated to
inactivate nonspecific inhibitors of H.
influenzae growth.
• An organism that grows only in the presence of
both growth factors is presumptively identified
as H. influenzae.
32

33. 33

34. • Other species of Haemophilus, such as H.
parainfluenzae, do not require both factors.
• Definitive identification can be made with
either biochemical tests or the capsular
swelling (quellung) reaction.
34

35. Treatment
• The treatment of choice for meningitis or
other serious systemic infections caused by
H. influenzae is ceftriaxone.
• 20-30% of H. influenzae type b isolates
produce β-lactamase that degrades ampicillin
but not ceftriaxone.
• Untreated H. influenzae meningitis has a
fatality rate of approximately 90%.
35

36. Prevention
• The vaccine contains capsular polysaccharide
of H. influenzae type b conjugated to
diphtheria toxoid or other carrier protein.
• This vaccine is much more effective in young
children than the unconjugated vaccine.
• Meningitis in close contacts of the patient can
be prevented by rifampin.
• Rifampin decreases respiratory carriage of
the organism, thereby reducing transmission.
36

37. Bordetella pertussis
• Pertussis = Whooping cough caused by
Bordetella pertussis.
• Toxin mediated infection.
• Symptoms are initially mild, and then develop
into severe coughing fits, which produce the
namesake "whoop" sound in infected babies
and children when they inhale air after
coughing.
• Despite the severity of the symptoms, the
organism is restricted to the respiratory tract
and blood cultures are negative.
37

38. • In adults, the characteristic whoop is often
absent, leading to difficulty in recognizing the
cough as caused by this organism.
• B. pertussis: Gram-negative, aerobic
coccobacillus, non-motile.
• Encapsulated.
• Fastidious.
• Preschool children (severe under 12 months).
Pathogenesis
• B. pertussis, pathogen only for humans, is
transmitted by airborne droplets.
38

39. • The organisms attach to the ciliated
epithelium of the upper respiratory tract but
do not invade the underlying tissue.
• Decreased cilia activity and subsequent
death of the ciliated epithelial cells are
important aspects of pathogenesis.
• Pertussis is a highly contagious disease that
occurs primarily in infants and young children
and has a worldwide distribution.
39

40. • Several factors play a role in the
pathogenesis:
(1) Attachment to the cilia of the epithelial
cells is mediated by a protein on the pili called
filamentous hemagglutinin. Antibody against
the filamentous hemagglutinin inhibits
attachment and protects against disease.
(2) Pertussis toxin: Leading to edema of the
respiratory mucosa that contributes to the
severe cough of pertussis.
Pertussis toxin also causes a striking
lymphocytosis in the blood.
40

41. (3) The organisms also synthesize, and export
adenylate cyclase.
This enzyme, when taken up by phagocytic cells
(neutrophils), can inhibit their bactericidal
activity. Bacterial mutants that lack cyclase
activity are avirulent.
(4) Tracheal cytotoxin is a fragment of the
bacterial peptidoglycan that damages ciliated
cells of the respiratory tract.
41

42. Laboratory Diagnosis
• The bacteria can be isolated from
nasopharyngeal swabs.
• Bordet-Gengou medium: Slow growing.
• Identification of the isolated organism can be
made by agglutination with specific antiserum or
by fluorescent-antibody staining.
42

43. • However, the organism grows very slowly in
culture, so direct fluorescent-antibody
staining of the nasopharyngeal specimens can
be used for diagnosis.
• Polymerase chain reaction–based tests are
highly specific and sensitive.
• Isolation of the organism in patients with a
prolonged cough is often difficult.
• Serologic tests that detect antibody in the
patient’s serum can be used.
43

44. Treatment
• Azithromycin is the drug of choice.
• Azithromycin reduces the number of organisms
in the throat and decreases the risk of
secondary complications but has little effect
on the course of the disease at the “prolonged
cough” stage because the toxins have already
damaged the respiratory mucosa.
• Supportive care (oxygen therapy and suction
of mucus) during the paroxysmal stage is
important, especially in infants.
44

45. Prevention
• There are two types of vaccines: acellular
vaccine containing purified proteins from the
organism and killed vaccine containing
inactivated B. pertussis organisms.
• The acellular vaccine contains five antigens
purified from the organism.
• The main immunogen in this vaccine is
inactivated pertussis toxin (pertussis toxoid).
• To protect new-borns, pregnant women should
receive pertussis vaccine.
• Anti-pertussis IgG will pass the placenta and
protect the new-born.
45

46. Quiz
Quiz
7%
From the beginning of Chapter 3
46

47. Brucella
• The brucellae are obligate parasites of
animals and humans and are characteristically
located intracellularly.
• Brucella melitensis typically infects goats;
Brucella suis, swine; Brucella abortus, cattle.
• The disease in humans, brucellosis (undulant
fever, Malta fever), is characterized by an
acute bacteremic phase followed by a chronic
stage that may extend over many years and
may involve many tissues.
47
from
swine
pika
Revision

48. Morphology and Identification
• The appearance in young cultures varies from
cocci to rods 1.2 μm in length (Short
coccobacillary forms).
• They are gram negative but often stain
irregularly.
• They are aerobic.
• Nonmotile, and non-spore forming.
• Catalase and oxidase are produced by the
four species that infect humans.
48
8940481
am
catalase oxidase positive

49. Culture
• Brucellae nutritional requirements are
complex.
• Fresh specimens from animal or human sources
are usually inoculated on trypticase-soy agar
or blood culture media.
• B. abortus requires 5–10% CO2 for growth,
the other three species grow in air.
• Small, convex, smooth colonies appear on
enriched media in 2–5 days.
• Hydrogen sulfide is produced by many strains.
49
a
culture characteristics

50. • Brucellae use carbohydrates but produce
neither acid nor gas in amounts sufficient for
classification.
• They are killed in milk by pasteurization.
• Differentiation among Brucella species is
made by their characteristic sensitivity to
dyes and their production of H2S.
• Because brucellae are hazardous in the
laboratory, tests to classify them should be
performed only in reference public health
laboratories using appropriate biosafety
precautions.
50
nogas youcan'tuse fermentation
to identification
DEAL

51. Pathogenesis
• Although each species of Brucella has a
preferred host, all can infect a wide range of
animals and humans.
• The common routes of infection in humans
are ingestion of infected milk, mucous
membranes (droplets), and skin (contact with
infected tissues of animals).
• Cheese made from unpasteurized goats’ milk
is a particularly common vehicle.
51

52. • The organisms progress from the portal of
entry via lymphatic channels and regional lymph
nodes to the thoracic duct and the
bloodstream, which distributes them to the
kidneys, adrenal glands, liver, spleen, and
pancreas.
• Granulomatous nodules that may develop into
abscesses form.
• In such lesions, the brucellae are principally
intracellular.
• Osteomyelitis, meningitis also occasionally
occurs.
52

53. • The main histologic reaction in brucellosis
consists of proliferation of mononuclear cells,
exudation of fibrin, coagulation necrosis, and
fibrosis.
• The granulomas consist of epithelioid and
giant cells, with central necrosis and
peripheral fibrosis.
• B. abortus usually causes mild disease without
suppurative complications.
• B. melitensis infection is more acute and
severe.
53
HE

54. • Placentas and fetal membranes of cattle,
swine, sheep, and goats contain erythritol, a
growth factor for brucellae.
• The proliferation of organisms in pregnant
animals leads to placentitis and abortion in
these species.
• There is no erythritol in human placentas, and
abortion is not part of Brucella infection of
humans.
54
erythritol Jiva goats die Nsb

55. Clinical Findings
• The incubation period ranges from 1–4 weeks.
• The onset is insidious, with malaise, fever,
weakness, and sweats.
• The fever usually rises in the afternoon; its fall
during the night is accompanied by sweat.
• There may be gastrointestinal and nervous
symptoms.
• Lymph nodes enlarge, and the spleen becomes
palpable.
• Hepatitis may be accompanied by jaundice.
55

56. • Deep pain and disturbances of motion,
particularly in vertebral bodies, suggest
osteomyelitis.
• These symptoms of generalized Brucella
infection generally subside in weeks or months,
although localized lesions and symptoms may
continue.
• After the initial infection, a chronic stage may
develop, characterized by weakness and pains,
low-grade fever, nervousness, and other
nonspecific manifestations.
56

57. Diagnostic Laboratory Tests
• Blood should be taken for culture, biopsy
material for culture (lymph nodes, bone), and
serum for serologic tests.
• Brucella agar was specifically designed to
culture Brucella species.
• In oxygenated form, the medium grows
Brucella species very well.
• 8–10% CO2 at 35–37°C should be observed for
3 weeks before being discarded as being
negative results; liquid media cultures should
be blindly subcultured during this time.
57
liquid I
subculture 45049media
14

58. • Brucella grow on trypticase-soy medium with
or without 5% sheep blood, brain–heart
infusion medium, and chocolate agar.
• Blood culture media readily grow Brucella.
• Liquid medium used to culture Mycobacterium
tuberculosis also supports the growth of at
least some strains.
• They are nonhemolytic.
• The observation of tiny gram-negative
coccobacilli that are catalase positive and
oxidase positive suggests Brucella species.
58
9

59. • A positive urease test result is characteristic
of Brucella species.
Serology
• (IgM) antibody levels rise during the first week
of acute illness, peak at 3 months, and may
persist during chronic disease.
• IgG antibody levels rise about 3 weeks after
onset of acute disease, peak at 6–8 weeks, and
remain high during chronic disease.
• IgA levels parallel the IgG levels.
• ELISA assays—IgG, IgA, and IgM antibodies
may be detected using enzyme-linked
immunosorbent assay (ELISA), which use
cytoplasmic proteins as antigens. 59
314hm affrgyweak
76 monthafter
thiswill
beni
gan
centra

60. Treatment
• Brucellae may be susceptible to tetracyclines,
rifampin, aminoglycosides, and some quinolones.
• Symptomatic relief may occur within a few
days after treatment with these drugs.
• However, because of their intracellular
location, the organisms are not readily
eradicated completely from the host.
• For best results, treatment must be prolonged.
• Combined treatment with a tetracycline (eg,
doxycycline) and either streptomycin for 2–3
weeks or rifampin for 6 weeks is recommended.
60

61. Prevention, and Control
• Because of occupational contact, Brucella
infection is much more frequent in men.
• Most infections remain asymptomatic (latent).
• Infection rates vary greatly with different
animals and in different countries.
• Active immunization of humans against Brucella
infection is experimental.
• Control rests on limitation of spread and
possible eradication of animal infection,
pasteurization of milk and milk products, and
reduction of occupational hazards wherever
possible.
61
51 5441
D8
more thanWomen

62. Enterobacteriaceae
• Most encountered bacteria in Microbiology
Lab.
• Gram-negative rods (Bacilli).
• Do not form spores.
• Motile by Peritrichous flagella or Nonmotile.
62

63. • They found primarily in the colon of humans and
other animals, many as part of the normal flora.
• These organisms are present in relatively small
numbers compared with anaerobes such as
Bacteroides.
• Grow aerobically and anaerobically.
• Active biochemically, ferment glucose and other
sugars with gas production.
• Catalase positive and Oxidase negative.
• Grow well on MacConkey agar and EMB.
• They cause a variety of diseases with different
pathogenetic mechanisms.
63

64. Escherichia coli
• Escherichia coli = E. coli.
• It’s discoverer - Theodor Escherich).
• Commonly found in the Lower Intestine.
• E. coli normally colonizes an infant's
gastrointestinal tract within 40 hours of birth,
arriving with food or water or with the
individuals handling the child.
• Most E. coli strains are harmless.
 Benefit hosts by producing Vitamin K.
 Preventing establishment of Pathogenic bacteria
within intestine.
64

65. • Contamination of the public water supply
system by sewage is detected by the presence
of coliforms in the water.
• In a general sense, the term coliform includes
not only E. coli, but also other inhabitants of
the colon such as Enterobacter and Klebsiella.
• Because E. coli is a large intestine organism, It
is used as the indicator of fecal contamination.
• E. coli and the enteric pathogens are killed by
chlorination of the drinking water.
65

66. Pathogenesis of E. coli
• Intestinal diseases (Gastroenteritis)
O157:H7. “traveler’s diarrhea,” a watery
diarrhea. Some strains of E. coli are
enterohemorrhagic and cause bloody diarrhea.
• Neonatal meningitis. capsular antigen K1.
• Urinary tract infections (UTI) Uropathogenic
E. coli (UPEC).
• It has three antigens that are used to identify
the organism in epidemiologic investigations: O,
or cell wall antigen; H, or flagellar antigen; and
K, or capsular antigen.
66

67. Virulence factors
E. coli components that contribute to its ability
to cause disease:
• Pili.
• Capsule.
• Flagella.
• Endotoxin.
• Three exotoxins (enterotoxins), two that
cause watery diarrhea and one that causes
bloody diarrhea and hemolytic–uremic
syndrome.
67

68. Intestinal Tract Infection
• The enterotoxin-producing strains do not
cause inflammation, do not invade the
intestinal mucosa, and cause watery, non-
bloody diarrhea.
• Certain strains of E. coli are enteropathic
(enteroinvasive) and cause disease by invasion
of the epithelium of the large intestine,
causing bloody diarrhea (dysentery)
accompanied by inflammatory cells
(neutrophils) in the stool.
68

69. • Certain enterohemorrhagic strains of E. coli
(those with the O157:H7 serotype) also cause
bloody diarrhea by producing exotoxin called
Shiga toxin, so called because it is very
similar to that produced by Shigella species.
• Some patients with bloody diarrhea caused by
O157:H7 strains also have life-threatening
complication called hemolytic–uremic syndrome
(HUS).
• It occurs when Shiga toxin enters the
bloodstream.
• This syndrome consists of hemolytic anemia,
thrombocytopenia, and acute renal failure.
69

70. • The hemolytic anemia and renal failure occur
because there are receptors for Shiga toxin
on the surface of the endothelium of small
blood vessels and on the surface of kidney
epithelium.
• Treatment of diarrhea caused by O157:H7
strains with antibiotics, such as ciprofloxacin,
increases the risk of developing HUS by
increasing the amount of Shiga toxin
released by the dying bacteria.
• For this reason, antibiotics should not be used
to treat diarrhea caused by EHEC.
70

71. Clinical findings
• Diarrhea caused by enterotoxigenic E.coli is
usually watery, non-bloody, self-limited, and of
short duration (1–3 days).
• It is frequently associated with travel
(Traveler’s diarrhea).
• Infection with enterohemorrhagic E. coli
(EHEC) results in a dysentery-like syndrome
characterized by bloody diarrhea, abdominal
cramping, and fever similar to that caused by
Shigella.
71

72. UTI
• Bacterial infection that affects any part of the
Urinary tract.
• Symptoms include frequent feeling to urinate,
pain during urination (Dysuria), and burning
sensation in the urethra.
• Although urine contains a variety of fluids,
salts, and waste products, it does not usually
have bacteria in it.
• The most common type of UTI is acute
Cystitis: referred to Bladder infection.
• An infection of the upper urinary tract or
Kidney known as Pyelonephritis: is potentially
more serious. (Fever and Abdominal pain). 72

73. 73

74. Risk factors
SEX Intercourse
• In young sexually active women.
• “Honeymoon cystitis": frequent UTIs during
early marriage.
• Spermicide use increases risk of UTIs.
Sex/Gender: Women are more prone to UTIs than
men due to:
 Much shorter length of Urethra.
 Women lack the bacteriostatic properties of
prostatic secretions.
 Among elderly, UTI frequency is roughly equal
proportions in women and men. 74

75. Urinary catheters
• It can be decreased by only using aseptic
technique for insertion.
UTI Causative Microbes
Gram negative
E. coli, Klebsiella pneumoniae (Lactose
fermentors).
Proteus spp., Pseudomonas aeroginosa (NLF).
Gram Positive
S. saprophyticus, Group B streptococci.
Fungi: Candida albicans.
Viruses: Rare.
75

76. Diagnosis
• Multiple bacilli (rod-shaped bacteria, shown as
black between white cells at urinary
microscopy.
• This is called Bacteriuria and Pyuria,
respectively.
76

77. • Samples: depending on the infection.
• Culture: MacConkey agar + EMB.
• Gram stain.
• Ferment all sugars with Gas. Indole +ve.
77

78. 78
Lactose Catalase Oxidase Indole Citrate Urease S
2
H
Escherichia
coli
+ + _ + _ _ _

79. Treatment
• Uncomplicated lower UTI (cystitis) can be
treated using oral trimethoprim-
sulfamethoxazole or nitrofurantoin.
• Pyelonephritis can be treated with ciprofloxacin
or ceftriaxone.
• E. coli sepsis requires treatment with third
generation cephalosporin, such as cefotaxime,
with or without an aminoglycoside, such as
gentamicin.
• For the treatment of neonatal meningitis, a
combination of ampicillin and cefotaxime.
79

80. Prevention
• There is no specific prevention for E. coli
infections, such as active or passive
immunization.
• However, various general measures can be
taken to prevent certain infections caused by
E. coli and other organisms.
80

81. pneumoniae
K.
• German microbiologist Edwin Klebs.
• They can be found in water, soil, plants,
animals and humans.
• Non-motile.
• They are usually opportunistic pathogens that
cause nosocomial infections, especially
pneumonia and urinary tract infections.
• K. pneumoniae is important respiratory tract
pathogen outside hospitals as well.
• It has very large polysaccharide capsule, which
gives its colonies striking mucoid appearance.
81

82. Pathogenesis
• Predisposing conditions for K. pneumoniae
infections include advanced age, chronic
respiratory disease, diabetes, or alcoholism.
• UTI and pneumonia are the usual clinical
entities associated with the bacteria, but
bacteremia and secondary spread to other
areas such as the meninges and liver occur.
• Pneumonia caused by Klebsiella, which
produces a thick sputum (“currant-jelly”) and
can progress to necrosis and abscess
formation.
82

83. Diagnosis
• Form large sticky colonies.
• Ferment sugars (glucose, lactose, sucrose, and
mannitol) with abundant gas.
• Citrate positive.
• Indole negative.
• Urease positive.
83

84. 84
Bacteria Lactose Sucrose Catalas
e
Oxidase Indole Citrate Urease S
2
H
Klebsiella
pneumoniae
+ + + _ _ d + _

85. Treatment
• Because of antibiotic resistance, the choice of
drug depends on sensitivity testing.
• Isolates from hospital-acquired infections are
frequently resistant to multiple antibiotics.
• Carbapenem-resistant strains are an
important cause of hospital-acquired infections
and are resistant to almost all antibiotics.
• An aminoglycoside (gentamicin) and
cephalosporin (cefotaxime) are used empirically
until the results of testing are known.
85

86. Salmonella
• Salmonella parasitise intestines of large
number of vertebrate species.
• Transmission = uncooked meats and eggs.
• Chickens: are major reservoir of Salmonella.
• Most Salmonella are carried by animals, S.
typhi is unique because it is only carried by
humans.
• Cause Typhoid fever (Enteric fever).
• S. typhimurium causes Gastroenteritis in
humans and other mammals.
86

87. Important Properties
• Salmonellae do not ferment lactose but
produce H2S—features used in their lab
identification.
• Their antigens—cell wall O, flagellar H, and
capsular Vi (virulence)—are important for
taxonomic and epidemiologic purposes.
• The Vi antigens (capsular polysaccharides)
are antiphagocytic and are important virulence
factor for S. typhi.
• The Vi antigens are also used for the serotyping
of S. typhi in the clinical laboratory.
87

88. • Clinically, Salmonella species are in two distinct
categories, namely, typhoidal species (cause
typhoid fever) and nontyphoidal species (cause
diarrhea [enterocolitis].
• The typhoidal species are S. typhi and S.
paratyphi.
• The non-typhoidal species are the serotypes of
S. enterica.
Pathogenesis
The three types of Salmonella infections
(enterocolitis, enteric fevers, and septicemia)
have different pathogenic features.
88

89. 1. Enterocolitis
• Characterized by invasion of the epithelial
and subepithelial tissue of the small and large
intestines with resulting inflammation and
diarrhea.
• Neutrophils limit the infection to the gut.
• Bacteremia is infrequent in enterocolitis.
(2) Typhoid and other enteric fevers:
• Infection begins in the small intestine, but
few gastrointestinal symptoms occur.
89

90. • The organisms enter, multiply in the mononuclear
phagocytes of Peyer’s patches, and then spread
to the phagocytes of the liver, gallbladder, and
spleen.
• This leads to bacteremia, which is associated
with the onset of fever and other symptoms,
probably caused by endotoxin.
• Survival and growth of the organism within
phagosomes in phagocytic cells are a striking
feature of this disease, as is the predilection for
invasion of the gallbladder, which can result in
establishment of the carrier state and
excretion of the bacteria in the feces for long
periods.
90

91. (3) Septicemia
• Accounts for only about 5-10% of Salmonella
infections and occurs in one of two settings:
 A patient with an underlying chronic disease,
such as sickle cell anemia or cancer.
 A child with enterocolitis.
• Osteomyelitis in a child with sickle cell
anemia is an important example of this type
of salmonella infection.
91

92. Clinical Findings
• Incubation period of 12 to 48 hours.
Enterocolitis: begins with nausea, vomiting and
then progresses to abdominal pain and
diarrhea, which can vary from mild to severe,
with or without blood.
• Usually the disease lasts a few days, is self-
limited, causes non-bloody diarrhea, and does
not require medical care except in very young
and very old.
• S. typhimurium is the most common species of
Salmonella to cause enterocolitis.
92

93. • Typhoid fever: caused by S. typhi, and in
enteric fever, caused by S. paratyphi A, B, and
C the onset of illness is slow, with fever and
constipation rather than vomiting and diarrhea
predominating (almost).
• Diarrhea may occur early but usually disappears
by the time the fever and bacteremia occur.
• After the first week, as the bacteremia
becomes sustained, high fever, tender
abdomen, and enlarged spleen occur.
• Rose spots (rose-colored macules on the
abdomen) are associated with typhoid fever
but occur rarely.
93

94. • Leukopenia and anemia are often seen.
• Liver function tests are often abnormal,
indicating hepatic involvement.
• The disease begins to resolve by the third
week, but severe complications such as
intestinal hemorrhage or perforation (hole) can
occur.
• About 3% of typhoid fever patients become
chronic carriers which is higher among women,
especially those with previous gallbladder
disease and gallstones.
94

95. Diagnosis
• The clinical picture together with information
on travel.
• Samples: Stool, Blood.
• Media are differential and slightly selective,
i.e., in addition to lactose and a pH indicator,
they contain an inhibitor for non-enterics.
• (e.g., MacConkey agar and Eosin-methylene
blue agar - EMB).
95

96. • Selective for Salmonella are SS agar.
• Xylose-Lisine-Deoxycholate (XLD) agar.
96

97. • Gram stain: Gram-negative bacilli.
• Sugar fermentation: Lactose negative; acid
and gas from glucose, mannitol, maltose.
• Biochemical tests
 Citrate positive.
 H2S produced from Sodium Thiosulfate.
• On TSI agar, an alkaline slant and acid butt
with both gas and H2S, are produced.
97

98. 98

99. Treatment
• Enterocolitis caused by Salmonella is self-
limited that resolves without treatment.
• Fluid and electrolyte replacement may be
required.
• Antibiotic treatment does not shorten the
illness or reduce the symptoms; in fact, it
may prolong excretion of the organisms,
increase the frequency of the carrier state,
and select mutants resistant to the
antibiotic.
99

100. • Antimicrobial agents are indicated only for
neonates or persons with chronic diseases
who are at risk for septicemia and
disseminated abscesses.
• The treatment of choice for typhoid fever
and septicaemia with metastatic infection is
either ceftriaxone or ciprofloxacin.
• Ampicillin or ciprofloxacin should be used in
patients who are chronic carriers of S. typhi.
100

101. Prevention
• Two vaccines are available, but they confer
limited (50 –80%) protection against S. typhi.
• One contains Vi capsular polysaccharide of
S. typhi (intramuscularly), and the other
contains a live, attenuated strain (Ty21a) of
S. typhi (orally).
• A new conjugate vaccine containing capsular
polysaccharide (Vi) antigen coupled to a
carrier protein is safe and immunogenic in
young children.
101

102. Shigella
• Discovered over 100 years ago.
• Japanese microbiologist - Shiga.
• Related to Escherichia and considered
another strain of E. coli.
• Shigella species cause enterocolitis (bacillary
dysentery).
• The term dysentery refers to bloody diarrhea.
• Shigellae are non–lactose-fermenting.
102

103. • Shigellae can be distinguished from salmonellae
by three criteria:
 Do not produce gas from the fermentation of
Glucose.
 They do not produce H2S.
 Nonmotile.
• All Shigella have O antigens (polysaccharide) in
their cell walls, and these antigens are used to
divide the genus into four groups:
 Serotype A- S. dysenteriae.
 Serotype B- S. flexneri.
 Serotype C- S. boydii.
 Serotype D- S. sonnei. 103

104. Pathogenesis
• Shigellae are the most effective pathogens
among the enteric bacteria.
• They have very low ID. Ingestion of as few as
100 organisms causes disease, whereas at least
105 V. cholerae or Salmonella are required to
produce symptoms.
• Shigellosis is only human disease (there is no
animal reservoir).
• The organism is transmitted by fecal–oral route.
The four (Fs—fingers, flies, food, feces).
104

105. • There is no prolonged carrier state with
Shigella infections, unlike that seen with S.
typhi.
• Shigella cause bloody diarrhea (dysentery) by
invading the cells of the mucosa of the distal
ileum and colon.
• Local inflammation accompanied by ulceration
occurs, but the organisms rarely penetrate
through the wall or enter the bloodstream,
unlike Salmonellae.
• Shiga toxins very similar to those produced by
Shigella are produced by enterohemorrhagic
E. coli O157:H7 strains that cause enterocolitis
and HUS. 105

106. Clinical Findings
• After an incubation period of 1 to 4 days,
symptoms begin with fever and abdominal
cramps, followed by diarrhea, which may be
watery at first but later contains blood and
mucus.
• The disease varies from mild to severe
depending on two major factors: the species of
Shigella and the age of the patient, with young
children and elderly people being the most
severely affected.
106

107. • The diarrhea frequently resolves in 2 or 3
days; in severe cases, antibiotics can shorten
the course.
Diagnosis
107
XLD

108. • No utilise Citrate as source of carbon.
• Do not form H2S.
• (Comparing to Salmonella).
108
Shigella on XLD
Salmonella on XLD

109. Proteus
• Distinguished from other members of the
Enterobacteriaceae by their ability to produce
the enzyme phenylalanine deaminase.
• They produce enzyme urease, which cleaves urea
to form NH3 and CO2.
109

110. • Certain species are very motile and produce
a striking swarming effect on blood agar,
characterized by expanding rings (waves) of
organisms over the surface of the agar.
110

111. • Proteus species are found in the human
intestinal tract as part of normal intestinal
flora, along with E. coli and Klebsiella species.
Pathogenesis
• It causes UTI due to their presence in the
colon and to colonization of the urethra,
especially in women.
• The motility of Proteus may contribute to their
ability to invade the urinary tract.
• Proteus species possess extracytoplasmic outer
membrane, contains lipid bilayer, lipoproteins,
polysaccharides, and lipopolysaccharides.
111

112. • Fimbriae facilitate adherence and thus enhance
the capacity of the organism to produce disease.
Specific chemicals located on the tips of pili
enable organisms to attach to selected host
tissue sites (eg, urinary tract endothelium).
• The ability of Proteus to produce urease and to
alkalinize urine by hydrolyzing urea to ammonia
makes it effective in producing an environment
in which it can survive.
• This leads to precipitation of organic and
inorganic compounds, which leads to Struvite
Stone formation. pH / Alkaline.
112

113. • Stones in the urinary tract obstruct urine
flow, damage urinary epithelium, and serve as
a nidus for recurrent infection by trapping
bacteria within the stone.
• Because alkaline urine also favors growth of
the organisms and more extensive renal
damage, treatment involves keeping the urine
at a low pH.
113

114. Clinical Findings
• The signs and symptoms of urinary tract
infections caused by these organisms cannot be
distinguished from those caused by E. coli or
other members of the Enterobacteriaceae.
• Proteus species can also cause pneumonia,
wound infections, and septicemia.
• P. mirabilis causes 90% of Proteus infections.
 Those with structural abnormalities of the
urinary tract.
 Those who have had urethral instrumentation.
• Another species is Proteus vulgaris.
114

115. Laboratory Studies
• Proteus organisms are easily recovered through
routine laboratory cultures.
• Most strains are lactose-negative.
• Demonstrate Swarming motility on agar plates.
• Growth on blood agar containing phenylethyl
alcohol inhibits swarming.
115

116. 116
Bacteria Lactose Sucro
se
Catalase Oxida
se
Indole Citrate Urease S
2
H
Proteus
vulgaris
_ + + _ + _ + +
Proteus
mirabilis
_ Slow
+
+ _ _ d + +

117. Other Enterobacteria
• Enterobacter.
• Serratia.
• Citrobacter.
• Yersinia.
117

118. Pseudomonas aeruginosa
• Gram-negative bacilli and aerobic.
• Motile by single polar flagellum.
• Has Capsule.
Diseases
• P. aeruginosa causes infections (sepsis,
pneumonia, and UTI) primarily in patients with
lowered host defenses.
• It also causes chronic lower respiratory tract
infections in patients with cystic fibrosis, wound
infections (cellulitis) in burn patients and
malignant otitis externa in diabetic patients.
118

119. • It is the most common cause of ventilator-
associated pneumonia.
Important Properties
• Pseudomonads are gram-negative rods that
resemble the members of the
Enterobacteriaceae but differ in that they are
strict aerobes (derive their energy only by
oxidation of sugars rather than by
fermentation).
119

120. • Because they do not ferment glucose, they are
called non-fermenters,in contrast to the
members of the Enterobacteriaceae, which do
ferment glucose.
• Oxidation involves electron transport by
cytochrome c (oxidase-positive).
• Pseudomonads are able to grow in water
containing only traces of nutrients (tap water),
and this favors their persistence in the hospital
environment.
• It withstands disinfectants; this accounts in
part for their role in hospital-acquired
infections.
120

121. • P. aeruginosa produces two pigments useful in
clinical and laboratory diagnosis:
(1) Pyocyanin: color the pus in a wound blue.
(2) Pyoverdin (fluorescein): yellow-green pigment
that fluoresces under ultraviolet light, a
property that can be used in the early
detection of skin infection in burn patients.
• In the laboratory, these pigments diffuse into
the agar, imparting blue-green color that is
useful in identification.
• P. aeruginosa is the only species of
Pseudomonas that synthesizes pyocyanin.
121

122. • Its optimum temperature for growth is 37C
and able to grow at 42C.
• Strains of P. aeruginosa isolated from cystic
fibrosis patients have a prominent slime layer
(glycocalyx), which gives their colonies a very
mucoid appearance.
• The slime layer mediates adherence of the
organism to mucous membranes of the
respiratory tract and prevents antibody from
binding to the organism.
122

123. Pathogenesis
• P. aeruginosa is found chiefly in soil and water,
although approximately 10% of people carry it
in the normal flora of the colon.
• It is found on the skin in moist areas and can
colonize the upper respiratory tract of
hospitalized patients.
• Its ability to grow in simple aqueous solutions
has resulted in contamination of respiratory
therapy and anesthesia equipment, intravenous
fluids, and even distilled water.
123

124. P. aeruginosa is primarily opportunistic
pathogen:
 Those with extensive burns, in whom the skin
host defenses are destroyed.
 Those with chronic respiratory disease
(cystic fibrosis), in whom the normal clearance
mechanisms are impaired.
 Those who are immunosuppressed.
 In those with indwelling catheters.
• The most common cause of gram-negative
nosocomial pneumonia, especially ventilator-
associated pneumonia.
124

125. • Pathogenesis is based on multiple virulence
factors: endotoxin, exotoxins, and enzymes.
 Its endotoxin like that of other gram-negative
bacteria, causes the symptoms of sepsis and
septic shock.
• The best known of the exotoxins is exotoxin A,
which causes tissue necrosis.
 It inhibits eukaryotic protein synthesis by the
same mechanism as diphtheria exotoxin.
 It also produces proteases that are histotoxic
and facilitate invasion of the organism into the
bloodstream.
• Pyocyanin damages the cilia and mucosal cells
of the respiratory tract. 125

126. Diagnosis
• Symotoms and sample depend on infection.
• Gram stain: gram negative bacilli.
• No ferment glucose and Lactose.
• Catalase positive.
• Oxidase Positive.
• Fruity odor colonies.
• Ability to grow at 42°C.
126

127. • Confirmatory tests: production of blue-green
pigment on Cetrimide agar.
• Cetrimide has bactericidal activity against Gram-
positive and certain Gram-negative organisms,
including species of pseudomonas other
than Pseudomonas aeruginosa .
127

128. 128
Bacteria Lactose Sucrose Catalase Oxidas
e
Indole Citrate Urease S
2
H
Pseudomon
as
aeruginosa
_ _ + + _ + d _

129. Treatment and Prevention
• P. aeruginosa is resistant to many
antibiotics.
• For infections caused by highly resistant
strains, colistin (polymyxin E) is useful.
• The drug of choice for UTI is ciprofloxacin.
• Removing indwelling catheters promptly.
• Taking special care of burned skin.
129

130. 130