This document summarizes several bacterial pathogens. It describes Staphylococcus aureus as spherical, golden in color due to carotenoid pigment, and catalase and coagulase positive. It is a virulent pathogen that can cause infections like furuncles. Streptococcus pyogenes produces toxins and enzymes that allow it to cause infections like pneumonia, skin infections, and non-suppurative complications. Clostridium species are anaerobic bacteria that can produce potent toxins causing diseases like gas gangrene, botulism, and C. difficile infection.

1. Systemic Bacteriology
Section 4
Basic microbiology teaching group

2. Spherical, clusters.
Golden color – carotenoid pigment
Catalase and coagulase – positive
β – hemolytic
Gram positive bacteria
Staphylococcus aureus

3. Virulence factors

4. Virulence factors
Cell wall structural components:
Polysaccharides,teichoic acid,protein A(bind IgG)
,capsule
Toxin production: hemolysin, enterotoxin,
fibrinolysin ,toxic shock syndrome toxin ,etc….
Enzyme productiion:
Catalse,coagulase, lipase,etc….
Protein receptors: facilitate staphylococcal
adhesion to host cell tissues
Resistance to antibitics: B-lactamase, methicillin
resistance(MRSA),etc…..

5. Pathogenicity
1.Cutaneous lesions:
Furuncles( infection of hair follicle), abscess,
impetigo(contagious superficial skin infection), etc…..
2.Staphylococcal food poisoning:
Enterotoxin -Diarrhea and vomiting set in within 6
hours of taking contaminated food.
3.Other infections : septicemia, scalded skin” syndrome,
Toxic shock syndrome, etc…..

6. Cocci , chains, Catalase – negative
Streptococcus pyogenes: B-hemolytic
 Streptococcus pneumoniae: alpha hemolytic
Gram positive bacteria
Streptococccus

7. Virulence factors
Streptococcus pyogenes
Toxin production:
Hemolysins
Erythrogenic toxin-- scarlet fever(fever, skin
rash, sore throat).
Enzymes: Streptokinase (fibrinolysin,
Deoxyribonucleases, Hyaluronidase(a
spreading factor),etc…

8. Streptococcus pyogenes Pathogenicity:
1. Respiratory infection:
Throat is the primary site of invasion causing sore throat
Scarlet fever, Otitis media, and Bronchopneumonia
2. Skin infection:
cause suppurative infection isolated from wound burns
3.Genital tract:
Puerperal sepsis
The source of infection is nasopharynx of doctors, nurses and
attendants, etc.
4.Non-suppurative complications:
a. Acute rheumatic fever
b. Acute glomerulonephritis.

9. Streptoccocus pneumoniae
 Capsulated
 Most common cause of pneumoniae in
human
Virulence Factors
1. Toxins like hemolysin
2. Capsule : association with virulence.
3. Enzymes –(neuraminidase): resembling
receptor destroying enzyme of influenza
virus

10. Gram positive bacteria
Clostridium:
Obligate anaerobes, rod - shaped , contain
endospores
C. tetani
C. botulinum
C. perfringens
C.difficile

11. Virulence and pathogenicity
 Clostridium tetani: (drum stick appearance)
 Toxin : hemolysin , neurotixins
 Tetanus: due to contamination of wound
 Clostridium pyrfringes
 Toxin : 4 major toxins alpha, beta, epsilon, Iota
 Capsule
 Alpha toxin cause toxemia of gas gangrene(tissue death)
 Food poisoning (cause diarrhea recovered after 24-48 hr)

12. virulence and pathogenicity
Clostridium botulinum:
Exotoxin :botulinum toxin
Cause botulism of preserved and canned food—
severe form of food poisoning cause death
Clostridium difficile—part of intestinal normal
flora
Enterotoxin----diarrhea
Cytotoxin----cytopathogenic effects in several
tissues
Pseudo membraneous colitis due to prolonged
use of broad spectrum antibiotics disrupt
intestinal normal flora

13. Gram positive bacteria
Bacillus
Rods,endospore forming, aerobic
Bacillus anthracis – Non motile
Have three main antigens: capsular, somatic polysaccharide,
somatic protein
Somatic protein ---is the only antigen that produce protective
antibodies
Exotoxin like substance
causes anthrax transmitted by accidental contact with infected
animals
 Bacillus cereus –motile
 food poisoning due to enterotoxin that causes diarrhea

14. Gram Negative bacteria
Pseudomonas
Aerobic, motile rods, produce pigments
 Pseudomonas aeruginosa
Virulence factors:
 Srtuctural antigens:somatic and flagellar
 Somatic antigens ,flagellar antigens ,plasma prtoteins
 Enzymes and hemolysin
 Exotoxin and endotoxin
Pathogensis:
 Nosocomial infections
 Secondary infections of wound , burns, chronic skin ulcers
 Cause infantile diarrhea due to enterotoxin production
 (Catheter associated) urinary tract infection , Chronic otitis
media , pulmonary infection,etc…

15. Gram Negative bacteria
Enterobactriaceae
Escherichia coli(opportunistic pathogen) :
Motile bacilli, extra-intestinal species are
encapsulated , facultative anaerobe
One of the most common inhabitants of the human
and animal intestinal tract
The most common cause of nosocomial infections,
It is a leading cause of community-acquired urinary
tract infections.
Indicates fecal contamination (water and food
resources)
Most common cause UTI in females
Travelers Diarrhea by ETEC(poor personal hygiene)
Food poisoning – E. coli 0157:H7

16. Gram Negative bacteria
Enterobactriaceae
 Mode of transmission:
 Endogenous spread (UTI)
 Person-Person in hospitals
 Fecal -oral for strains that are toxin producers
Proteus:(Opportunistic pathogen)
 Highly motile, inhabit human bowel , it
produce Urease enzyme
 Proteus cause: UTI , Wounds and ears
infection

17. Gram Negative bacteria
Enterobactriaceae
 Common species(P.vulgaris and P.Mirbilis
 Mode of transmission:
 Endogenous spread (UTI)
 Person-Person in hospitals settings
Klebsiella: opportunistic pathogen
 It is commonly found in
 Environment like water and in soil
 Mammals mucosal surfaces including animal
human

18. Gram Negative bacteria
Enterobactriaceae
Klebsiella
Klebsiella pneumoniae and K.oxytoca causes
community acquired and nosocomial pneumonia
and UTI in humans.
Mode of transmission:
 Endogenous spread (UTI)
 P-P in hospitals settings
Emergence of drug resistant Klebsiella in hospital
setting which can be detected by rectal swabs as
 ESBL: Extended Spectrum B lactamase
producer
 CRE :carbapenem-resistant

19. Gram Negative bacteria
Enterobactriaceae
Shigella : (overt pathogen; not part of human normal
flora, only human pathogen)
 Shigella dysenteriae
 S. sonnei
Causes
bacillary dysentery which is defined as acute
inflammatory colitis and bloody diarrhea characterized by
cramps, and bloody, mucoid stools.
S. sonni may produce only watery diarrhea.
 Mode of transmission:
Person-to-person spread by fecal-oral route,
especially in overcrowded areas, group settings

20. Gram Negative bacteria
Enterobactriaceae
 Salmonella (overt pathogen)
• Salmonellae inhabit intestinal tracts of human and many
animals especially poultry and cattle
Pathogenesis
 Enteric fever
– typhoid fever-S. enterica servar Typhi --infects only human
-Paratyphoid fever--S.Paratyphi A,S.Paratyphi B
 Salmonellosis(Gastroentiritis)---food poisining
 S. Typhimurium , S. Enteritides (mucous and blood in stool)
• Septicemia—S. Choleraesuis , S.Typhi & S. Paratyphi
• Mode of transmission
 Person-to-person spread by fecal-oral route/ ingestion of
contaminated food

21. Gram Negative bacteria
Vibrio
Curved , curved comma shaped actively motile
Vibrio cholerae
Virulence
Enterotxin-
Pathogenesis
 Cause cholera –Watery diarrhea
V. Parahaemolyticus
- causes food poisining
Transmitted to humans mostly by raw or undercooked
shellfish.

22. Gram Negative bacteria
Neisseria
Aerobic, non motile , oxidase positive cocci arranged in pairs.
Strict human parasite
N.meningitidis—intracellular diplococci
Virulence
 Endotoxin , Blocking IgA
 Pathogenicity
 Inter body through nasopharynx
 Cause meningococcal septicemia
N.gonorrhoeae
Virulence
 IgA protease , Antibiotic resistance
Pathogenecity:
 Gonorhea—venereal disease
 Opthalmia neonatorum—new born infection during delivery

23. Gram Negative bacteria
Gram negative coccobacilli
Brucella----Non motile,capsulated
Brucella abortus(from cattles)
Brucella melitensis(from goat)
Brucella suis(from pigs)
Antigenic structure:
(A & M) are present in different proportions among the
different species.
Superficial L antigen resembles the Vi antigen (virulence) of
Salmonella.
Pathogenicity
Cause brucellosis (malta fever, undulent fever)—zoonotic

24. Gram Negative bacteria
Gram negative coccobacilli
Hemophilus
Aerobic,Non motile,some strains are capsulated,pleomorphic,have
one or both accessory factros (X ) hemin and( V)NAD present in
blood
H.infleunzae
Type type b accounts for most infections
Cause meningitis,otitis media,pneumonia,etc—
H.aegypticus
Cause contagious form of conjunctivitis
Hemophilus ducreyi
Cause chancroid---venereal disease

25. Acid Fast Bacteria
Mycobacteria
Gram positive bacilli , aerobic, non motile

26. Acid Fast Bacteria
M. tuberculosis----human pathogen
Infection : inhalation,ingestion,inoculation
Virulence
Cording factors ---derivatives of mycolic acid
Cell wall glycolipids---inhibits phagolysome
formation allows intracellular survival
Antibiotic resistance
Pathogenesis
Tuberculosis---infection of the lungs

27. Spirochaetes
Motile without flagella ,,elongated spiral rods
Treponema
Treponema pallidum---venereal syphilis
Pathogenicity:
Congenital syphilis---from mother to fetus
Acquired syphilis---acquired by sexual
contact