This document summarizes several gram positive bacterial infections including Staphylococcus aureus, Streptococcus pyogenes, Corynebacterium diphtheriae, Listeria monocytogenes, Bacillus anthracis, and Nocardia. S. aureus causes a variety of pyogenic infections through toxin production or direct invasion. S. pyogenes causes conditions like strep throat, impetigo, and scarlet fever. C. diphtheriae produces a toxin that causes pseudomembrane formation and systemic effects. L. monocytogenes is a foodborne pathogen that can cause neonatal or adult listeriosis. B. anthracis produces anthrax through three syndromes: cutaneous, inhalational, or gastrointestinal

1. Sum 07
Gram positive bacterial infections
1. Staphylococci
2. Streptococci
3. C.diphtheriae
4. Listeria monocytogenes
5. Bacillus anthracis
6. Nocardia
Med_students0

2. Sum 07
Staphylococcus
Gram positive, organisms that form grape
like-clusters.
1. S.aureus
2. S.epidermidis
3. S.saprophyticus

3. Sum 07
Staphylococcus aureus
Coagulase positive
Cause pyogenic infections characterized by collection of
neutrophils and formation of pus (Suppurative
inflammation).
Clinical manifestations:
Due to production of toxins
The toxinoses
Due to direct invasion and destruction of tissue.
1. Skin infections
2. Others:
1. Bone and joint infections
2. Heart valve infections
3. Respiratory tract infections
4. Burn wound infections
5. Septicemia

4. Sum 07
The toxinoses
Diseases caused by action of toxins:
1. Staphylococcal scalded skin syndrome
(SSSS)**
2. Bullous impetigo
3. Staphylococcal food poisoning**
4. Toxic shock syndrome (TSS)**

5. Sum 07
MC seen in infants & children with Staph
infection of nasopharynx or skin.
Patients present with sunburn like rash that
begins on face  spreads over body.
Bullae and blisters form 
Rubbing  desquamation of skin.
= A positive Nikolsky’s sign
Scalded skin syndrome

6. Sum 07
Scalded Skin Syndrome
Nikolsky’s sign

7. Sum 07
Staphylococcal Food Poisoning
More common in summer months
Due to preformed heat-stable enterotoxin
produced in foods prior to ingestion.
Source: Custard filled pastries ,ham, salted
pork.
Symptoms occur between 2-6 hours after
ingestion of contaminated food with abrupt onset
of
nausea, vomiting, crampy abdominal pain, and
diarrhea  resolves within 12 hrs.
Culture food, not patient

8. Sum 07
Toxic Shock Syndrome (TSS)
MC affects menstruating women using tampons.
May also be associated with infected surgical
sites, septic abortion, etc.
Due to overgrowth of toxin producing strains
of S.aureus  elaborate TSST-1  in the
blood.
Clinical manifestations:
Start abruptly characterized by triad of
findings:
Fever, sunburn like rash and shock.
Failure of multiple organ systems (Renal
failure, liver failure, respiratory failure).

9. Sum 07
Cutaneous infections
1. Furuncles
2. Carbuncles
3. Folliculitis
4. Impetigo

10. Sum 07
Furuncles (boils)
Boils = deep seated infection in
and around the hair follicles.
Resulting in formation of
painful raised nodules with
collection of dead and
necrotic tissue (Pus).

11. Sum 07
Carbuncles
Deep-seated pyogenic infection of the skin
and subcutaneous tissues, usually arising in
several contiguous hair follicles.
Spreads laterally beneath the deep
subcutaneous tisue and erupts superficially
with multiple sinuses.
Associated with chills and fever and risk of
developing bacteremia.
Common location:
Skin of upper back and posterior neck

12. Sum 07
Carbuncle

13. Sum 07
Folliculitis
pyogenic infection
in the hair follicle.
the lesions may be
papules or pustules.

14. Sum 07
Deep localized infections
1. Staphylococcal Osteomyelitis:
Due to hematogenous spread from a site of
infection.
2. Staphylococcal Arthritis:
S. aureus most common cause of infection of
joint space in children.
3. Staphylococcal Endocarditis
S.aureus is the most common cause of acute
infective endocarditis in IV drug abusers.
Involves tricuspid valve in 50% of cases

15. Sum 07

16. Sum 07
Infections of burns and surgical wounds:
Source of organism: nasal flora, medical
personnel
Respiratory tract infections:
MC pathogen causing pneumonia following
influenza infection.
Common pathogen in cystic fibrosis
Common cause of pneumonia in IVDA
Common in nosocomial pneumonia as well

17. Sum 07
Coagulase negative staphylococci
Staphylococcus epidermidis
MCC of infections involving prosthetic devices
including:
IV catheters,Prosthetic heart
valves,Orthopedic prosthesis,Cerebrospinal
fluid shunts etc.
Staphylococcus saprophyticus***
10-20% of acute urinary tract infections in
young, sexually active females
second only to E. coli

18. Sum 07
Streptococci
Gram positive cocci in chains
1. Group A Streptococci
S. pyogenes
2. Group B streptococci
S. agalactiae
3. S. viridans
4. S.pneumoniae = pneumococci

19. Sum 07
S.pyogenes
1. Acute pharyngitis or “Strep throat”
2. Impetigo (pyoderma)
3. Erysipelas
4. Cellulitis
5. Necrotizing fasciitis
6. Scarlet fever
7. Rheumatic fever
8. Acute post streptococcal glomerulonephritis

20. Sum 07
Acute pharyngitis or “Strep throat”
S.pyogenes most common bacterial cause of sore
throats.
Most frequently seen in children from 5-15
years of age.
C/F: sore throat, fever, malaise, headache and
elevated WBC count.
Complications:
Extension of infection: peritonsillar or
retropharyngeal abscess formation (quinsy sore
throat)
Strep pharyngitis  poststerptococcal
glumerulonephritis or Rheumatic fever

21. Sum 07
Impetigo
A contagious superficial pyogenic infection
(pyoderma) restricted to epidermis.
caused by S.aureus and/or S. pyogenes
Begins with a superficial vesicle that ruptures
and forms a thick yellowish crust.
Mostly on the face and limbs

22. Sum 07
Erysipelas
Is erythematous swelling of skin (Erythros =
red; pellas = skin) caused by S.pyogenes.
Characterized by
erythematous swelling (beginning on the face)
spreading rapidly
Involved skin has sharp well demarcated border
; may form a butterfly distribution.
Most common in middle aged.

23. Sum 07
Erysipelas

24. Sum 07
Cellulitis
Inflammation of subcutaneous, loose connective
tissue.
Etiology
most commonly Strep. pyogenes .
Due to traumatic inoculation of organisms into
the skin.
Clinical
appears as Spreading areas of redness,
warmth and swelling.
Associated with systemic manifestations.

25. Sum 07
Streptococcal Cellulitis

26. Sum 07
Necrotizing Fasciitis
A soft-tissue infection primarily involving the
superficial fascia and resulting in extensive
damage of surrounding tissues (muscle,fat and
skin).
spreads along fascial planes
Usually occurs:
Postoperatively
After minor trauma
After inadequate care of abscesses or
cutaneous ulcers.

27. Sum 07
Necrotizing Fasciitis

28. Sum 07
Fournier’s Gangrene
A special case of necrotizing
fasciitis.
involves male or female
genitalia.
Usually seen in
Diabetics or
Immuno-compromised
patients
Often involves mixed infections
Gram (+) and Gram (-),
aerobic and anaerobic acting
synergistically

29. Sum 07
Scarlet fever
An acute disease caused by infection with
streptococcal organisms producing erythrogenic
toxin.
MC occurs in children following pharyngitis.
Characterized by fever and a generalized
eruption of red rash followed by desquamation
Develops over chest and spreads to
extremities.
Tongue may develop a yellow white coating,
which may shed to reveal a beefy red surface.

30. Sum 07
Scarlet Fever

31. Sum 07
Scarlet Fever
Tongue
Yellowish white coating (“white
strawberry tongue”)  shedding  “red
strawberry tongue”
White strawberry tongue Red strawberry tongue

32. Sum 07
Rheumatic Fever
Autoimmune disease
Occurs two to three weeks after initiation of
pharyngitis.
Due to cross reaction between ag of heart and
joint tissues and the antistrptococcal ab (esp
M prtoein)
Post streptococcal glomerulonephritis
Due to nephritogenic strains of group A
streptococci.
serotype 12 is the most nephritogenic

33. Sum 07
Group B streptococci
Streptococcus agalactiae***
Normal vaginal flora
Colonize the female genital tract
Disease:
Meningitis and sepsis in neonates**.
Also causes chorioamnionitis** in pregnant
women
Note: treat mother with ampicillin to
decrease transmission to baby.

34. Sum 07
Streptococcus
Viridans Group
Includes:
S. mutans: dental caries & endocarditis
S. mitior: endocarditis
S. sanguis: endocarditis
S. milleri: deep tissue abscesses, bacteremia

35. Sum 07
Streptococcus pneumoniae
Only gram positive diplococci
Also known as pneumococcus
Diseases:
Pneumonia**, Sinusitis, otitis media
meningitis

36. Sum 07
Corynebacterium diphtheria
Gram positive non-motile bacilli
“Chinese letter” appearance with staining
Disease:
Diphtheria : caused by local and systemic
effects of a single exotoxin.
MOA of toxin:
Two subunits A and B
A subunit: acts on elongation factor 2 (EF-2)
and interrupts protein synthesis.
B subunit: binds to target cells and permits
entry of A subunit.

37. Sum 07
Pathogenesis

38. Sum 07
C.diphtheriae
Proliferation
(Naso, Oropharynx & larynx )
Exotoxin
release
Necrosis of epithelium
Fibrinopurulent exudate
Coagulation of exudate
Formation
of tough,
gray/white membrane
Absorption
in circulation
Heart
•Fatty myoardial change
•Myofiber necrosis
Nerves
•Neuritis
Spleen and lymphnode
•Enlargment

39. Sum 07
Corynebacterium diphtheria
Exotoxin
Local effects of exotoxin
1. Pseudomembrane formation
Sloughing  bleeding and asphyxiation.
2. Bull-neck cervical lymphadenopathy
Systemic effects of exotoxin
1. Myocarditis
– causing arrhythmias ; may cause death
2. Damage to nerves and liver

40. Sum 07

41. Sum 07 Pseudomembrane
Bullneck
Lymphadenopathy

42. Sum 07
Listeriosis
Listeria monocytogenes
Gram positive intracellular bacteria
Causes severe food borne infection.
Source: dairy products, chicken and hotdogs.
People at risk:
Pregnant women
Neonates
Elderly and immunocompromised

43. Sum 07
Listeriosis
Categorized in two forms:
1) neonatal disease and
2) adult disease.

44. Sum 07
Neonatal Disease
Two forms:
Early onset disease,
acquired transplacetally in utero
Also k/a granulomatosus infantiseptica
abscesses and granulomas in multiple organs
Lung, liver, spleen and LN
frequently results in abortion.
Late onset disease acquired at birth or soon after birth.
Sepsis:
Papular red rash over the extremities
Listerial abscess in placenta
Meningitis:
Similar to one caused by pyogenic bacteria.

45. Sum 07
Adult Disease
Normal adults
gastroenteritis (associated with raw cabbage).
In immunosuppressed individuals
serious illness, leading to meningitis.
one of the leading causes of bacterial
meningitis in patients with cancer and in renal
transplant recipients.

46. Sum 07
Diagnosis
CSF:
Monocytosis
Gram positive intracellular bacilli
New born with sepsis:
Gram stain of meconium

47. Sum 07
Listeria monocytogenes organisms in
neutrophil

48. Sum 07
Anthrax
Bacillus anthracis : spore forming gram
positive rod shaped bacteria.
Spores : can be ground to a fine powder
making it an agent for bioterrorism.
1979: accidental release in a military
institute in Russia killed 66.
2001: 22 people in the US acquired
B.anthracis due to spores delivered in mail
!!

49. Sum 07
People become infected by
the cutaneous route (direct contact)
by inhalation (Woolsorter's disease), or by
ingestion (meat from diseased animals).
Typically acquired through exposure to animals
or animal products : hide and wool.
Three major anthrax syndromes
1. Cutaneous anthrax
2. Inhalational or pulmonary anthrax
3. Gastrointestinal anthrax

50. Sum 07
Cutaneous anthrax
Malignant pustule: is the cutaneous form of
anthrax.
Begins as painless papule  ruptures 
ulcer  covered with a black scab
Classically found on the hands, forearms
or head

51. Sum 07

52. Sum 07
Pulmonary or inhalational anthrax
Aka Woolsorter’s disease.
Caused by inhalation of spores.
Phagocytosed by the alveolar macrophages.
Organisms carried to hilar lymphnodes
Release of toxin causes hemorrhagic necrosis of
lymphnodes and hemorrhagic pneumonia.
Patients present with fever, cough and chest
pain followed by respiratory failure, shock and
death.

53. Sum 07
Gastrointestinal anthrax
By eating undercooked meat contaminated
with B.anthracis.
Ulceration of stomach and bowel and
invasion of regional lymphnodes.
Death due to  severe bloody diarrhea and
massive ascites

54. Sum 07
Pathogenesis
B anthracis Produces toxins:
Toxin has two subunits:
B subunit = protective ag
A subunit : two types:
Edema factor : is responsible for edema
Lethal toxin : causes
necrosis, fever, shock and cell death.

55. Sum 07
Morphology
Boxcar shaped
gram positive
bacilli in chains.

56. Sum 07
Nocardia
Aerobic gram positive bacteria
Grow in distinctive branched chains.
Are weakly acid fast
Cause opportunistic infections in
immunocompromised people.
Patients with HIV/AIDS
Prolonged steroid use

57. Sum 07
Nocardia
Two species cause disease in humans
N. brasiliensis and N. asteroides.
N. asteroides
pulmonary nocardiosis
Mistaken for TB
N. brasiliensis
Cutaneous lesions
Present as abscess or cellulitis.

58. Sum 07
Cutaneous nocardiosis

59. Sum 07
Diagnosis
depends on identification of slender gram
positive organism arranged in branching
filaments.
Beaded appearance due to irregular
staining.
Stain with modified acid fast stain.

60. Sum 07
Nocardia asteroides in a Gram-stained sputum
sample. Note the beaded, branched Gram-positive
organisms and leukocytes.