Microbiology (Gram negatives) and a few fungi

Question 1

Escherichia coli:

1. involved in what disease in infants?
2. Gram+ or gram-?
3. how to diagnose

Answer 1

1. osteomyelitis
2. G- bacilli, single or more.
3. growth and pink on MacConkey agar, must perform this test to distinguish from other G- (Enterotubes or API)

Question 2

Haemophilus influenzae:

1. invloved with osteomyelitis when?
2. Gram+ or gram-?
3. virulence factors
4. other facts

Answer 2

1. osteomyelitis in children
2. small G- coccobacilli
3. capsule (major virulence factor, have types a-f, type b Ag is polyribose-ribitol or PRP), proteases, endotoxin
4. fastidious: requires X factor (heme) and V factor (NAD) and chocolate agar for diagnosis.
   grows on sheep blood agar satellite to the streaks of Staph aureus (old school method instead of chocolate agar)

Question 3

Salmonella:

1. when does it cause osteomyelitis?
2. Gram+ or gram-?
3. structure and function
4. what family?
5. virulence factors
6. diagnose

Answer 3

1. sickle cell disease
2. G-
3. motile, rods
4. Enterobacteriaceae
5. Surface factors: O-Ag (LPS), H-Ag (flagellar), K-Ag (capsular)
6. non-lactose fermenter (clear colonies on MacConkey agar, distinguishes from E. coli)

Question 4

Nocardia:

1. when does it cause osteomyelitis?
2. how much oxygen does it need?
3. Gram- or Gram+?
4. what is it’s shape?
5. other info

Answer 4

1. immunosuppressed patients
2. strict aerobe
3. gram stain unrevealing
4. filamentous-like rods
5. partially acid-fast bacteria (for mycobacterium)

Question 5

Pseudomonas aeruginosa:

1. where is it commonly found?
2. Gram+ or gram-?
3. what does it produce?
4. what is it’s oxygen requirement?
5. other facts
6. virulence factors
7. diagnosis

Answer 5

1. hospitals, soil and water
2. gram- rods, motile
3. produces water-soluble pigments
4. obligate aerobe
5. invasive, toxogenic, important nosocomial pathogen (intestinal and skin normal flora)
6. Has a lot of them but not very virulent by itself.
   - –pigment production: pyocyanin (blueish), pyoverdin (greenish, fluorescent, binds iron for the bacteria to use), pyorubin (dark red), pyomelanin (black).
   - –highly resistant to multiple antibiotics
   - –ALGINATE slime prevents phagocytosis
   - –exotoxin A (prevents protein synthesis, ADP-ribosylate EF-2)
   - –iron sequestering mechanisms
   - –biofilms
7. green colonies, “goopy” bc highly encapsulated. oxidase positive, non-glucose fermenter (unlike Enterobacteriaceae), non-lactose fermenter.

Question 6

Coccidioides immitis (fungus):

1. when does it form osteomyelitis?
2. what is its form?
3. where is it endemic?

Answer 6

1. in endemic areas
2. dimorphic fungus (giant spherules w/ thick walls at body temp, septate hyphae at room temp)
3. endemic cause of pneumoniae in southwest US.

Question 7

Histoplasma capsulatum (fungus):

1. when does it form osteomyelitis?
2. what is its form?
3. where is it located?

Answer 7

1. in endemic areas
2. dimorphic fungus (tuberculate macroconidia at room temp, yeast at body temp)
3. in bat guano and bird droppings, endemic cause of pneumonia in Ohio/Mississippi River valley.

Question 8

N. gonorrhoeae:

1. how many cases per yr in the US?
2. Gram+ or Gram-? Shape?
3. where are they often located?
4. what’s their outer layer like?
5. other facts

Answer 8

1. 1-3 million cases of gonococcal per yr in the US (1-3% develop arthritis secondary to bacteremia)
2. Gram- diplococci
3. located often intracellular in PMNs
4. highly branched LPS = LOS (elicits inflammatory response
5. resistant to complement, iron acquisition ability, IgA1 proteases cleave heavy chain of IgA

Question 9

Mycobacterium tuberculosis:

1. What type of arthritis is it associated with?
2. how do these bacteria get into joint area?
3. What is it’s shape?
4. What’s its Gram stain classification?
5. Other facts
6. cell wall characteristics

Answer 9

1. CHRONIC monoarticular arthritis
2. bacteria are seeded in joint via blood (granulomatous response to bacteria in joint)
3. bacillus
4. no Gram classification, but may stain gram+
5. infection can involve tendon sheaths, patients may not have pulmonary symptoms, is aerobic and acid-fast, slow growing (4-6 wks on selective agar, usually Lowenstein-Jensen), can grow intracellularly usually in macrophages.
6. peptidoglycan and high concentration lipids

Question 10

Sporothrix schenckii (Fungus):

1. What type of arthritis is it associated with?
2. How is it typically obtained?
3. symptoms/characteristics of affected joints
4. characteristics of this fungus

Answer 10

1. CHRONIC monoarticular arthritis (most common agent of fungal arthritis (subQ mycoses)
2. associated w/ outdoor activities such as gardening, enters joint following trauma
3. joint is “boggy” w/ decreased ROM but often not red/tender (knee>wrist>elbow)
4. dimorphic (cigar-shaped budding yeast in tissue specimen [pus], hyphae bearing conidia at tip of conidiophores in lab)