Gram Negative Bacteria Flashcards
1
Q
N. meningitidis reservoir
A
- Nasopharynx of humans
- Spread by respiratory transmission
*strict human parasite
2
Q
N. meningitidis virulence factors
A
- Capsule: anti-phagocytotic
- IgA protease
- Unique proteins that can extract iron from transferrin, lactoferrin, and hemoglobin
- Pili: for adherence
3
Q
N. meningitidis toxins
A
- LPS endotoxin
4
Q
N. meningitidis clinical presentation
A
- Asymtomatic carriage in the nasopharynx
- Meningitis:
Fever
Nuchal rigidity
*Vomiting
Petechial rash - Septicemia
Fever
Petechial rash
Hypotension
5
Q
N. meningitidis treatment
A
Penicillin G
Ceftriaxone
Rifampin and cipro for prophylaxis of close contacts of infected persons
6
Q
Which demographic is most susceptible to N. meningitidis?
A
- Neonates–very susceptible from 6 to 24 months, when protective antimeningococcal IgG is low
- Army recruits
7
Q
N. gonorrhoeae clinical presentation
A
- Men: urethritis
- Women: cervical gonorrhea—->PID
- Both: septic arthritis
- Neonates: Conjunctivitis
8
Q
N. gonorrhoeae treatment
A
- Ceftriaxone ( + doxycycline for probable concurrent Chlamydia infection)
* penicillin resistant
9
Q
Chocolate agar Gram-negative diplococci in cerebrospinal fluid Lipooligosaccharide Petechiae Septic shock Thayer Martin agar Waterhouse-Friderichsen syndrome
A
N. meningitidis
10
Q
Chocolate agar Gram-negative diplococci Oxidase positive STD Thayer-Martin agar Urethritis
A
N. gonorrhoeae
11
Q
Produces fluroscein –> fruity, grape-like smell
A
Pseudomonas aeruginosa
12
Q
Pseudomonas aeruginosa virulence factors
A
Exotoxin A –> paralyzes host cell protein machinery (similar to diphtheria toxin)
Phospholipase C –> damages host cell membrane
Elastase –> allows microorganism to disseminate to better nutrient sources
Endotoxin –> shock
13
Q
Pseudomonas aeruginosa clinical presentation
A
UTIs (hospital patients; 3rd most common cause in all people) Pneumonia (CF patients) Burn wound infection Hot tub infections Endocarditis (IV drug users) Swimmer's ear
14
Q
Pseudomonas aeruginosa treatment
A
HIGHLY RESISTANT
Aminoglycosides
Ceftazidime
15
Q
Bordetella pertussis reservoir
A
Humans are the only natural carriers
16
Q
Bordetella pertusis mode of transmission
A
- Airborne transmission
- Adheres to cilia of respiratory epithelium via filamentous hemagglutinin (FHA)
- Releases exotoxins to generate disease
17
Q
Bordetella pertussis virulence factors
A
- Polysaccharide capsule
- Outer membrane protein (adhesion)
- Pertussis toxin –> AB toxin –> uninhibited adenylate cyclase (taken up by phagocytes; inhibits bactericidal activity)
- Tracheal cytotoxin –> destroys ciliated epithelial cells –> impairs mucuous clearance –> violent whooping cough –> promotes spread of bacteria
- FHA
18
Q
Pertussis exotoxin mechanism
A
increases cAMP
- ADP-ribosylates and inactivates G proteins –> uninhibited adenylate cyclase –> cAMP increase
- Increased cAMP –> negative feedback inhibition –> increased cAMP
19
Q
Pertussis toxin causes an increase in which hormone?
A
Insulin
Pertussis patients may also show signs of hypoglycemia
20
Q
Pertussis treatment
A
Erythromycin
21
Q
What percentage of pertussis patients will go on to develop pneumonia?
A
5%
22
Q
Brucella reservoir
A
Zoonosis
Commonly infects cattle ranchers, slaughter house workers, vets
23
Q
What agar does Brucella grow on?
A
Potator + eryhtritol (“Brusella agar”)
24
Q
Brucella clinical presentation
A
Undulating fever (rises and falls)
25
Brucella treatment
Tetracycline
| Rifampin
26
Most common complication of Brucella infection
Osteomyelitis
27
Francisella tularensis clinical presentation
Tularemias (site-specific infection + lymphadenopathy)
28
Pasturella multocida clinical presentation
Cellulitis, osteomyelitis following cat/dog bite
29
Two types of Haemophilus influenzae and their clinical presentations
1. Typable (Hib): infantile meningitis, epiglotittis
| 2. Non-typable: otitis media, sinusitis, bronchitis, conjunctivitis
30
H. influenzae agar
Chocolate agar; requires hemin (X factor) and NAD (V factor)
31
Bacteroides fragilis reservoir
Normal human flora
| Most abundant organism in colon
32
Bacteroides fragilis clinical presentation
Most common cause of intra-abdominal infections
Peritonitis
Diverticulitis
Post-op abdominal abscesses
33
B. fragilis agar
Bile esculin agar
34
What is the most common cause of infectious diarrhea?
Campylobacter jejuni ( > Shigella & Salmonella combined)
35
C. jejuni reservoir
Carried by poultry, cattle, dogs, and other domestic animals
| Transmitted by fecal-oral route, ingestion of undercooked poultry or unpasteurized milk
36
What grows on CAMPY agar?
C. jejuni
37
Which bacteria is associated with Guillain Barre syndrome?
C. jejuni
| syndrome is an example of molecular mimicry
38
C. jejuni treatment
Supportive (no abx)
39
H. pylori clinical presentation
Acute:
gastritis
Chronic:
antral gastritis
peptic ulcers
40
H. pylori treatment
Triple Chemotherapy:
1. Proton pump inhibitor (e.g. omeprazole)
2. Antibiotic (carithromycin, amoxicillin, or metronidazole)
3. Bismuth compound
41
How do you diagnose H. pylori infection?
Urease breath test
42
Vibrio cholerae agar
Flat yellow colonies on TCBS agar
43
Vibrio cholerae clinical presentation
Rice-water diarrhea
| Dehydration
44
What is the structure and mechanism of the cholera toxin?
Structure: Heat labile enterotoxin. A subunit plus 5 subunits encoded by separate genes in the CTX phage genome
Mechanism: B subunit binds to GM1 ganglioside receptor on host cell. A subunits are endocytosed and cause ADP ribosylation of G proteins --> adenylate cyclase --> cAMP increase --> loss of water, electrolytes
45
V. cholerae treatment
1. Fluid replacement
| 2. Tetracycline
46
All enterobacteriaceae are ______ ______ and _____ _____.
Oxidase negative / facultative anaerobes
47
Enterobacteriaceae are facultative anaerobes, which means they....
Ferment glucose and reduce nitrate
48
What is the difference between the pertussis toxin and the cholera toxin?
Pertussis toxin "turns off" Gi (off) protein in respiratory epithelium.
Cholera toxin "turns on" G3 (on) protein in intestinal epithelium.
Both act by the same mechanism and both increase adenylate cyclase.
49
Only gram-____ organisms grow on MacConkey agar.
Negative
50
Salmonella agar
Black colonies on XLD agar
51
```
Diarrhea
Gram-negative rod
Lactose positive
Neonatal meningitis
Oxidase negative
UTI
```
E. coli
52
Aspiration
Capsule
Currant jelly sputum
Pneumonia
Klebsiella pneumoniae
| Lung infection most common in alcoholic patients and those with poor pulmonary function
53
```
Dairy foods
Motile
Nonbloody diarrhea
Nonlactose fermenter
Raw eggs
Chicken
```
Salmonella
54
Gram-negative bacillus
Lactose negative
No hydrogen sulfide
Watery, bloody diarrhea
Shigella
55
Plague
Rodent and animal host
Fleas
Buboes (inflamed swollen lymph nodes)
Yersinia pestis
56
Elevated urine pH
Swarming growth on agar
Urease
UTI
Proteus mirabilis
57
```
Chocolate agar
Endotoxin
Gram-negative diplococci in CSF
Lipooligosaccharide
Meningitis
Oxidase positive
Petechiae
Thayer-Martin agar
Waterhouse-Friderichsen syndrome
```
Neisseria meningitidis
58
Chocolate agar
Gram-negative diplococci
Oxidase positive
Urethritis
Neisseria gonorrhoeae
59
Bordet-Gengou agar
DPT vaccine
Whooping cough
Bordatella pertussis
60
```
Capsule
Epiglottitis
Hib
Meningitis
Otitis
X and V factors
```
Haemophilus influenzae
61
Air conditioning
Atypical pneumonia
Charcoal yeast agar
Warm mist/shower/lukewarm water
Legionella pneumophila
62
```
Burn patient
Cystic fibrosis
Fruity smell
Hot tub folliculitis
Opportunistic
```
Pseudomonas aeruginosa
63
Chronic granulomatous disease
Cystic fibrosis
Pseudomonas-like
Burkholderia
64
A-B toxin
Comma (S) shaped
Rice water diarrhea
Shellfish
Vibrio cholerae
65
Bloody diarrhea
Thin, curved gram-negative
Undercooked poultry
Campylobacter jejuni
66
Bacteria causing bloody diarrhea
C. jejuni
Shigella
Yersinia enterocolitica
E. coli
*except in young children, C. jejuni is the primary cause of bloody diarrhea in the U.S.
67
Gastric or duodenal ulcer
Urease
Urease breath test
Helicobacter pylori
68
Shigella toxin mechanism
Blocks protein synthesis causing intestinal cell death
69
What is a significant virulence factor of uropathogenic E. coli?
Fimbriae
70
What is a common complication of Proteus-related UTIs?
Kidney stone formation. Proteus is urease positive, therefore it breaks down urea into ammonia. This leads to alkaline pH and stone formation.
71
What is the main virulence factor of Klebsiella?
Antiphagocytotic capsule / K antigen
72
Which virulence factor of H. pylori is linked with gastric adenocarcinoma?
cagA
73
What is the main virulence factor in Neisseria species?
LOS endotoxin
74
What is the main virulence factor of Pseudomonas aeruginosa?
Exotoxin A (ADP ribosylation of EF2 --> INHIBITS protein synthesis --> tissue damage)
75
Non-spore forming INTRACELLULAR pathogen
Neisseria
76
What is the mechanism of the Shiga toxin?
AB toxin: B5 binds specific glycosides on cell surface
A subunit causes irreversible inactivation of the 60S ribosomal subunit
This causes inhibition of protein synthesis, cell death, and hemorrhage
