GRAM NEGATIVE Flashcards
1
Q
Virulence factor of N. gonorrhoeae that has anti phagocytic effect.
A
Pili
In N. meningitidis incorporation of human sialic acid derivatives into the capsule prevents recognition by the host immune system. “Molecular Mimicry”
2
Q
Appearance of N. gonorrhea on gram stain?
A
Gram negative intracellular diplococci with polymorphonuclear cells.
3
Q
Appearance of N. gonorrhea and N. meningitidis on agar.
A
Convex , glistening , elevated, mucoid colonies that are transparent or opaque, non-pigmented and non-hemolytic.
4
Q
Gold standard in the diagnosis of N. gonorrhea.
A
Nucleic Acid Amplification Test
5
Q
Preferred regimen used in the treatment of uncomplicated genital infection caused by N. gonorrhea
A
Ceftriaxone 250mg IM single dose + Azithromycin 1g PO single dose.
The Azithromycin can also address the frequent co-infection with Chlamydia.
Doxycycline may be used as a substitute for Azithromycin, however it is not preferred due to higher rates of resistance to tetracyclines in N. gonorrhea.
6
Q
Stain used to visualize Legionella pneumophilia.
A
Silver stain
7
Q
Drug of choice for the most common cause of community acquired UTI in children.
A
Ampicillin or Sulfonamides
(most common cause is e.coli)
8
Q
Mechanism of enterotoxin of Vibrio cholerae.
A
Increase levels of cAMP , this results to prolonged hypersecretion of water and electrolytes
9
Q
Culture medium used to grow Camphylobacter jejuni.
A
Skirrow’s medium
10
Q
Organisms that are cultured in Xylose-Lysine-Deoxycholate agar.
A
Shigella & Salmonella
11
Q
Agents most commonly associated with diarrhea. (3)
A
- E coli
- V. cholera
- E. fecalis
12
Q
Most helpful lab test to confirm gonococcal arthritis.
A
Culture of the aspirate.
Suspect this infection in reproductive age patients with unilateral joint swelling and pain.
13
Q
Most appropriate initial investigation for smokers cough.
A
Chest X-ray
14
Q
Natural habitat of Enterobacteriaceae?
A
GI tracts of humans and animals.
15
Q
Gram-negative enteric rods that are rapid lactose fermenters?
A
- Klebsiella pneumoniae
- Enterobacter spp.
- E. coli
16
Q
Natural habitat of enterobacteriaceae.
A
GI tracts of humans and animals.
17
Q
Gram-negative enteric rods that are slow lactose fermenters.
A
- Serratia
- Citrobacter
18
Q
Does E. coli ferment lactose?
A
Yes ( Rapid fermenter)
19
Q
Antigen of e. coli found on its capsule?
A
H antigen
20
Q
Appearance of e. coli in EMB Agar.
A
Metallic green with an “iridescent sheen”
21
Q
Most common cause of UTI?
A
E. coli
22
Q
Important strain of E. coli causing travelers diarrhea?
A
ETEC (Enterotoxigenic E.coli)
23
Q
Important strain of E.coli causing diarrhea in infants in developing countries?
A
EPEC ( Enteropathogenic E.coli)
24
Q
The heat-labile enterotoxin of ETEC increases _________ intracellularly.
A
cAMP
25
The heat stable enterotoxin of ETEC increases __________ intracellularly.
cGMP
26
The heat labile enterotoxin of ETEC closely resembles the enterotoxin of what organism?
Vibrio cholerae
27
Important strain of e. coli causing hemorrhagic colitis.
STEC ( Shiga toxin producing E. coli)
28
Most common serotype of STEC?
O157:H7
29
Differentiating feature of serotype O157:H7 from other E.coli?
Does not ferment sorbitol
30
What systemic pathology is associated most commonly with the O157:H7 serotype of E.coli?
HUS : Hemolytic Uremic Syndrome
31
Important strain of E.coli causing persistent diarrhea that is very similar to Shigellosis?
EIEC ( Enteroinvasive E.coli)
sh**i**g**e**llosis
32
Important strain of E.coli causing diarrhea in HIV (+) patients?
EAEC (Enteroaggregative E.coli)
(HIV aggregative )
33
Triad of hemolytic uremic syndrome?
1. Hemolytic Anemia
2. Thrombocytopenia
3. Uremia
**T**riad of **Hemolytic Uremic** Syndrome
T for Thrombocytopenia
Hemolytic Anemia
Uremia
34
What bacteria can cause necrotizing pneumonia with currant jelly sputum?
Klebsiella pneumonia
K Kurrant Jelly
35
What lobes are more commonly affected in Klebsiella pneumonia?
Upper lobes
36
What population is at very high risk for Klebsiella pneumonia?
Alcoholics
37
Wha bacteria can cause a genital ulcer with Donovan bodies on biopsy?
Klebsiella granulomatis
38
What STI can Klebsiella granulomatis cause?
Granuloma inguinale ( Donovanosis)
39
Is the ulcer in donovanosis painful or painless?
Painless
40
Pigment responsible for the red appearance of Serratia?
Prodigiosin
41
Most common site of infection of Serratia species?
Urinary Tract
42
What bacteria can cause staghorn caliculi?
Proteus mirabilis
43
What type of renal stones does proteus mirabilis cause?
Struvite Stones ( Ammonium Magnesium Phosphate)
44
Proteus mirabilis expresses _____________ allowing it to form alkaline environment.
Proteus mirabilis
45
Classic motility of Proteus mirabilis?
Swarming motility
46
Spot-indole test in Proteus mirabilis?
Positive
47
Spot-indole test in Proteus vulgaris?
Negative
48
Is Shigella encapsulated?
No
49
Is Salmonella encapsulated?
Yes
50
Is Shigella motile?
No
51
Is Salmonella motile?
Yes
52
Does Shigella ferment lactose?
No, except Shigella sonnei
53
Invasion of _________ cells is essential in pathogenesis of Shigella Infections.
M cells in the mucosal epithelium
54
Shigella sonnei is aka as ?
Duval’s bacillus
55
The only lactose fermenting Shigella?
Shigella sonnei
56
Which agar detects the production of H2S?
Hektoen Agar
57
Most common causative agent of enteric fever?
Salmonella paratyphi
58
Lymphoid tissue in intestinal cells for Salmonella infection.
Peyer’s Patches
59
Lymphoid tissue in intestinal cells for Salmonella infection?
Peyer’s patches
60
Classic cutaneous manifestation of enteric fever?
Rose spots
61
Most common manifestation of Salmonella infection?
Enterocolotis (not typhoid fever)
62
Preferred specimen for diagnosis of non-typhoidal salmonella?
Freshly passed stool
63
Definitive diagnosis of enteric fever?
Culture of blood , bone marrow, urine, or intestinal secretions.
64
Highest sensitivity for diagnosis of enteric fever?
Bone marrow culture
65
What colonies does Salmonella form on bismuth sulfite medium?
Black cultures due to H2S production
66
Where does Salmonella colonize in chronic state carrier?
Gallbladder
67
Which strain of Salmonella can be acquired from turtles?
Salmonella enteritidis
68
What secretion system helps with the infectivity of Salmonella?
Type III secretion system
69
What is the common cause of osteomyelitis in sickle cell disease?
Salmonella
70
Which pigment gives Pseudomonas culture bluish pigment?
Pyocyanin
71
Which pigment gives Pseudomonas cultures a greenish pigment?
Pyoverdin
72
Which pigment gives Pseudomonas cultures a dark red pigment?
Pyorubin
73
Which pigment gives Pseudomonas cultures a brown-black pigment?
Pyomelanin
74
What virulence factors of Pseudomonas generates reactive oxygen species?
Pyocyanin
75
What virulence factor of Pseudomonas acts as a siderophore?
Pyoverdin
76
How is Pseudomonas aeruginosa differentiated from other Pseudomonas species?
Growth 42 c
77
Is P. aeruginosa oxidase positive?
Yes
78
What virulence factor of P. aeruginosa is responsible for the mucoid colonies on culture?
Alginate
79
Hemorrhagic necrosis of the skin in Pseudomonas infection!
Ecthyma gangrenosum
80
What Pseudomonas toxin has a similar MOA of diphtheria toxin?
Exotoxin A
81
Pseudomonas is a significant cause of mortality & morbidity in these patients?
1. Cystic fibrosis patients
2. Burn patients
82
What is the MOA of exotoxin A in Pseudomonas?
Inactivates EF-2 via ADP-ribosylation
83
Characteristic odor of Pseudomonas infection?
Grape like odor
84
Which of the comma-shaped gram negative bacteria grows best at 42 c ?
Campylobacter jejuni
85
Which of the comma shaped gram negative bacteria is urease positive?
Helicobacter pylori
86
Which of the comma shaped gram negative bacteria grows best in an alkaline media?
Vibrio Cholera
87
All species of Vibrio require this for growth?
NaCl
Hence, the term halophilic or salt-loving for vibrio
88
Selective agar for vibrio species?
TCBS Agar (Thiosulfate -Citrate-Bile salts - Sucrose)
89
Is V. cholera sucrose fermenting?
Yes
90
Is V. vulnificus sucrose fermenting?
No
91
Is V. parahemolyticus sucrose fermenting?
No
92
What pH is best for Vibrio growth?
Basic / Alkaline
93
What antigen is seen in V. cholerae?
H Antigen
94
What medication can increase susceptibility to cholera?
Proton Pump Inhibitor ( Since cholera grows in a basic environment)
95
Characteristic motility of V. cholerae?
Shooting star motility
96
What bacteria can cause necrotizing skin infections in shellfish handlers?
V. vulnificus
97
What halophilic bacteria can cause acute gastroenteritis after ingestion of raw shellfish?
V. parahemolyticus
98
What is the characteristic description of diarrhea in cholera?
Voluminous rice water stools
99
What is the MOA of cholera enterotoxin in producing diarrhea?
Causes increase in intracellular cAMP causing prolonged hyper-secretion of water from enteric cells.
100
What gram negative rod is described as having “sea gull wing” shape?
Camphylobacter jejuni
101
Selective media for C. jejuni?
Campy-blood agar and Skirrow’s media
102
Campylobacter grows best at this temperature.
42 c
103
Is C. jejuni oxidase positive ?
Yes
104
Is C. jejuni catalase positive?
Yes
105
Is C. jejuni catalase positive?
Yes
106
Is C. jejuni urease positive?
No
107
What Cancer can H. pylori cause and is associated with resolution once infection is cleared?
Gastric MALT ( mucosa-associated lymphoid tissue) Lymphoma
108
What type of ulcer is H. pylori most associated with?
(gastric vs doudenal )
Duodenal 90%
109
What are the noninvasive test for diagnosis of H. pylori infection?
1.Serology
2.Urea breath test
3.Stool antigen test
110
Triple therapy for H. pylori infection?
OCA
1. Omeprazole
2. Clarithromycin
3. Amoxicillin
111
Alternative quadruple therapy for H. pylori infection?
1. PPI
2. Metronidazole
3. Tetracycline
4. Bismuth
112
Which area of the stomach is initially affected by H. pylori gastritis?
Antrum
113
What mainly allows H. pylori to survive in the acidic environment of the stomach?
Urease production
114
What is the causative agent of chancroid?
Haemophilus ducreyi
115
Is chancroid painful or painless?
Painful
(Chancre is painless)
116
What factor does H. ducreyi require for growth?
X factor (hematin) only
117
What component of H. influenza is used for typing?
The capsule antigen
118
What phenomenon does H. influenza exhibit when growing in blood agar?
Satellite phenomenon (grows in close proximity to staph aureus)
119
What factors are necessary for H. Influenzae to grow on medium?
1. Factor V (NAD+)
2. Factor X (hematin)
120
What bacteria will H. influenza grow in proximity with on blood agar.
Staph aureus ( because it produce factor V)
121
The majority of invasive H. influenzae is of what type?
Type B
122
Most common cause of acute epiglottitis in an unvaccinated population?
Hib
123
Most common radiographic sign seen in epiglottitis?
Thumb sign
124
Most common bacterial cause of exacerbations of COPD?
Non-typeable H. influenzae
(Not Hib)
125
What is conjugated to the Hib vaccine?
Diphtheria toxoid
126
What type of capsule does H. influenzae type B possesses?
Ribosyl-Ribitol Phosphate Capsule
127
Most serious manifestation of Hib infection ?
Bacterial meningitis
128
Three most common bacterial causes of childhood otitis media?
1. Strep pneumonia
2. H. influenza
3. Moraxella catarrhalis
129
Chemoprophylaxis for household contacts exposed to Hib?
Oral Rifampin
130
Preferred medium for B. pertussis?
Regan-Lowe ( Preferred over Bordet-Gengou)
131
What virulence factor of Bordetella pertussis mediates adhesion to ciliated epithelium?
Filamentous hemagglutinin
132
What toxin of Bordetella pertussis mediates adhesions to ciliated epithelium?
Filamentous hemagglutinin
133
What toxin of Bordetella pertussis causes necrosis of respiratory epithelium?
Tracheal Cytotoxin
134
What toxin of Bordetella pertussis inhibits phagocytosis?
Adenylate cyclase toxin (act)
135
What are the 3 stages of pertussis?
1. Catarrhal stage
2. Paroxysmal stage
3. Convalescent stage
136
What is the classic description of cough in pertussis?
Whooping cough
137
Characteristic CBC finding of pertussis?
Absolute lymphocytosis (even if its bacterial)
138
What disease caused by Legionella presents with high fever and pneumonia?
Legionnaire’s Disease
139
What disease caused by Legionella presents with high fever but no pneumonia?
Pontiac fever
140
Electrolyte abnormality most associated with Legionnaires disease?
Hyponatremia
141
Growth of Legionella requires the presence of ? (2)
Iron & Cysteine
142
What stain can be used to best visualize Legionella?
Silver Stain
143
What should be elicited in travel history of patients with Legionella?
Staying in hotels, cruise ships.
144
Mode of transmission of Legionella pneumonia?
Via aerosols of environmental water
(Eg. Aircon, cooling tower)
145
Which specie of Neisseria is encapsulated?
(Gonococci vs Meningococci)
Meningococci
146
Which specie of Neisseria have plasmids?
( Gonococci vs Meningococci)
Gonococci
147
Species of Neisseria that metabolize both glucose & maltose?
N. meningitides
148
Species of Neisseria that metabolize glucose but not maltose?
N. gonorrhea
149
Shape of Neiserria cocci?
Kidney bean shaped
150
What virulence factor of gonococci prevent phagolysosome fusion?
Por protein
151
What virulence factor of gonococci is mainly responsible for antigenic variation?
Pili ( Fimbriae)
152
What virulence factor of honococci promotes adhesion to host cells?
Opa proteins
153
What endotoxin does gonococci possess?
Lipooligosaccharide (LOS)
154
What STI can cause the arthritis-dermatitis syndrome?
Gonorrhea
155
Test of choice for diagnosing gonorrhea in women?
NAAT ( Nucleic Acid Amplification Test)
156
Portal of entry of Meningococci?
Nasopharynx
157
Drug of choice for meningococcal disease?
Penicillin G
158
What specific immunodeficiency predisposes one to meningococcal infections?
Late complement deficiency ( Inability to perform membrane attack complex)
159
What species of Neisseria has a polysaccharide capsule!
Neisseria meningitides
160
Complication of PID that involves liver capsule inflammation.
Fitz Hugh Curtis Syndrome
161
Adrenal Hemorrhage from N. meningitides infection.
Waterhouse - Friderichsen Syndrome
162
Virulence factor of Neisseria that cleaves IgA?
IgA protease
163
What Bordetella pertussis toxin disables Gi receptors?
Pertussis toxin
164
At what stage of pertussis are antibiotics effective?
Catarrhal stage
165
Brucella Spp are mostly found within _____________.
Macrophages ( Facultative Intracellular)
166
What zoonotic bacteria presents with undulating fevers?
Brucella Species
167
Mode of transmission of brucellosis?
Direct contact with farm animals or ingestion of contaminated dairy
168
What is the vector of tularemia?
Dermacentor ticks
169
Reservoir of tularemia? (2)
Rabbit & Deer
170
Shape of F. tularensis?
Coccobacillus
171
Drug of choice for tularemia?
Streptomycin or Gentamycin
172
What pathology is seen in lymphadenopathy found in tularemia?
Caseating granulomas
173
Staining pattern of Yersinia pestis?
Safety pin staining (bipolar staining)
174
Vector of Yersinia pestis?
Flea ( Xenopsylla cheopis)
175
What species of Yersinia can mimic appendicitis?
Yersinia enterocolitica
176
Characteristic lymphadenopathy in Yersinia pestis?
Buboes ( swollen, tender lymph nodes)
177
Three forms of disease produced by Yersinia pestis?
1. Bubonic plague
2. Pneumonic plague
3. Septicemic plague
178
Drug of choice in Y. pestis infection?
Streptomycin
179
Most common clinical manifestation of Yersinia pestis infection?
Bubonic plague
180
How do you increase yield of Y. enterocolitica in culture?
Through cold enrichment
181
Shape of Pasteurella multocida?
Coccobacillus
182
Staining pattern of Pasteurella multocida ?
Bipolar appearance
183
Drug of choice in P. multocida infection?
Penicillin G
184
How is P. multocida usually transmitted to humans?
Cat or dog bite
185
Vibrio vulnificus natural history.
Eating seafood, especially shellfish , then getting bullous eruptions on skin , may produce necrotizing fasciitis and septic shock.
186
Most common cause of UTI.
E. coli
187
Incubation period of salmonella infection?
1-3 days
188
Most common symptom of uti in children under 2 years of age.
Abdominal pain
189
Characteristic of carrier state of N. meningitides. (3)
1. Can exhibit URTI symptoms
2. Penicillin is effective in eradicating carrier states
3. Nasopharyngeal swab cultures can be used for surveys
190
Bacteria with the lowest infective dose.
Shigella
191
Multiple episodes of disseminated gonococcal infection.
1. Complement deficiency
2.Unable to control Neisseria infections
192
Bacteria that has the lowest infective dose.
Shigella
193
Female sex worker had purulent vaginal discharge now with papules and pustules on her arms, forearm, and legs and painful swelling wrists. What’s the diagnosis?
Gonococcal arthritis
194
Most commonly involved in PID.
N. gonorrhoeae
195
Most commonly involved in PID.
N. gonorrhea
196
How is PID confirmed?
Laparoscopic visualization
197
Major complication of PID if not treated adequately.
Infertility
198
Reproductive age female consulted because of lower abdominal pain accompanied by frequent urination, dysuria, tenderness on palpation of suprapubic area. What’s your clinical impression?
UTI
199
Most common causative agent of UTI.
E. Coli
200
Profuse diarrhea, vomiting, rice watery stool , rapid dehydration, electrolyte imbalance. What’s the causative agent?
Vibrio cholerae
201
Round smooth, fluorescent, greenish-colored colonies, hemolytic and oxidase positive
Pseudomonas
202
What is the term used in Pseudomonas infection with necrosis of the skin involved in burn?
Ecthyma gangrenosum
203
Describe Typhoid fever. (7)
1. Profuse diarrhea, nausea, vomiting
2. Stool exam : gram negative bacilli
3. Non-lactose fermenter
4. Culture negative
5. Antimicrobial therapy is essential
6. Important carriers are humans working as food handlers
7. Multiplies in lymphoid tissue
204
Most common complication of gonococcal PID?
Infertility / Sterility
