Microbiology Flashcards
(94 cards)
1
Q
MRSA dets
A
Altered penicillin binding protein (PBP 2a) , encoded by MecA gene
2
Q
Anaerobic organism that causes double zone of beta hemolysis-
A
Clostridium perfringens
Has gas production on thioglycolate broth
Lecithinase activity seems on egg 🥚 yolk agar
3
Q
Gram negative rod that is oxidase and catalase positive :
A
Pseudomonas aeruginosa
Beta hemolytic on blood agar.
Lactose nonfermentor
4
Q
Streptococcus susceptible to bacitracin
A
Streptococcus pyogenes
Confirmatory: PYR positive
5
Q
Bordetella pertussis, gold standard method of confirmation
A
Culture (very specific)
Regan-Lowe is preferred (fastidious) - charcoal agar with horse blood and cephalexin
B. Pertussis fluorescent antibody stain
6
Q
Enriched and differential media for c. Diphtheria
A
Gram pos rods, Chinese characters
Loeffler medium
Tellurite medium - black colonies
7
Q
Optochin susceptible organism
A
Streptococcus pneumonia
Alpha hemolytic on blood agar
Rapid ID (*)
Antigen detection in blood Cx- pneumoslide
Antigen detection in Urine
8
Q
H. Flu requirements
A
X factor - hemin
V factor - NAD+
Grows best on chocolate agar
9
Q
Quad plate features
A
Factor X (hemin) and factor V (NAD+)
Both needed: H. Inf, H. Aegyptius, H. Haemolyticus
X factor needed: H.ducreyi
V factor needed: H.parainfluenzae and H. Paraheamolyticus
10
Q
Legionella pneumophilia rapid turn around test
A
Urine antigen test (EIA)
Remember: it needs L-cysteine supplements to grow ( buffered charcoal yeast extract - BCYE)
11
Q
Mycoplasma detection - gold std
A
PCR has replaced culture in many places
12
Q
Percentage of patients with cold antigen response with mycoplasma….
A
60%
Sub clinical AIHA ( IgM antibody against I antigen on RBC membranes)
Positive Coombs
⬆️ retic count
13
Q
Sulfur granules seen in infection with
A
Actinomyces infection
Branched filamentous Gram positive rods
AFB negative
14
Q
N. Astreroides VS N. Brasiliensis features
A
NA: immunocompromised host. Acquired by inhalation. Invasive pulm and CNS
NB: normal hosts
Acquired by penetrating injury or trauma. Mycetoma, lymphocutaneous and skin= cutaneous infections
15
Q
Organism with Medusa head colonies
A
Bacillus 🦠 Anthracis
Large GPR, sub terminal or central spores
Catalase positive
Stands up when picked with a loop
16
Q
Native valve endocarditis causes
A
Stept Viridans Streptococcus Bovis Group A strept ( strept pyogenes) S aureus Enterococci
17
Q
Prosthetic valve endocarditis
A
Early onset ( nosocomial /Sx ) —————- Coag. Neg staphylococcus ( staph epidermidis) Staph Aureus Gram neg rods - enterococci Candida Late onset (> 1 year later) —————- Strept viridans S. Aureus Enterococci
18
Q
Alpha hemolytic strept how to diff
A
Optochin sensitive: strept pneumo
Optochin resistant ————————— PYR + and bile esculin + = enterococcus Both neg= strept viridans Bile esculin pos, PYR - = strept bovis
19
Q
Vancomycin resistant enterococcus details
A
E. Faecium
Intrinsically amp resistant
High level vancomycin resistant is encoded by Van A, B and D gene 🧬 clusters
Check both Amp and Vanc on disc diffusion
20
Q
Name one catalase positive urease positive organism of bioterrorism
A
Brucellosis
Small gram neg coccobacilli
Oxidase positive
Urease positive
21
Q
Unusual strain of C. Difficile
A
NAP1/027 intrinsically resistant to fluoroquinones ; exposure to them is a risk factor..
Hyper produces toxins A and B - due to partial deletion in tdcC gene (which represses toxin A and B production) .
22
Q
Tests for c. Diff
A
- ELISA/ICTs for toxin A and B
- high specificity , low sensitivity
- tests for both
- diagnostic yield increased by testing 2-3 sps - Common antigen test ( Glutamate dehydrogenase or GDH test)
- very sensitive
- screening tool to decide which specimens to evaluate using another assay (e.g toxin EIA) - PCR
- Cell cytotoxicity assay (most sensitive, technically demanding)
23
Q
Organism positive for hippurate hydrolysis test:
A
Campylobacter jejuni Gram neg rods, S / gull wing shaped Catalase pos Oxidase pos Selective growth at 42 degree
24
Q
ESBL notes
A
AMP resistant klebsiella and E. coli Contain genes for B lactamases ( SHV-1, TEM-1 or TEM-2)
Ceftaz, cefotax with and without clavulanic acid
> 3 dilation change or > 5mm zone size change =ESBL
25
Which is the novibiocin resistant staphylococcus?
Staph saprophyticus
26
Methods to confirm Group B strept
CAMP test: positive
Rapid hippurate hydrolysis test: positive
Lancefield group B by particle agglutination.
27
Which species of shigella is most prominent in the US?
Shigella Sonnei ( serogroup D)
28
Which species of shigella is associated with HUS?
S. Dysenteriae
29
What is true of E. Coli 0157:H7?
Does not ferment sorbitol
30
Which organism is relatively narrow, regularly septated, hyaline hyphae, with acute angle branching and resembles Aspergillus ?
Pseudoallescheria boydii/scedosporium apiospermum
31
Dimorphism fungus that produces diffusable red pigment on standard media?
Penicillium marneffei
32
Scotochromogen in reference to mycobacterium means
Pigmented whether grown in dark or light
33
Examples of slow and rapid mycobacterium
SLOW: M. TB, MAC, M. Kansasii, M. Xenopi, M. Marinum, M.Gordonae
RAPID: M. Fortuitium, M. Chelonae, M. Abscessus
34
Pigmentations and photoreactivity of tuberculosis
Photochromogens: non-pigmented in dark, pigment in light —— M. Kansasii, M. Marinum
Scitochromogens: pigmented in dark and light —— some MAC, M. Gordonae, M. Xenopi
Nonchromogens: nonpigmented in both —— M.TB, most MAC, rapid growers (CAF)
35
MDR tb means resistance to what drugs ??
Rifampicin
And
isoniazid
XDR tb: MDR+ resistance to fluroquinolone and 1 of 3 injectable drugs ( amikacin, kanamycin and capreomycin)
36
M. Kansasii features
Slow grower
Photochromogen
Prefer higher temp - 42C
Second only to MAC as a cause of NTM lung disease.
Chronic pulm infection and involves upper lobes
37
M.Xenopi features
```
Hot water systems
Optimum growth at 42C
Slow grower
Scotochromogen
Chronic pulm disease in adults with underlying disease ( COPD or bronchiectasis)
Extrapulm infection only in
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38
M. Marinum features
```
Cutaneous infection, exposure to fresh water 💦 fish 🐠 tanks or saltwater foll trauma
‘Fish tank granuloma’ -
2-3 weeks after inoculation
Mostly slow, few rapid growers
30 degree C
Photochromogenic
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39
M. Gordonae features
Most commonly recovered non-pathogenic NTM
Non pathogenic even in immunocompromised pts
Soil and water
Frequent contaminant in respiratory specimens
Slow growth
30 degrees C
Scotochromogen
40
Rapid growers NTB features
Chelonae, abscessus and fortuitum (CAF )
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Post - trauma , post - surgical infection
Pulm infection ( M. abscessus)
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Nonchromogens
25-30 degree C
3 day arylsulfatase positive
Grow on mMAC agar lacking crystal violet
RPLF analysis is now popular
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41
Thermally dimorphic / endemic fungi
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Histoplasma capsulatum
Blastomyces dermatitis
Coccidiodes immitis
Paracoccidiodes brasiliensis
Sporothrix schenckii
Penicillium marneffei
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42
Which candida is positive for RAT test - rapid accumulation of trehalose ?
Candida Glabrata
43
Recently identified problematic candida is
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Candida dubliniensis
Newly recognized
Oral cavity of AIDS patients
Readily develops azole resistance
Germ 🦠 tube + like Candida A( so can be ID’ed as albicans)
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44
Antifungal sensitivities and susceptibility of candida types
C. Albicans- generally sensitive to azoles
C. Glabrata- 10% azole resistant
C. KRUSEI- resistant to FLUCONZOLE (MCQ)
C. Lusitaniae- resistant to amphotericin
45
Cryptococcus method of transmission
Bat 🦇 caves
Aged pigeon and 🐦 bird droppings and soil with bird guano
Not transmissible from human to human
46
What the heck is prototheca wickerhamii?
Achlorophyllous algae
Causes mycosis- like infections, often mistaken for yeast
Endospores look like ⚽️ soccer balls, no budding, no hyphae
Grows rapidly on plate - creamy yeast- like colonies
47
Deferroxamine therapy associates with which bug 🐛
Mucormycosis
48
Which of the NTB mycobacterium is a scotochromogen at 37 but a photochromogen at 25?
M. Szulgai
49
Two nematodes that pierce the skin to cause infections
Filariform larvae
1) ancylostoma duodenal
2) strongyloides stercoralis
50
Gram neg coccobacilli that resemble “grains of sand” and rapidly hydrolyse urea and a positive cytochrome oxidase reaction ( spot test).
Brucella
51
Best method to diagnose chikungunya?
RT-PCR and IgM antibody
Viral nucleic acid detectable in first 8 days : so RT - PCR best
IgM antibody develops typically after 7 days in average :
52
Spines on schistosomiasis
Lateral spine - S. Mansoni
No spine - S. Japonicum
Terminal Spine - S. Hematobium
53
Which organism has NO intrinsic resistance?
E. Coli has no intrinsic resistance but readily picks up resistance mechanisms such as ESBLs and KPC.
54
Organism that has recently been transmitted through the transfusion of apheresis platelets ?
L. Monocytogenes
55
Mycobacterium associated with contaminated tattoo ink and can cause subcutaneous infections
M. Chelonae
| Runyon group IV ( rapid grower)
56
Mycobacterium that is the most common cause of lymphadenopathy in children
M. Scrofulaceum
57
Test to differentiate M.TB from M. Bovis?
M. Bovis will show no growth on TCH ( thiophene-2-carboxylic hydrazine) medium, while M. tuberculosis will show positive growth.
58
Bacteroides fragilis is mostly susceptible to ..
MEROPENEM and METRONIDAZOLE
It’s resistant to penicillins, 2 nd and 3rd gen cephalosporins and clindamycin
59
Organism causing fever. SAB agar shows pink-coral colonies ?
Rhodotorula mucilganosa and spp
Emerging pathogen
Immunocompromised
Urease positive
60
Best method to detect MAC in stool specimen
DNA probes
61
Quad plate :
Organism that only requires V-factor
H. Parainfluenza
Others:
H. Ducreyi needs X factor only
H. Inf and Aegyptius need both
62
What is the important virulence factor in H. Influenza type B?
Polyribosyl ribitol phosphate (PRP)
| Renders h. Inf resistant to phagocytosis by PMN in the absence of a specific anticapsular antibody .
63
Organism causing infection in army sergeant returning from Lebanon ?
Beta coronavirus MERS-CoV
Middle eastern respiratory syndrome
Saudi Arabia in 2012
64
Person from Navajo reservation with fatigue and muscle aches with breathing difficulties. He dies of ARDS .. cause if his illness is ?
Hantavirus
65
Non human reservoir for below:
1) Ebola
2) hantavirus
3) dengue fever
4) Marburg
5) chikungunya
1) Ebola - bats
2) hantavirus - mice
Deer mouse ( peromysus maniculatus)
3) dengue fever - monkeys
4) Marburg - grivet monkey 🐒
5) chikungunya - cattle , bird and rodents
66
Rat 🐀 bite fever causes
1) streptococcus moniliformis
| 2) spirillum minus also a cause of rat bite fever or sodoku- endemic in ASIA NOT in US
67
Amblyomma Americanum is a vector for which organisms
It is the lone star tick - and vector for Ehrlichia and Francisella Tularensis, heartland virus and STARI (Southern tick associated rash illness).
68
Ornithodorus spp are vectors for
Soft shelled ticks which are vectors for relapsing fever borelia including B. Parkerii, B. Turicate, B. Hermsii.
69
Ixodes ticks vector which organisms
Ixodes scapularis and i. Pacificus are hard ticks and are vectors for - borelia burgdorferi and anaplasma phagocytophilum .
I. Scapularis can also be a vector for babesia and deer tick virus.
70
What causes rice 🍚 like bodies in stools of children ?
Dipylidium caninum ( dog tapeworm)
Motile when released
Double pored tapeworm
Rx: aggressive flea abatement
71
Knowing PCR for BK virus from urine has low specificity, which other test can be ordered to make a more def diagnosis ?
BK virus PCR from plasma
72
Antibody response to EBV and patterns
Acute infection :
VCA IgG+, VCA IgM+, Anti early antigen (EA)+/- and EBNA (EB nuclear antigen) -
Recent infection: VCA IgG+, VCA IgM+/-, Anti early antigen (EA)+\- and EBNA (EB nuclear antigen) +/-
Past infection:
VCA IgG+, VCA IgM-, Anti early antigen (EA) - and EBNA (EB nuclear antigen) +
If no previous infection, ALL Negative
73
Viral CPE time and pattern
CMV : 2 weeks - round retractile cell as well as focal clusters of plaques
Enterovirus : 1-7 days - tear shaped cells
Adenovirus: 2-7 days - grape 🍇 like clusters
RSV : 2 weeks - syncytial cells
HSV - sweeping 🧹, large balloon 🎈 cells
74
Which bugs appears red on modified acid fast stain of stool specimen
1) Cryptosporidium Parvum ( spherical)
2) cyclospora cayetanensis (spherical)
3) isospora belli ( oval)
75
Microsporidia MCQ
Common type- enterocytozoon bieneusi
Can cause chronic diarrhea and AIDS cholangiopathy, cholangitis
Can coinfect with cryptosporidium
IMP MCQ: seen on modified trichromatic stain In fecal smears as clusters of spores ( red)
76
Which mycobacterium grows only on chocolate agar?
M. Haematophilum has fastidious growth requirements (hemin, hemoglobin or ferric ammonium citrate) provided by chocolate agar.
77
Which stool parasite is NOT readily detected on traditional trichrome stain and therefore need additional steps for detection ?
Cyclospora cayetanensis
| Needs modified AFB staining and / or auto fluorescence detection with UV light .
78
To which antibiotic can salmonella spp and shigella app appear active in vitro but should NEVER be reported as it would be clinically ineffective ?
Aminoglycosides like GENTAMICIN and 2nd gen cephalosporins like cephamycins.
79
Name a few urease positive fungi
C. Neoformans
Rhodotorula spp ( coral red colonies)
Trichophyton spp
80
Which microorganism 🦠 needs lipid supplementation to grow in culture?
Malassezia spp
81
Some features about the agents of bioterrorism
F tularensis: gram neg coccobacilli, oxidase neg, weakly catalase pos, non motile, blood and chocolate agar with NO froth on MAC agar.
B anthracis: gram pos rods
Y pestis: grows on MAC agar
Brucella spp: oxidase, catalase and urease +++
B. Pseudomallei: oxidase positive, motile
82
The most commonly acquired Arbovirus infection in the USA?
West Nile Virus
83
To which antibiotics is pseudomonas aeruginosa intrinsically resistant ?
Intrinsically resistant to ampicillin, amoxicillin, ampicillin- Sulbactam, amoxicillin-clavulanate, cefotaxime, ceftriaxone, ertapenem, tetracycline, tigecycline. TMP- SMX, and chloramphenicol
84
Best antibiotic combination for KPC ( klebsiella pneumoniae carbapenemase) which confers resistance to mist beta lactate antibiotics is
Ceftazidime- avibactam
85
Name a single stranded DNA virus
Parvovirus
| Most are double stranded
86
Name a single stranded RNA virus
Reovirus
| Most are double stranded
87
Pulmonary disease in patients with underlying pneumoconiosis is caused by
M. Kansasii
88
Mycobacterium associated with colon cancer
M. Bovis
89
Mycobacterium that is major lab 💦 water contaminant -Tap water 💧 bacillus
M. Gordonae
90
Mycobacterium associated with Crohns?
M. Paratuberculosis
91
Mycobacterium causing buruli ulcer ??
M. Ulcerans
92
DNA viruses 🦠
HeHe PoPa Par ADe
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He= Herpes
He=Hepadna ( HBV)
Po= pox ( smallpox, molluscum)
Pa=papilloma (HPV 6,11,16,18), polyoma
Par=parvovirus (SS DNA)
ADe=Adenovirus
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93
Quad plate reading
Both factor X and V with hemolysis: H. Hemolyticus
Both factor X and V without hemolysis: H. Influenza
Requires only X factor without hemolysis : H. Ducreyi
Requires factor V with hemolysis: H. Parahemolyticus
Requires factor V without hemolysis: H. Parainfluenza
94
Pathogen and infected cell type pairs
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Plasmodium vivax - reticulocytes
Ehrlichia chaffeensis - monocytes
Anaplasma phagocytophilum - granulocytes
Babesia mucroti - mature red blood cells
T. Cruzi - cardiac myocytes and paraesophageal neuronal cells and extra cellular in peripheral blood 🩸
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