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Path Boards > Microbiology > Flashcards

Microbiology Flashcards

1
Q

MRSA dets

A

Altered penicillin binding protein (PBP 2a) , encoded by MecA gene

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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

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3
Q

Gram negative rod that is oxidase and catalase positive :

A

Pseudomonas aeruginosa
Beta hemolytic on blood agar.
Lactose nonfermentor

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4
Q

Streptococcus susceptible to bacitracin

A

Streptococcus pyogenes

Confirmatory: PYR positive

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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

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6
Q

Enriched and differential media for c. Diphtheria

A

Gram pos rods, Chinese characters

Loeffler medium
Tellurite medium - black colonies

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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

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8
Q

H. Flu requirements

A

X factor - hemin
V factor - NAD+

Grows best on chocolate agar

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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

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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)

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11
Q

Mycoplasma detection - gold std

A

PCR has replaced culture in many places

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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

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13
Q

Sulfur granules seen in infection with

A

Actinomyces infection
Branched filamentous Gram positive rods
AFB negative

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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

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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

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16
Q

Native valve endocarditis causes

A 
Stept Viridans
Streptococcus Bovis 
Group A strept ( strept pyogenes) 
S aureus 
Enterococci
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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
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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
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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

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20
Q

Name one catalase positive urease positive organism of bioterrorism

A

Brucellosis
Small gram neg coccobacilli
Oxidase positive
Urease positive

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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) .

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22
Q

Tests for c. Diff

A
  1. ELISA/ICTs for toxin A and B
    - high specificity , low sensitivity
    - tests for both
    - diagnostic yield increased by testing 2-3 sps
  2. 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)
  3. PCR
  4. Cell cytotoxicity assay (most sensitive, technically demanding)
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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
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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

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25
Q

Which is the novibiocin resistant staphylococcus?

A

Staph saprophyticus

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26
Q

Methods to confirm Group B strept

A

CAMP test: positive
Rapid hippurate hydrolysis test: positive
Lancefield group B by particle agglutination.

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27
Q

Which species of shigella is most prominent in the US?

A

Shigella Sonnei ( serogroup D)

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28
Q

Which species of shigella is associated with HUS?

A

S. Dysenteriae

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29
Q

What is true of E. Coli 0157:H7?

A

Does not ferment sorbitol

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30
Q

Which organism is relatively narrow, regularly septated, hyaline hyphae, with acute angle branching and resembles Aspergillus ?

A

Pseudoallescheria boydii/scedosporium apiospermum

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31
Q

Dimorphism fungus that produces diffusable red pigment on standard media?

A

Penicillium marneffei

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32
Q

Scotochromogen in reference to mycobacterium means

A

Pigmented whether grown in dark or light

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33
Q

Examples of slow and rapid mycobacterium

A

SLOW: M. TB, MAC, M. Kansasii, M. Xenopi, M. Marinum, M.Gordonae

RAPID: M. Fortuitium, M. Chelonae, M. Abscessus

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34
Q

Pigmentations and photoreactivity of tuberculosis

A

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)

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35
Q

MDR tb means resistance to what drugs ??

A

Rifampicin
And
isoniazid

XDR tb: MDR+ resistance to fluroquinolone and 1 of 3 injectable drugs ( amikacin, kanamycin and capreomycin)

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36
Q

M. Kansasii features

A

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

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37
Q

M.Xenopi features

A 
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
Q

M. Marinum features

A 
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
39
Q

M. Gordonae features

A

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
Q

Rapid growers NTB features

A

Chelonae, abscessus and fortuitum (CAF )

Post - trauma , post - surgical infection
Pulm infection ( M. abscessus)
Nonchromogens 
25-30 degree C
3 day arylsulfatase positive
Grow on mMAC agar lacking crystal violet
RPLF analysis is now popular
41
Q

Thermally dimorphic / endemic fungi

A 
Histoplasma capsulatum 
Blastomyces dermatitis 
Coccidiodes immitis 
Paracoccidiodes brasiliensis 
Sporothrix schenckii 
Penicillium marneffei
42
Q

Which candida is positive for RAT test - rapid accumulation of trehalose ?

A

Candida Glabrata

43
Q

Recently identified problematic candida is

A 
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)
44
Q

Antifungal sensitivities and susceptibility of candida types

A

C. Albicans- generally sensitive to azoles
C. Glabrata- 10% azole resistant
C. KRUSEI- resistant to FLUCONZOLE (MCQ)
C. Lusitaniae- resistant to amphotericin

45
Q

Cryptococcus method of transmission

A

Bat 🦇 caves
Aged pigeon and 🐦 bird droppings and soil with bird guano
Not transmissible from human to human

46
Q

What the heck is prototheca wickerhamii?

A

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
Q

Deferroxamine therapy associates with which bug 🐛

A

Mucormycosis

48
Q

Which of the NTB mycobacterium is a scotochromogen at 37 but a photochromogen at 25?

A

M. Szulgai

49
Q

Two nematodes that pierce the skin to cause infections

A

Filariform larvae

1) ancylostoma duodenal
2) strongyloides stercoralis

50
Q

Gram neg coccobacilli that resemble “grains of sand” and rapidly hydrolyse urea and a positive cytochrome oxidase reaction ( spot test).

A

Brucella

51
Q

Best method to diagnose chikungunya?

A

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
Q

Spines on schistosomiasis

A

Lateral spine - S. Mansoni

No spine - S. Japonicum

Terminal Spine - S. Hematobium

53
Q

Which organism has NO intrinsic resistance?

A

E. Coli has no intrinsic resistance but readily picks up resistance mechanisms such as ESBLs and KPC.

54
Q

Organism that has recently been transmitted through the transfusion of apheresis platelets ?

A

L. Monocytogenes

55
Q

Mycobacterium associated with contaminated tattoo ink and can cause subcutaneous infections

A

M. Chelonae

Runyon group IV ( rapid grower)

56
Q

Mycobacterium that is the most common cause of lymphadenopathy in children

A

M. Scrofulaceum

57
Q

Test to differentiate M.TB from M. Bovis?

A

M. Bovis will show no growth on TCH ( thiophene-2-carboxylic hydrazine) medium, while M. tuberculosis will show positive growth.

58
Q

Bacteroides fragilis is mostly susceptible to ..

A

MEROPENEM and METRONIDAZOLE

It’s resistant to penicillins, 2 nd and 3rd gen cephalosporins and clindamycin

59
Q

Organism causing fever. SAB agar shows pink-coral colonies ?

A

Rhodotorula mucilganosa and spp
Emerging pathogen
Immunocompromised
Urease positive

60
Q

Best method to detect MAC in stool specimen

A

DNA probes

61
Q

Quad plate :

Organism that only requires V-factor

A

H. Parainfluenza

Others:
H. Ducreyi needs X factor only
H. Inf and Aegyptius need both

62
Q

What is the important virulence factor in H. Influenza type B?

A

Polyribosyl ribitol phosphate (PRP)

Renders h. Inf resistant to phagocytosis by PMN in the absence of a specific anticapsular antibody .

63
Q

Organism causing infection in army sergeant returning from Lebanon ?

A

Beta coronavirus MERS-CoV
Middle eastern respiratory syndrome
Saudi Arabia in 2012

64
Q

Person from Navajo reservation with fatigue and muscle aches with breathing difficulties. He dies of ARDS .. cause if his illness is ?

A

Hantavirus

65
Q

Non human reservoir for below:

1) Ebola
2) hantavirus
3) dengue fever
4) Marburg
5) chikungunya

A

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
Q

Rat 🐀 bite fever causes

A

1) streptococcus moniliformis

2) spirillum minus also a cause of rat bite fever or sodoku- endemic in ASIA NOT in US

67
Q

Amblyomma Americanum is a vector for which organisms

A

It is the lone star tick - and vector for Ehrlichia and Francisella Tularensis, heartland virus and STARI (Southern tick associated rash illness).

68
Q

Ornithodorus spp are vectors for

A

Soft shelled ticks which are vectors for relapsing fever borelia including B. Parkerii, B. Turicate, B. Hermsii.

69
Q

Ixodes ticks vector which organisms

A

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
Q

What causes rice 🍚 like bodies in stools of children ?

A

Dipylidium caninum ( dog tapeworm)
Motile when released
Double pored tapeworm

Rx: aggressive flea abatement

71
Q

Knowing PCR for BK virus from urine has low specificity, which other test can be ordered to make a more def diagnosis ?

A

BK virus PCR from plasma

72
Q

Antibody response to EBV and patterns

A

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
Q

Viral CPE time and pattern

A

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
Q

Which bugs appears red on modified acid fast stain of stool specimen

A

1) Cryptosporidium Parvum ( spherical)
2) cyclospora cayetanensis (spherical)
3) isospora belli ( oval)

75
Q

Microsporidia MCQ

A

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
Q

Which mycobacterium grows only on chocolate agar?

A

M. Haematophilum has fastidious growth requirements (hemin, hemoglobin or ferric ammonium citrate) provided by chocolate agar.

77
Q

Which stool parasite is NOT readily detected on traditional trichrome stain and therefore need additional steps for detection ?

A

Cyclospora cayetanensis

Needs modified AFB staining and / or auto fluorescence detection with UV light .

78
Q

To which antibiotic can salmonella spp and shigella app appear active in vitro but should NEVER be reported as it would be clinically ineffective ?

A

Aminoglycosides like GENTAMICIN and 2nd gen cephalosporins like cephamycins.

79
Q

Name a few urease positive fungi

A

C. Neoformans
Rhodotorula spp ( coral red colonies)
Trichophyton spp

80
Q

Which microorganism 🦠 needs lipid supplementation to grow in culture?

A

Malassezia spp

81
Q

Some features about the agents of bioterrorism

A

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
Q

The most commonly acquired Arbovirus infection in the USA?

A

West Nile Virus

83
Q

To which antibiotics is pseudomonas aeruginosa intrinsically resistant ?

A

Intrinsically resistant to ampicillin, amoxicillin, ampicillin- Sulbactam, amoxicillin-clavulanate, cefotaxime, ceftriaxone, ertapenem, tetracycline, tigecycline. TMP- SMX, and chloramphenicol

84
Q

Best antibiotic combination for KPC ( klebsiella pneumoniae carbapenemase) which confers resistance to mist beta lactate antibiotics is

A

Ceftazidime- avibactam

85
Q

Name a single stranded DNA virus

A

Parvovirus

Most are double stranded

86
Q

Name a single stranded RNA virus

A

Reovirus

Most are double stranded

87
Q

Pulmonary disease in patients with underlying pneumoconiosis is caused by

A

M. Kansasii

88
Q

Mycobacterium associated with colon cancer

A

M. Bovis

89
Q

Mycobacterium that is major lab 💦 water contaminant -Tap water 💧 bacillus

A

M. Gordonae

90
Q

Mycobacterium associated with Crohns?

A

M. Paratuberculosis

91
Q

Mycobacterium causing buruli ulcer ??

A

M. Ulcerans

92
Q

DNA viruses 🦠

A

HeHe PoPa Par ADe

He= Herpes
He=Hepadna ( HBV)
Po= pox ( smallpox, molluscum) 
Pa=papilloma (HPV 6,11,16,18), polyoma 
Par=parvovirus (SS DNA) 
ADe=Adenovirus
93
Q

Quad plate reading

A

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
Q

Pathogen and infected cell type pairs

A 
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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