Microbiology Flashcards
MRSA dets
Altered penicillin binding protein (PBP 2a) , encoded by MecA gene
Anaerobic organism that causes double zone of beta hemolysis-
Clostridium perfringens
Has gas production on thioglycolate broth
Lecithinase activity seems on egg 🥚 yolk agar
Gram negative rod that is oxidase and catalase positive :
Pseudomonas aeruginosa
Beta hemolytic on blood agar.
Lactose nonfermentor
Streptococcus susceptible to bacitracin
Streptococcus pyogenes
Confirmatory: PYR positive
Bordetella pertussis, gold standard method of confirmation
Culture (very specific)
Regan-Lowe is preferred (fastidious) - charcoal agar with horse blood and cephalexin
B. Pertussis fluorescent antibody stain
Enriched and differential media for c. Diphtheria
Gram pos rods, Chinese characters
Loeffler medium
Tellurite medium - black colonies
Optochin susceptible organism
Streptococcus pneumonia
Alpha hemolytic on blood agar
Rapid ID (*)
Antigen detection in blood Cx- pneumoslide
Antigen detection in Urine
H. Flu requirements
X factor - hemin
V factor - NAD+
Grows best on chocolate agar
Quad plate features
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
Legionella pneumophilia rapid turn around test
Urine antigen test (EIA)
Remember: it needs L-cysteine supplements to grow ( buffered charcoal yeast extract - BCYE)
Mycoplasma detection - gold std
PCR has replaced culture in many places
Percentage of patients with cold antigen response with mycoplasma….
60%
Sub clinical AIHA ( IgM antibody against I antigen on RBC membranes)
Positive Coombs
⬆️ retic count
Sulfur granules seen in infection with
Actinomyces infection
Branched filamentous Gram positive rods
AFB negative
N. Astreroides VS N. Brasiliensis features
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
Organism with Medusa head colonies
Bacillus 🦠 Anthracis
Large GPR, sub terminal or central spores
Catalase positive
Stands up when picked with a loop
Native valve endocarditis causes
Stept Viridans Streptococcus Bovis Group A strept ( strept pyogenes) S aureus Enterococci
Prosthetic valve endocarditis
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
Alpha hemolytic strept how to diff
Optochin sensitive: strept pneumo
Optochin resistant ————————— PYR + and bile esculin + = enterococcus Both neg= strept viridans Bile esculin pos, PYR - = strept bovis
Vancomycin resistant enterococcus details
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
Name one catalase positive urease positive organism of bioterrorism
Brucellosis
Small gram neg coccobacilli
Oxidase positive
Urease positive
Unusual strain of C. Difficile
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) .
Tests for c. Diff
- 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)
Organism positive for hippurate hydrolysis test:
Campylobacter jejuni Gram neg rods, S / gull wing shaped Catalase pos Oxidase pos Selective growth at 42 degree
ESBL notes
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
Which is the novibiocin resistant staphylococcus?
Staph saprophyticus
Methods to confirm Group B strept
CAMP test: positive
Rapid hippurate hydrolysis test: positive
Lancefield group B by particle agglutination.
Which species of shigella is most prominent in the US?
Shigella Sonnei ( serogroup D)
Which species of shigella is associated with HUS?
S. Dysenteriae
What is true of E. Coli 0157:H7?
Does not ferment sorbitol
Which organism is relatively narrow, regularly septated, hyaline hyphae, with acute angle branching and resembles Aspergillus ?
Pseudoallescheria boydii/scedosporium apiospermum
Dimorphism fungus that produces diffusable red pigment on standard media?
Penicillium marneffei
Scotochromogen in reference to mycobacterium means
Pigmented whether grown in dark or light
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
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)
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)
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
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
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
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
Rapid growers NTB features
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
Thermally dimorphic / endemic fungi
Histoplasma capsulatum Blastomyces dermatitis Coccidiodes immitis Paracoccidiodes brasiliensis Sporothrix schenckii Penicillium marneffei
Which candida is positive for RAT test - rapid accumulation of trehalose ?
Candida Glabrata
Recently identified problematic candida is
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)
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
Cryptococcus method of transmission
Bat 🦇 caves
Aged pigeon and 🐦 bird droppings and soil with bird guano
Not transmissible from human to human
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
Deferroxamine therapy associates with which bug 🐛
Mucormycosis
Which of the NTB mycobacterium is a scotochromogen at 37 but a photochromogen at 25?
M. Szulgai
Two nematodes that pierce the skin to cause infections
Filariform larvae
1) ancylostoma duodenal
2) strongyloides stercoralis
Gram neg coccobacilli that resemble “grains of sand” and rapidly hydrolyse urea and a positive cytochrome oxidase reaction ( spot test).
Brucella
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 :
Spines on schistosomiasis
Lateral spine - S. Mansoni
No spine - S. Japonicum
Terminal Spine - S. Hematobium
Which organism has NO intrinsic resistance?
E. Coli has no intrinsic resistance but readily picks up resistance mechanisms such as ESBLs and KPC.
Organism that has recently been transmitted through the transfusion of apheresis platelets ?
L. Monocytogenes
Mycobacterium associated with contaminated tattoo ink and can cause subcutaneous infections
M. Chelonae
Runyon group IV ( rapid grower)
Mycobacterium that is the most common cause of lymphadenopathy in children
M. Scrofulaceum
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.
Bacteroides fragilis is mostly susceptible to ..
MEROPENEM and METRONIDAZOLE
It’s resistant to penicillins, 2 nd and 3rd gen cephalosporins and clindamycin
Organism causing fever. SAB agar shows pink-coral colonies ?
Rhodotorula mucilganosa and spp
Emerging pathogen
Immunocompromised
Urease positive
Best method to detect MAC in stool specimen
DNA probes
Quad plate :
Organism that only requires V-factor
H. Parainfluenza
Others:
H. Ducreyi needs X factor only
H. Inf and Aegyptius need both
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 .
Organism causing infection in army sergeant returning from Lebanon ?
Beta coronavirus MERS-CoV
Middle eastern respiratory syndrome
Saudi Arabia in 2012
Person from Navajo reservation with fatigue and muscle aches with breathing difficulties. He dies of ARDS .. cause if his illness is ?
Hantavirus
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
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
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).
Ornithodorus spp are vectors for
Soft shelled ticks which are vectors for relapsing fever borelia including B. Parkerii, B. Turicate, B. Hermsii.
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.
What causes rice 🍚 like bodies in stools of children ?
Dipylidium caninum ( dog tapeworm)
Motile when released
Double pored tapeworm
Rx: aggressive flea abatement
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
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
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
Which bugs appears red on modified acid fast stain of stool specimen
1) Cryptosporidium Parvum ( spherical)
2) cyclospora cayetanensis (spherical)
3) isospora belli ( oval)
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)
Which mycobacterium grows only on chocolate agar?
M. Haematophilum has fastidious growth requirements (hemin, hemoglobin or ferric ammonium citrate) provided by chocolate agar.
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 .
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.
Name a few urease positive fungi
C. Neoformans
Rhodotorula spp ( coral red colonies)
Trichophyton spp
Which microorganism 🦠 needs lipid supplementation to grow in culture?
Malassezia spp
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
The most commonly acquired Arbovirus infection in the USA?
West Nile Virus
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
Best antibiotic combination for KPC ( klebsiella pneumoniae carbapenemase) which confers resistance to mist beta lactate antibiotics is
Ceftazidime- avibactam
Name a single stranded DNA virus
Parvovirus
Most are double stranded
Name a single stranded RNA virus
Reovirus
Most are double stranded
Pulmonary disease in patients with underlying pneumoconiosis is caused by
M. Kansasii
Mycobacterium associated with colon cancer
M. Bovis
Mycobacterium that is major lab 💦 water contaminant -Tap water 💧 bacillus
M. Gordonae
Mycobacterium associated with Crohns?
M. Paratuberculosis
Mycobacterium causing buruli ulcer ??
M. Ulcerans
DNA viruses 🦠
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
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
Pathogen and infected cell type pairs
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 🩸
