Microbiology Flashcards
How does gonorrhea cause recurrent infections?
Its pili undergoes antigenic and phase variation
What’s pathognomonic for Human Granulocyte Anaplasmosis?
Morulae (berry-like) clusters of the intracellular orgs
Which orgs have the Ixodes tick as their vector?
Anaplasma \+ Borrelia burgdorferi \+ Babesia microti
Which orgs have the louse as their vector?
Borrelia recurrentis
+
Rickettsia prowazekii
Which orgs have the Dermacentor tick as their vector?
Francisella tularensis
+
Rickettsia rickettsii
Which orgs have the flea as their vector?
Rickettsia typhi
+
Yersinia pestis
What is a characteristic histological trait for CMV?
Owl-eye inclusion (singular)
How does cryptosporidium cause diarrhea in AIDS pts?
Intracellular multiplication in the brush border
Under which circumstances do M. tuberculosis and M. avium-intracellulare infect AIDS pts?
TB = CD >400
M. avium = CD
How do you test for Mono (EBV)?
Monospot test: heterophile antibody test
What characteristic differentiates Campylobacter jejuni from other diarrhea-causing organisms?
Growth at 42C
What is the virulence factor for C. diptheriae? and what does it do?
Exotoxin encoded by beta-prophage DNA;
inhibits protein synthesis by ADP-ribosylation of eEF-2
How does anaerobic bacteroides infection present in alcoholics?
rust-colored sputum from aspiration pneumo (normal oral flora causing lung abscesses)
How does toxoplasmosis manifest in IC pt?
reactivation of latent infection =
-multiple ring-enhacing lesions on CT but no neuro symps
Whats the serology for acute HBV infection?
HB-s-Ag
HB-e-Ag
anti-HB-c-IgM Ab
What is the clinical manifestation of H. ducreyi?
papule w red base that progresses to painful ulcer (chancroid) and inguinal adenopathy
What are the hallmarks of actinomyces infection?
- branching rods
- sulfur granules
- IUD
What is a parasitic risk factor for pigmented gallstones?
chlonorchis sinensis (oriental liver fluke)
What are key symptoms of bordatella pertussis infection?
whooping cough and hypoglycemia
What are the hallmarks of atypical “walking” pneumo?
mycoplasma pneumo = cold agglutinins (IgM)
What is a diagnostic marker for E. histolytica?
Cysts with up to 4 nuclei + RBCs in the cytoplasm
What org is the most common cause of pseudoappendicitis in the US and what is its cause?
Yersinia enterocolitica; transmitted via contaminated milk or pork
What virulence factor causes the fever and rash in Scarlet fever?
pyrogenic exotoxins A-C
When an HIV+ person enters early symptomatic stage, what happens to their levels of anti-p24?
Decreases bc immune system loses ability to make antibodies
What phase of the bacterial growth curve has the greatest spore production?
Stationary phase (F)
How does pseudomonas exotoxin A work? and what other org works the same way?
inhibits protein synthesis by ADP-ribosylation of eEF-2;
C. diptheriae
What mechanism mediates resistance to aminoglycosides?
enzymatic inactivation
Whats the most important virulence factor in E. coli that causes neonatal meningitis?
K1 capsule
Where in the brain does neonatal herpes encephalitis usually manifest?
temporal lobes (bilaterally)
Tests for Hep B in pregnant woman?
HBsAg: - = recovered, + = carrier
IgG for HBsAg: + = immunity/recovery
Which bacterial toxins are expressed by lysogenic conversion?
COBEDS: Cholera O toxin of Salmonella Botulinum toxin Erythrogenic toxin of S. pyogenes Diptheria toxin Shiga toxin
What is the key virulence factor in G- bacteria?
Lipid A in LPS
O is the antigen = immunity
How to tell generalized v specialized transduction?
generalized = lytic phage specialized = lysogenic phage (near insertion site)
Which C. perfringens toxin in assoc w gas gangrene?
Alpha toxin
Whats the major difference between s. aureus pneumo and strep pneumo?
s. aureus pneumo = cavitary lesion
Describe cat-scratch disease?
Cause: bartonella henselae from cats (esp kittens)
hallmarks: papule w regional lymphadenopathy
Histo: stellate granulomas
What is the HepB window period?
When neither HBsAg nor HBsAb can be detected.
What is the Ghon complex?
Primary TB infection w granulomas in mid zone of lung + hilar nodes
Any obstructive lesion in urinary tract (esp in older adults) indicates what bacteria?
E. coli (can lead to bacteremia and ARDS)
What parasites cause calcifying lung masses in IC pts? and how do you tell them apart?
Histoplasma (small yeasts in macros, Midwest) or Blastocyes (broard-based yeast, Eastern US)
On what medium does the genus Vibrio grow on?
alkaline medium
Which organisms are encapsulated?
Some Killers Have Pretty Nice Capsules: Strep pneumo Klebsiella H. flu Pseudomonas Neisseria Cryptococcus
What is the histological hallmark for P. vivax/ovale?
Schuffner dots = oval body w brick-red dots in RBCs
Note: vivax only occurs in Panama
What are the clinical manifestations of lyme disease years after the tick bite?
MSK: monoarthritis (knees)
Neuro: Bell’s palsy
What are the taxonomic characterisitics of B. anthracis?
G+ rod; box-car shaped; aerobic; spore-forming
What is Reiter Syndrome and its symtpoms?
Autoimmune rxm to previous infection of: Campylobacter Chlamydia Yersinia Salmonella Shigella
Symptoms (triad): arthritis, urethritis, conjunctivitis
Describe molluscum contangiosum.
Benign, self-limiting umbilicated warts in school children from Poxvirus
What is the most common cause of bloody diarrhea in the US?
Shigella
What is the first thing RSV does when it enters a cell?
Creates complimentary copy of its genome using RNA-dep-RNA-poly
What is the most common means of transmission for toxoplasmosis in the US?
Cysts from undercooked pork
What parasite is associated w Vit B12 def with macrocytic anemia?
Diphyllobothrium latum from freshwater fish (Great Lakes tapeworm)
Pregnant woman with CMV infection will have which symptoms?
flu-like: mild fever, generalized lymphadenopathy
What causes blister-like lesions that progress to yellow crust?
Non-bullous impetigo (s. aureus or s. pyogenes)
What’s the difference between bullous and non-bullous impetigo?
bullous = s. aureus; brown crust non-bullous = aureus/pyogenes; yellow crust
What organism causes food poisoning from pastries, poultry, eggs, salad in just a few hours?
s. aureus via enterotoxin A
What orgs cause atypical pneumo in adults?
myco pneumo: non-productive cough
legionella: ac, smoking
chlam psittaci: birds, hepatitis
p. jirovecii: AIDs
What are the hallmarks of Paracoccidioidomycosis?
- Latin America
- budding yeast w “Captain’s wheel” formation
Which bacteria are natural transformers?
H. flu
Strep pneumo
Neisseria
What org associates colon cancer with endocarditis?
Strep bovis
Which virus families have a segmented genome?
ROBA: Rotavirus Orthomyxo Bunya Arena
Describe JC virus reactivation in AIDS pts.
Progressive multifocal leukoencephalopathy = nonenhancing areas of demyelination on MRI
What are the hallmarks of a premature infant pneumocystis pneumo?
P. jirovecii = surfectant-rich exudate w cysts that stain w methenamine silver
What is giardia lambia’s key mode of pathogenesis?
Adherence to mucosal surface via ventral sucking disk (never penetrates the bowel)
UTI w (+)leukocyte esterase and (-)nitritrie indicates what organism?
Enterococcus faecalis or S. saprophyticus
Which hepatitis has the highest mortality amongst pregnant women?
Hep E (hep-e-viridae)
What org is the most common cause of epiglottitis?
H. influenza
What kind of vaccine is used against H. flu?
toxoid + polyribitol phosphate capsular polysaccharide
Which org is the leading cause of shellfish-related deaths in the US?
Vibrio vulnificus (others: Vibrio parahaemolyticus, Hep A)
Which org infects AIDS pts with CD
CD
What feature of M. tuberculosis causes a (+) PPD test?
Outer surface protein tuberculin
How do enterococcal species gain penicillin and tetracycline resistance?
transposons
What is the best test to diagnose p. jirovecii infection?
Direct fluorescent antibody test
Why are antibodies against Mumps ineffective?
They transfer from cell-to-cell via syncytia and thus, are never exposed outside of cell
-need cell-mediated immunity
How do macrolides (-mycin) work?
Interferes with translocation by binding 23s (50s)
Lacey EBV cells are derived from which type of cell?
Reactive cytotoxic T cells
Org causes vegetation on tricuspid valve on echocardiography?
s. aureus
How do you know if a protease inhibitor is working?
There is a lack of a mature core (which requires protease in order to be formed)
What is the virulence factor for E.coli in UTIs?
p-pili (adhesins), allow them to adhere to urinary tract
Neuraminidase inhibitor mechanism of action?
prevents release of virus from infected epithelial cells
Whats the MOA for fluoroquinolones?
inhibiting DNA gyrase
Treatment for all Rickettsial and vector-borne illnesses?
Doxycycline
Why does M. leprae infect the skin and not visceral organs?
It prefers cooler temps
Reservoir = armadillos
What makes up the pseudomembrane on c.diff colitis?
inflammatory cells + fibrin + necrotic cells
