Micro (Gen Principles) Flashcards
Aspergillus in relation to liver
fungus that produces **aflatoxin; contaminate in CORN; high dietary intake is associated with hepatocellular carcinoma (HCC); non-industrialized countries
Clonorchis sinensis in ascending cholangitis
Watch for Chinese liver fluke, may have just consumed sushi - helminth found in infected fish; you will see peripheral eosinophilia
Strep Bovis
normal colonic bacteria; gram + cocci and gamma hemolytic; Lancefield group D; cases bacteremia and **endocarditis; STRONGLY associated w/ colon cancer
pt w/ Step Bovis organism identified (endocarditis), what test should you do next?
Colonoscopy; STRONGLY associated w/ colon cancer
Malaria
caused by Plasmodium falciparum on blood smear RBCs will have multiple small rings representing developing trophozoites; antimalarials such as chloroquine, atovaquone-proguanil or artemisinins
Acute exacerbation of COPD due to viruses
the most common viral pathogens are rhinoviruses, influenza and respiratory syncytial virus
Treponema pallidum gold standard diagnosis
single, painless ulcer at inoculation site with heaped-up borders and clean base; pt w early syphilis often have false-negative initial serologic testing; direct visualization of the organism by dark-field microscopy or fluorescent antibody testing is gold standard
Haemophilus influenza
commonly causes epiglottis causing inspiratory stridor, dyspnea and severe agitation; major virulence factor is polysaccharide capsule which is composed of polyribosylribitol phosphate (PRP)
Disseminated gonococcal infection
when Neisseria gonorrhoeae spreads from the GU tract to the bloodstream; confined diagnosis w Thayer-martin media (chocolate agar); infection spread via sexual contact and prevented via consistent condom use
Phthirus pubis
pubic louse w crab-like claws that allow it to grab pubic hair; transmitted via skin to skin contact and causes intense pruritus; eggs can visualized on exam; tx is topical permethrin
Ebstein-Barr virus (EBV)
commonly infects B cells stimulating them to enter the cell cycle and proliferate continuously; oncogenic virus promotes heterophiles antibody production; heterophiles antibody test is sensitive and highly specific for EBV
CMV pneumonitis
in transplant pts, pneumonia w intranuclear and cytoplasmic inclusion bodies histologically points to opportunities infection w CMV; enveloped virus that contains dsDNA
Azoles
anti fungal med that inhibits the demethylation of lanosterol to ergosterol which is an important component of the cell membrane; they use the fungal P450 enzymes and also suppress the human P450 system resulting in many drug-drug interactions
Tertiary syphillis
can result in thoracic aortic aneurysm; if aneurysm compresses adjacent structures and dilates the aortic valve ring, a murmur and mediastinal widening can be present; pathogenesis begins w vasa vasorum endarteritis and obliteration
Acute exacerbation of COPD (bacterial cause)
3 most common bacteria during AECOPD are nontypeable Haemophilus, influenza, Moraxella
Acute exacerbation of COPD (viral cause)
3 most common bacteria during AECOPD are: rhinovirus, influenza, and RSV
Staph epidermidis
gram (+) coccus that grows in clusters (similar to staph aureus) but is coagulase-NEG; common cause of infection in pts with prosthetic devices (artificial joints/heart valves); susceptible to novobiocin (unlike Staph saprophyticus)
Novobiocin
antibiotic that is used to differentiate Staph saprophyticus (resistant) from Staph epidermidis (sensitive)
Replication of Hep B
occurs within newly synthesized capsid through the action of reverse transcriptase on an RNA template; the mature capsid contains partially ds circular DNA and reverse transcriptase
Coxsackie virus genome
with in the Picornaviridae family and composed of icosahedral nucleocapsid and a (+) ssRNA genome
Alcohol-based disinfectants kill which type of viruses
enveloped viruses (ex: influenza) by dissolving their outer lipid envelope
Influenza
enveloped orthomyxovirus w segmented, negative-sense, ssRNA genome; transmission is by contaminated, large particle droplets (droplet precautions)
Media for Neisseria
a selective media such as Thayer-Martin
malaria
Genetic reassortment
viruses w segmented genomes (ex: influenza); 2 distinct strains infect the same cell leading to a novel strain leading to the phenomenon of antigenic shift
Protein A
virulence factor found in the peptidoglycan cell wall of Staph aureus that binds to the Fc portion of IgG leading to impaired complement activation, opsonization and phagocytosis
sOrbitol-MacConkey agar
detection for E. coli 0157:H7 strains (shiga-like toxin)
sOribital = 0157
Shiga toxin
cytotoxin produced by E. coli 0157:H7 and Shigella dysenteriae; inhibits the 60S ribosomal subunit in human cells; blocking protein synthesis and causing cell death
UTIs
E. coli most common cause; primary virulence factors are P fimbriae (pili) which allow the bacteria to adhere to uroepithelial cells and infect the bladder, ureters and kidneys
Inadequate sterilizations of autoclaves increases the risk of infection caused by which bacteria?
spore-forming bacteria can survive boiling temps; Bacillus and Clostridium species are common pathogenic spore-forming bacteria
Phenotypic mixing
co-infection of a host cell by 2 viral strains resulting in progeny that contain nucleocapsid proteins from one strain and the unchanged parental genome of the other strain; because there is no change in the underlying viral genomes (no genetic exchange) the next generation of visions revert to their original, unmixed phenotypes
an example of what?
phenotype mixing
black necrotic eschar in the nasal cavity is characteristic of what infection?
mucormycosis caused by Mucor or Rhizopus
Mucormycosis
presents as facial pain, HA and a black necrotic eschar in the nasal cavity of a pt w DKA; histo is needed to confirm dx - shows broad septate hyphae w right-angled branching; tx is surgical debridement and anti fungal therapy
MOA of human infection by animal viruses
tissue tropism of viruses is primarily mediated by viral *surface glycoproteins that bind specific host cell receptors; mut can alter tissue tropism and cause noninfective viruses to become infectious
pear-shaped trophozoite
Giardia lamblia causes injury to the duodenal and jejunal mucosa by adhering to the intestinal brush border and releasing molecules that induce a mucosal inflam response; secretory IgA which impairs adherence, is the major component of adaptive immunity against this infection; conditions causing IgA deficiency predispose pts to chronic giardiasis
lac operon
regulated by two distinct mechanisms: negatively by binding of the repressor protein to the operator locus and positively by cAMP-CAP binding upstream from the promotor regions; constitutive expression of the structural genes of the lac operon occurs within mut that impair the binding of the repressor protein (lac I) to its regulatory sequence in the operator region
Enterococcus cause of UTIs
important cause of UTIs; gram (+) cocci in pairs/chains and when grown on blood agar, does not cause hemolysis (gamma-hemolytic)
Genetic variations during HCV replication
causes a marked variety of antigenic structures of HCV envelope proteins; the production of host antibodies lags behind that of new mutant HCV strains, preventing infected individuals from mounting an effective immune response
an example of what?
recombination
Recombination
gene exchange that occurs through the crossing over of 2 nonsegmented dsDNA molecules; resulting progeny can have recombined genomes with traits from both parent viruses
S Saprophyticus cause of UTIs
responsible for almost half of UTIs in sexually active young women; gram (+) cocci, catalase (+), coagulase (-) and novobiocin resistant
Shigella
non-lactose fermenting organism that does not produce hydrogen sulfide on triple sugar iron agar; mucosal invasion is the primary pathogenic mechanism for Shigella infection, which presents w bloody/mucoid diarrhea
Erythema infectiosum (fifth disease)
caused by parvovirus B19 and presents w nonspecific prodrome (malaise, fever, congestion) followed by classic “slapped-cheek” facial rash and a lacy, reticular body rash; parvovirus is highly tropic for erythroid precursor cells and replicates predominantly in bone marrow
caused by parvovirus B19 and presents w nonspecific prodrome (malaise, fever, congestion) followed by classic “slapped-cheek” facial rash and a lacy, reticular body rash; parvovirus is highly tropic for erythroid precursor cells and replicates predominantly in bone marrow
transformation process of Strep pneumoniae
able to undergo transformation which allows the bacterium to take up exogenous DNA fragments and express the encoded proteins (direct uptake of extracellular DNA)
Maternal rubella infection
classically causes a maculopapular rash w cephalocaudal progression, joint pain and post auricular lymphadenopathy; transplacental transmission to the fetus leads to congenital rubella syndrome, which is characterized by sensorineural deafness, cataracts, patent ductus arteriosus and growth restriction
trichomonas vaginalis
sexually transmitted motile protozoan which can be seen on wet mount microscopy of vaginal discharge; presents w yellow-green, frothy vaginal discharge and vulvovaginal erythema
West Nile virus
harbored in birds and transmitted to humans by mosquitos; most pts are asymptomatic but virus can cause influenza-like illness or neuroinvasivn disease w meningitis, encephalitis, and flaccid paralysis
Listeriosis
most commonly transmitted through food infestation and can cause meningitis in immunocompromised adults; listeria is a gram (+) rod w tumbling motility; grows in cold temperatures and can therefore contaminate refrigerated food
Sporotrichosis
Sporothrix schenckii is a dimorphic fungus that exists as yeasts at body temp; found primarily in decaying plant matter and is usually transmitted via cutaneous or subcutaneous inoculation while a person is farming, gardening or landscaping; major manifestation is a slowly progressing nonpurulent, nonpainful, nodular lymphangitis that progresses proximally along the lymphatic chain
antibiotic use in association w Candida overgrowth
antibiotic use alters the balance of normal vaginal flora (decrease # of gram+) and facilitates Candida overgrowth; pts develop vulvovaginal candidiasis which presents w vulvar/vaginal/perianal pruritus; erythema; and a thick, white vaginal discharge
Aseptic meningitis
fever; meningeal signs (HA, neck stiffness) and CSF w lymphocytic pleocytosis and a modestly elevated protein level and normal glucose is suggestive of aseptic meningitis; enteroviruses are the most common cause
Differences between bacterial and viral meningitis
Differential diagnosis of vaginitis
bacterial vaginosis (BV) associated w a grayish-white, malodorous vaginal discharge due to an overgrowth of Gardnerella vaginalis, a facultative anaerobic, gram-variable rod; clue cells are seen on wet mount microscopy or cytology
Primary genital herpes
presents w multiple, grouped vesicles on the genitals that progress to ulcers; primary infections can cause systemic symptoms and painful inguinal lymphadenopathy; HSV can invade and lie latent in sacral DRG pts are at risk for viral reactivation and recurrent genital lesions
Infectious genital ulcers
Neisseria meningitidis
can cause sepsis and rapid circulatory collapse in previously healthy young individuals; lipo-oligosaccharide, a virulence factor in the pathogen’s outer membrane, is the major underlying cause of disease severity
Toxoplasma encephalitis
Toxoplasma gondii is an intracellular parasite that is typically transmitted to humans after accidental infestation of contaminated cat feces; most are symptomatic however organism can establish a latent infection that can reactivate in severe immunocompromised particularly AIDs; pt usually develop encephalitis w multiple ring-enhancing lesions
multiple ring-enhancing lesions
Pts w HIV are often unaware of infection and come to clinical attention due to an AIDs-defining illness; the presence of multiple ring-enhancing lesions in a pt with AIDs most likely indicates toxoplasmosis
Cryptococcus neoformans
round/oval yeast w thick polysaccharide capsule; it is a common cause meningoencephalitis in pts w untreated AIDs; yeast can frequently be visualized in the CSF by India ink or silver stain
Tetanus
caused by infection w toxigenic strains of the anaerobic bacterium Clostridium tetani; transmissions typically occurs when spores are inoculated into the skin via a puncture wound; toxin spreads in a retrograde fashion through the LMNs in the SC
Wet mount shows clue cells
Bacterial vaginosis; characterized by thin, gray-whitish malodorous vaginal discharge; clue cells (squamous epithelial cells w adherent bacteria)
frequent causes of osteomyelitis
hematogenous osteomyelitis
predominately a disease of children that affects long bones; staph aureus is implicated in most cases secondary to a bacteremic event; strep pyogenes is the 2nd most common
Pathogensis of rabies
virus replicates locally in muscle tissue for several days or weeks before spreading in a retrograde fashion through the peripheral nerve axons to the CNS
Transmission of cryptococcus neoformans
found primarily in soil contaminated by bird droppings; inhalation of the pathogen into the lungs leads to asymptomatic primary infection usually followed by life-long latent infection; immunocompromised (AIDS pts) are at high risk for reactivation w spread to CNS
Tx of cryptococcus meningitis
amphotericin B and flucytosine is required first followed by long-term fluconazole maintenance therapy
Guillain-Barré syndrome
represents a group of immune-mediated polyneuropathies that are thought to be caused by molecular mimicry, leading to demyelination of the peripheral nerves; 1/3rd cases are preceded by *Campylobacter jejuni infection
Congenital rubella syndrome
classic triad: cataracts, sensorineural hearing loss and patent ductus arteriosus; prevention consists of maternal preconception immunization with the live attenuated rubella vaccine
HSV encephalitis
HSV1 encephalitis is a fatal complication from primary infection or reactivation of latent dz; nervous system invasion leads to necrosis of the *temporal lobe which can result in aphasia and personality changes in addition to classic features of encephalitis (HA, fever, altered mental status and seizure)
Septic abortion
symptoms of fever, abdominal pain, uterine tenderness, and/or malodorous discharge after pregnancy termination; common pathogens include Enterobacteriacae, group A Strep and Staph aureus; tx involves urgent surgical evacuation ad broad-spectrum antibiotics
MOA of bacterial toxins
Anaerobic bacteria
although oxygen is relatively toxic to anaerobic organisms, some can tolerate oxygen exposure due to the expression of enzymes (ex: superoxide dismutase, catalase, peroxidase) that neutralize toxic oxygen byproducts
Staph epidermidis
Histoplasmosis capsulatum
a dimorphic fungus that exists as a small, ovoid yeast at tissue temperatures; it replicates within macrophages and spreads through the lymphatic and reticuloendothelial system; immunocompetent pts usually have an asymptomatic pulmonary infection, but those who are immunocompromised can develop disseminated disease of the liver, spleen and bone marrow
