ABPath Medical Microbiology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

BSL-3 agents

Biosafety level 3 applies to agents that can cause serious disease via aerosol inhalation, such as Mycobacterium tuberculosis; work requires negative-pressure rooms and respiratory protection.

Sentinel laboratory role

A clinical laboratory that recognizes suspicious organisms (e.g., Bacillus anthracis, Francisella tularensis) and refers isolates to a Laboratory Response Network reference laboratory.

Standard precautions

Infection control practices applied to all patients and body fluids regardless of diagnosis, including hand hygiene, gloves, gowns, and safe sharps handling.

Westgard 2-2s rule

Two consecutive QC values fall more than 2 standard deviations on the same side of the mean, indicating systematic error and rejection of the run.

Autoclave biological indicator

Geobacillus stearothermophilus spores are used to verify steam sterilization efficacy; growth indicates sterilization failure.

CLSI M100

Document providing standardized antimicrobial susceptibility testing methods and interpretive breakpoints for bacteria, used to guide reporting of susceptible, intermediate, and resistant results.

Binomial nomenclature rules

The genus is capitalized and the species is lowercase, both italicized; after first mention the genus is abbreviated, as in Escherichia coli then E. coli.

Dimorphic fungi

Fungi that grow as molds at 25 degrees Celsius and as yeasts at 37 degrees Celsius, including Histoplasma, Blastomyces, Coccidioides, and Sporothrix.

16S rRNA sequencing

A molecular method that sequences the bacterial 16S ribosomal RNA gene to establish phylogenetic relationships and identify unknown isolates.

Blood culture collection

Adults should have two to three sets collected from separate sites, each set including aerobic and anaerobic bottles, with adequate volume to improve sensitivity.

Sputum acceptability criteria

A good-quality sputum specimen shows more than 25 polymorphonuclear cells and fewer than 10 squamous epithelial cells per low-power field.

CSF transport caution

Cerebrospinal fluid should not be refrigerated when fastidious organisms such as Neisseria meningitidis or Haemophilus influenzae are suspected; process immediately.

Endotoxin mechanism

Lipopolysaccharide from Gram-negative outer membranes binds TLR4, triggering cytokine release that can cause fever, shock, and disseminated intravascular coagulation.

Superantigen mechanism

Toxins such as TSST-1 cross-link MHC class II with T-cell receptors, causing nonspecific massive T-cell activation and cytokine storm.

Capsule virulence function

A polysaccharide capsule resists phagocytosis, enhancing survival of organisms such as Streptococcus pneumoniae, Klebsiella pneumoniae, and Cryptococcus neoformans.

Aminoglycoside target

Aminoglycosides bind the 30S ribosomal subunit, causing misreading of mRNA and inhibiting protein synthesis; they are bactericidal and require aerobic conditions.

Fluoroquinolone mechanism

Fluoroquinolones inhibit DNA gyrase and topoisomerase IV, blocking DNA replication and causing double-strand breaks in bacteria.

MRSA confirmation

Methicillin resistance is confirmed by cefoxitin disk testing, oxacillin MIC, PBP2a latex agglutination, or detection of the mecA or mecC gene.

MacConkey agar

A selective and differential medium containing bile salts and crystal violet that inhibits Gram-positives and differentiates lactose fermenters (pink) from nonfermenters.

Gram stain sequence

Crystal violet, iodine mordant, alcohol decolorizer, and safranin counterstain; Gram-positive cells retain purple and Gram-negative cells appear pink.

Acid-fast stain principle

Mycolic acid in mycobacterial cell walls retains carbolfuchsin despite acid-alcohol decolorization, so acid-fast bacilli appear red against a blue background.

Chocolate agar

Heated blood agar that releases factors V and X, supporting growth of fastidious organisms such as Haemophilus influenzae and Neisseria species.

MALDI-TOF MS identification

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry identifies organisms by comparing protein mass spectra to reference databases, rapidly and cost-effectively.

NAAT advantages

Nucleic acid amplification tests detect pathogen DNA or RNA with high sensitivity and speed, but cannot distinguish viable from nonviable organisms.

Serology window period

The interval after infection before antibodies become detectable, during which serologic tests may be falsely negative despite active infection.

Stool O&P examination

Microscopic examination of concentrated stool for ova and parasites; multiple specimens on separate days improve sensitivity for intestinal parasites.

Critical value notification

Immediate communication of life-threatening results, such as positive blood cultures or CSF Gram stains, to the responsible clinician to guide urgent therapy.

Antimicrobial de-escalation

Narrowing empirical broad-spectrum therapy to the most targeted effective agent once culture and susceptibility results are available, reducing resistance and toxicity.

Coagulase-negative staphylococcus bacteremia

Isolation from a single blood culture bottle often reflects skin contamination, whereas growth in multiple bottles suggests true bloodstream infection.

Vancomycin therapeutic monitoring

Serum trough or AUC monitoring balances efficacy against nephrotoxicity for vancomycin therapy, especially in serious infections.

Reportable disease reporting

Notifiable conditions must be reported to public health authorities per jurisdiction-specific lists and timeframes to enable surveillance and outbreak control.

Biofilm resistance

Surface-attached microbial communities resist antibiotics and host defenses, complicating infections of catheters and prosthetic devices.