MMSC438 TEST PAPER QUESTIONS AND
SOLUTIONS EXPERT VERIFIED STUDY
CONTENT
●● Distinguishing contaminants from true pathogens
Answer: Contaminants are often skin flora or environmental organisms
present in small numbers, isolated only once, or inconsistent with
clinical presentation.
●● Common contaminants for skin specimens
Answer: Skin: coagulase-negative staph, Corynebacterium spp.
●● Common contaminants for respiratory specimens
Answer: Respiratory: oral streptococci, Neisseria spp.
●● Common contaminants for urine specimens
Answer: Urine: Lactobacillus, skin flora.
●● Common contaminants for wound specimens
Answer: Wounds: skin flora or environmental bacteria.
●● Common pathogens isolated from skin specimens
,Answer: Skin: S. aureus, S. pyogenes.
●● Common pathogens isolated from urine specimens
Answer: Urine: E. coli, Klebsiella spp.
●● Common pathogens isolated from respiratory specimens
Answer: Respiratory: S. pneumoniae, H. influenzae.
●● Common pathogens isolated from wound specimens
Answer: Wounds: S. aureus, P. aeruginosa.
●● Common pathogens isolated from blood specimens
Answer: Blood: S. aureus, E. coli, Enterococcus spp.
●● Effective laboratory approach for diagnosing infections
Answer: Collect aspirates or biopsy aseptically; perform Gram stain;
culture aerobically and anaerobically; identify organisms via
biochemical tests, MALDI-TOF, or PCR as indicated.
●● Evaluating specimen collection and transport
Answer: Check for sterile container use, proper labeling, correct
transport temperature, minimal delay, and sample integrity; reject
improperly collected or contaminated specimens.
, ●● Using case history data to indicate infectious agent
Answer: Correlate patient symptoms, exposure history, and lab findings
(culture results, Gram stain morphology, antigen/antibody tests) to
identify the most likely pathogen.
●● Defense mechanisms of the skin
Answer: Intact epidermis, keratinized layer, acidic pH, low moisture,
normal microbiota, antimicrobial peptides, and immune cells in the
dermis.
●● Pathogenesis of skin infections
Answer: Microorganisms enter via breaks or hair follicles, evade
immune defenses, produce toxins or enzymes, multiply locally, and
induce inflammation; some can disseminate systemically.
●● Etiologic agents of impetigo
Answer: Impetigo: nonbullous - S. pyogenes; bullous - S. aureus.
●● Etiologic agents of erysipelas
Answer: Erysipelas: S. pyogenes (Group A Streptococcus).
●● S. pyogenes
SOLUTIONS EXPERT VERIFIED STUDY
CONTENT
●● Distinguishing contaminants from true pathogens
Answer: Contaminants are often skin flora or environmental organisms
present in small numbers, isolated only once, or inconsistent with
clinical presentation.
●● Common contaminants for skin specimens
Answer: Skin: coagulase-negative staph, Corynebacterium spp.
●● Common contaminants for respiratory specimens
Answer: Respiratory: oral streptococci, Neisseria spp.
●● Common contaminants for urine specimens
Answer: Urine: Lactobacillus, skin flora.
●● Common contaminants for wound specimens
Answer: Wounds: skin flora or environmental bacteria.
●● Common pathogens isolated from skin specimens
,Answer: Skin: S. aureus, S. pyogenes.
●● Common pathogens isolated from urine specimens
Answer: Urine: E. coli, Klebsiella spp.
●● Common pathogens isolated from respiratory specimens
Answer: Respiratory: S. pneumoniae, H. influenzae.
●● Common pathogens isolated from wound specimens
Answer: Wounds: S. aureus, P. aeruginosa.
●● Common pathogens isolated from blood specimens
Answer: Blood: S. aureus, E. coli, Enterococcus spp.
●● Effective laboratory approach for diagnosing infections
Answer: Collect aspirates or biopsy aseptically; perform Gram stain;
culture aerobically and anaerobically; identify organisms via
biochemical tests, MALDI-TOF, or PCR as indicated.
●● Evaluating specimen collection and transport
Answer: Check for sterile container use, proper labeling, correct
transport temperature, minimal delay, and sample integrity; reject
improperly collected or contaminated specimens.
, ●● Using case history data to indicate infectious agent
Answer: Correlate patient symptoms, exposure history, and lab findings
(culture results, Gram stain morphology, antigen/antibody tests) to
identify the most likely pathogen.
●● Defense mechanisms of the skin
Answer: Intact epidermis, keratinized layer, acidic pH, low moisture,
normal microbiota, antimicrobial peptides, and immune cells in the
dermis.
●● Pathogenesis of skin infections
Answer: Microorganisms enter via breaks or hair follicles, evade
immune defenses, produce toxins or enzymes, multiply locally, and
induce inflammation; some can disseminate systemically.
●● Etiologic agents of impetigo
Answer: Impetigo: nonbullous - S. pyogenes; bullous - S. aureus.
●● Etiologic agents of erysipelas
Answer: Erysipelas: S. pyogenes (Group A Streptococcus).
●● S. pyogenes
