CSFA Microbiology Practice Questions (30 Flashcards)

Staphylococcus aureus is the most likely pathogen. It is a Gram-positive coccus that grows in clusters and is distinguished from other Staphylococci by being coagulase-positive. Primary reservoir: Human nares (nostrils) and skin. Clinical Pearl: S. aureus is the leading cause of SSIs globally. For the CSFA exam, remember that coagulase-positive is the pathognomonic lab finding for S. aureus, while S. epidermidis is coagulase-negative. NBSTSA often tests the distinction between these two in prosthetic joint scenarios.

Pseudomonas aeruginosa. Key biochemical markers for the exam: 1. Gram-negative rod. 2. Non-lactose fermenter (distinguishes it from E. coli/Klebsiella). 3. Oxidase-positive (distinguishes it from the Enterobacteriaceae family). Pseudomonas is a leading cause of HAIs in ventilated patients and is known for its efflux pumps which contribute to multi-drug resistance (MDR). CSFA Relevance: CSFA's must be aware of cross-contamination risks in the OR for patients with pre-existing Pseudomonas colonization.

Yes. OSHA's Bloodborne Pathogens Standard defines Other Potentially Infectious Materials (OPIM) to include synovial, amniotic, cerebrospinal, pleural, pericardial, and peritoneal fluids, along with any fluid visibly contaminated with blood. NBSTSA Tip: Distinguish between OPIM and fluids like sweat, tears, or saliva (unless blood is present), which generally do not carry the same regulatory requirements for universal precautions in the absence of visible blood.

The suction canister. Regulated Medical Waste (Red Bag) is defined by OSHA as waste capable of releasing infectious materials in a liquid or semi-liquid state, or items caked with dried blood that could release it during handling. A blood-tinged sponge that does not drip when squeezed is usually considered non-regulated waste. Clinical Pearl: Over-segregation leads to high costs, but under-segregation is a safety violation. NBSTSA tests the drip, pour, or flake rule.

Organ/Space SSI. Rationale: Because an implant (prosthetic joint) was placed, the surveillance period for SSI extends to 90 days (per CDC/NBSTSA 2026 guidelines). Since the infection involves the joint space (the specific organ/space manipulated during surgery) and not just the skin or fascia, it is an Organ/Space SSI. Key Exam Point: Differentiate Deep Incisional (involving fascia/muscle) from Organ/Space (involving the actual cavity/joint). For NBSTSA, the 90-day window for implants is a high-yield fact.