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ABPath Medical Microbiology study materials
ABPath Medical Microbiology study resources

ABPath Medical Microbiology practice questions

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Question 1Medical microbiology administrative and safety practices

Which biosafety level is appropriate for routine work with clinical specimens that may contain organisms such as Salmonella or Candida species?

  1. Biosafety level 4
  2. Biosafety level 2 Correct answer.
  3. Biosafety level 3
  4. Biosafety level 1

Explanation

BSL-2 applies to work with agents of moderate hazard that are associated with human disease and are treatable, such as most routine bacterial and fungal pathogens. Standard precautions plus restricted access and biosafety cabinets for aerosol-generating work define BSL-2.

Question 2Medical microbiology administrative and safety practices

A laboratory is processing a sputum specimen for suspected Mycobacterium tuberculosis. Which combination of engineering control and respiratory protection is recommended?

  1. Laminar flow hood with no respirator
  2. Fume hood with a cloth mask
  3. Biosafety cabinet with an N95 respirator Correct answer.
  4. Open bench work with a surgical mask

Explanation

M. tuberculosis is transmitted by the aerosol route, so manipulations should be performed in a biosafety cabinet and staff should wear respiratory protection fitted to N95 or higher. This corresponds to BSL-3 practices for aerosol-generating procedures.

Question 3Medical microbiology administrative and safety practices

Which of the following is the primary purpose of a biological safety cabinet in the clinical microbiology laboratory?

  1. To incubate cultures at controlled temperature
  2. To protect the worker and environment from aerosols Correct answer.
  3. To filter water used in reagent preparation
  4. To sterilize instruments between uses

Explanation

A biological safety cabinet uses HEPA-filtered airflow to contain aerosols and protect the operator and the environment. It is a containment device, not a sterilization or incubation instrument.

Question 4Medical microbiology administrative and safety practices

A used needle must be discarded after blood collection. What is the correct practice?

  1. Place directly into a puncture-resistant sharps container without recapping Correct answer.
  2. Recap with two hands and discard in a regular waste bin
  3. Recap with one hand and place in a sharps container
  4. Break the needle from the syringe and discard in biohazard bag

Explanation

Needles should never be recapped, bent, or broken; they are placed immediately into a rigid, puncture-resistant sharps container. This practice reduces the risk of needlestick injury and bloodborne pathogen exposure.

Question 5Medical microbiology administrative and safety practices

After a needlestick injury from a contaminated needle, what is the recommended first action?

  1. Wait for symptoms before seeking evaluation
  2. Apply a tight tourniquet above the injury
  3. Scrub the wound with bleach
  4. Wash the site with soap and water and report immediately Correct answer.

Explanation

Immediate wound care with soap and water, followed by prompt reporting and post-exposure evaluation, is the standard response to a needlestick. Antiretroviral or other prophylaxis is time-sensitive, so delay is inappropriate.

Question 6Medical microbiology administrative and safety practices

Which of the following best describes the appropriate use of gloves in the microbiology laboratory?

  1. Gloves should be worn only when handling cultures, not specimens
  2. Gloves replace the need for hand hygiene
  3. One pair of gloves may be worn for an entire shift
  4. Gloves should be changed between patient specimens Correct answer.

Explanation

Gloves are single-use personal protective equipment that must be changed between patient specimens and whenever torn or contaminated. Hand hygiene is still required after glove removal.

Question 7Medical microbiology administrative and safety practices

A specimen container arrives in the laboratory leaking and visibly contaminated on the outside. What is the most appropriate action?

  1. Open the container and process the specimen immediately
  2. Refuse the specimen and notify the sender per policy Correct answer.
  3. Place the container on the bench for later handling
  4. Wipe the outside with a dry paper towel and process

Explanation

Leaking or externally contaminated specimens pose an exposure risk and are rejected according to laboratory policy, with notification of the submitting site. Processing them risks contamination of the work area and staff.

Question 8Medical microbiology administrative and safety practices

Which statement correctly describes the standard for hand hygiene in the laboratory?

  1. Gloves eliminate the need for hand hygiene during the shift
  2. Handwashing with soap and water is required after visible contamination Correct answer.
  3. Hand hygiene is needed only before leaving the laboratory
  4. Alcohol-based rub is preferred when hands are visibly soiled

Explanation

When hands are visibly soiled or contaminated with proteinaceous material, washing with soap and water is required; alcohol rubs are used when hands are not visibly soiled. Hand hygiene is performed at multiple points, not only at exit.

Question 9Medical microbiology administrative and safety practices

Which of the following is the correct method for decontaminating a work surface after a spill of a potentially infectious specimen?

  1. Cover with paper and leave overnight
  2. Rinse with water only
  3. Apply fresh 1:10 dilution of household bleach, allow contact time, then wipe Correct answer.
  4. Wipe with 70% alcohol for one second

Explanation

A freshly prepared 1:10 dilution of household bleach (approximately 0.5% sodium hypochlorite) with adequate contact time is the standard for decontaminating blood or body fluid spills. The area is then cleaned and the waste disposed of as biohazardous.

Question 10Medical microbiology administrative and safety practices

Which of the following is a required component of a laboratory chemical hygiene plan?

  1. A schedule of staff vacations
  2. Patient billing records
  3. A list of employee home addresses
  4. Procedures for safe use and storage of hazardous chemicals Correct answer.

Explanation

A chemical hygiene plan documents safe handling, storage, and emergency procedures for hazardous chemicals under occupational safety rules. It does not include personal employee information or unrelated administrative records.

Question 11Medical microbiology administrative and safety practices

A laboratory worker is exposed to a splash of blood in the eyes. What should be done first?

  1. Close the eyes and rest for 30 minutes
  2. Apply antibiotic ointment to the eye
  3. Wait to see whether redness develops
  4. Flush the eyes at an eyewash station for at least 15 minutes Correct answer.

Explanation

Immediate irrigation with water or saline at an eyewash station for at least 15 minutes is the first step after a mucous membrane exposure. The exposure is then reported for post-exposure evaluation.

Question 12Medical microbiology administrative and safety practices

Which of the following best describes the purpose of an autoclave in the microbiology laboratory?

  1. To sterilize materials using pressurized steam Correct answer.
  2. To filter particulates from air
  3. To disinfect surfaces with ultraviolet light
  4. To incubate anaerobic cultures

Explanation

Autoclaves sterilize by exposure to saturated steam under pressure at temperatures typically around 121°C. This inactivates microorganisms, including spores, on instruments and waste.

Question 13Medical microbiology administrative and safety practices

Which of the following is an appropriate indicator of autoclave effectiveness?

  1. Biological indicator containing Geobacillus stearothermophilus spores Correct answer.
  2. Recording the cycle start time
  3. Visual inspection of the load only
  4. Color change of the autoclave tape alone

Explanation

Biological indicators using heat-resistant spores such as Geobacillus stearothermophilus verify that the sterilization cycle achieved microbial kill. Chemical and physical indicators are useful but do not directly demonstrate spore inactivation.

Question 14Medical microbiology administrative and safety practices

A laboratory is planning to introduce a new molecular assay for a respiratory pathogen. Which is the most appropriate first step in the pre-analytical planning process?

  1. Begin testing patient specimens
  2. Order additional reagents
  3. Write a standard operating procedure and train staff Correct answer.
  4. Validate the assay against a reference method

Explanation

Before implementation, a written standard operating procedure and documented staff training establish consistent, safe performance. Validation and verification follow, and patient testing begins only after these steps are complete.

Question 15Medical microbiology administrative and safety practices

Which of the following is the primary purpose of proficiency testing in a clinical microbiology laboratory?

  1. To reduce the number of specimens received
  2. To assess laboratory performance against peer laboratories Correct answer.
  3. To evaluate individual staff salaries
  4. To replace internal quality control

Explanation

Proficiency testing uses unknown specimens to compare a laboratory's results with those of peer laboratories and reference values. It is an external quality assessment tool and does not replace daily internal quality control.

Question 16Medical microbiology administrative and safety practices

A laboratory reports a result that is later found to be erroneous. According to quality management principles, which action is most appropriate?

  1. Document the event and conduct a root cause analysis Correct answer.
  2. Ignore the error if the patient was not harmed
  3. Reassign the technologist without investigation
  4. Discard the record to avoid confusion

Explanation

Quality management requires documenting errors and investigating root causes to prevent recurrence, even when no harm occurred. Corrective action follows the analysis.

Question 17Medical microbiology administrative and safety practices

Which statement best describes the role of the clinical laboratory in public health reporting?

  1. Laboratories may report only aggregate annual data
  2. Reporting is optional for all organisms
  3. Certain reportable diseases must be reported to public health authorities Correct answer.
  4. Reporting is limited to viral pathogens

Explanation

Laws require laboratories to report specified diseases and organisms to public health authorities to enable surveillance and outbreak response. Reporting obligations apply to many bacterial, viral, and other agents, not just viruses.

Question 18Medical microbiology administrative and safety practices

A technologist is asked to transport a Category B infectious substance. Which packaging is appropriate?

  1. A single plastic bag with the specimen
  2. A glass jar sealed with tape
  3. Triple packaging with absorbent material and proper labeling Correct answer.
  4. A cardboard box with no absorbent material

Explanation

Category B infectious substances require triple packaging: a primary leakproof container, absorbent material, and a rigid secondary package with correct labeling. This protects handlers and the environment during transport.

Question 19Medical microbiology administrative and safety practices

Which of the following best describes the correct practice for disposing of cultures of a bacterial pathogen after work is complete?

  1. Decontaminate by autoclaving before disposal Correct answer.
  2. Pour down the sink with running water
  3. Discard in regular trash
  4. Store indefinitely in the refrigerator

Explanation

Cultures and contaminated materials are decontaminated by autoclaving or another validated method before disposal. This prevents release of viable pathogens into the environment.

Question 20Medical microbiology administrative and safety practices

A new employee begins work in a BSL-2 laboratory. Which of the following is the most appropriate initial safety requirement?

  1. Immediate assignment to BSL-3 work
  2. Independent handling of all specimens without supervision
  3. Waiver of training because of prior experience
  4. Completion of documented biosafety training before handling specimens Correct answer.

Explanation

Personnel must complete documented biosafety training before working with infectious materials, regardless of prior experience. Training covers practices, PPE, and emergency procedures.

Question 21Medical microbiology administrative and safety practices

Which of the following is the primary reason for restricting access to the microbiology laboratory?

  1. To limit exposure of unauthorized persons to infectious agents Correct answer.
  2. To comply with fire codes only
  3. To reduce energy costs
  4. To protect proprietary equipment

Explanation

Access is restricted to trained personnel to minimize the risk of exposure to infectious agents and to maintain containment. This is a core element of biosafety practice.

Question 22Medical microbiology administrative and safety practices

A laboratory receives a request to perform a test for which it has no validated procedure or reference. What is the most appropriate response?

  1. Refer the specimen to a laboratory that offers the validated test Correct answer.
  2. Perform the test using a published protocol without validation
  3. Delay the result indefinitely
  4. Report an estimated result

Explanation

Laboratories should perform only tests they have validated or verified; otherwise, referral to a qualified laboratory is appropriate. Reporting unvalidated results risks patient harm.

Question 23Medical microbiology administrative and safety practices

Which of the following best describes the correct handling of a centrifuge tube that breaks during operation in a BSL-2 laboratory?

  1. Leave the centrifuge closed and continue other work
  2. Spray the closed centrifuge with water and restart
  3. Open the centrifuge immediately and remove the debris by hand
  4. Wait an appropriate time for aerosols to settle, then decontaminate with PPE Correct answer.

Explanation

After a breakage, the centrifuge should remain closed for an appropriate time to allow aerosols to settle, then be opened and decontaminated while wearing appropriate PPE. Immediate opening releases aerosols.

Question 24Quality control and infection prevention

Which statement correctly describes the purpose of a biological safety cabinet in the clinical microbiology laboratory?

  1. It provides directed airflow and HEPA filtration to protect the worker, the product, and the environment from aerosols. Correct answer.
  2. It is designed only to protect the culture from airborne contamination and not the operator.
  3. It maintains a positive-pressure, unfiltered airflow that pushes contaminants away from the sample.
  4. It uses ultraviolet light as the primary barrier to sterilize all surfaces during work.

Explanation

A Class II biological safety cabinet combines inward airflow with HEPA-filtered supply and exhaust air to protect the operator, the sample, and the environment. UV lamps are adjuncts for surface decontamination between uses and never replace airflow containment during work. Protection of both product and personnel is the defining function, so a cabinet designed only for product protection is not a biosafety cabinet.

Question 25Quality control and infection prevention

A laboratory technician sustains a needlestick with a contaminated needle. Which action should be taken first?

  1. Apply a tight tourniquet above the injury to limit venous spread.
  2. Complete the incident report before doing anything else.
  3. Wash the wound with soap and water and flush the site, then report and seek post-exposure evaluation. Correct answer.
  4. Wait 24 hours to see whether symptoms develop before reporting.

Explanation

Immediate first aid-washing the site with soap and water and flushing mucous membranes-is followed promptly by reporting and post-exposure prophylaxis evaluation. Delaying evaluation forfeits the window in which prophylaxis for bloodborne pathogens is most effective. Documentation is important but follows first aid and reporting.

Question 26Quality control and infection prevention

Which concentration of sodium hypochlorite is commonly recommended for decontaminating blood spills on hard surfaces?

  1. 5% (50,000 ppm) available chlorine
  2. 0.05% (500 ppm) available chlorine
  3. 0.5% (5000 ppm) available chlorine Correct answer.
  4. 0.005% (50 ppm) available chlorine

Explanation

A 1:10 dilution of household bleach yields approximately 0.5% (5000 ppm) available chlorine, which is the standard for blood and body-fluid spills. Higher concentrations increase corrosiveness and irritant fumes without added benefit, while much lower concentrations are inadequate for gross contamination.

Question 27Quality control and infection prevention

A spore strip used to monitor a steam autoclave shows growth after incubation. What is the most appropriate interpretation?

  1. The result is irrelevant because chemical indicators are the definitive measure of sterilization.
  2. Growth indicates the sterilization cycle failed, so the load must not be released and the sterilizer should be investigated. Correct answer.
  3. The strip was probably defective, so the load can be released.
  4. Growth is expected because spore strips always grow after autoclaving.

Explanation

Biological indicators containing Geobacillus stearothermophilus spores are the most reliable verification of steam sterilization; growth means the cycle did not achieve sterilization. The affected load must be held, and the sterilizer should be evaluated and requalified before reuse. Chemical indicators are process monitors and do not substitute for biological verification.

Question 28Quality control and infection prevention

Which practice is required when handling specimens in the microbiology laboratory under standard precautions?

  1. Treat all blood and body fluids as potentially infectious regardless of the patient's known diagnosis. Correct answer.
  2. Disinfect gloved hands with alcohol instead of washing between patients.
  3. Recap needles using one hand before discarding them into the sharps container.
  4. Wear gloves only when the patient is known to have a bloodborne pathogen.

Explanation

Standard precautions apply universally, treating all blood and body fluids as infectious because a patient's infectious status is often unknown. Gloves are worn for anticipated contact with any specimen, and needles are never recapped. Hand hygiene is performed after glove removal, not by disinfecting gloves for reuse.

Question 29Quality control and infection prevention

A culture of a multidrug-resistant organism is spilled inside a biosafety cabinet. Which sequence best reflects appropriate spill response?

  1. Keep the cabinet running, cover the spill with absorbent material and disinfectant, allow contact time, then clean from the edges inward and disinfect the surface. Correct answer.
  2. Spray the spill with disinfectant and immediately wipe it dry with a paper towel.
  3. Wipe the spill outward toward the front grille and then resume work without further disinfection.
  4. Immediately turn off the cabinet and open the sash to ventilate the workspace.

Explanation

The cabinet remains operating to maintain containment while the spill is covered with absorbent material and flooded with an appropriate disinfectant for the required contact time. Cleaning proceeds from the periphery toward the center to avoid spreading contamination, followed by a final surface disinfection. Turning off airflow or wiping outward spreads contamination.

Question 30Quality control and infection prevention

Which of the following is the primary purpose of an antimicrobial susceptibility testing quality control strain such as E. coli ATCC 25922?

  1. To calibrate the spectrophotometer used for McFarland standards.
  2. To verify that the medium, reagents, and testing conditions are performing within established limits. Correct answer.
  3. To serve as a positive patient isolate for reporting to clinicians.
  4. To determine the breakpoints used for interpreting zone diameters.

Explanation

Reference QC strains with known susceptibility patterns verify that reagents, media, discs, and technique are working correctly, so results on patient isolates can be trusted. They are not reported as patient results and do not set interpretive breakpoints, which come from consensus standards. Their role is to detect systematic error in the test system.

Question 31Quality control and infection prevention

A new lot of Mueller-Hinton agar is placed in service. When must QC testing with reference strains be performed?

  1. Before the lot is used for patient testing, verifying performance within acceptable limits. Correct answer.
  2. Only when the laboratory changes its disc supplier.
  3. Only after a patient isolate gives an unexpected result.
  4. Once per year regardless of lot changes.

Explanation

Each new lot or shipment of medium must be checked with appropriate QC organisms before being used for patient isolates, confirming that performance falls within acceptable ranges. This detects lot-to-lot variation in factors such as pH, cation content, and thymidine levels. Periodic or reactive testing alone would allow a defective lot to generate erroneous results.

Question 32Quality control and infection prevention

Which statement best describes the role of a chemical indicator (such as an autoclave tape or internal strip) in sterilization monitoring?

  1. It proves that all microorganisms, including spores, have been killed.
  2. It replaces the need for biological indicators in routine practice.
  3. It shows that the physical conditions of the process were met at the location of the indicator. Correct answer.
  4. It measures the bioburden of the items being sterilized.

Explanation

Chemical indicators change in response to parameters such as temperature, time, or steam exposure and confirm that process conditions reached the indicator's location. They are process monitors and cannot by themselves prove sterility, which requires biological indicators. They complement, rather than replace, biological and physical monitoring.

Question 33Quality control and infection prevention

A laboratory reports an elevated rate of contaminated blood culture sets. Which pre-analytical practice most directly reduces this contamination?

  1. Increasing the volume of blood collected per bottle.
  2. Disinfecting the bottle septa with alcohol and allowing them to dry before inoculation. Correct answer.
  3. Delaying incubation of the bottles until the end of the shift.
  4. Collecting the specimen from an existing intravenous line without additional preparation.

Explanation

Contamination most often arises from skin flora introduced at collection, so proper skin antisepsis and disinfection of the bottle septum with an alcohol-based agent, allowed to dry, are key. Collecting through existing lines and delaying incubation increase contamination and reduce recovery. Blood volume affects sensitivity, not contamination rate.

Question 34Quality control and infection prevention

Which of the following best describes the correct use of a Class II biological safety cabinet with respect to airflow and work practices?

  1. Large equipment should be stored inside the cabinet permanently to save bench space.
  2. Materials should be placed over the front air grille to keep the workspace organized.
  3. Work should be performed at least several inches inside the front edge, with minimal rapid movements and no blocking of the grilles. Correct answer.
  4. The sash should be fully raised during work to allow easy access.

Explanation

Working well inside the cabinet and keeping the front and rear grilles unobstructed preserves the airflow curtain that protects the operator and product. Rapid movements disrupt airflow, and the sash must be at or below the certified operating height. Blocking grilles or storing equipment inside compromises containment.

Question 35Quality control and infection prevention

Which of the following is the most appropriate method to verify that an autoclave has reached the required temperature and pressure during a cycle?

  1. Confirming that the door seal is intact before starting.
  2. Reviewing the physical parameters recorded by the sterilizer's gauges and printout. Correct answer.
  3. Checking that the autoclave tape changed color on the outside of the pack.
  4. Observing that the packs appear dry after the cycle.

Explanation

Physical monitoring through time, temperature, and pressure records confirms that the sterilizer achieved and held the specified parameters. External chemical tape only indicates exposure at the surface, and dryness or seal integrity are separate observations. Physical records are one of the three complementary monitoring methods along with chemical and biological indicators.

Question 36Quality control and infection prevention

A laboratory uses a broth microdilution panel and the positive-growth control well fails to show growth. What is the most likely interpretation?

  1. The organism is highly susceptible to all agents tested.
  2. The organism is a fastidious species that always yields valid MICs.
  3. The panel has expired but results may still be used.
  4. The test is invalid because the inoculum or medium did not support growth, so results cannot be reported. Correct answer.

Explanation

The growth control well must show turbidity to confirm that the inoculum was viable and the medium supported growth. Failure of the control invalidates the run because low MICs could reflect inadequate growth rather than true susceptibility. The test should be repeated with a verified inoculum.

Question 37Quality control and infection prevention

Which of the following best describes the principle of aseptic technique when subculturing a broth culture?

  1. Work with the tube opening pointed upward and the loop held high above the flame.
  2. Hold the tube caps in the palm of the hand while the tube is open to save time.
  3. Set the tube caps down on the bench top while transferring the inoculum.
  4. Flame the loop, allow it to cool near the flame, and work close to the flame with brief exposure of the tube openings. Correct answer.

Explanation

Aseptic transfer relies on sterilizing the loop, allowing it to cool, working near the flame, and minimizing the time containers are open to the air. Caps should be held in the hand and never placed on the bench, and manipulations are done close to the flame to reduce airborne contamination. These practices protect both the culture and the worker.

Question 38Quality control and infection prevention

Which of the following is an example of an engineering control that reduces laboratory-acquired infection risk?

  1. A training session on hand hygiene.
  2. A sign on the door restricting laboratory access.
  3. A sealed centrifuge with safety cups or a rotor lid. Correct answer.
  4. A written standard operating procedure for specimen handling.

Explanation

Engineering controls are physical devices or design features that remove or isolate a hazard, such as sealed centrifuge safety cups that contain aerosols. Procedures, training, and signage are administrative or work-practice controls. The hierarchy of controls places engineering controls above administrative measures because they do not depend on individual behavior.

Question 39Quality control and infection prevention

A laboratory is preparing to culture a specimen suspected of containing Mycobacterium tuberculosis. Which precaution level and practice are appropriate?

  1. Standard precautions only, performed on an open bench.
  2. Airborne precautions with work performed in a certified biological safety cabinet and appropriate respiratory protection. Correct answer.
  3. Contact precautions with gown and gloves but no respiratory protection.
  4. Droplet precautions with the specimen handled at the bench using a face shield.

Explanation

M. tuberculosis is transmitted by airborne droplet nuclei, so manipulations that generate aerosols must be done in a biological safety cabinet with airborne precautions and fitted respiratory protection. Standard or droplet precautions alone do not address airborne transmission. Contact precautions address surface contamination rather than inhalation risk.

Question 40Quality control and infection prevention

In disk diffusion susceptibility testing, which factor most directly affects the accuracy of zone diameter measurements?

  1. The brand name printed on the disk dispenser.
  2. The time of day the plate is read.
  3. The color of the colony used to prepare the inoculum.
  4. The depth of the agar in the plate and the density of the standardized inoculum. Correct answer.

Explanation

Zone diameters depend on standardized conditions, including agar depth (approximately 4 mm) and a 0.5 McFarland inoculum, because these govern diffusion and growth. Deviations in agar depth or inoculum density shift zones and can cause misclassification. Colony color and dispenser branding do not affect zone size.

Question 41Quality control and infection prevention

Which of the following best describes the appropriate action when a laboratory's hand hygiene compliance audits show poor performance?

  1. Reduce the frequency of audits to avoid discouraging staff.
  2. Provide targeted education, ensure accessible supplies, and re-audit to measure improvement. Correct answer.
  3. Ignore the data because hand hygiene is a personal matter.
  4. Discipline all staff regardless of individual performance.

Explanation

Improving hand hygiene requires a multimodal approach: education, removing barriers such as poorly placed dispensers, feedback, and repeated measurement. Auditing without action or punitive blanket measures does not address the underlying causes. Re-auditing confirms whether interventions worked.

Question 42Quality control and infection prevention

Which statement correctly describes the difference between disinfection and sterilization?

  1. Sterilization is only required for items that contact intact skin.
  2. Disinfection is always performed with steam under pressure.
  3. Disinfection kills all microbial life including high numbers of bacterial spores.
  4. Sterilization destroys all microbial life including bacterial spores, whereas disinfection reduces or eliminates most vegetative organisms but not necessarily spores. Correct answer.

Explanation

Sterilization is a validated process that destroys all microorganisms including spores, while disinfection reduces vegetative organisms and may be high-level but is not sporicidal in all forms. Items contacting sterile body sites require sterilization, whereas intact-skin contact needs only low-level disinfection. Steam under pressure is one sterilization method, not a definition of disinfection.

Question 43Quality control and infection prevention

A laboratory's proficiency testing (PT) result for organism identification is unacceptable. Which of the following is the most appropriate corrective action?

  1. Repeat the same PT challenge until an acceptable result is obtained and report only that.
  2. Investigate the root cause, document corrective action, and monitor subsequent performance. Correct answer.
  3. File the result without review because PT is optional.
  4. Attribute the failure to the PT provider without internal review.

Explanation

Unacceptable PT results require root-cause analysis, documented corrective action, and follow-up monitoring to prevent recurrence. PT is a required external quality assessment, not optional. Repeated testing to obtain a passing result or blaming the provider avoids the underlying problem.

Question 44Quality control and infection prevention

Which of the following best explains why a laboratory performs environmental monitoring of its biological safety cabinets on a defined schedule?

  1. To replace the need for annual cabinet certification.
  2. To determine whether the room's housekeeping staff are cleaning adequately.
  3. To verify that the HEPA filter removes all chemical vapors.
  4. To confirm that the cabinet continues to contain aerosols and maintain airflow within certified specifications. Correct answer.

Explanation

Periodic performance verification confirms that airflow, filter integrity, and containment remain within certified specifications after installation, moves, or repairs. It does not assess housekeeping, and HEPA filters remove particles rather than chemical vapors. Monitoring supports, but does not replace, formal certification by qualified personnel.

Question 45Quality control and infection prevention

Which of the following is the most appropriate method for decontaminating a reusable, heat-sensitive bronchoscope between patients?

  1. Rinsing with tap water and drying with a cloth.
  2. Wiping the exterior with an alcohol swab only.
  3. Sterilization in a gravity displacement autoclave at standard cycle.
  4. High-level disinfection with a validated chemical process after thorough cleaning. Correct answer.

Explanation

Flexible endoscopes are semi-critical devices that require thorough cleaning followed by high-level disinfection with a validated agent, since heat sterilization would damage them. Cleaning is essential because organic material protects organisms from the disinfectant. Surface wiping alone is inadequate for lumened instruments.

Question 46Quality control and infection prevention

A patient is placed under contact precautions for a multidrug-resistant organism. Which practice is most important for preventing transmission in the laboratory?

  1. Disinfecting gloved hands between specimens instead of changing gloves.
  2. Using a surgical mask for all interactions with the specimen.
  3. Placing the specimen in a biohazard bag only after results are reported.
  4. Wearing gloves and a gown for contact with the patient's specimens and performing hand hygiene after removal. Correct answer.

Explanation

Contact precautions target transmission via direct and indirect contact, so gloves and gown are worn for contact with the patient or contaminated items, followed by hand hygiene after removal. Masks address respiratory transmission, and disinfecting gloves is not a substitute for changing them. Specimens are bagged at collection, not after reporting.

Question 47Taxonomy, classification, and nomenclature

In the Linnaean hierarchy used for bacteria, which taxonomic rank is immediately above genus?

  1. Family Correct answer.
  2. Species
  3. Order
  4. Class

Explanation

The standard hierarchy runs domain, kingdom, phylum, class, order, family, genus, species. The rank directly above genus is family, and family names in bacteriology conventionally end in -aceae.

Question 48Taxonomy, classification, and nomenclature

Which molecule is most widely used as the primary criterion for delimiting bacterial species in modern taxonomy?

  1. Colony pigmentation
  2. Guanine-plus-cytosine content
  3. 16S rRNA gene sequence Correct answer.
  4. Cell wall thickness

Explanation

The 16S rRNA gene is universally present, functionally conserved, and contains variable regions suitable for phylogenetic comparison. It is the standard molecular marker for genus and species-level placement.

Question 49Taxonomy, classification, and nomenclature

Bacteria that lack a cell wall and therefore cannot be classified as Gram-positive or Gram-negative belong to which genus?

  1. Mycoplasma Correct answer.
  2. Bacillus
  3. Neisseria
  4. Clostridium

Explanation

Mycoplasma species are bounded only by a plasma membrane and have no peptidoglycan, so Gram staining does not apply. Their taxonomy places them in the class Mollicutes.

Question 50Taxonomy, classification, and nomenclature

In bacterial nomenclature, what does the designation 'subsp.' indicate?

  1. A genus synonym
  2. A subspecies rank below species Correct answer.
  3. A serological variant
  4. A strain maintained in culture

Explanation

'subsp.' is the abbreviation for subspecies, a rank subordinate to species used when consistent phenotypic or genomic differences justify formal recognition. It is written in lowercase and not italicized.