Infection control practices US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Infection control practices. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Infection control practices US Medical PG Question 1: A 29-year-old man comes to the physician for a routine health maintenance examination. He feels well. He works as a nurse at a local hospital in the city. Three days ago, he had a needlestick injury from a patient whose serology is positive for hepatitis B. He completed the 3-dose regimen of the hepatitis B vaccine 2 years ago. His other immunizations are up-to-date. He appears healthy. Physical examination shows no abnormalities. He is concerned about his risk of being infected with hepatitis B following his needlestick injury. Serum studies show negative results for hepatitis B surface antigen, hepatitis B surface antibody, and hepatitis C antibody. Which of the following is the most appropriate next step in management?
- A. Revaccinate with 3-dose regimen of hepatitis B vaccine
- B. Revaccinate with two doses of hepatitis B vaccine
- C. Administer hepatitis B immunoglobulin
- D. Administer hepatitis B immunoglobulin and 3-dose regimen of hepatitis B vaccine (Correct Answer)
- E. Administer hepatitis B immunoglobulin and single dose hepatitis B vaccine
Infection control practices Explanation: ***Administer hepatitis B immunoglobulin and 3-dose regimen of hepatitis B vaccine***
- This patient had prior vaccination but current serology shows **negative HBsAb**, indicating **non-response** to the vaccine (failure to develop protective antibodies).
- Given exposure to a hepatitis B positive patient, immediate post-exposure prophylaxis with **HBIG** is crucial for passive immunity and immediate protection.
- A **complete 3-dose revaccination series** should be initiated simultaneously, as per **CDC/ACIP guidelines** for vaccine non-responders with occupational exposure [1].
- This provides both immediate passive protection (HBIG) and attempts to establish active immunity through revaccination [1].
*Revaccinate with 3-dose regimen of hepatitis B vaccine*
- While revaccination is necessary due to the non-response, starting a 3-dose regimen alone without **HBIG** would leave the patient vulnerable during the initial period before vaccine response develops.
- After high-risk exposure in a non-responder, both passive (HBIG) and active (vaccine) immunity are required.
*Revaccinate with two doses of hepatitis B vaccine*
- A 2-dose regimen is insufficient; the standard revaccination schedule for non-responders is **3 doses** at 0, 1, and 6 months [1].
- Additionally, this option lacks **HBIG** for immediate protection after the high-risk exposure.
*Administer hepatitis B immunoglobulin*
- **HBIG** alone provides immediate passive immunity, which is crucial given the recent exposure and the patient's non-immune status.
- However, offering only HBIG without initiating active immunization (vaccine series) would leave the patient unprotected once the passive immunity wanes (approximately 3-6 months).
- This approach fails to address the need for long-term protection through revaccination.
*Administer hepatitis B immunoglobulin and single dose hepatitis B vaccine*
- While HBIG is appropriate for immediate protection, giving only a **single dose** of vaccine is inadequate.
- Standard post-exposure management for vaccine non-responders requires initiating a **complete 3-dose revaccination series**, not just one dose [1].
- A single dose would not provide adequate long-term protection for this non-responder.
Infection control practices US Medical PG Question 2: A medical technician is trying to isolate a pathogen from the sputum sample of a patient. The sample is heat fixed to a slide then covered with carbol fuchsin stain and heated again. After washing off the stain with clean water, the slide is covered with 1% sulfuric acid for decolorization. The sample is rinsed again and stained with methylene blue. Microscopic examination shows numerous red, branching filamentous organisms. Which of the following is the most likely isolated pathogen?
- A. Cryptococcus neoformans
- B. Tropheryma whipplei
- C. Nocardia asteroides (Correct Answer)
- D. Rickettsia rickettsii
- E. Staphylococcus aureus
Infection control practices Explanation: ***Nocardia asteroides***
- The described staining procedure is a **modified acid-fast stain**, indicated by the use of **carbol fuchsin**, heating, and decolorization with **weak acid (1% sulfuric acid)**, followed by a counterstain with methylene blue.
- **Nocardia species** are **weakly acid-fast bacteria** that resist decolorization with weak acids (1-3% sulfuric acid), appearing as **red, branching filamentous organisms** under this staining method.
- The **modified acid-fast stain** uses weaker decolorizing agents compared to the standard Ziehl-Neelsen stain, making it suitable for detecting weakly acid-fast organisms like Nocardia.
- Nocardia are aerobic actinomycetes commonly found in soil and can cause pulmonary infections, especially in immunocompromised patients.
*Cryptococcus neoformans*
- This is a **yeast** that is typically identified using an **India ink stain** to visualize its polysaccharide capsule, or through fungal stains like Gomori methenamine silver (GMS).
- It would not appear as acid-fast red branching filaments with the described technique.
*Tropheryma whipplei*
- This bacterium is typically identified by **periodic acid-Schiff (PAS) stain** in tissue biopsies, which highlights its cell wall glycoproteins (appears magenta).
- It is not acid-fast and would not retain the carbol fuchsin after acid decolorization.
*Rickettsia rickettsii*
- This is an **obligate intracellular bacterium** that is difficult to culture and is often diagnosed by **serological tests** or **immunohistochemistry** on skin biopsy specimens.
- It is not acid-fast and would not be detected by this staining technique.
*Staphylococcus aureus*
- This is a **Gram-positive coccus** that would be stained **purple** by a Gram stain as it retains crystal violet.
- It is not acid-fast and would be completely decolorized by sulfuric acid in the described procedure, appearing blue (counterstain color) rather than red.
Infection control practices US Medical PG Question 3: A 57-year-old man comes to the physician because of generalized malaise, yellowish discoloration of the eyes, and pruritus on the back of his hands that worsens when exposed to sunlight for the past several months. He has not seen a physician in 15 years. Physical examination shows scleral icterus and mild jaundice. There is a purpuric rash with several small vesicles and hyperpigmented lesions on the dorsum of both hands. The causal pathogen of this patient's underlying condition was most likely acquired in which of the following ways?
- A. Ingestion of raw shellfish
- B. Inhalation of spores
- C. Needlestick injury (Correct Answer)
- D. Bathing in freshwater
- E. Sexual contact
Infection control practices Explanation: ***Needlestick injury***
- The jaundice, scleral icterus, pruritus, and **purpuric rash worsened by sunlight** (suggesting **Porphyria Cutanea Tarda**) are highly indicative of **chronic Hepatitis C virus infection**.
- **Hepatitis C** is primarily transmitted through **blood-to-blood contact**, with **needlestick injuries** and intravenous drug use being the most common routes.
*Ingestion of raw shellfish*
- **Hepatitis A virus** and **Vibrio vulnificus** can be acquired this way, but they typically cause acute, self-limiting illness or severe sepsis, respectively, not chronic liver disease with porphyria.
- **Hepatitis A** does not lead to chronic hepatitis or the dermatological manifestations described.
*Inhalation of spores*
- **Inhalation of spores** is associated with fungal infections like **histoplasmosis** or **coccidioidomycosis**, which do not typically cause chronic hepatitis, jaundice, pruritus, or porphyria cutanea tarda.
- These infections primarily affect the lungs, though disseminated forms can occur, they do not match the presented symptoms.
*Bathing in freshwater*
- **Bathing in freshwater** can transmit pathogens like **Leptospira** or **Schistosoma**, causing leptospirosis or schistosomiasis, respectively.
- These infections present with different clinical pictures and are not associated with chronic hepatitis, jaundice, or porphyria cutanea tarda.
*Sexual contact*
- While **Hepatitis C** can be transmitted sexually, this route is significantly **less efficient** than blood-to-blood contact.
- **Hepatitis B** is more commonly associated with sexual transmission and can also cause chronic liver disease, but the presence of **Porphyria Cutanea Tarda** is a characteristic extrahepatic manifestation strongly associated with **chronic Hepatitis C infection**.
- Given the clinical presentation, **needlestick injury or intravenous drug use** (blood-borne transmission) is the most likely route of HCV acquisition.
Infection control practices US Medical PG Question 4: A 28-year-old soldier is brought back to a military treatment facility 45 minutes after sustaining injuries in a building fire from a mortar attack. He was trapped inside the building for around 20 minutes. On arrival, he is confused and appears uncomfortable. He has a Glasgow Coma Score of 13. His pulse is 113/min, respirations are 18/min, and blood pressure is 108/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 96%. Examination shows multiple second-degree burns over the chest and bilateral upper extremities and third-degree burns over the face. There are black sediments seen within the nose and mouth. The lungs are clear to auscultation. Cardiac examination shows no abnormalities. The abdomen is soft and nontender. Intravenous fluid resuscitation is begun. Which of the following is the most appropriate next step in management?
- A. Insertion of nasogastric tube and enteral nutrition
- B. Intravenous antibiotic therapy
- C. Intubation and mechanical ventilation (Correct Answer)
- D. Immediate bronchoscopy
- E. Intravenous corticosteroid therapy
Infection control practices Explanation: ***Intubation and mechanical ventilation***
- The patient exhibits several signs of impending **airway compromise** due to **inhalation injury**, including perioral burns, black sediments in the nose and mouth, and being trapped in a fire.
- While current oxygen saturation is 96%, **airway edema** can rapidly worsen, leading to respiratory failure. **Early intubation** is crucial to secure the airway before it becomes obstructed.
*Insertion of nasogastric tube and enteral nutrition*
- A nasogastric tube is often placed in burn patients to decompress the stomach and provide nutritional support, but it is **not the immediate priority** when there is a risk of airway obstruction.
- **Enteral nutrition** is important but should be initiated only after airway control is established and the patient is stable for feeding.
*Intravenous antibiotic therapy*
- **Prophylactic antibiotics** are generally **not recommended** in the immediate management of burn patients unless there is clear evidence of infection, which is not present here.
- Unnecessary antibiotic use can lead to **antibiotic resistance** and fungal infections.
*Immediate bronchoscopy*
- While **bronchoscopy** can confirm the extent of inhalation injury, it is not the primary immediate step. **Securing the airway** through intubation takes precedence over diagnostic procedures when airway compromise is imminent.
- Bronchoscopy can be considered *after* intubation to assess the lower airway for damage and guide further management.
*Intravenous corticosteroid therapy*
- **Corticosteroids** are typically **contraindicated** in the management of inhalation injury because they can **impair immune function** and increase the risk of infection in burn patients.
- Evidence does not support the routine use of corticosteroids to reduce inflammation in inhalation injury, and they may worsen outcomes.
Infection control practices US Medical PG Question 5: The occupational health department at a hospital implements new safety precautions to prevent laboratory-acquired infections. One of the new precautions includes disinfecting the microbiology laboratory benches with 70% ethanol before and after use. This measure is most likely to be effective in preventing the transmission of which of the following viruses?
- A. Hepatitis A virus
- B. Herpes simplex virus (Correct Answer)
- C. Poliovirus
- D. Parvovirus
- E. Polyomavirus
Infection control practices Explanation: ***Herpes simplex virus***
- Herpes simplex virus is an **enveloped virus**, meaning it has a lipid outer layer that is easily disrupted by disinfectants like **70% ethanol**.
- The disruption of its envelope renders the virus inactive and unable to infect host cells, making this a highly effective prevention strategy.
*Hepatitis A virus*
- Hepatitis A virus is a **non-enveloped virus**, making it relatively **resistant to many common disinfectants**, including alcohol-based ones.
- Its robust protein capsid protects its genetic material, requiring stronger disinfection methods than 70% ethanol for inactivation.
*Poliovirus*
- Poliovirus is another **non-enveloped virus** that exhibits significant **resistance to alcohol-based disinfectants** due to its stable protein capsid.
- Effective inactivation typically requires disinfectants with greater germicidal activity, such as chlorine-based solutions.
*Parvovirus*
- Parvovirus is one of the **most resistant non-enveloped viruses** to disinfection, including inactivation by 70% ethanol.
- Its small size and extremely stable capsid make it challenging to eliminate from surfaces, often necessitating harsh chemical treatments.
*Polyomavirus*
- Polyomaviruses are **non-enveloped DNA viruses** that are generally more **resistant to alcohol-based disinfectants** than enveloped viruses.
- Their lack of a lipid envelope provides protection against agents like ethanol that target lipid bilayers.
Infection control practices US Medical PG Question 6: A scientist is studying the mechanisms by which bacteria become resistant to antibiotics. She begins by obtaining a culture of vancomycin-resistant Enterococcus faecalis and conducts replicate plating experiments. In these experiments, colonies are inoculated onto a membrane and smeared on 2 separate plates, 1 containing vancomycin and the other with no antibiotics. She finds that all of the bacterial colonies are vancomycin resistant because they grow on both plates. She then maintains the bacteria in liquid culture without vancomycin while she performs her other studies. Fifteen generations of bacteria later, she conducts replicate plating experiments again and finds that 20% of the colonies are now sensitive to vancomycin. Which of the following mechanisms is the most likely explanation for why these colonies have become vancomycin sensitive?
- A. Point mutation
- B. Gain of function mutation
- C. Viral infection
- D. Plasmid loss (Correct Answer)
- E. Loss of function mutation
Infection control practices Explanation: ***Plasmid loss***
- The initial **vancomycin resistance** in *Enterococcus faecalis* is often mediated by genes located on **plasmids**, which are extrachromosomal DNA.
- In the absence of selective pressure (vancomycin), bacteria that lose the plasmid (and thus the resistance genes) have a **growth advantage** over those that retain the energetically costly plasmid, leading to an increase in sensitive colonies over generations.
*Point mutation*
- A **point mutation** typically involves a change in a single nucleotide and could lead to loss of resistance if it occurred in a gene conferring resistance.
- However, since there was no selective pressure for loss of resistance, it is less likely that 20% of the population would acquire such a specific point mutation to revert resistance.
*Gain of function mutation*
- A **gain of function mutation** would imply that the bacteria acquired a *new* advantageous trait, not the *loss* of resistance.
- This type of mutation would not explain why some colonies became sensitive to vancomycin after the drug was removed.
*Viral infection*
- **Viral infection** (bacteriophages) can transfer genes through transduction or cause bacterial lysis, but it's not the primary mechanism for a widespread reversion of resistance in the absence of antibiotic pressure.
- It would not explain the observed increase in vancomycin-sensitive colonies due to evolutionary pressure.
*Loss of function mutation*
- While a **loss of function mutation** in a gene conferring resistance could lead to sensitivity, it's generally less likely to explain a 20% shift without selective pressure than **plasmid loss**.
- Plasmids are often unstable and are easily lost in the absence of selection, whereas a specific gene mutation causing loss of function would need to arise and become prevalent in the population.
Infection control practices US Medical PG Question 7: A 36-year-old man comes to the physician because of a 2-week history of productive cough, weight loss, and intermittent fever. He recently returned from a 6-month medical deployment to Indonesia. He appears tired. Physical examination shows nontender, enlarged, palpable cervical lymph nodes. An x-ray of the chest shows right-sided hilar lymphadenopathy. A sputum smear shows acid-fast bacilli. A diagnosis of pulmonary tuberculosis is made from PCR testing of the sputum. The patient requests that the physician does not inform anyone of this diagnosis because he is worried about losing his job. Which of the following is the most appropriate initial action by the physician?
- A. Request the patient's permission to discuss the diagnosis with an infectious disease specialist
- B. Assure the patient that his diagnosis will remain confidential
- C. Confirm the diagnosis with a sputum culture
- D. Notify all of the patient's household contacts of the diagnosis
- E. Inform the local public health department of the diagnosis (Correct Answer)
Infection control practices Explanation: ***Inform the local public health department of the diagnosis***
- **Tuberculosis** is a **reportable disease** to public health authorities due to its significant public health implications, including the risk of transmission.
- Physicians have a **legal and ethical obligation** to report such diagnoses to protect the community, even against a patient's wishes for secrecy.
*Request the patient's permission to discuss the diagnosis with an infectious disease specialist*
- While consulting an infectious disease specialist is often beneficial for managing TB, the immediate and most appropriate initial action is related to **public health notification**.
- Delaying notification to seek patient permission first would **compromise public health safety** regarding a reportable disease.
*Assure the patient that his diagnosis will remain confidential*
- This assurance would be **misleading and unethical** because TB is a reportable condition, meaning its confidentiality is necessarily breached for public health purposes.
- Physicians are bound by law to report communicable diseases, which supersedes general confidentiality in this specific context.
*Confirm the diagnosis with a sputum culture*
- The diagnosis of pulmonary tuberculosis has already been established by a **sputum smear showing acid-fast bacilli** and **PCR testing**, which are highly reliable.
- While a sputum culture provides drug susceptibility information, it is not the *initial* most appropriate action regarding the patient's stated concerns about confidentiality in the context of a reportable disease.
*Notify all of the patient's household contacts of the diagnosis*
- While contact tracing is an important part of TB control, it is typically initiated and managed by the **public health department** after notification.
- The physician's primary responsibility is to notify the health department, who then assumes the role of **contact investigation** and management.
Infection control practices US Medical PG Question 8: A 67-year-old man is brought to the emergency department because of severe dyspnea and orthopnea for 6 hours. He has a history of congestive heart disease and an ejection fraction of 40%. The medical history is otherwise unremarkable. He appears confused. At the hospital, his blood pressure is 165/110 mm Hg, the pulse is 135/min, the respirations are 48/min, and the temperature is 36.2°C (97.2°F). Crackles are heard at both lung bases. There is pitting edema from the midtibia to the ankle bilaterally. The patient is intubated and admitted to the critical care unit for mechanical ventilation and treatment. Intravenous morphine, diuretics, and nitroglycerine are initiated. Which of the following is the most effective method to prevent nosocomial infection in this patient?
- A. Nasogastric tube insertion
- B. Suprapubic catheter insertion
- C. Daily oropharynx decontamination with antiseptic agent (Correct Answer)
- D. Daily urinary catheter irrigation with antimicrobial agent
- E. Condom catheter placement
Infection control practices Explanation: ***Daily oropharynx decontamination with antiseptic agent***
- **Oropharyngeal decontamination** helps reduce the bacterial load in the oral cavity, which is crucial for preventing **ventilator-associated pneumonia (VAP)** in intubated patients.
- Regular cleaning with an antiseptic agent disrupts the formation of **biofilms** and the aspiration of pathogenic bacteria into the lower respiratory tract.
*Nasogastric tube insertion*
- While a nasogastric tube can be important for nutrition and medication delivery, it does not directly prevent **nosocomial infections** and can even be a source of infection if not properly managed.
- It does not address the primary risk of pneumonia or other infections related to intubation and critical illness.
*Suprapubic catheter insertion*
- A suprapubic catheter is used for drainage of the bladder, but it is an invasive procedure with its own risks of **urinary tract infections (UTIs)** and is not indicated for preventing nosocomial infections in this patient's primary presentation.
- It is not a standard method to prevent the most common nosocomial infections in an intubated patient in the ICU.
*Daily urinary catheter irrigation with antimicrobial agent*
- Irrigating a urinary catheter daily with an antimicrobial agent is **not recommended** as a routine practice to prevent **catheter-associated urinary tract infections (CAUTIs)**.
- Such irrigation can disrupt the natural flora and potentially lead to **antimicrobial resistance** or further infection by promoting the growth of resistant organisms.
*Condom catheter placement*
- A condom catheter is a non-invasive external device used for urinary incontinence in males, but it's generally **less effective** than indwelling catheters for critical care patients requiring precise fluid output monitoring.
- It does not address the risk of **VAP**, which is a major concern for intubated patients, and may not be feasible or adequate for all bedridden patients in the ICU.
Infection control practices US Medical PG Question 9: A 35-year-old man is brought into the emergency department by emergency medical services with his right hand wrapped in bloody bandages. The patient states that he is a carpenter and was cutting some wood for a home renovation project when he looked away and injured one of his digits with a circular table saw. He states that his index finger was sliced off and is being brought in by his wife. On exam, his vitals are within normal limits and stable, and he is missing part of his second digit on his right hand distal to the proximal interphalangeal joint. How should the digit be transported to the hospital for the best outcome?
- A. In a sterile plastic bag wrapped in saline moistened gauze on ice (Correct Answer)
- B. In a sterile bag of tap water
- C. In the pocket of a coat or a jacket
- D. Wrapped in a towel
- E. In a sterile plastic bag wrapped in saline moistened gauze
Infection control practices Explanation: ***In a sterile plastic bag wrapped in saline moistened gauze on ice***
- The amputated digit should be wrapped in **saline-moistened gauze** to prevent tissue desiccation and then placed in a **sterile plastic bag**.
- This bag should then be placed on **ice** (indirect contact) to cool the tissue and minimize ischemic damage, preserving viability for potential re-implantation.
*In a sterile bag of tap water*
- Placing the digit directly in **tap water** can cause significant cellular damage due to osmotic differences, leading to cell lysis and making re-implantation less successful.
- Tap water is also not sterile, increasing the risk of **infection** for the amputated part.
*In the pocket of a coat or a jacket*
- Transporting the digit in a pocket provides no **temperature control** or **sterility**, leading to rapid tissue degradation and increased risk of bacterial contamination.
- This method offers no protection against **trauma or loss** of the amputated part.
*Wrapped in a towel*
- Wrapping the digit in a towel alone does not provide adequate **sterility** or **moisture**, leading to tissue desiccation and increased contamination risk.
- A towel offers no means of **cooling** the tissue, which is crucial for preserving cell viability.
*In a sterile plastic bag wrapped in saline moistened gauze*
- While wrapping in **saline-moistened gauze** and a sterile bag is a good start, the absence of **cooling** (ice) significantly reduces the time window for successful re-implantation.
- Without cooling, the **metabolic rate** of the tissue remains high, accelerating ischemic damage and tissue death.
Infection control practices US Medical PG Question 10: A 70-year-old woman comes to the physician for the evaluation of loss of urine for the last several months. She loses small amounts of urine without warning after coughing or sneezing. She also sometimes forgets the names of her relatives. She is retired and lives at an assisted-living facility. She has type 2 diabetes mellitus and hypertension. Her older sister recently received a ventriculoperitoneal shunt. She does not smoke or drink alcohol. Medications include metformin and enalapril. Vital signs are within normal limits. She walks without any problems. Sensation to pinprick and light touch is normal. Which of the following is the most likely underlying cause of this patient's symptoms?
- A. Detrusor overactivity
- B. Urethral hypermobility
- C. Decreased cerebrospinal fluid absorption (Correct Answer)
- D. Loss of sphincter control
- E. Bacterial infection of the urinary tract
Infection control practices Explanation: ***Decreased cerebrospinal fluid absorption***
- The patient's symptoms of **urinary incontinence** (losing urine without warning after coughing/sneezing) and **cognitive impairment** (forgetting names of relatives) in an older adult, especially with a family history of **ventriculoperitoneal shunt** (suggesting hydrocephalus), are highly suggestive of **Normal Pressure Hydrocephalus (NPH)**.
- Reduced reabsorption of CSF leads to ventricular enlargement and the classic NPH triad: **gait disturbance**, **urinary incontinence**, and **dementia**.
*Detrusor overactivity*
- This typically presents as **urge incontinence**, characterized by a sudden, strong need to urinate followed by involuntary urine loss, often with large volumes.
- While it causes incontinence, it does not explain the co-occurring **cognitive deficits**.
*Urethral hypermobility*
- This is a common cause of **stress incontinence**, where urine leakage occurs with increased intra-abdominal pressure (e.g., coughing, sneezing).
- However, **urethral hypermobility** does not account for the patient's **cognitive symptoms**.
*Loss of sphincter control*
- This can be a feature of **stress incontinence** or intrinsic sphincter deficiency, leading to urine leakage with exertion.
- Similar to urethral hypermobility, it does not explain the presence of **cognitive decline** in this patient.
*Bacterial infection of the urinary tract*
- A **urinary tract infection (UTI)** can cause new-onset incontinence, dysuria, urgency, and sometimes altered mental status in older adults.
- However, the patient's long-standing symptoms over "several months" and the presence of **memory loss** make a simple UTI less likely as the primary underlying cause; UTIs are typically acute.
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