Epidemiology of Hospital Infections — MCQs
Which infection commonly spreads to newborns through caregivers?
What is the best way to control the MRSA infection in the ward?
Which disease comes under International Surveillance?
Which of the following is true about annual risk of TB (ARI)
Which of the following is the LEAST likely risk factor for developing acute otitis externa?
Most common mode of transmission of nosocomial infection is -
Most common cause of infection caused by intravascular catheter -
Nosocomial infections are diagnosed after how many hours of hospitalization / admission?
Nosocomial infections are diagnosed after how many hours of hospitalization/admission?
Which of the following is true about Extended spectrum beta-lactamases?
Epidemiology of Hospital Infections Indian Medical PG Practice Questions and MCQs
Question 1: Which infection commonly spreads to newborns through caregivers?
- A. Candida parapsilosis (Correct Answer)
- B. Candida albicans
- C. Candida tropicalis
- D. Candida glabrata
Explanation: ***Candida parapsilosis*** - This species is a well-known cause of **nosocomial bloodstream infections** in neonates, particularly in **premature infants** and those with central venous catheters. It is often spread via the hands of **healthcare workers**. - Its ability to form **biofilms on medical devices** (like catheters) further facilitates its transmission and makes it a significant infectious agent in neonatal intensive care units (NICUs). *Candida albicans* - While *Candida albicans* is the **most common Candida species** causing infections in humans, including superficial and invasive candidiasis in neonates, its transmission is less frequently linked to direct caregiver spread in the context of outbreaks compared to *C. parapsilosis*. - Neonatal *C. albicans* infections are often acquired **vertically from the mother** or through endogenous gut colonization. *Candida tropicalis* - *Candida tropicalis* can cause **invasive candidiasis**, especially in immunocompromised patients, but it is less frequently implicated in **outbreaks** attributed to hand-to-patient transmission by caregivers in NICUs than *C. parapsilosis*. - It is often associated with **neutropenia** and broad-spectrum antibiotic use. *Candida glabrata* - *Candida glabrata* is a significant pathogen, particularly in adults and immunocompromised individuals, known for its **fluconazole resistance**. - While it can cause bloodstream infections, it is not typically recognized as a primary cause of **caregiver-spread outbreaks** in newborns to the same extent as *C. parapsilosis*.
Question 2: What is the best way to control the MRSA infection in the ward?
- A. Fumigation of ward frequently
- B. Washing hand before and after attending patients (Correct Answer)
- C. Wearing masks during invasive procedures in ICU
- D. Vancomycin given empirically to all the patients
Explanation: **Washing hand before and after attending patients** - **Hand hygiene** is the single most effective measure in preventing the transmission of **healthcare-associated infections**, including **MRSA**. - **Healthcare workers' hands** are the primary vehicle for spreading pathogens from one patient to another. *Fumigation of ward frequently* - **Fumigation** is generally not recommended for routine infection control and has limited efficacy against resistant organisms like **MRSA** in this context. - It does not address the primary mode of transmission, which is direct contact via **contaminated hands** or surfaces. *Wearing masks during invasive procedures in ICU is important.* - While important for preventing infections during **invasive procedures** and protecting against **aerosolized pathogens**, masks are not the primary strategy for controlling the spread of **MRSA** in routine ward settings. - **MRSA transmission** is predominantly contact-based, not airborne. *Vancomycin given empirically to all the patients* - **Empirical broad-spectrum antibiotic use** for all patients is a significant driver of **antibiotic resistance**, including **MRSA**. - It should be reserved for patients with suspected or confirmed **MRSA infections** based on clinical criteria and culture results, not as a general preventive measure.
Question 3: Which disease comes under International Surveillance?
- A. Typhoid fever (Correct Answer)
- B. Chikungunya fever
- C. Hepatitis B
- D. Salmonellosis
Explanation: ***Typhoid fever*** - **Typhoid fever** is monitored by the **World Health Organization (WHO)** through global surveillance systems to track incidence, guide vaccination strategies, and implement control measures. - While **not on the mandatory notification list** under the International Health Regulations (IHR) 2005, typhoid is included in **WHO's global disease surveillance** programs due to its significant disease burden in endemic regions. - Among the given options, typhoid fever has the **strongest international surveillance framework** through WHO's Global Foodborne Infections Network and regional surveillance systems. - **Note:** Diseases under **mandatory IHR surveillance** include cholera, plague, yellow fever, smallpox, poliomyelitis, SARS, and novel influenza subtypes. *Chikungunya fever* - Chikungunya is primarily monitored through **national and regional surveillance** systems rather than comprehensive international surveillance frameworks. - WHO tracks outbreaks through epidemic intelligence but it is **not part of mandatory IHR notification**. - Surveillance focuses on **vector control** and outbreak detection at local levels. *Hepatitis B* - **Hepatitis B** surveillance is conducted primarily at **national levels** through prevalence studies, vaccination coverage monitoring, and chronic infection programs. - It is **not under mandatory international surveillance** per IHR, though WHO maintains global estimates and monitoring frameworks. - Focus is on **prevention through vaccination** and treatment of chronic infections. *Salmonellosis* - Non-typhoidal **salmonellosis** is monitored mainly through **national food safety** and public health surveillance systems. - **Not designated for mandatory international surveillance** under IHR 2005. - International coordination occurs through networks like WHO's Global Foodborne Infections Network for outbreak investigation.
Question 4: Which of the following is true about annual risk of TB (ARI)
- A. ARI of 1% = 50 new cases
- B. It represents new cases of TB
- C. Current ARI in India is 1.7%
- D. It is assessed by tuberculin conversion in previously non-vaccinated children (Correct Answer)
Explanation: ***It is assessed by tuberculin conversion in previously non-vaccinated children*** - Annual Risk of Infection (ARI) is estimated by measuring the rate of **tuberculin skin test conversion** in populations, particularly in **children who have not been vaccinated** with BCG. - Tuberculin conversion in a child indicates recent exposure and infection with **Mycobacterium tuberculosis**. *ARI of 1% = 50 new cases* - This statement is a **misinterpretation** of ARI; the standard epidemiological conversion is that **1% ARI corresponds to approximately 50 new smear-positive TB cases per 100,000 population per year**. - However, **ARI represents new infections**, not a fixed number of disease cases. The number of **active TB cases** depends on several factors, including progression rate from infection to disease and population characteristics. *It represents new cases of TB* - **ARI represents new infections**, not new cases of active TB disease. Only a proportion of infected individuals (approximately 5-10% lifetime risk) will develop active TB disease. - **TB incidence** refers to new cases of active TB disease, whereas ARI refers to the infection rate in the population. *Current ARI in India is 1.7%* - Recent estimates for ARI in India have shown significant decline due to effective TB control programs, with current ARI estimated at **approximately 0.5-1%** or lower in many regions. - The **actual ARI varies** by region and is influenced by factors like TB control programs, population density, and socioeconomic conditions.
Question 5: Which of the following is the LEAST likely risk factor for developing acute otitis externa?
- A. Presbycusis (Correct Answer)
- B. Tympanic membrane perforation
- C. Frequent swimming
- D. Use of hearing aids
Explanation: ***Presbycusis*** - **Presbycusis** is age-related sensorineural hearing loss affecting the **inner ear (cochlea)** and auditory nerve pathways - It is a **degenerative condition** with NO involvement of the external auditory canal - There is **no pathophysiological mechanism** linking presbycusis to acute otitis externa, as it does not affect the ear canal's skin barrier, moisture balance, or susceptibility to infection - This is the **LEAST likely** risk factor among the options *Frequent swimming* - **Major risk factor** for acute otitis externa ("swimmer's ear") - Water exposure washes away protective **cerumen** and increases canal pH - Creates a **moist environment** ideal for bacterial proliferation, especially ***Pseudomonas aeruginosa*** and *Staphylococcus aureus* - Maceration of canal skin compromises the natural barrier *Use of hearing aids* - **Well-documented risk factor** for otitis externa - Hearing aids **occlude the ear canal**, trapping moisture and debris - Can cause **mechanical trauma** to the delicate canal skin - Creates a warm, humid environment promoting bacterial and fungal growth - Regular users are at increased risk, especially with poor hygiene *Tympanic membrane perforation* - While primarily associated with **chronic otitis media**, a perforation can predispose to external canal complications - May allow **moisture entry** and middle ear drainage into the canal - However, the direct risk for acute otitis externa is less significant compared to factors that directly affect the external canal environment - Still more relevant than presbycusis, which has no connection to the external ear
Question 6: Most common mode of transmission of nosocomial infection is -
- A. Hand contact (Correct Answer)
- B. Droplet infection
- C. Blood and blood products
- D. Contaminated water
Explanation: ***Hand contact*** - **Direct contact** with healthcare workers' contaminated hands is the primary way pathogens are transferred between patients in a healthcare setting. - Failure to perform adequate **hand hygiene** between patient contacts is the single most important factor contributing to nosocomial infection transmission. *Droplet infection* - While droplet transmission can cause nosocomial infections, especially for respiratory viruses, it is not the most common mode of transmission for the overall burden of healthcare-associated infections. - **Droplets** usually travel short distances and deposit on mucous membranes of the nose, mouth, or eyes of a susceptible host. *Blood and blood products* - Transmission through **blood and blood products** is a significant concern for specific infections (e.g., HIV, hepatitis B/C), but the incidence is relatively low due to stringent screening and safety protocols. - This mode accounts for a small fraction of overall nosocomial infections compared to contact transmission. *Contaminated water* - **Contaminated water** can lead to outbreaks (e.g., *Legionella*, *Pseudomonas*), especially in immunocompromised patients, but it is not the most frequent mode of transmission on a day-to-day basis across all types of nosocomial infections. - Healthcare facilities implement measures to ensure water safety, limiting this as the primary route.
Question 7: Most common cause of infection caused by intravascular catheter -
- A. Pseudomonas
- B. E. coli
- C. Staph aureus
- D. Coagulase negative staphylococci (Correct Answer)
Explanation: ***Coagulase negative staphylococci*** - **Coagulase-negative staphylococci** (e.g., *Staphylococcus epidermidis*) are the most common cause of **catheter-related bloodstream infections (CRBSI)**. - They are normal skin flora that can colonize catheters and form **biofilms**, making them difficult to eradicate. *Pseudomonas* - **Pseudomonas aeruginosa** is a common cause of healthcare-associated infections, but it is less frequently responsible for primary bloodstream infections from intravascular catheters compared to staphylococci. - It is often associated with infections in **immunocompromised patients** or those with prolonged hospital stays. *E. coli* - **Escherichia coli** is a common cause of **urinary tract infections (UTIs)** and intra-abdominal infections, which can sometimes lead to bacteremia. - While it can cause bloodstream infections, it is not the most common causative agent for infections directly originating from intravascular catheters. *Staph aureus* - **Staphylococcus aureus** is a significant cause of CRBSI and can lead to more severe, invasive infections like **endocarditis** and **septic shock**. - Although it is a common pathogen in CRBSI, **coagulase-negative staphylococci** collectively cause a greater number of these infections due to their prevalence as skin commensals and biofilm-forming capabilities.
Question 8: Nosocomial infections are diagnosed after how many hours of hospitalization / admission?
- A. 48 hours (Correct Answer)
- B. 96 hours
- C. 72 hours
- D. 24 hours
Explanation: ***48 hours*** - Nosocomial infections, also known as **hospital-acquired infections (HAIs)**, are defined as infections that develop at least **48 hours** after hospital admission. - This time frame helps differentiate infections acquired in the hospital setting from those the patient was incubating upon admission. *96 hours* - A 96-hour threshold is **too long** for the standard definition of a nosocomial infection. - Infections emerging after this extended period would almost certainly be considered hospital-acquired, but the conventional diagnostic window is shorter. *72 hours* - While 72 hours might capture many HAIs, it is **not the universally accepted or most common cutoff** for defining a nosocomial infection. - The 48-hour mark is more widely used for epidemiological and diagnostic purposes. *24 hours* - Infections diagnosed within **24 hours** of admission are typically considered to have been present or incubating **prior to hospitalization**. - This short timeframe is generally insufficient to classify an infection as hospital-acquired.
Question 9: Nosocomial infections are diagnosed after how many hours of hospitalization/admission?
- A. 96 hours
- B. 72 hours
- C. 48 hours (Correct Answer)
- D. 24 hours
Explanation: **48 hours (Correct Answer)** - A nosocomial infection, or **healthcare-associated infection (HAI)**, is defined as an infection acquired in a healthcare setting that was not present or incubating at the time of admission. - The standard definition specifies that the infection must manifest **48 hours or more after admission**, or within a certain period after discharge, to be classified as nosocomial. - This is the universally accepted cutoff used by the CDC and WHO for epidemiological surveillance. *96 hours (Incorrect)* - This duration is longer than the generally accepted timeframe for diagnosing nosocomial infections. - While some specific infections might manifest later, the universal cutoff for classification is **48 hours**. *72 hours (Incorrect)* - Although similar to the correct answer, **72 hours** is not the universally accepted definition for the onset of a nosocomial infection. - The **48-hour** mark is the widely used standard for epidemiological surveillance and clinical classification. *24 hours (Incorrect)* - An infection diagnosed within **24 hours** of admission is generally considered to be **community-acquired**, meaning the patient was likely infected before entering the healthcare facility. - This timeframe is too short to attribute the infection to the healthcare environment, as it does not account for the typical incubation period.
Question 10: Which of the following is true about Extended spectrum beta-lactamases?
- A. Only seen in gram positive bacteria
- B. Plasmid mediated (Correct Answer)
- C. Only seen in gram negative bacteria
- D. Associated only in community acquired disease
Explanation: ***Plasmid mediated*** - **Extended-spectrum beta-lactamases (ESBLs)** are primarily encoded on **plasmids**, which allows for easy horizontal transfer of resistance genes between bacteria. - This **plasmid-mediated dissemination** is a major reason for the rapid spread of ESBL resistance among various bacterial species. *Only seen in gram positive bacteria* - ESBLs are predominantly found in **Gram-negative bacteria**, particularly members of the **Enterobacteriaceae family** like *E. coli* and *Klebsiella pneumoniae*. - While some beta-lactamases exist in Gram-positive bacteria, ESBLs specifically refer to those with an extended spectrum of activity against modern beta-lactams in Gram-negative organisms. *Only seen in gram negative bacteria* - While **ESBLs are predominantly found in Gram-negative bacteria**, the phrasing "only seen in gram negative bacteria" is too restrictive because there have been rare reports of ESBL genes detected in some Gram-positive strains, though this is not their primary epidemiology. - The main concern with ESBLs lies in their prevalence and impact on Gram-negative infections. *Associated only in community acquired disease* - ESBLs are associated with both **hospital-acquired (nosocomial)** and **community-acquired infections**. - The prevalence of community-acquired ESBL infections has been increasing, posing a significant public health challenge.
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