Hospital-Acquired Infections — MCQs
Most common catheter-related bloodstream infection is due to:
A patient develops sepsis following the use of a central venous catheter. Which organism is most commonly associated with this condition?
Extended-spectrum beta-lactamases (ESBLs) are characterized by activity against all except :
To prevent ventilator associated pneumonia, the most effective and evidence based results are seen with which of the following for critically ill patients:
Nosocomial infections are diagnosed after how many hours of hospitalization/admission?
Which of the following is true about Extended spectrum beta-lactamases?
What is the most common mode of transmission of HIV?
Measles is infective for:
What is the Chandler's Index for Hookworm that indicates a significant health problem?
A 15-month-old child presents with fever and cough since the last two days, the respiratory rate is 55/min and there is no drawing of the chest. According to the National Programme for Acute Respiratory Infections, the line of management should be
Hospital-Acquired Infections Indian Medical PG Practice Questions and MCQs
Question 1: Most common catheter-related bloodstream infection is due to:
- A. Coagulase-negative Staphylococci (CoNS) (Correct Answer)
- B. Candida species
- C. Gram-negative bacilli
- D. Staphylococcus aureus (S. aureus)
Explanation: ***Coagulase-negative Staphylococci (CoNS)*** - **Coagulase-negative Staphylococci (CoNS)**, particularly *Staphylococcus epidermidis*, are the most common cause of **catheter-related bloodstream infections (CRBSIs)** due to their ability to form **biofilms** on catheter surfaces. - Their ubiquity on the skin, combined with their capacity for **adherence** and **biofilm production**, facilitates their entry and proliferation within the catheter lumen. *Candida species* - While *Candida species* (e.g., *Candida albicans*) are significant causes of CRBSIs, especially in **immunocompromised** patients or those on **broad-spectrum antibiotics**, they are less common overall than CoNS. - Risk factors for *Candida* CRBSIs include prolonged hospitalization, total parenteral nutrition, and **central venous catheters**. *Gram-negative bacilli* - **Gram-negative bacilli** (e.g., *Klebsiella pneumoniae*, *Escherichia coli*, *Pseudomonas aeruginosa*) are important pathogens in CRBSIs, often associated with **severe sepsis** and higher mortality rates. - However, their overall incidence in catheter-induced infections is lower than that of CoNS, though they are more prevalent in certain hospital units like **ICUs**. *Staphylococcus aureus (S. aureus)* - **Staphylococcus aureus** causes clinically significant CRBSIs, often leading to more severe infections, including **endocarditis** and **septic emboli**, than CoNS. - While *S. aureus* infections are serious, CoNS remain the most frequently isolated organism in all CRBSI cases, partly due to the high carriage rate of *S. epidermidis* on human skin.
Question 2: A patient develops sepsis following the use of a central venous catheter. Which organism is most commonly associated with this condition?
- A. Candida spp.
- B. Staphylococcus epidermidis (Correct Answer)
- C. Escherichia coli (E. coli)
- D. Pseudomonas species
Explanation: ***Staphylococcus epidermidis*** - This organism is a common commensal on the skin and the most frequent cause of **catheter-related bloodstream infections (CRBSI)** due to its ability to form **biofilms** on medical devices. - Its presence on the skin makes it an opportunistic pathogen that can easily contaminate and colonize the surface of central venous catheters, leading to systemic infection. *Candida spp.* - While fungal infections can occur with central venous catheters, especially in immunocompromised patients or those on prolonged antibiotics, **Candida** is less common than bacterial causes like *Staphylococcus epidermidis* in general sepsis cases. - **Candidemia** in the setting of CVCs is often associated with total parenteral nutrition, abdominal surgery, or broad-spectrum antibiotic use. *Escherichia coli (E. coli)* - **E. coli** is a common cause of sepsis, particularly from **urinary tract infections (UTIs)** or intra-abdominal infections, but it is not the most common organism associated "directly" with central venous catheter-related sepsis. - While *E. coli* can cause CRBSIs, it typically indicates a source other than simple skin colonization of the catheter, often due to translocation from the gut. *Pseudomonas species* - **Pseudomonas** species, notably *P. aeruginosa*, are typically associated with catheter-related infections in specific contexts, such as in neutropenic patients, those with significant underlying lung disease (e.g., cystic fibrosis), or those in critical care settings. - While it can cause severe CRBSIs, it is not the *most common* overall pathogen compared to coagulase-negative staphylococci like *S. epidermidis*.
Question 3: Extended-spectrum beta-lactamases (ESBLs) are characterized by activity against all except :
- A. Carbapenems (Correct Answer)
- B. Oxyimino-cephalosporins
- C. Penicillins
- D. Cephalosporins
Explanation: ***Carbapenems*** - **Extended-spectrum beta-lactamases (ESBLs)** typically do not hydrolyze **carbapenems**, making these antibiotics generally effective against most ESBL-producing bacteria. - The retention of activity against carbapenems is a key distinction between ESBLs and other beta-lactamases like **carbapenemases**. *Oxyimino-cephalosporins* - ESBLs are specifically named for their ability to hydrolyze and inactivate **oxyimino-cephalosporins**, such as **cefotaxime**, **ceftriaxone**, and **ceftazidime**. - This hydrolysis makes these vital third-generation cephalosporins ineffective for treating infections caused by ESBL-producing organisms. *Penicillins* - ESBLs can effectively hydrolyze and render many **penicillins** inactive, especially those lacking beta-lactamase inhibitors. - This broadens the resistance spectrum beyond just cephalosporins to include common penicillins. *Cephalosporins* - ESBLs primarily confer resistance to a wide range of **cephalosporins**, particularly the **first-, second-, and third-generation agents**. - This resistance is a major clinical challenge, necessitating the use of alternative antibiotic classes.
Question 4: To prevent ventilator associated pneumonia, the most effective and evidence based results are seen with which of the following for critically ill patients:
- A. Powered brushing
- B. Manual brushing
- C. Betadine mouthwash
- D. Oral hygiene procedures plus chlorhexidine (Correct Answer)
Explanation: Oral hygiene procedures plus chlorhexidine - **Chlorhexidine** mouthwash, when combined with mechanical oral hygiene, significantly reduces the oral bacterial load, preventing aspiration of pathogenic bacteria into the lungs. - This comprehensive approach is a **gold standard** strategy for VAP prevention in critically ill patients, supported by strong evidence. *Betadine mouthwash* - While Betadine (povidone-iodine) has **antiseptic properties**, its efficacy in preventing VAP is not as well-established or consistently supported by evidence as chlorhexidine. - There are concerns about potential **mucosal irritation** and systemic absorption with prolonged use in critically ill patients. *Powered brushing* - Though powered brushing can provide effective plaque removal, it primarily focuses on **mechanical cleaning** without the added antimicrobial benefits of an antiseptic agent like chlorhexidine. - Its effectiveness alone in preventing VAP has **not been shown to be superior** to comprehensive oral care including antiseptics. *Manual brushing* - Manual brushing is a basic component of oral hygiene but, similar to powered brushing, lacks the **antimicrobial action** necessary to drastically reduce bacterial colonization in critically ill, intubated patients. - It is important for general oral cleanliness but **insufficient on its own** for preventing VAP effectively.
Question 5: 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 6: 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.
Question 7: What is the most common mode of transmission of HIV?
- A. Occupational exposure (needle stick injury)
- B. Perinatal transmission (mother to child)
- C. Sexual contact (Correct Answer)
- D. Transmission via blood and blood products
Explanation: ***Sexual contact*** - **Unprotected sexual intercourse**, both heterosexual and homosexual, is overwhelmingly the most common way HIV is transmitted globally. - The virus can be exchanged through **bodily fluids** such as semen, vaginal fluids, and rectal fluids during sexual activity. - Accounts for approximately **80% of new HIV infections** worldwide. *Occupational exposure (needle stick injury)* - While a recognised mode of transmission, **needle stick injuries** account for a very small percentage of total HIV infections, primarily affecting healthcare workers. - The risk of transmission per exposure is relatively low (approximately **0.3%**), especially compared to sexual contact. *Perinatal transmission (mother to child)* - **Mother-to-child transmission** can occur during pregnancy, childbirth, or breastfeeding. - Although significant, especially in resource-limited settings, global efforts and **PMTCT programs** have resulted in a significant reduction in this type of transmission. *Transmission via blood and blood products* - This mode was once a major concern but is now extremely rare in countries with robust **blood screening programs**. - While sharing contaminated needles among **intravenous drug users** remains a risk, transfusion-related HIV is largely controlled.
Question 8: Measles is infective for:
- A. One day before and 4 days after rash
- B. Entire incubation period
- C. Four days before and four days after rash (Correct Answer)
- D. Only during scabs falling
Explanation: ***Four days before and four days after rash*** - Measles is highly contagious, and individuals are infective from approximately **4 days before rash onset** to **4 days after the rash appears**. - This period includes the initial **prodromal phase** (fever, cough, coryza, conjunctivitis) when the patient may not yet have a characteristic rash, making containment challenging. - The **maximum period of communicability** is thus about 8-9 days. *One day before and 4 days after rash* - This option underestimates the **pre-rash infectivity period** significantly. - Measles infectivity begins earlier, typically 4 days before rash onset during the prodromal phase. *Entire incubation period* - The **incubation period** for measles is typically 10-14 days from exposure to rash onset, but the patient is not infective for the entire duration. - Infectivity begins with the onset of the **prodromal symptoms** (about 4 days before rash), not from the moment of exposure. *Only during scabs falling* - Measles does not typically produce **scabs** in the way varicella (chickenpox) does, and the virus is transmitted primarily through **respiratory droplets**, not skin lesions. - Infectivity is highest during the **prodrome** and early rash phase, not during any scab-falling stage.
Question 9: What is the Chandler's Index for Hookworm that indicates a significant health problem?
- A. > 200
- B. > 100
- C. > 300
- D. > 50 (Correct Answer)
Explanation: ***> 50*** - A Chandler's Index of **> 50** indicates a significant public health problem due to **hookworm infection**. - **Chandler's Index** is calculated as the **average egg count per person in a community** (total hookworm eggs counted ÷ number of persons examined), used to assess the population-level burden of hookworm infection. - A value **> 50** suggests that the community has a significant hookworm problem requiring public health intervention. *> 300* - This value is significantly higher than the threshold for a significant public health problem and would indicate an **extremely severe burden of infection**. - While this represents a very high Chandler's Index, it's not the standard cut-off for defining a "significant" health problem (which is the lower threshold of >50). *> 200* - A Chandler's Index of **> 200** would denote a very high intensity of hookworm infection in the community. - However, this is not the standard threshold used to define when hookworm becomes a "significant" public health issue - the threshold is lower at >50. *> 100* - A Chandler's Index of **> 100** represents a substantial level of hookworm infection within a population. - However, the widely recognized cutoff for a "significant health problem" is **> 50**, indicating public health concern even at this moderate level of community infection burden.
Question 10: A 15-month-old child presents with fever and cough since the last two days, the respiratory rate is 55/min and there is no drawing of the chest. According to the National Programme for Acute Respiratory Infections, the line of management should be
- A. Immediate referral of the child to hospital for urgent admission
- B. Administration of treatment for fever at home, advising the mother to return after two days for assessment of the need for an antibiotic
- C. Referral of the child to hospital for admission, after administration of first dose of antibiotic
- D. Administration of antibiotic at home along with treatment for fever, advising the mother to return for reassessment after two days (Correct Answer)
Explanation: ***Administration of antibiotic at home along with treatment for fever, advising the mother to return for reassessment after two days*** - A respiratory rate of 55/min in a 15-month-old child indicates **fast breathing**, which is a sign of pneumonia. However, the **absence of chest indrawing** means it's classified as **non-severe pneumonia**. - According to the National Programme for Acute Respiratory Infections (ARI) guidelines, **non-severe pneumonia** in children 2 months to 5 years without severe illness signs should be managed with **oral antibiotics at home** and outpatient follow-up. *Immediate referral of the child to hospital for urgent admission* - This action is indicated for **severe pneumonia** or **very severe disease**, characterized by signs such as chest indrawing, stridor, central cyanosis, or inability to drink, which are not present here. - While the child has fast breathing, the **absence of chest indrawing** suggests a less severe presentation that does not immediately warrant urgent hospital admission. *Administration of treatment for fever at home, advising the mother to return after two days for assessment of the need for an antibiotic* - This approach is inappropriate because **fast breathing** is a definitive sign of pneumonia in this age group, requiring immediate antibiotic treatment. - Delaying antibiotic administration could lead to the **progression of the infection** to a more severe form. *Referral of the child to hospital for admission, after administration of first dose of antibiotic* - Admission to the hospital is not required for **non-severe pneumonia** if the child can be managed at home and there are no signs of severe disease. - The guidelines suggest home management with oral antibiotics unless specific **danger signs** for referral are present.
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