Hospital Acquired Infections Practice Questions

Q: Nosocomial infections are diagnosed after how many hours of hospitalization / admission?

48 hours. ***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.

Q: A patient develops sepsis following the use of a central venous catheter. Which organism is most commonly associated with this condition?

Staphylococcus epidermidis. ***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*.

Q: A patient operated for transurethral resection of prostate [TURP] develops UTI. The organism most commonly grown on culture will be -

E. coli. ***E. coli*** - **_E. coli_** is the most common pathogen responsible for both **community-acquired** and **healthcare-associated urinary tract infections (UTIs)**, including those following surgical procedures like TURP. - It accounts for **50-70% of healthcare-associated UTIs** and has enhanced ability to adhere to urothelial cells and form biofilms. - Its virulence factors make it the predominant uropathogen in post-operative settings. *Proteus* - While **_Proteus mirabilis_** can cause UTIs, particularly those associated with **struvite stones** due to urease production, it is not as common as _E. coli_ in post-TURP UTIs. - It accounts for approximately **5-10% of healthcare-associated UTIs** and often causes **alkaline urine** with characteristic "swarming" growth on culture. *Pseudomonas* - **_Pseudomonas aeruginosa_** is an important cause of **healthcare-associated UTIs**, especially in catheterized patients or those with complicated infections. - However, it accounts for only **10-15% of nosocomial UTIs** and is less common than _E. coli_ unless there are specific risk factors such as prolonged catheterization or previous antibiotic exposure. *Klebsiella* - **_Klebsiella pneumoniae_** is the **second most common cause of UTIs** after _E. coli_, accounting for **10-15% of cases**. - It is particularly associated with **healthcare settings**, catheter-related infections, and patients with diabetes or immunosuppression. - While important, it is still less common than _E. coli_ in post-TURP UTIs.

Q: Which type of microorganism is most commonly associated with nosocomial infections?

Gram-negative bacilli. ***Gram-negative bacilli*** - Common examples like **_Pseudomonas aeruginosa_**, **_Klebsiella pneumoniae_**, and **_Escherichia coli_** are significant causes of **hospital-acquired infections**, particularly **urinary tract infections**, **pneumonia**, and **surgical site infections**. - Their intrinsic and acquired **antibiotic resistance mechanisms** make them challenging to treat in healthcare settings. *Gram-negative cocci* - While **_Neisseria_ species** (e.g., **_N. meningitidis_**, **_N. gonorrhoeae_**) are Gram-negative cocci, they are less frequently implicated in overall nosocomial infections compared to Gram-negative bacilli or certain Gram-positive organisms. - **_Moraxella catarrhalis_** is another Gram-negative coccus that can cause opportunistic infections but is not a primary driver of widespread nosocomial outbreaks. *Fungi* - **Fungal infections** (e.g., **_Candida_ species**, **_Aspergillus_ species**) are important causes of nosocomial infections, especially in **immunocompromised patients** and those with central venous catheters. - However, in terms of overall burden across all types of nosocomial infections, bacteria, particularly Gram-negative bacilli, are generally more prevalent. *Gram-positive bacilli* - While some Gram-positive bacilli like **_Clostridium difficile_** (a significant cause of **healthcare-associated diarrhea**) and **_Bacillus cereus_** (food poisoning) are relevant in nosocomial settings, they do not collectively represent the most common type of microorganism for all nosocomial infections. - The most prominent Gram-positive nosocomial pathogens are typically cocci, such as MRSA (**methicillin-resistant _Staphylococcus aureus_**), not bacilli.

Q: Most common route of nosocomial infection [Hospital-acquired infection]?

Direct contact. **Direct contact** - **Direct contact** with colonized or infected patients is the predominant mode of transmission for many common nosocomial pathogens like **MRSA** and **VRE**. - This often involves healthcare workers' hands becoming contaminated and then touching other patients. *Droplet transmission* - Involves the transmission of infectious agents through **respiratory droplets** produced during coughing, sneezing, or talking. - While significant for some infections (e.g., influenza, pertussis), it is not the most common route overall for nosocomial infections. *Indirect contact* - Occurs when an infectious agent is transferred via a **contaminated intermediate object** or person. - Although important (e.g., contaminated medical devices), it is generally less frequent than direct patient-to-patient transmission. *Vehicle transmission* - Involves transmission through **contaminated inanimate vehicles** like food, water, medications, or surgical instruments. - While outbreaks can occur via this route (e.g., contaminated endoscopes), it is not the most common day-to-day transmission mechanism in hospitals.

Q: Most common organism causing ventilator associated pneumonia -

Pseudomonas. ***Pseudomonas*** - **Pseudomonas aeruginosa** is one of the most common causes of **ventilator-associated pneumonia (VAP)**, particularly in **late-onset VAP** (≥5 days) and in patients with prolonged mechanical ventilation, prior antibiotic exposure, or underlying lung disease. - Its ability to form **biofilms** and its intrinsic antibiotic resistance contribute to its prevalence in hospital-acquired infections. - Along with **Staphylococcus aureus** (especially MRSA), Pseudomonas is consistently among the leading causes of VAP in ICU settings. *Legionella* - **Legionella** is a less common cause of VAP and is typically associated with contaminated water sources, manifesting as **Legionnaires' disease**. - It usually causes severe, rapidly progressive pneumonia and is often harder to culture than other bacteria. *Pneumococcus* - **Streptococcus pneumoniae (Pneumococcus)** is the most common cause of **community-acquired pneumonia (CAP)**, but it is less frequently implicated in VAP. - While it can cause severe pneumonia and may be seen in **early-onset VAP**, its incidence in late-onset VAP is lower compared to Gram-negative rods like Pseudomonas. *Coagulase negative staphylococcus* - **Coagulase-negative Staphylococci** (e.g., *Staphylococcus epidermidis*) are common **contaminants** in cultures and primarily cause device-related infections, such as those associated with central venous catheters. - They are rarely a primary cause of VAP, as they typically have low virulence in the respiratory tract.

Q: Which MRSA strain type is most commonly associated with hospital-acquired infections?

Phage type 80/81. ***Phage type 80/81*** - This **phage type**, particularly **epidemic methicillin-resistant *Staphylococcus aureus* (EMRSA) 15 and 16**, is historically and currently the most common cause of **hospital-acquired MRSA infections** worldwide. - It rapidly diversified and spread globally, becoming a significant nosocomial pathogen. *Phage type 83A* - While this phage type has been associated with **MRSA outbreaks**, it is not the most common strain type globally for hospital-acquired infections. - Its prevalence is more regional and sporadic compared to the widespread dominance of EMRSA 15/16. *Phage type 84* - **Phage type 84** is not widely recognized as a predominant strain associated with the majority of **hospital-acquired MRSA infections**. - Other, more virulent and successful clonal types have outcompeted it to become the most prevalent. *Phage type 85* - Similar to other less common types, **phage type 85** does not represent the major lineage responsible for the bulk of **hospital-acquired MRSA cases**. - The landscape of MRSA epidemiology is dominated by a few highly successful clonal complexes, of which 80/81 is a prime example.

Q: The best way to prevent MRSA outbreak in indoor patients is:

Practice proper meticulous hand washing. ***Practice proper meticulous hand washing*** - **Hand hygiene** is the most effective measure to prevent the transmission of **healthcare-associated infections**, including Methicillin-resistant *Staphylococcus aureus* (**MRSA**). - Consistent **hand washing** by healthcare workers removes transient microorganisms and significantly reduces cross-contamination between patients. *Administer vancomycin to all patients* - Administering **vancomycin** to all patients would lead to widespread **antibiotic resistance**, making infections harder to treat. - This practice is inappropriate as **vancomycin** is a broad-spectrum antibiotic and should be reserved for confirmed infections or specific prophylaxis. *Conduct fumigation of the ward* - **Fumigation** is generally not recommended for routine MRSA prevention as it has limited efficacy against bacterial spores and poses risks to staff and patients. - It is an extreme measure reserved for specific, highly contaminated environments and does not address the primary mode of MRSA transmission (person-to-person). *Use sodium hypochlorite for floor disinfection* - While **sodium hypochlorite** is an effective disinfectant, focusing solely on floor disinfection is insufficient for preventing **MRSA outbreaks**. - MRSA primarily spreads through direct contact via contaminated hands, rather than contact with contaminated floors.

Q: What is the most common and serious cause of infection by Pseudomonas aeruginosa in hospitalized patients?

Patients with indwelling catheters. ***Patients with indwelling catheters*** - **Indwelling catheters** (e.g., urinary catheters, central venous catheters) provide a direct route for *Pseudomonas aeruginosa* to enter the body, making them the most common source of serious infections in hospitalized patients due to widespread use [1]. - The biofilm formation on catheter surfaces by *P. aeruginosa* makes these infections difficult to treat and a major cause of **catheter-associated urinary tract infections (CAUTIs)** and **catheter-related bloodstream infections (CRBSIs)** [1]. *Burn injuries* - While *Pseudomonas aeruginosa* is a significant cause of **wound infections** in patients with severe **burns**, these are not the most common source of *P. aeruginosa* infections in the overall hospital setting. - Burn wounds provide a large, open surface for bacterial colonization and systemic infection, but the prevalence of burn patients is lower than that of patients with indwelling catheters. *Neutropenic patients* - **Neutropenic patients** are highly susceptible to severe infections from *Pseudomonas aeruginosa* due to their compromised immune system, often leading to **bacteremia** or **pneumonia**. - Although *P. aeruginosa* infections in neutropenic patients are serious and life-threatening, the initial source of infection can often be linked to environmental exposure or compromised skin/mucosal barriers, rather than directly to neutropenia as the primary cause or common entry point. *None of the options* - This option is incorrect because **indwelling catheters** are a well-established and highly prevalent source of *Pseudomonas aeruginosa* infections in hospitalized patients [1]. - The routine use of various catheters across different patient populations makes them a leading cause of nosocomial infections.

Question 1

Nosocomial infections are diagnosed after how many hours of hospitalization / admission?

Accepted Answer

48 hours

Answer

96 hours

Answer

72 hours

Answer

24 hours

Question 2

A patient develops sepsis following the use of a central venous catheter. Which organism is most commonly associated with this condition?

Accepted Answer

Staphylococcus epidermidis

Answer

Candida spp.

Answer

Escherichia coli (E. coli)

Answer

Pseudomonas species

Question 3

A patient operated for transurethral resection of prostate [TURP] develops UTI. The organism most commonly grown on culture will be -

Accepted Answer

E. coli

Answer

Proteus

Answer

Pseudomonas

Answer

Klebsiella

Question 4

Which type of microorganism is most commonly associated with nosocomial infections?

Accepted Answer

Gram-negative bacilli

Answer

Gram-negative cocci

Answer

Fungi

Answer

Gram-positive bacilli

Question 5

Most common route of nosocomial infection [Hospital-acquired infection]?

Accepted Answer

Direct contact

Answer

Droplet transmission

Answer

Indirect contact

Answer

Vehicle transmission

Question 6

Which of the following specific microorganisms are most commonly implicated in infections after hemodialysis?

Accepted Answer

Staphylococcus aureus and coagulase-negative staphylococci (Gram positive organisms)

Answer

Escherichia coli (Gram negative)

Answer

Bacteroides (Anaerobes)

Answer

Chlamydia

Question 7

Most common organism causing ventilator associated pneumonia -

Accepted Answer

Pseudomonas

Answer

Legionella

Answer

Pneumococcus

Answer

Coagulase negative staphylococcus

Question 8

Which MRSA strain type is most commonly associated with hospital-acquired infections?

Accepted Answer

Phage type 80/81

Answer

Phage type 83A

Answer

Phage type 85

Answer

Phage type 84

Question 9

The best way to prevent MRSA outbreak in indoor patients is:

Accepted Answer

Practice proper meticulous hand washing

Answer

Administer vancomycin to all patients

Answer

Conduct fumigation of the ward

Answer

Use sodium hypochlorite for floor disinfection

Question 10

What is the most common and serious cause of infection by Pseudomonas aeruginosa in hospitalized patients?

Accepted Answer

Patients with indwelling catheters

Answer

None of the options

Answer

Burn injuries

Answer

Neutropenic patients

Hospital Acquired Infections — MCQs

Hospital Acquired Infections — MCQs

On this page

Practice by Chapter

Want unlimited practice?