Hospital Acquired Infections Practice Questions

Q: An outbreak of staphylococcal infection involving umbilical cords of seven newborn babies was reported in the nursery. Bacteriological survey reveals that two nurses have a large number of Staphylococcus aureus in the nasopharynx. What test should be performed to determine whether these nurses may have been responsible for the outbreak?

Bacteriophage typing. ***Bacteriophage typing*** - **Bacteriophage typing** involves using specific **bacteriophages** to identify different strains within a bacterial species based on their susceptibility to lysis by these phages. - This method helps determine if the specific strain of **Staphylococcus aureus** found in the nurses' nasopharynx matches the strain causing the outbreak in the newborns' umbilical cords, thereby establishing an epidemiological link. - This is the **classical method** for *S. aureus* strain typing in outbreak investigations. Modern molecular methods like PFGE, MLST, and whole genome sequencing have largely replaced bacteriophage typing, but it remains a fundamental concept tested in medical examinations. *Coagulase testing* - **Coagulase testing** differentiates **Staphylococcus aureus** (coagulase-positive) from other coagulase-negative staphylococci. - While it identifies the species, it does not provide the **strain-level differentiation** needed to link a specific individual to an outbreak. *Nasopharyngeal culture on mannitol salt agar* - **Mannitol salt agar** is a selective and differential medium used to isolate and identify **Staphylococcus aureus** from mixed cultures due to its ability to ferment mannitol and tolerate high salt concentrations. - This test would confirm the presence of **Staphylococcus aureus** in the nasopharynx but would not provide the detailed **strain-specific information** required to trace the source of the outbreak. *Protein A typing* - **Protein A** is a common cell wall component of **Staphylococcus aureus** that binds to the Fc region of immunoglobulins. - While its presence is characteristic of **Staphylococcus aureus**, **Protein A typing** does not offer the necessary **strain-specific resolution** to epidemiologically link an individual carrier to a specific outbreak strain.

Q: Most common cause of infection caused by intravascular catheter -

Coagulase negative staphylococci. ***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.

Q: Which infection commonly spreads to newborns through caregivers?

Candida parapsilosis. ***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*.

Q: Which gram-negative organism is particularly notorious for causing late-onset VAP with multidrug resistance?

Acinetobacter. ***Acinetobacter*** - *Acinetobacter baumannii* is particularly notorious for causing **late-onset VAP** (>5 days) with extensive **multidrug resistance**, including pan-drug resistant strains (resistant to carbapenems, polymyxins, and tigecycline). - Its ability to survive on surfaces for prolonged periods, form biofilms, and its intrinsic resistance mechanisms make it a significant challenge in ICU environments. - Often exhibits resistance to nearly all available antibiotics, earning it a place in the **ESKAPE pathogens** group. *Klebsiella* - While *Klebsiella pneumoniae* can cause VAP and exhibits multidrug resistance through **extended-spectrum beta-lactamase (ESBL)** and carbapenemase production, it is not as characteristically associated with late-onset VAP as *Acinetobacter* and *Pseudomonas*. - More commonly causes **healthcare-associated infections** including urinary tract infections and bloodstream infections. *Pseudomonas aeruginosa* - *Pseudomonas aeruginosa* is also a major cause of **late-onset VAP** with significant **multidrug resistance** potential, particularly in patients with prolonged mechanical ventilation and underlying lung disease. - Can exhibit carbapenem resistance and is part of the ESKAPE pathogens. - However, *Acinetobacter baumannii* is considered particularly "notorious" due to its more extensive pan-drug resistance patterns and extremely limited treatment options. *Staphylococcus aureus* - *Staphylococcus aureus* is a **Gram-positive** organism, not Gram-negative, making it incorrect based on the question's specification. - While **MRSA** is a common cause of both early and late-onset VAP, it does not meet the Gram-negative criterion.

Q: All the following are common nosocomial infections except:

Mycobacterium. ***Mycobacterium*** - **Mycobacterium** species are not typically considered common causes of **acute nosocomial infections** because they are slow-growing and usually cause chronic infections. - While healthcare workers or patients can acquire tuberculosis in healthcare settings, it is less common for *Mycobacterium* to be the cause of rapidly developing, typical healthcare-associated infections like pneumonia or bloodstream infections. *Staph. aureus* - **_Staphylococcus aureus_** is a very common cause of **nosocomial infections**, particularly **MRSA (methicillin-resistant *S. aureus*)**, leading to surgical site infections, bloodstream infections, and pneumonia. - It colonizes healthcare workers and patients, making it easily transmissible in hospital environments. *Enterobacteriaceae* - **Enterobacteriaceae** (e.g., _E. coli_, _Klebsiella_, _Enterobacter_) are frequently implicated in **nosocomial infections**, especially **urinary tract infections (UTIs)**, pneumonia, and bloodstream infections. - These bacteria are part of the normal flora but can cause serious infections when introduced into sterile sites or in immunocompromised patients. *P. aeruginosa* - **_Pseudomonas aeruginosa_** is a significant cause of **nosocomial infections**, particularly in intensive care units (ICUs) and among immunocompromised patients. - It is known for causing **ventilator-associated pneumonia (VAP)**, UTIs, and wound infections, often exhibiting multidrug resistance.

Q: Most common catheter-related bloodstream infection is due to:

Coagulase-negative Staphylococci (CoNS). ***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.

Q: Commonest cause of nosocomial infection is

Staphylococci. ***Staphylococci*** - **Staphylococci**, particularly *Staphylococcus aureus* (including MRSA) and coagulase-negative staphylococci, are the **most common cause** of nosocomial infections according to current surveillance data from CDC, WHO, and Indian hospital studies. - They are the leading cause of **surgical site infections**, **catheter-related bloodstream infections**, **ventilator-associated pneumonia**, and **skin and soft tissue infections** in hospital settings. - Their ability to form biofilms on medical devices, antibiotic resistance (especially MRSA), and widespread colonization of healthcare workers and patients make them the predominant nosocomial pathogen. *Enterobacteriaceae* - The family **Enterobacteriaceae** (including *E. coli*, *Klebsiella*, *Enterobacter*) represents a major group of gram-negative nosocomial pathogens. - They are very common causes of **urinary tract infections**, **pneumonia**, and **bloodstream infections**, particularly associated with indwelling catheters and ventilators. - While collectively representing a large proportion of nosocomial infections, they are the **second most common** group after Staphylococci in most contemporary studies. *Pseudomonas* - *Pseudomonas aeruginosa* is an important nosocomial pathogen, particularly in **ventilator-associated pneumonia**, **burn infections**, and infections in immunocompromised patients. - It accounts for approximately 10-15% of nosocomial infections and is especially problematic due to its intrinsic antibiotic resistance. *Klebsiella* - **Klebsiella** (particularly *K. pneumoniae*) is a member of the Enterobacteriaceae family and an important individual pathogen causing **pneumonia** and **urinary tract infections** in healthcare settings. - While a common pathogen, it represents only a subset of both the Enterobacteriaceae family and overall nosocomial infections, making it less common than the entire Staphylococci group.

Q: Most effective way of preventing hospital infection is:

Hand washing. ***Hand washing*** - **Hand hygiene** is the single most important and effective measure for **preventing nosocomial infections** and the transmission of multidrug-resistant organisms. - It physically removes transient microorganisms and reduces the resident flora on hands, thereby **breaking the chain of infection**. - Recommended by **WHO** and **CDC** as the cornerstone of infection prevention in healthcare settings. *Fumigation* - **Fumigation** is a process involving the use of gaseous disinfectants to kill pests or microbes, primarily for **terminal disinfection of rooms** or large spaces. - While it can reduce microbial load on surfaces, it is **not used routinely** for preventing day-to-day transmission of pathogens from person to person. - Not practical or effective for continuous infection control. *Sterilization* - **Sterilization** is a process that destroys all forms of microbial life, including spores, primarily applied to **medical instruments** and surgical equipment. - While critical for preventing infection during invasive procedures, it is **not a direct method** for preventing general person-to-person transmission within a hospital environment. - Cannot be applied to hands or routine patient care activities. *Early diagnosis and treatment* - **Early diagnosis and treatment** are crucial for managing existing infections in patients, which can help prevent their spread within the hospital. - However, these measures primarily address **patient care** rather than directly interrupting the *transmission* of pathogens from healthcare workers to patients or between patients. - This is a **secondary prevention** measure, not primary prevention of transmission.

Q: The most common pathogens responsible for nosocomial pneumonia in ICU are

Gram-negative bacteria. ***Gram-negative bacteria*** - **Gram-negative bacteria** such as *Pseudomonas aeruginosa*, *Klebsiella pneumoniae*, and *Escherichia coli* are frequently colonizers of the critically ill. - Patients in the ICU are at high risk for ventilator-associated pneumonia and healthcare-associated pneumonia, often due to **multi-drug resistant gram-negative bacteria**. *Mycoplasma* - **Mycoplasma pneumoniae** is a common cause of **community-acquired pneumonia**, particularly in younger adults. - It is **rarely a cause of nosocomial pneumonia** and is not typically associated with the severe illnesses seen in ICU settings. *Virus* - While viruses can cause pneumonia, especially in immunocompromised individuals, they are **less common as primary causative agents of nosocomial pneumonia** in ICU settings compared to bacterial pathogens. - Viral pneumonia like **influenza** or **RSV** are usually community-acquired but can lead to secondary bacterial infections. *Gram-positive bacteria* - **Gram-positive bacteria**, particularly **methicillin-resistant *Staphylococcus aureus* (MRSA)**, are important causes of nosocomial pneumonia and are increasingly prevalent. - However, **Gram-negative bacteria** are still **more frequently isolated** in general nosocomial and ventilator-associated pneumonia cases in the ICU setting.

Q: Contact isolation is done for:

MRSA. ***MRSA*** - **Methicillin-resistant *Staphylococcus aureus* (MRSA)** is transmitted primarily through direct contact with infected patients or contaminated environmental surfaces, necessitating **contact isolation** measures. - These measures include the use of **gloves and gowns** upon entering the patient's room to prevent spread. *Mumps* - Mumps is a viral infection primarily transmitted via **respiratory droplets**, requiring **droplet isolation** rather than contact isolation. - The virus spreads through coughing and sneezing, necessitating measures like wearing a surgical mask. *Diphtheria* - Diphtheria, caused by *Corynebacterium diphtheriae*, is spread through **respiratory droplets** from close contact with an infected person, requiring **droplet isolation**. - This typically involves wearing a mask and sometimes eye protection. *Typhoid* - Typhoid fever is a **fecal-oral disease** caused by *Salmonella Typhi*, transmitted through contaminated food and water. - While proper hand hygiene is crucial, it generally does not require specific isolation precautions beyond **standard precautions** in a hospital setting for most patients.

Question 1

An outbreak of staphylococcal infection involving umbilical cords of seven newborn babies was reported in the nursery. Bacteriological survey reveals that two nurses have a large number of Staphylococcus aureus in the nasopharynx. What test should be performed to determine whether these nurses may have been responsible for the outbreak?

Accepted Answer

Bacteriophage typing

Answer

Coagulase testing

Answer

Nasopharyngeal culture on mannitol salt agar

Answer

Protein A typing

Question 2

Most common cause of infection caused by intravascular catheter -

Accepted Answer

Coagulase negative staphylococci

Answer

Pseudomonas

Answer

E. coli

Answer

Staph aureus

Question 3

Which infection commonly spreads to newborns through caregivers?

Accepted Answer

Candida parapsilosis

Answer

Candida albicans

Answer

Candida tropicalis

Answer

Candida glabrata

Question 4

Which gram-negative organism is particularly notorious for causing late-onset VAP with multidrug resistance?

Accepted Answer

Acinetobacter

Answer

Klebsiella

Answer

Pseudomonas aeruginosa

Answer

Staphylococcus aureus

Question 5

All the following are common nosocomial infections except:

Accepted Answer

Mycobacterium

Answer

Staph. aureus

Answer

Enterobacteriaceae

Answer

P. aeruginosa

Question 6

Most common catheter-related bloodstream infection is due to:

Accepted Answer

Coagulase-negative Staphylococci (CoNS)

Answer

Candida species

Answer

Gram-negative bacilli

Answer

Staphylococcus aureus (S. aureus)

Question 7

Commonest cause of nosocomial infection is

Accepted Answer

Staphylococci

Answer

Klebsiella

Answer

Enterobacteriaceae

Answer

Pseudomonas

Question 8

Most effective way of preventing hospital infection is:

Accepted Answer

Hand washing

Answer

Fumigation

Answer

Sterilization

Answer

Early diagnosis and treatment

Question 9

The most common pathogens responsible for nosocomial pneumonia in ICU are

Accepted Answer

Gram-negative bacteria

Answer

Mycoplasma

Answer

Virus

Answer

Gram-positive bacteria

Question 10

Contact isolation is done for:

Accepted Answer

MRSA

Answer

Mumps

Answer

Diphtheria

Answer

Typhoid

Hospital Acquired Infections — MCQs

Hospital Acquired Infections — MCQs

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