Are Klebsiella pneumoniae, Enterobacter cloacae, and Citrobacter freundii contagious?

Klebsiella pneumoniae, Enterobacter cloacae, and Citrobacter freundii Transmission and Contagion

Yes, Klebsiella pneumoniae, Enterobacter cloacae, and Citrobacter freundii are contagious and can be transmitted between patients, particularly in healthcare settings, which is why strict infection control measures are recommended by clinical guidelines. 1

Transmission Mechanisms

These Enterobacteriaceae organisms are primarily transmitted through:

1. Direct contact transmission:

   • Healthcare worker hands (primary route)
   • Patient-to-patient contact
   • Contact with contaminated surfaces and medical equipment

2. Environmental reservoirs:

   • Contaminated surfaces (mattresses, beds, bedside tables, chairs)
   • Medical equipment (especially respiratory equipment and endoscopes)
   • Washbasins and sinks

3. NOT typically airborne:

   • Unlike respiratory pathogens such as Streptococcus pneumoniae, these Enterobacteriaceae are not generally transmitted through airborne droplets 1
   • They do not spread through coughing or sneezing like common respiratory pathogens

Evidence of Transmission

• Hospital outbreaks have been documented, particularly with carbapenemase-producing strains
• A 2017 study documented an outbreak of KPC-producing Citrobacter freundii in a tertiary care hospital in Florida, where 3 cases in the same ICU were caused by the identical clone, confirming person-to-person transmission 2
• Hospital wastewater studies have identified high burdens of carbapenemase-producing Enterobacterales, including these species, suggesting environmental contamination and potential for transmission 3

Prevention of Transmission

The European Society of Clinical Microbiology and Infectious Diseases (ESCMID) recommends several evidence-based measures to prevent transmission 1:

Hand Hygiene

• Strong recommendation despite varying evidence levels
• Alcohol-based hand rub before and after all patient contacts
• Soap and water when hands are visibly soiled
• Regular monitoring of compliance and feedback

Contact Precautions

• Strong recommendation for all colonized or infected patients
• Wearing gloves and gowns when entering patient rooms
• Prompt removal after care followed by hand hygiene
• Regular auditing of adherence

Patient Isolation

• Strong recommendation to isolate colonized and infected patients in single rooms
• Monitor for potential adverse effects of isolation (reduced contact with healthcare providers, psychological effects)

Active Screening

• Strong recommendation for screening high-risk patients
• Screening cultures should include:
  • Stool samples or rectal/perirectal swabs
  • Inguinal area samples
  • Samples from catheters and wounds
• Consider weekly screening in high-risk units

Environmental Cleaning

• Strong recommendation for enhanced cleaning protocols
• Specify which items need disinfection and appropriate agents
• Dedicate non-critical equipment to colonized/infected patients
• Consider unit closure for intensive cleaning during outbreaks

Special Considerations

• Healthcare Worker Screening: Conditional recommendation to screen staff epidemiologically linked to case clusters 1
• Antimicrobial Stewardship: Strong recommendation to restrict antibiotic usage to reduce spread 1, 4
• Alert Systems: Use alert codes to identify previously positive patients upon readmission 1
• Staff Cohorting: Strong recommendation to dedicate specific staff to care for colonized/infected patients 1

Common Pitfalls in Prevention

1. Failure to distinguish colonization from infection: Important to avoid unnecessary antibiotic use while still implementing appropriate isolation 4

2. Inadequate environmental cleaning: Specific protocols for disinfection of endoscopes and respiratory equipment are essential 1

3. Overlooking less common species: While Klebsiella pneumoniae is most frequently isolated, Citrobacter freundii and Enterobacter cloacae can also cause outbreaks and may be underdetected 2

4. Delayed recognition of outbreaks: Molecular typing methods like whole genome sequencing may be needed to identify related cases 2

By implementing comprehensive infection control measures, healthcare facilities can significantly reduce the transmission of these potentially dangerous pathogens and prevent outbreaks.