Nosocomial Infections and Their Common Causative Agents: Introduction, Types, List of Microbial Agents, and Keynotes

Introduction of Nosocomial Infections

Nosocomial infections are also called hospital-acquired infections (HAI) that occur during hospital stay and microbes are the causative agent of such infections.

Common Nosocomial Infections

The most commonly occurring nosocomial infections are as follows-

• Intravenous catheter-related bloodstream infection(CRBSI)
• Ventilator-associated pneumonia(VAP)
• Catheter-associated urinary tract infections(CAUTI)
• Surgical site infections(STI)
• Clostridium difficile-associated diarrhea (CDAD)

Microbial Etiological Agents of Common Nosocomial Infections

The most common microbes causing hospital-acquired infections (HAI) are-

• Bacteria including multidrug-resistant (MDR) bacteria-
  

1. Acinetobacter baumannii Complex(ABC)
2. Klebsiella species
3. Escherichia coli
4. Enterobacter species
5. Pseudomonas aeruginosa
6. Staphylococcus aureus
7. Vancomycin-resistant enterococci (VRE)
8. Clostridium difficile
9. Mycobacterium tuberculosis
   

• Fungi

1. Candida albicans
2. Non-albicans candida species
3. Aspergillus species
4. Mucor species

• Viruses

1. Blood-borne infection: Human immunodeficiency virus (HIV), Hepatitis B virus (HBV), hepatitis C virus (HCV)
2. Respiratory infection: influenza A and B viruses, respiratory syncytial virus(RSV), rhinovirus, adenovirus
3. Faeco-orally transmitted infections: Rotavirus, enteroviruses

Gallery of Microbial Etiological Agents of Common Nosocomial Infections

Mucoid lactose fermenter colonies of Klebsiella pneumoniae on Macconkey agar

E. coli on blood agar

Keynotes

• Role of the microbiologist to control nosocomial infections are-

1. Handling clinical specimens to maximize the likelihood of a microbiological
   diagnosis.
2. Guidelines development for the appropriate collection, transport, and handling of specimens.
3. Implementing good laboratory practice.
4. Ensuring safe laboratory practice to avoid infections in staff.
5. Performing antimicrobial susceptibility testing (AST) following internationally recognized
   methods, and providing summary reports of the prevalence of resistance.
6. Monitoring sterilization, disinfection, and the environment where necessary.
7. Timely communication of results to the Infection Control Committee (ICC) or the hygiene
   officer.
8. Epidemiological typing of hospital microbes where necessary.

• Together the above-mentioned infections account for over 90% of all hospital-acquired infections.

Further Readings

• https://www.ncbi.nlm.nih.gov/books/NBK559312/
• https://www.osmosis.org/answers/nosocomial-infection
• https://inivos.com/blog/5-most-common-hospital-acquired-infections-hais/
• https://apps.who.int/iris/bitstream/handle/10665/67350/WHO_CDS_CSR_EPH_2002.12.pdf