How are human reservoirs of infection characterized in the healthcare setting?

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Last updated: May 4, 2026 • View editorial policy

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Human Reservoirs of Infection in Healthcare Settings

In healthcare settings, human reservoirs of infection are characterized as colonized patients and healthcare workers who harbor pathogenic organisms asymptomatically or symptomatically and serve as the primary sources for transmission of healthcare-associated infections. 1

Key Characteristics of Human Reservoirs

Colonized Patients as Primary Reservoirs

Colonized patients represent the most significant human reservoir in healthcare settings. These individuals:

  • Harbor antibiotic-resistant organisms without active infection, particularly multidrug-resistant Gram-negative bacteria (MDR-GNB) 2
  • Carry organisms at multiple body sites including throat, skin lesions, rectum, nose, anus, and vagina 3
  • Precede infection with colonization - rectal colonization with resistant Enterobacterales has been shown to precede surgical site infections 2
  • Less than 5% of adults carry Group A Streptococcus (GAS) in their throat, making positive screening highly indicative of transmission risk 3

The evidence strongly demonstrates that rectal colonization screening is particularly important before high-risk procedures. The 2023 ESCMID/EUCIC guidelines conditionally recommend rectal screening for fluoroquinolone-resistant Enterobacterales before prostate biopsy and for extended-spectrum cephalosporin-resistant Enterobacterales in colorectal surgery and solid organ transplantation 2.

Healthcare Workers as Vectors and Reservoirs

Healthcare workers function as both reservoirs and vectors of transmission:

  • Asymptomatic carriage at multiple anatomical sites (throat, skin lesions, nose, anus, vagina) 3
  • Initial screening should prioritize throat and skin lesions, with expanded screening to nose, anus, and vagina when initial sites are negative but epidemiological links exist 3
  • Skin conditions and dermatitis require special attention, as exfoliating skin conditions can harbor and transmit pathogens 3
  • Healthcare workers' hands serve as the primary vector for transmission between colonized reservoirs and susceptible patients 1

Clinical Implications and Screening Approach

When to Screen Human Reservoirs

Screening is indicated when:

  • Epidemiological investigation links healthcare workers to cases of healthcare-associated infection 3
  • Patients are undergoing high-risk procedures (transrectal prostate biopsy, colorectal surgery, solid organ transplantation) 2
  • Local epidemiology suggests high rates of carbapenem-resistant Enterobacterales (CRE) or carbapenem-resistant Acinetobacter baumannii (CRAB) before transplant surgery 2

Screening Sites Priority

For healthcare workers:

  1. First-line: Throat and skin lesions (including all exfoliating conditions)
  2. Second-line: Anterior nares, anus, vagina when first-line negative but epidemiological link exists 3

For patients:

  • Rectal screening for MDR-GNB before high-risk surgeries 2

Important Caveats

Decolonization is NOT routinely recommended for MDR-GNB carriers before surgery due to lack of long-term efficacy and risk of selecting for antibiotic resistance 2. This is a critical pitfall to avoid - the focus should be on targeted perioperative antibiotic prophylaxis rather than attempting decolonization.

The 2013 ECDC guidance emphasizes that periodical active surveillance should be performed by trained personnel to adjust antibiotic prophylaxis selection 2, highlighting that screening programs require proper infrastructure and expertise.

Occupational health involvement is essential for healthcare worker screening to maintain confidentiality and ensure proper examination for skin lesions and dermatitis 3.

Human reservoirs place enormous responsibility on healthcare providers to recognize their role in transmission and adhere to infection prevention protocols 1.

References

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.