Health and Community 11: Nosocomial and Community Infections

Nosocomial and Community Infections

Introduction

  • Microbes play a significant role in our lives and the health of our communities.
  • Focus on nosocomial (healthcare-associated) and community infections.
Aims:
  • Define hospital and community infections.
  • Increase understanding of the burden of specific microbes in healthcare and community settings.
  • Develop awareness of common prevention and control methods.

Definitions

Nosocomial Infections
  • Also known as healthcare-associated infections (HAIs).
  • Infection develops in a patient after 48 hours or more in a healthcare setting.
  • Distinction is important due to immunocompromised patients and microbial contacts in healthcare.
Non-Nosocomial Infections
  • Community-acquired infections.
  • Acquired outside of a healthcare setting.
  • Infections diagnosed within the first 48 hours are assumed to be community-acquired.
  • Difficulty in completely separating the origin of infections can arise.

Basic Statistics

  • Approximately 7% of hospitalized patients in high-income countries acquire HAIs.
  • Around 10% in low and middle-income countries.
  • Indicates a significant challenge in managing infection and transmission within healthcare settings.

Nosocomial Pathogens of Interest

  • E. coli, norovirus, Klebsiella species, Clostridium difficile, influenza, Candida, COVID-19.
  • COVID-19 transmission in healthcare settings:
    • Red bars indicate increasing proportion of transmission over time.
    • Acute care settings: transmission occurs, but relatively few (10%) acquire COVID-19.
    • Residential settings (e.g., old people's homes): high proportion (approaching 100%) acquire COVID-19.
    • Elderly patients sent home from hospitals led to sustained transmission in residential care settings.

Main Types of Nosocomial Infections

  • Central line-associated infections.
  • Catheter-associated UTIs.
  • Nosocomial pneumonia (e.g., ventilator-associated pneumonia).
  • Surgical site infections.
  • Gastrointestinal infections.

Gastrointestinal Infections

  • Foodborne and waterborne diseases pose a risk to patients in healthcare settings.
  • Patients may be particularly young, old, or immunocompromised.
  • Norovirus is highly infectious and can lead to closing hospital wards.

Transmission Routes in Healthcare Settings

  • Patient themselves (endogenous bacteria).
  • Patient to patient (direct contact, droplets).
  • Healthcare workers (hygiene, hand hygiene practices, fecal-oral transmission).
  • Environment (presence of bacteria on medical devices, surfaces, food, water, air contaminants, pests).
  • Aim is to cut any lines of transmission to the patient.

Control and Prevention

  • Safe disposal of waste, especially healthcare-associated waste.
  • Proper training for healthcare workers.
  • Public health bodies: Public Health England (PHE), NICE, Care Quality Commission (CQC).
  • PHE sets standards and principles for environment, hand hygiene, PPE, safe disposal of sharps, aseptic technique.
  • CQC monitors compliance with these standards.
  • Keep the hospital clean.
  • Hand hygiene.
  • Specific high-risk areas: indwelling urethra catheters, IV access points.
  • Increased risk with duration of stay, particularly in ICU.
  • Acquiring a healthcare-associated infection increases the risk of death.
  • Mitigating risk is important, but avoidance of hospital and interventions is associated with worse outcomes.

Pathogens: Closer Look

Clostridioides difficile (C. Diff)
  • Gram-positive, rod-shaped, obligate anaerobe.
  • Transmitted via fecal-oral route.
  • Moderate danger, significant morbidity.
  • Biggest cause of infectious diarrhea in hospital patients.
  • Causes mild to severe diarrhea, bowel perforation.
Virulence Factors:
  • Spore-forming: spores resistant to heat, oxygen, ethanol-based disinfectants.
  • Spores ingested, pass through digestive processes, germinate in large colon.
  • Toxin-producing: bacteria invade gut epithelia and release toxins that damage host cells.
  • Damage leads to gut porosity and pro-inflammatory response.
Risk Factors:

  • Elderly, those in healthcare settings, those on antibiotics.

  • Disruption of microbiome allows C. Diff to proliferate.

  • Antibiotic use, proton pump inhibitors, inflammatory bowel disease.

  • Major link to dysbiosis.

  • Changes in treatment and control:

    • Reviewing medicines, cautious antibiotic use.
    • Isolation, appropriate hand hygiene, PPE.
    • Bleach cleaning (concentrated).
Klebsiella
  • Associated with ventilator-associated pneumonia.
  • Family Enterobacteriaceae, transmitted via fecal-oral routes.
  • Klebsiella is ubiquitous, found across different tissues and in the environment.
  • Main species of interest: Klebsiella pneumoniae.
  • Gram-negative, rod-shaped, encapsulated.
  • Forms a biofilm.
  • Resistant to some last-line antibiotics.
Virulence
  • Dangerousness is moderate, depends on location.
  • Sepsis associated with Klebsiella has a high mortality rate (~50%).
  • High fever, chest pain, currant jelly sputum.
Epidemiology
  • Ubiquitous in nature, found in water, sewage, soil.
  • Many are carriers in gut and nasopharynx.
  • Emergence of drug resistance, disinfectant resistance.
  • Transmission is complex, via person-to-person contact and environmental contamination.
  • Medical devices (ventilators, catheters, wounds) at risk.
Biofilm Formation
  • Complex bacterial community encased in an extracellular matrix (proteins, carbohydrates, DNA).
  • Protects bacteria from environmental degradation (disinfectants) and host immune response.
Virulence Factors Contributing to Biofilm Formation
  • Capsule inhibits complement decomposition, opsonization, and phagocytosis.
    • As of 2023, 134 capsule types identified. Variability allows Klebsiella to avoid host immune response.
    • Capsule has bactericidal effects on other bacteria.
  • LPS (lipopolysaccharide) promotes attachment to surfaces.
  • Fimbriae associated with adhesion and binding.
    • Type 1: binding to mucosa.
    • Type 3: binding to abiotic factors.
  • Siderophores: upregulate iron uptake, downregulate inflammatory responses.
  • Quorum sensing: communication mechanism within the biofilm that allows it to adapt and change.
Antibiotic Resistance
  • Rise of antibiotic resistance in Klebsiella.
  • Healthcare-associated infections are often antimicrobially resistant.
  • Driven by antibiotic use within healthcare settings.

Community-Acquired Infections

  • Outside the hospital.
  • Person-to-person transmission, fecal-oral transmission, zoonoses, vector-borne.
C. Diff in the Community
  • Emergence of disease has been growing over the past twenty years.
  • Risk factors are the same as in the hospital.
  • Additional environmental sources: animal and environmental sources.
Community-Acquired Pneumonia
  • No medical device involved.
  • Down to bacteria, co-infection with viruses.
  • Cases: Streptococcus pneumoniae is the largest contributor.
  • Gram-positive facultative anaerobe (Streptococcus pneumoniae).
  • Transmission is direct person-to-person via droplet.
  • Toxin-forming, polysaccharide capsule, evidence of multi-drug resistance.
Control Measures
  • Hygiene and cleanliness.
  • Vaccination (childhood vaccination for pneumococcal diseases).

Summary

  • Nosocomial infections occur in hospital, community infections are outside.
  • Less understandable infection source is more complex in community environment.
  • Gastro infections and pneumonia occur in both, but causative agents may differ.