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ID6 Infectious Diseases
Nosocomial Infections Toronto Notes 2019
Transmission of Infectious Diseases
Table 6. Mechanism of Transmission
Mechanism
Contact
Droplet/ Contact
Airborne
Food/ Waterborne
Zoonotic
Vertical
Mode of Transmission
Direct physical contact, or indirect contact with a fomite
Respiratory droplets (>5 μm) can be projected short distances (≤2 m) and deposit on mucosal surfaces of the recipient (e.g. by coughing, sneezing, or talking); transmission can also occur by direct physical contact of respiratory fluids or indirect contact with a fomite contaminated with respiratory fluids
Airborne droplet nuclei (<5 μm) remain infectious over time and distance
Ingestion of contaminated food or water
Disease transmission from animals to humans either directly or via an insect vector
Spread of disease from parent to offspring
Examples
Skin-to-skin (MRSA) Sexual (N. gonorrhoeae, C. trachomatis, HSV, HIV) Blood-borne (HIV, HBV, HCV)
Influenza, mumps
N. meningitidis, Bordetella pertussis
M. tuberculosis,
disseminated VZV, measles
V. cholerae, Salmonella, HAV, HEV
Animals (rabies, Q fever) Arthropods (malaria, Lyme disease, West Nile virus)
Congenital syndromes (TORCH infections) Perinatal (HIV, HBV, GBS)
Preventative Measure
For patients in health care facilities: Contact precautions
Barrier precautions
Safe needlestick/sharp practices
For patients in health care facilities: Contact/droplet precautions
For patients in health care facilities: Airborne precautions
Prophylactic vaccinations where available
Ensure clean food/water supply
For patients in health care facilities:
Contact precautions used for admitted patients with fecal incontinence when stool is unable to be contained in diapers
Prophylactic medications, vaccinations
Protective clothing, insect repellent, mosquito nets, tick inspection
Prenatal screening Prophylactic treatment
Table 7. Common Nosocomial Infectious Agents
Nosocomial Infections
• definition:infectionsacquired>48hafteradmissiontoahealthcarefacilityORwithin30dfromdischarge • riskfactors:prolongedhospitalstay,antibioticuse,surgery,hemodialysis,intensivecare,colonization
with a resistant organism, immunodeficiency
■ patientswithnosocomialinfectionshavehighermortality,longerhospitalstays,andhigherhealthcare
costs
• handhygieneisanessentialprecaution
Bacteria
Methicillin-Resistant S. aureus (MRSA)
Vancomycin-Resistant Enterococcus (VRE)
Clostridium difficile (C. difficile)
Extended Spectrum β-lactam Producers (ESBL producing
E. coli, K. pneumoniae)
Characteristics
Gram-positive cocci
Majority are E. faecium Resistant if minimum inhibitory concentration of vancomycin is ≥32 μg/mL
Releases exotoxins A and B Hypervirulent strain (NAP1/ B1/027) has been responsible for increase in incidence and severity
Resistant to most β-lactam antibiotics except carbapenams
e.g. penicillins, aztreonam,** and cephalosporins
Manifestation
Skin and soft tissue infection Bacteremia
Pneumonia
Endocarditis
Osteomyelitis
Rarely causes disease in healthy people UTI
Bacteremia
Endocarditis
Meningitis
Fever, nausea, abdominal pain Watery diarrhea Pseudomembranous colitis Severe: toxic megacolon
Risk of bowel perforation Associated with antibiotic use Leukocytosis
UTI
Pulmonary infection
Bacteremia
Liver abscess in susceptible patients Meningitis
Investigations
Admission screening culture from nares and peri-anal region identifies colonization
Culture of infection site
CXR
Rectal or perirectal swab OR stool culture for colonization
Culture of infected site
Stool PCR for toxin A and B genes Stool immunoassay for
toxins A and B (less sensitive than PCR)
AXR (may see colonic dilatation) Sigmoidoscopy for pseudomembranes; avoid if known colonic dilatation
Blood, sputum, urine, or aspirated body fluid culture
Imaging at infection site
(CXR, CT, U/S)
Management
Contact precautions
For infection: vancomycin or daptomycin or linezolid To decolonize: 2% chlorhexidine wash OD (+ rifampin + (doxycycline or TMP/SMX) + mupirocin cream bid to nares) x 7 d
Contact precautions*
Ampicillin if susceptible
Otherwise, linezolid, tigecycline, or daptomycin depending on site of infection
No effective decolonization methods identified
Contact precautions
Stop culprit antibiotic therapy (primarily fluoroquinolones and clindamycin)
Supportive therapy (IV fluids)
Empiric treatment with either vancomycin or fidaxomicin
If access to empiric treatment is limited, then metronidazole may be used
For fulminant C. difficle infection (previously called severe), oral vancomycin is used. IV metronidazole added to regimen if ileus present
Carbapenems or non-β-lactam antibiotics can be used for empiric therapy
*TheuseofcontactprecautionsforVREvariesdependingoninstitutionalpolicies. **NotavailableinCanada