113. Microbiological Aspects of Healthcare-Associated Infections (HAIs)
Covers healthcare-associated infections, defined by timing of onset relative to admission and discharge, and why they matter for morbidity, mortality and resistance. It then sets out a table linking common infection types, such as CAUTI, CLABSI, VAP, surgical site infection and C. difficile infection, to their usual pathogens. Risk factors, laboratory diagnosis by specimen type, treatment choices for multidrug-resistant organisms such as MRSA, ESBL producers, Pseudomonas, Acinetobacter and VRE, and infection control measures close the note.
Topic 113 of 113 in the MU Sofia syllabus for Microbiology (Dental Medicine, Year 2). The free AceMed note covers it in 7 sections, about 200 words (2 min of reading), with 14 flashcards.
In this note
Microbiological Aspects of Healthcare-Associated Infections (HAIs)
I. Definition and Overview
II. Common Types of HAIs and Their Pathogens
III. Risk Factors and Pathogenesis
IV. Laboratory Diagnosis
V. Treatment and Antibiotic Resistance
VI. Prevention and Infection Control
I. Definition and Overview
Healthcare-associated infections (HAIs) are infections acquired ≥48 hours after admission or soon after discharge, not present or incubating at the time of admission.
HAIs are major causes of morbidity, mortality, and antibiotic resistance in hospitals.
Transmission is often via contaminated hands, devices, surfaces, or aerosolization.
III. Risk Factors and Pathogenesis
Invasive procedures: catheters, intubation, surgery
Antibiotic use: disrupts normal flora → overgrowth of resistant strains
Immunosuppression: cancer, organ transplant, steroids
Poor hygiene & asepsis: hand hygiene failure is a major contributor
Biofilm formation on medical devices → chronic infection and resistance
IV. Laboratory Diagnosis
Urine culture: CAUTI
Blood culture: CLABSI (multiple sites, catheter tip if removed)
Endotracheal aspirate/BAL: for VAP
Wound swabs or tissue: for SSIs
Stool toxin assay / PCR: for C. difficile
All should be paired with antimicrobial susceptibility testing to guide therapy.
V. Treatment and Antibiotic Resistance
Many HAI pathogens are multidrug-resistant (MDR):
MRSA: use vancomycin or linezolid
ESBL-producing Enterobacteriaceae: use carbapenems
Pseudomonas/Acinetobacter: may require colistin or ceftolozane-tazobactam
VRE (vancomycin-resistant Enterococcus): use linezolid or daptomycin
Early empirical therapy is critical, adjusted after cultures.
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