Microbiology, Infection Control and Transmissible Disease
Microbiology
What you are actually dealing with
Microorganisms fall into bacteria (prokaryotic, with a cell wall, Gram-positive or Gram-negative), viruses (no cell wall, obligate intracellular, so antibiotics are irrelevant), fungi, protozoa, and prions - infectious proteins with no nucleic acid. Bacterial spores are the most resistant cellular form; prions are more resistant still, surviving formaldehyde, alcohol and standard autoclaving. Growth requires moisture, nutrients, warmth and time, all of which a cadaver supplies.
The organisms that matter
Gut and skin flora translocate after death: Escherichia coli, Klebsiella, Proteus, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus pyogenes, and anaerobes such as Clostridium perfringens, the classic cause of tissue gas. Bloodborne viruses (hepatitis B and C, HIV) remain viable in blood and body fluids after death. Tuberculosis is a respiratory hazard at aspiration, and respiratory viruses such as SARS-CoV-2 are a droplet risk. Prion disease changes practice completely.
The chain of infection
Infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, susceptible host. Infection control works by breaking any link - usually PPE, hand hygiene, safe sharps and decontamination.
Traps and a rule of thumb
Common errors: assuming death sterilises a body; assuming formaldehyde destroys prions; confusing colonisation with infection; believing one mask protects against everything. Rule of thumb: blood and body fluids are infectious whatever the stated cause of death, so treat every deceased person as potentially infectious.
Infection Control and Transmissible Disease
Standard precautions
Apply to every body regardless of known diagnosis. Hand hygiene at the WHO moments, gloves, apron or gown, eye protection when splashing is likely, safe sharps practice, waste segregation, and decontamination of surfaces and instruments. PPE is put on and removed in the correct order, and hand hygiene follows removal - gloves are never a substitute for washing hands.
The decontamination ladder
Cleaning (physical removal of soil) always comes first; then disinfection (kills most organisms, not necessarily spores); then sterilisation (kills all, including spores). Chlorine-releasing agents are used at about 1,000 ppm available chlorine for blood-contaminated surfaces and 10,000 ppm for spills. Contact time matters, and organic matter inactivates chlorine, which is why cleaning precedes disinfection.
Sharps and exposures
Never recap a needle. Use resheathing devices or take the sharps container to the point of use. A needlestick from a source known to carry hepatitis B, hepatitis C or HIV requires immediate washing, reporting, risk assessment and post-exposure prophylaxis; HIV PEP is most effective when started within hours.
Traps and a rule of thumb
Examiners test gloves used instead of hand hygiene, reuse of single-use gloves, alcohol gel on visibly blood-stained hands, forgotten contact times, and the assumption that a body bag is sterile. Rule of thumb: clean it, then kill it - no disinfectant works through blood, and every sharps injury is a reportable incident.