Infection Prevention and Respiratory Care Microbiology

Microbiology is the study of microorganisms, including bacteria, viruses, protozoa, and fungi.
Microorganisms are present in every environment and are categorized as pathogenic (producing infectious disease in susceptible hosts) or normal flora (normally residing at specific body sites without causing disease).
Clostridium difficile causes a disruption in the normal flora.
Germ theory, described by Pasteur, establishes that diseases are caused by microorganisms.
Diagnosis requires isolation of the suspected pathogen from the infection site via culture using aseptic technique, followed by microscopic examination with biological staining.
Virulence represents the ability of a microorganism to cause disease, ranging from low to maximum.

Bacteria classification is based on staining characteristics:
- Gram-positive bacteria retain gentian violet stain after an alcohol wash and appear blue or violet (e.g., Streptococcus pneumoniae, Staphylococcus aureus).
- Gram-negative bacteria do not retain gentian violet stain and appear red (e.g., Pseudomonas aeruginosa, E. coli).
- Acid-fast stain (Ziehl-Neelsen) identifies Mycobacterium species (e.g., Tuberculosis), which retain red dye after an acid wash.
Bacterial growth requires moisture, nutrients (autotrophs require simple inorganic; heterotrophs require complex organic), and specific oxygen conditions (aerobes, anaerobes, or facultative).
Viruses are non-living pathogens composed of DNA or RNA that cannot self-replicate and require a susceptible host (e.g., SARS-CoV-2, influenza, HIV).
Fungal infections are caused by yeast or mold and affect skin, mouth, nails, lungs, or systemic structures (e.g., Thrush).
Protozoan infections are caused by single-celled parasites that infect blood, the intestinal tract, brain, skin, eyes, or other structures (e.g., Pneumocystis Jirovecii).

Infection transmission requires a source/reservoir, a route of transmission, and a susceptible host.
Primary sources include humans (patients, personnel, visitors), contaminated fluids (waterborne pathogens include Legionella species and nontuberculous mycobacteria), and insects or rodents.
Contact Transmission:
- Direct contact occurs person-to-person.
- Indirect contact involves intermediate objects (fomites) or vehicles; examples include Staphylococcus.
Airborne Transmission:
- Microscopic organisms are transported by air currents over long distances (e.g., TB, measles, Legionella).
- Requires isolation in a negative air pressure room with doors closed, laminar flow in ICU/ER/surgery, and PPE including N95 masks (filtering at least $95\%$ of particles) or PAPR.
Droplet Transmission:
- Transmission occurs via large respiratory droplets generated by coughing, sneezing, talking, or procedures (e.g., bronchoscopy, aerosol therapy, suctioning, changing circuits).
- Requires a private room and PPE including surgical masks when within $3\,\text{feet}$ of the patient (e.g., Influenza).
Vehicle Transmission:
- Indirect contact through contaminated intermediate objects such as ventilators, PFT machines, or ECG machines.
Vector Transmission:
- Involves intermediate hosts such as insects, plants, or animals (e.g., Plague, Lyme disease, Zika).

Community Acquired infections develop outside healthcare facilities.
Nosocomial (Hospital Acquired) infections develop at least $72\,\text{hours}$ after hospital admission.
Healthcare personnel are the primary cause of nosocomial infections due to inadequate hand washing or nasal discharge.
Containers and bottles must be labeled with the date and time of opening and used within $24\,\text{hour}$ of opening.
Ventilator Associated Pneumonia (VAP) is caused by the aspiration of bacteria colonizing the upper GI tract or oropharynx (e.g., Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia spp., Serratia marcescens, Acinetobacter calcoaceticus-baumannii, Proteus mirabilis, Haemophilus pneumoniae).
Respiratory Therapy Equipment Protocols:
- Use one-way valves or personal sampling chambers on devices used with multiple patients, such as Wright respirometers.
- Use unit dose aerosol medications, or administer aerosolized medications via MDI to minimize cross-contamination.
- Double bag equipment from patients with HIV/AIDS and hepatitis prior to gas sterilization.
- Keep clean and dirty equipment physically separated, and place dirty equipment in plastic bags during transport.

Hand hygiene is the single most effective method to prevent contact transmission; use alcohol-based products, or soap and water when hands are visibly soiled.
Donning Sequence for PPE:
1. Hand Hygiene
2. Gown
3. Mask or Respirator
4. Eye Protection (goggles or face shield)
5. Gloves
Doffing Sequence for PPE:
1. Gloves
2. Goggles or Face Shield
3. Gown
4. Mask or Respirator
5. Hand Hygiene
Sharps Management: Never recap needles or remove them from disposable syringes by hand; discard immediately into puncture-resistant, tamper-proof containers.
Waste Disposal: Biohazardous/medical waste must be placed in marked biohazard bags inside rigid containers with lids kept on at all times.

Facilities foster a culture of safety using "stop the line" authority and a "just culture" allowing error reporting without fear of retaliation.
Employee immunizations (e.g., Hep B, flu, varicella, MMR) reduce presenteeism (working while sick).

Question: Why do healthcare workers go to work when sick, especially when they know it puts others at risk for infection (such as vulnerable patients)?