9. The surrounding environment as a factor for spreading causative agents of infectious diseases. Microbial flora in water, soil, air. Microorganisms in foodstuff, hospital services, etc. Microorganisms of sanitary importance.

I. Introduction: Microorganisms in the Environment

• Microorganisms are ubiquitous and play crucial roles in biogeochemical cycles, biodegradation, and ecosystem balance.
• Environmental microbiology studies the diversity, distribution, and impact of microbes in various ecological and human-related habitats.

II. Microorganisms in Different Environments

A. Soil Microbes

• Soil harbors the richest microbial diversity.
• Key groups:
• Bacteria: Bacillus, Clostridium, Pseudomonas, Streptomyces (decomposers)
• Fungi: Aspergillus, Penicillium
• Actinomycetes: important for antibiotic production
• Nitrogen fixers: Rhizobium, Azotobacter
• Roles:
• Decomposition of organic matter
• Nutrient cycling (N, S, P)
• Bioremediation

B. Water Microorganisms

• Surface water contains algae, protozoa, bacteria, viruses
• Pathogenic waterborne microbes:
• Vibrio cholerae, Salmonella, Shigella, E. coli (ETEC, EHEC), enteric viruses (HAV, norovirus), protozoa (Giardia, Entamoeba)
• Indicators of pollution:

• Fecal coliforms (E. coli) → indicator of fecal contamination
• Enterococci
• Significance:
• Waterborne diseases (cholera, typhoid, dysentery, hepatitis A, giardiasis)
• Pollution monitoring and water safety

C. Air Microorganisms

• Microbes in air are mostly transient, carried via aerosols, dust particles, droplets
• Common airborne microbes:
• Staphylococcus, Streptococcus, Mycobacterium tuberculosis, fungal spores (Aspergillus, Penicillium)
• Significance:
• Airborne diseases: tuberculosis, influenza, measles, COVID-19
• Hospital ventilation and sterilization are key

D. Food Microorganisms

• Food can be a vehicle or substrate for microbial growth
• Types:
• Spoilage organisms: Pseudomonas, Lactobacillus, Penicillium
• Pathogens: Salmonella, Listeria monocytogenes, E. coli O157:H7, Clostridium botulinum
• Sources:
• Improper storage, contaminated water, unclean handling
• Preservation:
• Refrigeration, pasteurization, sterilization, irradiation, preservatives

E. Healthcare-Associated Microorganisms

• Nosocomial pathogens: Staphylococcus aureus (MRSA), Pseudomonas, Acinetobacter, Klebsiella, Clostridioides difficile
• Biofilm formation on surfaces, catheters, ventilators
• High-risk units: ICUs, surgical wards
• Transmission:
• Airborne, contact (hands, surfaces), invasive devices
• Requires strict infection control measures