bio 251

Overview of Key Concepts

  • Asymptomatic Carriers

    • Definition: Individuals who carry a disease but show no symptoms or signs of the infection.
    • Often found in oral and nasal cavities.

  • Symptoms of Illness

    • Initial symptom: Bacteremia (presence of bacteria in the blood) caused by toxins.
    • Other symptoms include fever, headache, and a stiff neck (rigid neck where bending or movement is painful).
    • If not treated, progression can lead to coma and death within hours.

High-Risk Groups

  • At-Risk Populations:
    • Infants under 2 years old.
    • College students, particularly those living in dormitories.
    • Importance of early detection for treatment with antibiotics, which can prevent severe outcomes like brain damage or hearing loss.
    • Mention of vaccines available, particularly around school seasons to prevent meningitis.

Neisseria Genus

  • Mentioned as a concern in beta proteobacteria group.

Gamma Proteobacteria

  • Overview:
    • A very diverse group with various shapes, arrangements, metabolic types, and reproductive strategies.
    • Ribosomal studies classify them into five main subgroups.

Main Subgroups of Gamma Proteobacteria

  1. Purple Sulfur Bacteria

    • Obligate anaerobes that oxidize hydrogen sulfide to sulfur producing sulfur granules instead of using oxygen.

  2. Intracellular Pathogens

    • Definition: Facultative intracellular parasites (can reproduce both inside and outside of host cells).
    • Genus of interest: Legionella (Legionella pneumophila).
    • Common in water systems such as air conditioning and hot water tanks.
    • Causes Legionnaires' disease, contracted through aerosols and water mists, linked to outbreaks in contexts like conventions.

  3. Coxiella

    • Obligate intracellular parasites.
    • Causes acute fever; humans infected via aerosols from domestic animals.
    • At-risk groups include farmers, veterinarians, and slaughterhouse workers.
    • Illness usually presents as flu-like and may not require antibiotics.

  4. Methane Oxidizers

    • Utilize methane as a carbon source.

  5. Facultative Anaerobes

    • Families included: Enterobacteriaceae, Vibrionaceae, Pasteurellaceae.
    • Called the enterics; found in intestinal tracts of humans and other mammals.
    • Most ferment glucose and some produce bacterial toxins known as bacteriocins that kill or inhibit other bacteria.

Key Examples of Enteric Bacteria

  • Escherichia coli (E. coli)

    • Important in microbiology; easily cultured and a known indicator of contamination in food and water.
    • Generally not pathogenic; can be opportunistic and cause urinary tract infections.
    • Some strains produce enterotoxins leading to diarrhea; particularly strain O157:H7, linked to severe outcomes like hemolytic uremic syndrome (kidney failure).
    • Risk factors: children, older adults, immunocompromised individuals.
    • Noted sources of contamination include raw meat, especially hamburger, and produce contaminated by fecal material.

  • Salmonella

    • Common pathogens usually found in the intestinal tracts of animals like cattle and poultry.
    • Only two species of note affecting humans:
    1. Salmonella enterica
    2. Salmonella Typhi - responsible for typhoid fever (noted for its association with Typhoid Mary).
    • Mode of transmission: oral-fecal route and can lead to severe diarrhea if untreated, with a 2-3 week incubation period.

  • Shigella

    • Causes shigellosis, with 450,000 infections annually in the US, leading to significant medical costs.
    • Symptoms include diarrhea (often bloody), vomiting, and dehydration.
    • Highly contagious; transmitted via oral-fecal route and through contact with contaminated objects.

  • Yersinia pestis

    • Noted for being the causative agent of bubonic plague (the Black Death).

Other Noteworthy Bacteria

  • Chronobacter

    • Notably associated with infant formula recalls in 2021 and 2022, causing meningitis and necrotizing enterocolitis in infants.

  • Uropathogenic Enterobacteriaceae

    • Common causes of urinary tract infections and other healthcare-associated infections, known as nosocomial infections.
    • Examples include Serratia marcescens and Proteus (e.g., Proteus mirabilis and Proteus vulgaris).

Conclusion

  • This presentation ends here; further detailed discussions are planned for future sessions, especially on topics not yet covered, including the bubonic plague and other related pathogens.