TABLE 2-1 Part 1: Examples of Emergent Bacteria, Rickettsiae, and Chlamydiae


Related Diseases/Symptoms

Mode of Transmission

Cause(s) of Emergence

Aeromonas species

Aeromonad gastroenteritis, cellulitis, wound infection, septicemia

Ingestion of contaminated water or food; entry of organism through a break in the skin

Immunosuppression; improved technology for detection and differentiation

Borrelia burgdorferi

Lyme disease: rash, fever, neurologic and cardiac abnormalities, arthritis

Bite of infective Ixodes tick

Increase in deer and human populations in wooded areas

Campylobacter jejuni

Campylobacter enteritis: abdominal pain, diarrhea, fever

Ingestion of contaminated food, water, or milk; fecal-oral spread from infected person or animal

Increased recognition; consumption of uncooked poultry

Chlamydia pneumoniae (TWAR strain)

TWAR infection: fever, myalgias, cough, sore throat, pneumonia

Inhalation of infective organisms; possibly by direct contact with secretions of an infected person

Increased recognition

Chlamydia trachomatis

Trachoma, genital infections, conjunctivitis; infection during pregnancy can result in infant pneumonia

Sexual intercourse

Increased sexual activity; changes in sanitation

Clostridium difficile

Colitis: abdominal pain, watery diarrhea, bloody diarrhea

Fecal-oral transmission; contact with the organism in the environment

Increased recognition; immunosuppression

Ehrlichia chaffeensis

Ehrlichiosis: febrile illness (fever, headache, nausea, vomiting, myalgia)

Unknown; tick is suspected vector

Increased recognition; possibly increase in host and vector populations

Escherichia coli O157:H7

Hemorrhagic colitis; thrombocytopenia; hemolytic uremic syndrome

Ingestion of contaminated food, esp. undercooked beef and raw milk

Likely due to the development of a new pathogen

Haemophilus influenzae biogroup aegyptius

Brazilian purpuric fever: purulent conjunctivitis, high fever, vomiting, and purpura

Contact with discharges of infected persons; eye flies are suspected vectors

Possibly an increase in virulence due to mutation

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