CONDITIONAL PATHOGENS
Cause disease, other than trivial local infections, only in persons with reduced resistance to infection (including new-born infants and old people) or when implanted directly into tissue or a normally sterile body area. Examples:
ORGANISM
TYPE
SOURCE
DISEASE
Streptococcus agalactiae
Bacteria
Normal flora
Infections e.g. pneumonia, UTI, meningitis
Enterococcus spp.
Bacteria
Normal flora
Infections e.g. UTI, meningitis
Clostridium tetani
Bacteria
Soil
Tetanus
Escherichia coli
Bacteria
Normal flora
Gastroenteritis, UTI, neonatal meningitis
Klebsiella spp
Bacteria
Normal flora
Infections
Serratia marcescens
Bacteria
Everywhere
Nosocomial infections
Acinetobacter baumanii
Bacteria
Equipments
Nosocomial infections
Pseudomonas aeruginosa
Bacteria
Everywhere
Infections, nosocomial infections
Candida spp.
Fungi
Normal flora
Candidiasis
table
OPPORTUNISTIC PATHOGENS
Cause generalized disease, but only in patients with profoundly diminished resistance to infection. Examples:
ORGANISMS
TYPE
SOURCE
DISEASE
atypical mycobacteria
Bacteria
Surfaces
Infections
Nocardia asteroides
Bacteria
Air, soil
Nocardiosis
Pneumocystis pneumonia
Fungi
Unknown
Pneumonia
EMERGING INFECTIOUS PATHOGENS
These are pathogens that cause diseases that are not been seen before or were once common in previous era. Examples are the exotic diseases:
ORGANISMS
TYPE
SOURCE
DISEASE
Helicobacter pylori
Bacteria
Food, water
Peptic ulcer disease
MRSA
Bacteria
Food, water, contact
Troublesome infections
Influenza virus
Virus
Air
Influenza e.g. H5N1, H1N1
SARS coronavirus
Virus
Air
Severe Acute Respiratory Syndrome (SARS)
Haemorrhagic Fever Viruses
Virus
Infected persons
Haemorrhagic fevers e.g. Lassa fever, Ebola fever
table
