Bacteriology, Virology, Mycology, and Parasitology

Causes of Error in Microbiology

False Positive mycology, parasitology

False Negative

Permissive site cultured (normal flora vs pathogen)

Sample contamination (eg, Blood culture, CSF)

Lab contaminant (eg, PCR)

Bacteriology, virology,

Lab error ( QC, interpretation)

Wrong test ( eg, ToRCH)

Old, unrelated infection

Wrong test

Insensitive test (eg, CSF - encepha litis)

Inadequate sample ( eg, Blood cul ture)

Lab error bacteriology, virology

Site	Organisms
Nose	s. aureus (30-50%). S. pneumoniae (40-60%), H. influenzae (30-50%), N. meningitidis (20%), CMV, adenovirus
Throat	Same as above, Gp A streptococcus (20%)
Skin	S. aureus (5%), Acinetobacter, Coagulase negative Staphylococcus
Colon	E. coil, Poliovirus (vaccine), Adenovirus
Vagina	Gp B Streptococcus (30% adults)