Mycobacterium tuberculosis typing: usefulness of DRE-PCR to confirm cross-contamination in the mycobacteriology laboratory of a general reference hospital for AIDS.
In this study two molecular typing methods, a simple double repetitive element PCR-based assay and the standardized restriction fragment length polymorphism (RFLP), were used to confirm cross-contamination in the mycobacteriology laboratory. Clinical specimens from 12 patients, submitted for acid-fast bacilli stain smear and processed for culture in Lowenstein-Jensen on the same day, resulted in positive bacterioscopy (+++) and confluent growth only for one of the patients. The specimens from all the other patients but two were smear-negative and culture-positive, with one or two colonies. None of them had clinical symptoms and radiological findings for active tuberculosis (TB). The suspicion of false-positive cultures arose when a health care worker who had had a PPD skin test conversion, claimed to be healthy and had no TB symptoms, was found to have a positive sputum culture. DRE-PCR demonstrated that all nine cultures typed belonged to one cluster, further confirmed by RFLP. Although DRE-PCR has been found to be poorly reproducible, it has enough discriminatory power to be useful for rapid epidemiological investigation in selected settings.
Filho
L A
LA
Hospital Universitário Clementino Fraga Filho, Universidade Federal do Rio de Janeiro, Brasil.
Kritski
A L
AL
Salles
C L G
CL
Sardella
I G
IG
Silva
M G
MG
Fonseca
L S
LS
Saad
M H F
MH
D000163:Acquired Immunodeficiency Syndrome; D015373:Bacterial Typing Techniques; D001938:Brazil; D003428:Cross Infection / Q000175:diagnosis*; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000032:analysis; D005189:False Positive Reactions; D006769:Hospitals, General; D006801:Humans; D007755:Laboratories, Hospital; D009169:Mycobacterium tuberculosis / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012150:Polymorphism, Restriction Fragment Length; D012680:Sensitivity and Specificity; D013048:Specimen Handling; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000382:microbiology*
D004269:DNA, Bacterial