Specificity of diagnostic PCR amplification for M. avium using the probe pMAV22.

We characterized the serovar specificity of the probe pMAV22 using ATCC isolates. Primers from this sequence amplified DNA from serovars 1-6, 8-10, and ATCC strain 19075 but did not amplify MAIS serovars 7, 11, 12, 14, 17-20. This confirmed that the M. avium probe pMAV22 is specific for M. avium, not M. intracellulare.

Comparison of genus- and species-specific probes for PCR detection of mycobacterial infections.

We describe experiments comparing use of different DNA probes to detect mycobacteria in clinical specimens after PCR. The objective was to assess correlation between results using Mycobacterium genus-specific, and species-specific M. tuberculosis probes. Given sufficient concordance, sequential use of such probes would provide a useful screening tool. An evaluation of genus-specific probes compared use of repetitive sequences in the clone pMAv17 with the 65-kDa sequences. Sensitivity was 100% for pMAv17, 93% using the 65-kDa sequence; specificity was 70% for both. We then compared M. tuberculosis-specific probes developed by us (Tb400) with IS6110 and mpt40. Sensitivity using Tb400 was 100%; using IS6110 was 97%, and using mpt40 was 50%. Specificity using Tb400 and IS6110 was 68%, and was 70% using mpt40. Fourteen specimens which were PCR-positive and culture-negative, were positive using both genus probes, and the M. tuberculosis-specific probes Tb400, and IS6110. Ten of these were positive using mpt40.

Chorioamnionitis caused by Capnocytophaga: case report and review.

We report a case of pathologically demonstrated chorioamnionitis due to Capnocytophaga species. The mother had high fever and marked uterine tenderness, and the infant had poor Apgar scores, fever, and pulmonary infiltrates. Both recovered after receiving specific antibiotics. Pathological examination of the placenta revealed acute chorioamnionitis, subchorionitis, and vasculitis of the umbilical vein. The dramatic clinical and pathological features of this case are compared with those of the nine previously reported cases of infection due to Capnocytophaga species occurring in pregnancy.

Diagnosis of Mycobacterium avium bacteremia by polymerase chain reaction.

We describe a rapid polymerase chain reaction (PCR)-based test for diagnosing Mycobacterium avium directly from blood specimens. Blood was collected in anticoagulant (EDTA) from patients who also had blood cultures performed by the lysis-centrifugation method. Blood samples were centrifuged on a Ficoll-Hypaque gradient to purify peripheral blood mononuclear cells. The purified cells were washed and incubated in the presence of Chelex-100 (a divalent cation-binding resin), boiled to release mycobacterial DNA, and then amplified with M. avium-specific PCR primers. Amplification was detected by hybridization with radiolabelled probe, and the results were compared with the culture results. The PCR assay gave positive results for 12 of 15 specimens that were taken from patients with positive cultures for M. avium complex (sensitivity, 80%). The three PCR-negative specimens in this group showed evidence of PCR inhibition. The PCR assay gave positive results for 32 of 228 specimens taken from patients with negative cultures (specificity, 86%). Of these 32 PCR-positive culture-negative specimens, 27 were also positive when amplified with primers specific for the genus Mycobacterium, suggesting that PCR may be more sensitive than culture.

Pulmonary infections in immigrants and refugees.

Immigrants and refugees are susceptible to a wide array of pulmonary diseases, including familiar infections that are acquired after entry and unusual infections that are imported from abroad. The challenges are great; tuberculosis (TB) is now 13 times more prevalent among immigrants than among the general US population. Melioidosis, paracoccidioidomycosis, and paragonimiasis are often mistaken for TB. Pulmonary disease caused by parasites is uncommon and particularly perplexing unless a peripheral blood eosinophilia suggests helminthic infection. TB, melioidosis, fungal infections, and strongyloidiasis may remain inapparent for years and then produce devastating illness in the setting of immunosuppressive therapy or the acquired immunodeficiency syndrome. Proper health care of immigrants requires an understanding of unusual exposures and infections and should include preventive measures as well.