Subtyping ofMycobacterium aviumcomplex (MAC) isolates by thin-layer chromatography – distribution of subtypes from patients with AIDS compared with clinically non-significant isolates

Abstract

SUMMARYThin-layer chromatography (TLC) was compared with seroagglutination for subtyping of Mycobacterium avium complex (MAC) bacteria. Seventy-five significant MAC isolates from patients with AIDS were typed by both methods and 36 isolates, judged to be clinically non-significant, were examined by TLC only. Overall, 75 % of isolates tested were typable by seroagglutination and 91 % by TLC; the results correlated between the two except for minor discrepancies.Serovars 1, 8 and 21 and mixed serovars 1-21 and 1-8-21 were common among isolates from AIDS patients and together represented 83 % of isolates compared wvith only 36% in the non-significant group (odds ratio 8-4; 95% confidence interval 3 4-23 3). This difference remained significant after exclusion of serovar 41 (M. scrofulaceum), which was the commonest isolate (28%) in the nonsignificant group but was not isolated from patients with AIDS.

Genetic characterization ofMycobacterium aviumisolates recovered from humans and animals in Australia

“…The organism is present in the environment, may be found in the faeces of healthy people [3], and can be isolated from granulomas in animals [4,5] and in human patients without any predisposing conditions [6,7]. It is considered to be an opportunistic pathogen in humans, and has been reported to cause disseminated infection in up to 50 % of patients with AIDS in the USA [8,9], and in 17% of such patients in Australia [10,11]. The resistance of the organisms to antimycobacterial drugs makes them important clinically [12,13].…”

“…a seroagglutination test was introduced by Shaefer [14], and modified by Reznikov and Leggo [15], and has been used by several researchers [10,16]. Others have used thin layer chromatography for subtyping [11,17], and this has the advantage that it can differentiate isolates which autoagglutinate or are untypable in the seroagglutination test. Correlations have been reported between the distribution of isolates in different geographical areas and their serovar [10,16,18] but molecular genetic techniques, such as restriction fragment length polymorphism of DNA (RFLP), have shown such isolates to be closely related [19,20].…”

Comparison of Mycobacterium avium isolates from Greek AIDS and human immunodeficiency virus-negative patients by pulsed-field gel electrophoresis

“…However, the major drawback of serotyping is that it requires large amounts of these slowgrowing organisms. In addition, the number of untypable strains and of mixed serovars is high [2,3,8,9].…”

“…Common serovars with differing geographic frequencies are often observed among M. avium isolates from AIDS and HIV‐negative patients [7–11]. However, the major drawback of serotyping is that it requires large amounts of these slow‐growing organisms.…”

“…In contrast, chromosomal DNA fingerprinting methods for epidemiologic typing, whether by pulsed‐field gel electrophoresis (PFGE), RFLP and PCR with probes or primers derived from mycobacterial insertion sequences, such as IS 1245 [12–17], have proved very useful and discriminatory, compared to serotyping, plasmid profiling, or multilocus enzyme electrophoresis [8,18–20].…”