Typing of human Mycobacterium avium isolates in Italy by IS1245-based restriction fragment length polymorphism analysis

Molecular typing and genetic characterization of Mycobacterium avium subsp. hominissuis isolates from humans and swine in Japan

Mycobacterium avium subsp. hominissuis (MAH) causes disease in both humans and swine; however, the genetic variations in MAH isolates are unclear. The aim of this study was to elucidate the genetic variations in MAH isolates from humans and swine in Japan. We analysed the 16S-23S rDNA internal transcribed spacer (ITS) sequence and variable number of tandem repeats (VNTRs) using the Mycobacterium avium tandem repeat loci, prevalence of ISMav6 and clarithromycin resistance for MAH isolates from patients with pulmonary MAC (pMAC) disease (n=69), and HIV-seropositive and blood culture-positive (HIV-MAC) patients (n=28) and swine (n=23). In the minimum spanning tree based on VNTR analysis, swine MAC isolates belonged to a cluster distinguishable from that of human pMAC isolates. Isolates from HIV-MAC were scattered throughout both clusters. The three major distinct sequevars, Mav-A, Mav-B and Mav-F, were determined according to 16S-23S rDNA ITS sequence analysis in addition to three new sequevars, Mav-Q, Mav-R and Mav-S. Mav-A and Mav-F comprised the majority of human pMAC strains; in contrast, Mav-B predominated in swine isolates. Distribution of ITS sequevars in the minimum spanning tree based on VNTR analysis showed similar clusters of isolates from different origins, i.e. human pMAC, HIV-MAC and swine. These results, together with ISMav6 possession and clarithromycin resistance, revealed the genetic diversity of MAH strains recovered from humans and swine. Molecular epidemiology and genetic characterization in the present study showed the distinctive genetic evolutionary lineage of MAH strains isolated from human pMAC diseases and swine.

Evidence of the presence of IS1245 and IS1311 or closely related insertion elements in nontuberculous mycobacteria outside of the Mycobacterium avium complex

A PCR assay based on the simultaneous detection of IS1245 and IS1311 was developed and used to determine the host range of these insertion elements. Specific PCR products were observed in Mycobacterium malmoense, Mycobacterium scrofulaceum, and Mycobacterium nonchromogenicum, indicating that IS1245 and IS1311 are not limited to the Mycobacterium avium complex.

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

OBJECTIVE

To compare the chromosomal types of Mycobacterium avium strains infecting HIV-negative and AIDS patients in Greece.

METHODS

In total, 41 Mycobacterium avium isolates, 23 from AIDS and 18 from HIV-negative patients, were compared by pulsed-field gel electrophoresis of genomic DNA after XbaI digestion. The majority (87%) of AIDS isolates were from disseminated infection, while the majority (61%) of HIV-negative isolates were from children with cervical lymphadenitis.

RESULTS

Pulsed-field gel electrophoresis classified strains whose electrophoretic patterns were at least 85% similar into three clusters, A (four isolates), B (12 isolates), and C (15), while 10 isolates remained outside of these clusters. There was no statistically significant correlation of any PFGE cluster with a specific patient group. Within each patient group, no significant correlation of PFGE type with time, place of residence or, in the case of AIDS patients, hospital attended was observed.

CONCLUSIONS

Genotypic similarities between isolates responsible for disseminated infection in AIDS patients and lymphadenitis in HIV-negative children suggest that related strains, possibly from an environmental source, cause both types of infections.

Genetic diversity of mycobacterium avium recovered from AIDS patients in the caribbean as studied by a consensus IS1245-RFLP method and pulsed-field gel electrophoresis

A total of 45 strains of Mycobacterium avium from 31 human immunodeficiency virus (HIV)-positive patients in the French Caribbean islands and Guiana were subjected to DNA fingerprinting using a recently described consensus IS1245 restriction fragment length polymorphism (RFLP) method, and pulsed-field gel electrophoresis (PFGE). The IS1245-RFLP resulted in three distinct clusters composed of three 27-banded isolates from two patients (cluster A), nine two-banded isolates from six patients (cluster B), and three 20-banded isolates from three patients (cluster C). PFGE results obtained after XbaI and DraI digestions gave similar clustering results irrespective of the enzyme used, and confirmed the molecular clonality for high IS1245 copy number isolates (clusters A and C). However, PFGE further discriminated the low IS1245 copy number cluster B into two distinct subclusters: subcluster I containing six isolates from four patients during the same time period from a single hospital in Guadeloupe, and subcluster IV composed of four isolates from two patients, out of which three isolates were from a single patient (patient 19). Interestingly, in the latter case, PFGE grouped together all three isolates from patient 19 despite the fact that IS1245 fingerprinting permitted grouping only two of the three isolates (the remaining unclustered isolate contained two additional bands of 3.5 and 5 kbp, and was initially considered as evidence of polyclonal infection). A combined numerical analysis of the IS1245-RFLP and PFGE results corroborated the existence of four instead of three clusters. A comparison of IS1245-RFLP versus PFGE results suggested that the standardized RFLP procedure is compatible with PFGE only for M. avium isolates containing > or = 5 copies of IS1245. Consequently, the typing results for low IS1245 copy number isolates (31% of isolates in this study) should be reconsidered for secondary typing using PFGE. Lastly, the absence of a predominant genotype of M. avium infecting HIV-positive patients over a 5-year period in this tropical region argues in favor of a lack of a privileged ecological niche for M. avium, and instead suggests that microepidemics of M. avium may prevail during limited periods of time.

Molecular analysis of Mycobacterium avium isolates by using pulsed-field gel electrophoresis and PCR

Genetic relationships among 46 isolates of Mycobacterium avium recovered from 37 patients in a 2,500-bed hospital from 1993 to 1998 were assessed by pulsed-field gel electrophoresis (PFGE) and PCR amplification of genomic sequences located between the repetitive elements IS1245 and IS1311. Each technique enabled the identification of 27 to 32 different patterns among the 46 isolates, confirming that the genetic heterogeneity of M. avium strains is high in a given community. Furthermore, this retrospective analysis of sporadic isolates allowed us (i) to suggest the existence of two remanent strains in our region, (ii) to raise the question of the possibility of nosocomial acquisition of M. avium strains, and (iii) to document laboratory contamination. The methods applied in the present study were found to be useful for the typing of M. avium isolates. In general, both methods yielded similar results for both related and unrelated isolates. However, the isolates in five of the six PCR clusters were distributed among two to three PFGE patterns, suggesting that this PCR-based method may have limitations for the analysis of strains with low insertion sequence copy numbers or for resolution of extended epidemiologic relationships.