Multiple isolates from aids patients: aspects of an analysis by a genotypic marker and antimicrobial susceptibilities variations

Methods for Detecting Mycobacterial Mixed Strain Infections-A Systematic Review

Mixed strain infection (MSI) refers to the concurrent infection of a susceptible host with multiple strains of a single pathogenic species. Known to occur in humans and animals, MSIs deserve special consideration when studying transmission dynamics, evolution, and treatment of mycobacterial diseases, notably tuberculosis in humans and paratuberculosis (or Johne's disease) in ruminants. Therefore, a systematic review was conducted to examine how MSIs are defined in the literature, how widespread the phenomenon is across the host species spectrum, and to document common methods used to detect such infections. Our search strategy identified 121 articles reporting MSIs in both humans and animals, the majority (78.5%) of which involved members of the Mycobacterium tuberculosis complex, while only a few (21.5%) examined non-tuberculous mycobacteria (NTM). In addition, MSIs exist across various host species, but most reports focused on humans due to the extensive amount of work done on tuberculosis. We reviewed the strain typing methods that allowed for MSI detection and found a few that were commonly employed but were associated with specific challenges. Our review notes the need for standardization, as some highly discriminatory methods are not adapted to distinguish between microevolution of one strain and concurrent infection with multiple strains. Further research is also warranted to examine the prevalence of NTM MSIs in both humans and animals. In addition, it is envisioned that the accurate identification and a better understanding of the distribution of MSIs in the future will lead to important information on the epidemiology and pathophysiology of mycobacterial diseases.

Low-intensity ultrasound promotes the horizontal transfer of resistance genes mediated by plasmids in E. coli

Widespread of pathogenic bacteria resistant to antibiotics has become a worldwide public health concern. Conjugative transfer between bacteria is an important mechanism for the horizontal transfer of antibiotic resistance genes. Ultrasound has been widely applied in many fields, but the effect of ultrasound on horizontal transfer of antibiotic-resistant genes is still not clear. We discovered that low-intensity (≤ 0.05 W/cm²) ultrasound had no effect on bacterial growth and survival rates, but increased the permeability of cell membrane, and consequentially elevated the transfer rates of plasmid. Low-intensity  ultrasound enhanced conjugation between bacteria, induced expression of conjugation genes TrpBp and TrfAp, and inhibited expression of global regulatory genes KorA, KorB, TrbA, and TrbK. In conclusion, low-intensity ultrasound promoted horizontal transfer of antibiotic-resistant genes by enhancing conjugation and regulating expression of horizontal transfer-related genes.

Molecular features of Mycobacterium avium human isolates carrying a single copy of IS1245 and IS1311 per genome

Human clinical isolates of the Mycobacterium avium complex, from hospitals in Bogotá, were studied using a wide range of molecular tests including PCR restriction-enzyme analysis (PRA) of the hsp65 gene. Up to 21 of the isolates were identified as M. avium PRA variant III (Mav III), a variant obtained only from isolates on the American continent. In contrast to previous reports, restriction fragment length polymorphism analysis using IS1245 and IS1311 showed a single copy for each insertion sequence (IS) in the majority (19/21) of the Colombian Mav III isolates under study. In order to analyse whether the ISs were inserted in a relevant genomic region, experimental conditions were established to determine the insertion loci of each single copy of both ISs in the genome. Analysis of genomic insertion loci indicated that both IS1245 and IS1311 were present in areas containing putatively truncated integrases and/or transposases, which may have an influence on the mobility of the inserted IS. In addition, a conserved genomic region was identified for the insertion of IS1311; this region could be part of the IS1311 itself.

Detection of mixed infections with Mycobacterium lentiflavum and Mycobacterium avium by molecular genotyping methods

Three mycobacterial isolates, one from the blood of an HIV-infected patient and two consecutive isolates from a woman with unknown HIV status, had been identified as belonging to the Mycobacterium avium complex by conventional procedures. In both patients, using genetic analysis procedures such as PCR-restriction enzyme analysis (PRA) of the hsp65 gene, a commercially available reverse hybridization-based assay (INNO-LiPA mycobacteria) and/or sequencing analysis of the 16S-23S internal transcribed spacer (ITS), the presence of Mycobacterium lentiflavum was also demonstrated. At the time of detection, both cases were also infected with M. avium, suggesting an underestimation of infection with M. lentiflavum and co-infection with different Mycobacterium species.

Mycobacterium avium restriction fragment length polymorphism-IS IS1245 and the simple double repetitive element polymerase chain reaction typing method to screen genetic diversity in Brazilian strains

Simple double repetitive element polymerase chain reaction (MaDRE-PCR) and Pvu II-IS1245 restriction fragment length polymorphism (RFLP) typing methods were used to type 41 Mycobacterium avium isolates obtained from 14 AIDS inpatients and 10 environment and animals specimens identified among 53 mycobacteria isolated from 237 food, chicken, and pig. All environmental and animals strains showed orphan patterns by both methods. By MaDRE-PCR four patients, with multiple isolates, showed different patterns, suggesting polyclonal infection that was confirmed by RFLP in two of them. This first evaluation of MaDRE-PCR on Brazilian M. avium strains demonstrated that the method seems to be useful as simple and less expensive typing method for screening genetic diversity in M. avium strains on selected epidemiological studies, although with limitation on analysis identical patterns except for one band.

A comparison of mycolic acid analysis for nontuberculous mycobacteria identification by thin-layer chromatography and molecular methods

The development of fast, inexpensive, and reliable tests to identify nontuberculous mycobacteria (NTM) is needed. Studies have indicated that the conventional identification procedures, including biochemical assays, are imprecise. This study evaluated a proposed alternative identification method in which 83 NTM isolates, previously identified by conventional biochemical testing and in-house M. avium IS1245-PCR amplification, were submitted to the following tests: thin-layer chromatography (TLC) of mycolic acids and PCR-restriction enzyme analysis of hsp65(PRA). High-performance liquid chromatography (HPLC) analysis of mycolic acids and Southern blot analysis for M. avium IS1245 were performed on the strains that evidenced discrepancies on either of the above tests. Sixty-eight out of 83 (82%) isolates were concordantly identified by the presence of IS1245 and PRA and by TLC mycolic acid analysis. Discrepant results were found between the phenotypic and molecular tests in 12/83 (14.4%) isolates. Most of these strains were isolated from non-sterile body sites and were most probably colonizing in the host tissue. While TLC patterns suggested the presence of polymycobacterial infection in 3/83 (3.6%) cultures, this was the case in only one HPLC-tested culture and in none of those tested by PRA. The results of this study indicated that, as a phenotypic identification procedure, TLC mycolic acid determination could be considered a relatively simple and cost-effective method for routine screening of NTM isolates in mycobacteriology laboratory practice with a potential for use in developing countries. Further positive evidence was that this method demonstrated general agreement on MAC and M. simiae identification, including in the mixed cultures that predominated in the isolates of the disseminated infections in the AIDS patients under study. In view of the fact that the same treatment regimen is recommended for infections caused by these two species, TLC mycolic acid analysis may be a useful identification tool wherever molecular methods are unaffordable.

IS1245 restriction fragment length polymorphism typing of Mycobacterium avium from patients admitted to a reference hospital in Campinas, Brazil

Mycobacterium avium is an important pathogen among immunodeficient patients, especially patients with AIDS. The natural history of this disease is unclear. Several environmental sources have been implicated as the origin of this infection. Polyclonal infection with this species is observed, challenging the understanding of its pathogenesis and treatment. In the present study 45 M. avium strains were recovered from 39 patients admitted to a reference hospital between 1996 and 1998. Species identification was performed using a species-specific nucleic acid hybridization test (AccuProbe) from Gen-Probe. Strains were genotyped using IS1245 restriction fragment length polymorphism typing. Blood was the main source of the organism. In one patient with disseminated disease, M. avium could be recovered more than once from potentially sterile sites. Strains isolated from this patient had different genotypes, indicating that the infection was polyclonal. Four patient clones were characterized in this population, the largest clone being detected in eight patients. This finding points to a common-source transmission of the organism.

IS1311 and IS1245 restriction fragment length polymorphism analyses, serotypes, and drug susceptibilities of Mycobacterium avium complex isolates obtained from a human immunodeficiency virus-negative patient

Six isolates of Mycobacterium avium of genotype dnaJ(+) IS901(-) IS1311(+) IS1245(+) and serotypes 6 (n = 1), 6/9, (n = 2), and 9 (n = 3) were obtained within a 5-month period from a human immunodeficiency virus-negative patient treated for tuberculosis. The isolates were identified with PvuII restriction fragment length polymorphism (RFLP) analysis as a single IS1311 RFLP type and six different IS1245 RFLP types. Six separate colonies/clones obtained by subculture from each of the six isolates were tested for MICs of a set of 10 drugs. This report documents the appearance of isolates that are resistant to antimycobacterial drugs as the duration of therapy increases. Because isolates recovered from the patient following longer duration of treatment were more likely to be resistant to more antimycobacterial drugs, we would conclude that there was selection for antimycobacterial drug-resistant isolates. Analyses of all 36 clones identified three IS1311 and 22 IS1245 types forming three clusters. Tests of 105 environmental samples collected in the home and the work place of the patient yielded 16 mycobacterial isolates, of which one M. avium from soil was of genotype dnaJ(+) IS901(+) IS1311(+) IS1245(+) and serotype 2, and the second M. avium from a vacuum cleaner was of genotype dnaJ(+) IS901(-) IS1311(+) IS1245(+) and serotype 9. Overall analyses of the results did not reveal any relation between serotype, RFLP type, and drug susceptibility. Based on the course of the disease in the patient and different serotypes, IS1311 and IS1245 RFLP types of isolates of M. avium we suppose represent polyclonal infection.