Comparison of Methods for Identification of Mycobacterium abscessus and M. chelonae Isolates

Abstract

Mycobacterium abscessus and Mycobacterium chelonae are two closely related species that are often not distinguished by clinical laboratories despite the fact they cause diseases requiring different treatment regimens. Multilocus enzyme electrophoresis, PCR-restriction fragment length polymorphism analysis of the 65-kDa heat shock protein gene, biochemical tests, and high-performance liquid chromatography of mycolic acids were used to identify 75 isolates as either M. abscessus or M. chelonae that were originally submitted for drug susceptibility testing. Only 36 of these isolates were submitted with an identification at the species level. Using the above methods, 46 of the isolates were found to be M. abscessus and 29 were identified as M. chelonae. Eight isolates originally submitted as M. chelonae were identified as M. abscessus, and one isolate submitted as M. abscessus was found to be M. chelonae. The four identification methods were in agreement in identifying 74 of the 75 isolates. In drug susceptibility testing, all isolates of M. abscessus exhibited resistance to tobramycin (MIC of 8 to >16 g/ml), while all isolates of M. chelonae were susceptible to this drug (MIC of <4 g/ml). The results suggest that once an identification method is selected, clinical laboratories should be able to easily identify isolates of M. abscessus and M. chelonae.Mycobacterium abscessus and Mycobacterium chelonae are two species of rapidly growing mycobacteria frequently associated with nosocomial outbreaks and pseudo-outbreaks (1,11,24). Widespread outbreaks of postinjection abscesses have occurred due to medications contaminated with M. abscessus (6,22). Contamination of hospital equipment and medications can generally be traced to the ubiquitous presence of these organisms in tap water and their resistance to commonly used disinfectants (24).It is clinically important to correctly identify these organisms since they cause infections requiring different treatment regimens (R. J. Wallace, Jr., B. A. Brown, D. E. Griffith, Letter, Pediatr. Infect. Dis. J. 16:829, 1997). Prior to 1992, M. abscessus was considered a subspecies of M. chelonae. Though Kusunoki and Ezaki (10) firmly established through DNA hybridization that these organisms are separate species, they are nearly indistinguishable phenotypically. Only two biochemical tests, those for sodium chloride tolerance and utilization of citrate, are useful for identifying these organisms at the species level (17), but these tests may take up to 4 weeks to complete (5). Identification of rapidly growing species using high-performance liquid chromatography (HPLC) of mycolic acids has been limited with M. abscessus and M. chelonae because they produce very similar mycolic acid patterns (2). Recently, PCRbased methods targeting polymorphic regions of the 65-kDa heat shock protein (HSP) gene have been used successfully to identify isolates of M. abscessus and M. chelonae (8, 15; A. R. Lakshmy, N. Siddiqi, M. Shamim, M. Deb, G. Mehta, and S. E. Hasnain, Letter, Emerg. Infect. Dis. 6...

Microbiological contamination of a hemodialysis center water distribution system

“…It should be noted that in our study the potentially pathogenic M. kansasii 3 was isolated three times; this species has been responsible for infections in immunodeficient patients 12 . On the other hand, although M. lentiflavum was isolated just once, it has often been found during outbreaks of hospital infection, contaminating equipment and medicines 37,39 . Bacteria of the genes Mycobacterium have been isolated from a variety of natural aquatic habitats and are capable of growing in treated water and dialysis fluids, colonizing surfaces inside tanks, kidney machines and components of the water treatment system such as deionizing resins and reverse-osmosis membranes 11,32 .…”

LightCycler-Based Differentiation of Mycobacterium abscessus and Mycobacterium chelonae

“…Likewise, interpretation of fragment sizes is sometimes difficult because of the similarity of restriction patterns. Alternative diagnostic procedures include glycan analysis of the bacterial capsule using high-performance liquid chromatography, which is highly reliable but can be performed only in specialized laboratories (13). In this study, we developed a simple and rapid method based on LightCycler technology to distinguish M. abscessus and M. chelonae.…”

“…The differences in antimicrobial susceptibilities between M. abscessus and M. chelonae demand an easy differentiation of these two closely related species (14). Restriction analysis of an hsp65 gene fragment has been used to this end for over 10 years (7,12,13). However, this method requires subsequent gel analysis of amplified DNA.…”

“…Biochemical profiling included testing for growth on 5% sodium chloride and growth on citrate as the sole carbon source as suggested by Yakrus and colleagues (13). Briefly, bacteria were precultured in liquid medium using mycobacterial growth indicator tubes (MGIT) (Becton Dickinson, Oxford, United Kingdom).…”

Detection and Genotyping of Mycobacterium Species from Clinical Isolates and Specimens by Oligonucleotide Array

“…Discrimination of nontuberculous mycobacteria (NTM) from Mycobacterium tuberculosis is needed for patient management, considering that many NTM are resistant to the antibiotics used for the treatment of tuberculosis. The identification of mycobacterial isolates to the species level has been accomplished by the analysis of the phenotypic and biochemical characteristics of the organisms after culture (25). These approaches can be limited in their ability to detect specific mycobacteria because of time-consuming processes and poor discrimination (11).…”