Multisite Reproducibility of Results Obtained by the Broth Microdilution Method for Susceptibility Testing of Mycobacterium abscessus , Mycobacterium chelonae , and Mycobacterium fortuitum

Abstract

A multicenter study was conducted to assess the interlaboratory reproducibility of broth microdilution testing of the more common rapidly growing pathogenic mycobacteria. Ten isolates (fourMycobacterium fortuitum group, three Mycobacterium abscessus, and three Mycobacterium chelonae isolates) were tested against amikacin, cefoxitin, ciprofloxacin, clarithromycin, doxycycline, imipenem, sulfamethoxazole, and tobramycin (M. chelonae only) in four laboratories. At each site, isolates were tested three times on each of three separate days (nine testing events per isolate) with a common lot of microdilution trays. Agreement among MICs (i.e., mode ± 1 twofold dilution) varied considerably for the different drug-isolate combinations and overall was best for cefoxitin (91.7 and 97.2% for one isolate each and 100% for all others), followed by doxycycline, amikacin, and ciprofloxacin. Agreement based on the interpretive category, using currently suggested breakpoints, also varied and overall was best for doxycycline (97.2% for one isolate and 100% for the rest), followed by ciprofloxacin and clarithromycin. Reproducibility among MICs and agreement by interpretive category was most variable for imipenem. Based on results reported from the individual sites, it appears that inexperience contributed significantly to the wide range of MICs of several drugs, especially clarithromycin, ciprofloxacin, and sulfamethoxazole. New interpretive guidelines are presented for the testing of M. fortuitum against clarithromycin; M. abscessus andM. chelonae against the aminoglycosides; and all three species against cefoxitin, doxycycline, and imipenem.

Treating Primary Arthroprosthesis Infection Caused byMycobacterium abscessussubsp. abscessus

“…In addition to phenotypic DST, the isolate also underwent gene sequencing using the Illumina platform MiniSeq ( Table 2). Results revealed the presence of the wildtype gene erm(41) conferring inducible clarithromycin resistance [17,20,22,23], while no mutations for the gene 23s affecting macrolide susceptibility and the gene 16s affecting amikacin susceptibility were found. e patient was readmitted on the 20 th of October, 3 months after the prosthesis had been explanted, at the Infectious Disease Clinic to be evaluated for prosthesis reimplant.…”

“…Drug susceptibility testing (DST), was performed on the M. abscessus subsp. abscessus isolate using the E-test (AB Biodisk, Solna, Sweden) and the broth microdilution methods, the former with both 4 day and 14 day readings (Sensititre, Trek Diagnostic Systems, USA) [20,21]. Results were evaluated according to the breakpoints reported in the CLSI document from 2011 (Table 2) [19].…”

The Changing Pattern of Nontuberculous Mycobacterial Disease

“…It became quickly apparent that knowledge of nontuberculous mycobacterial epidemiology and taxonomy was weak, and that improved methods for isolating and identifying these pathogens was needed. This led to the development of improved methods for their isolation (21) and identification (12), antibiotic-susceptibility testing (22,23) and regimens for antimicrobial therapy (14-16). In addition, basic studies of ecology, physiology and genetics were initiated and continue to this day (2).…”

Structure elucidation and biological activity of antibacterial compound from Micromonospora auratinigra , a soil Actinomycetes

“…Among all pathogenic bacteria, Staphylococcus aureus, Pseudomonas aeruginosa, Proteus vulgaris, Bacillus subtilis are important due to their role in several nosocomial as well as community-acquired diseases with a high mortality rate (Alhede et al 2014). Mycobacterium abscessus, a rapidly growing mycobacteria, is a leading cause of lung infections in patients having cystic fibrosis and chronic pulmonary disease in addition to post-traumatic and postsurgical infections (Chan et al 2010) and is extremely difficult to treat and eradicate (Wood et al 1999). Diarrhoeagenic Escherichia coli is an important agent of childhood diarrhoea which represents a major public health problem in developing countries (Akinjogun et al 2009).…”