Comparison of clinical isolates and in vitro selected mutants reveals that tlyA is not a sensitive genetic marker for capreomycin resistance in Mycobacterium tuberculosis.

Abstract

OBJECTIVES:

The aim of this study was to clarify the conflicting data regarding cross-resistance and drug-resistance mechanisms for the cyclic peptide capreomycin and the aminoglycosides amikacin and kanamycin by comparing genotypes and phenotypes of clinical isolates and in vitro selected mutants of Mycobacterium tuberculosis.

METHODS:

The genes rrs and tlyA and the promoter region of eis of 152 M. tuberculosis clinical isolates (including 55 capreomycin resistant) and 44 in vitro selected capreomycin-, amikacin- and kanamycin-resistant mutants were sequenced. In addition, MICs of capreomycin, amikacin and kanamycin on Middlebrook 7H10 were determined.

RESULTS:

The results clearly show major differences in genotypes and cross-resistance patterns to amikacin and kanamycin between the capreomycin-resistant clinical isolates and in vitro selected mutants. tlyA mutations were found almost exclusively among the in vitro selected capreomycin-resistant mutants, while only four were found among the clinical isolates, of which two were capreomycin susceptible. In contrast, 53 of the 55 capreomycin-resistant clinical isolates had a mutation at position 1401 in rrs and were resistant to capreomycin, amikacin and kanamycin. Low-level resistance to kanamycin was correlated to mutations in the promoter region of eis.

CONCLUSIONS:

Our findings are consistent with the belief that a mutation at position 1401 in rrs leads to resistance to capreomycin, amikacin and kanamycin. The data also show that tlyA is not a sensitive genetic marker for capreomycin resistance in clinical isolates of M. tuberculosis, as mutations in this gene are infrequent and not all mutations in tlyA lead to capreomycin resistance.

• Authors: Anna Engström, Nasrin Perskvist, Jim Werngren, Sven E Hoffner, Pontus Juréen
• Journal: The Journal of antimicrobial chemotherapy (J Antimicrob Chemother) Vol. 66 Issue 6 Pg. 1247-54 (Jun 2011) ISSN: 1460-2091 [Electronic] England
• PMID: 21427106 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antigens, Bacterial
• Antitubercular Agents
• Bacterial Proteins
• DNA, Bacterial
• Genetic Markers
• RNA, Ribosomal, 16S
• TlyA protein, Mycobacterium tuberculosis
• Capreomycin
• Kanamycin
• Amikacin
• Acetyltransferases
• Eis protein, Mycobacterium tuberculosis

Topics

• Acetyltransferases
• Amikacin (pharmacology)
• Antigens, Bacterial (genetics)
• Antitubercular Agents (pharmacology)
• Bacterial Proteins (genetics)
• Capreomycin (pharmacology)
• DNA, Bacterial (chemistry, genetics)
• Drug Resistance, Bacterial
• Genetic Markers
• Humans
• Kanamycin (pharmacology)
• Microbial Sensitivity Tests
• Mycobacterium tuberculosis (drug effects, genetics)
• Point Mutation
• Promoter Regions, Genetic
• RNA, Ribosomal, 16S (genetics)
• Sensitivity and Specificity
• Sequence Analysis, DNA