Screening of mutator phenotype in clinical strains of Acinetobacter baumannii. (March 2017)

• Record Type: Journal Article
• Authors: Deiham, Behnaz; Douraghi, Masoumeh; Adibhesami, Habibeh; Yaseri, Mehdi; Rahbar, Mohammad
• Is Part Of: Microbial pathogenesis. Volume 104(2017)
• Page Start: 175
• Page End: 179
• Publication Date: 2017-03
• Subjects: Acinetobacter baumannii -- Antibiotic resistance -- Mutator -- Mutation frequency -- Rifampicin; Pathogenic microorganisms -- Periodicals; Pathology, Molecular -- Periodicals; Communicable Diseases -- microbiology -- Periodicals; Communicable Diseases -- parasitology -- Periodicals; Micro-organismes pathogènes -- Périodiques; Pathologie moléculaire -- Périodiques; Electronic journals; 616.9041
• DOI: 10.1016/j.micpath.2017.01.033
• Languages: English
• ISSNs: 0882-4010

Abstract

Abstract: To our knowledge, no study has considered the growing colonies of A. baumannii in the inhibition zone of antibiotic disks as an indication of mutator. Here, we screened the mutator phenotype in a large series of clinical strains of A. baumannii . A collection of 300 strains were tested for antibiotic susceptibility and yielding colonies in the inhibition zone of antibiotic disks. The mutation frequency (MF) of strains was determined using rifampicin screen agar (300 μg/mL). Among strains tested, 180 had colonies in the inhibition zone of at least one or more than one (≤7) antibiotic. Sixty strains also generated mutant colonies on rifampicin screen agar with MF mean of 4.9 × 10 −9 . One strain was found with 59-fold (2.9 × 10 −7 ) increase of MF than the mean value, only yielded colonies in the inhibition zone of imipenem, and classified as strong mutator or hypermutator. The MF ranged from 1 × 10 −12 to 6.6 × 10 −10 in remaining strains (n = 59), corresponded to non-mutator phenotype. There was a significant correlation between the number of colonies that grew in inhibition zone of amikacin disk and MF ( P = 0.002). We showed that mutator phenotype emerged among clinical strains of A. baumannii as expected frequency in other bacterial species from non-chronic infections. This study revealed that wide screening of strains yielding colonies in the inhibition zone of antibiotics can be utilized to identify mutators. The mutant colonies need to be considered as a subpopulation of bacteria that may affect the interpretation of antibiotic susceptibility testing and consequently lead to treatment failure. Highlights: Mutator phenotype has emerged among clinical strains of A. baumannii . The mutant colonies should not be ignored through interpretation of antibiotic susceptibility testing. Mutant colonies need to be considered as a subpopulation of bacteria which may lead to treatment failure.