Prevalence of ISAba1 in epidemiologically unrelated Acinetobacter baumannii clinical isolates

Seventy-five Acinetobacter baumannii strains belonging to different pulsetypes, plus one ceftazidime-susceptible strain, from a pulsetype in which all strains were resistant, were included in this study. The minimum inhibitory concentration of ceftazidime was determined by the microdilution method. The bla(ADC)-like gene, the ISAba1 element and the ISAba1 located in the bla(ADC)-like promoter were detected by PCR. The objective of the study was to determine the prevalence of ISAba1 in a collection of epidemiologically unrelated A. baumannii clinical isolates. The bla(ADC)-like gene was detected in 74 (97.3%) out of the 76 strains analysed. In these 74 strains, 51 (69%) were positive for the IS element and it was not detected in 23 (31%) strains. Among the A. baumannii strains containing the IS element, 40 (78.4%) had the IS element located in the promoter region of the bla(ADC)-like gene. In a high percentage of A. baumannii clinical isolates carrying the ISAba1, this is inserted into the promoter region of the bla(ADC)-like gene. In addition, two clinical isolates belonging to the same pulsetype, one with and one without the ISAba1, can be found in the clinical setting, suggesting the potential acquisition or loss of this genetic element in the hospital environment.