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Prevalence of IS(Aba1) in epidemiologically unrelated Acinetobacter baumannii clinical isolates
Marc Ruiz1, Sara Marti, Felipe Fernandez-Cuenca
1Servei de Microbiologia, Centre de Diagnòstic Biomèdic, Hospital Clinic, IDIBAPS, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain.
Abstract:
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 IS(Aba1) element and the IS(Aba1) located in the bla(ADC)-like promoter were detected by PCR. The objective of the study was to determine the prevalence of IS(Aba1) 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 IS(Aba1), 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 IS(Aba1), can be found in the clinical setting, suggesting the potential acquisition or loss of this genetic element in the hospital environment.
Insights
The insertion element IS(Aba1) is frequently found in the promoter region of the bla(ADC)-like gene in Acinetobacter baumannii. This genetic element
Area of Science:
- Microbiology
- Genetics
- Antimicrobial Resistance
Background:
- Acinetobacter baumannii is a significant opportunistic pathogen.
- The bla(ADC)-like gene confers resistance to ceftazidime in A. baumannii.
- Insertion sequences (IS elements) can influence gene expression and bacterial adaptation.
Purpose of the Study:
- To determine the prevalence of the IS(Aba1) element in clinical isolates of Acinetobacter baumannii.
- To investigate the location of IS(Aba1) relative to the bla(ADC)-like gene promoter.
Main Methods:
- Analysis of 76 epidemiologically unrelated A. baumannii clinical isolates.
- Determination of ceftazidime minimum inhibitory concentrations (MICs) via microdilution.
- Detection of the bla(ADC)-like gene and IS(Aba1) using Polymerase Chain Reaction (PCR).
Main Results:
- The bla(ADC)-like gene was present in 97.3% of isolates.
- IS(Aba1) was detected in 69% of strains harboring the bla(ADC)-like gene.
- In 78.4% of these strains, IS(Aba1) was located in the promoter region of bla(ADC)-like.
Conclusions:
- IS(Aba1) is prevalent in A. baumannii clinical isolates and often inserted into the bla(ADC)-like promoter.
- The presence and location of IS(Aba1) suggest its role in regulating ceftazidime resistance.
- Co-existence of IS(Aba1)-positive and -negative isolates within the same strain type indicates potential acquisition or loss in hospital environments.
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