Identification of an atypical integron carrying an IS26-disrupted aadA1 gene cassette in Acinetobacter baumannii

Han, Hu; Jang, Sook Jin; Park, Geon; Kook, Joong-Ki; Shin, Jong Hee; Shin, Sung Heui; Kim, Dong-Min; Cheon, Ji Seon; Moon, Dae Soo; Park, Young Jin

doi:10.1016/j.ijantimicag.2008.03.009

Cited by 12 publications

(6 citation statements)

References 14 publications

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“…The presence in the recipient of nonfunctional IS 26 could also allow the capture of additional resistance genes by homologous recombination-mediated DNA integration, if a homologous IS 26 region is present in the donor DNA fragments. Such recombination scenario could explain, for example, the dissemination of the chromosomally-located integron-IS 26 in A. baumannii in South Korea [88], [90]. A previous bioinformatics-based study of Partridge et al [41] also indicated transposition as a possible mechanism of integron movement.…”

Section: Discussionmentioning

confidence: 93%

Natural Transformation Facilitates Transfer of Transposons, Integrons and Gene Cassettes between Bacterial Species

et al. 2012

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We have investigated to what extent natural transformation acting on free DNA substrates can facilitate transfer of mobile elements including transposons, integrons and/or gene cassettes between bacterial species. Naturally transformable cells of Acinetobacter baylyi were exposed to DNA from integron-carrying strains of the genera Acinetobacter, Citrobacter, Enterobacter, Escherichia, Pseudomonas, and Salmonella to determine the nature and frequency of transfer. Exposure to the various DNA sources resulted in acquisition of antibiotic resistance traits as well as entire integrons and transposons, over a 24 h exposure period. DNA incorporation was not solely dependent on integrase functions or the genetic relatedness between species. DNA sequence analyses revealed that several mechanisms facilitated stable integration in the recipient genome depending on the nature of the donor DNA; homologous or heterologous recombination and various types of transposition (Tn21-like and IS26-like). Both donor strains and transformed isolates were extensively characterized by antimicrobial susceptibility testing, integron- and cassette-specific PCRs, DNA sequencing, pulsed field gel electrophoreses (PFGE), Southern blot hybridizations, and by re-transformation assays. Two transformant strains were also genome-sequenced. Our data demonstrate that natural transformation facilitates interspecies transfer of genetic elements, suggesting that the transient presence of DNA in the cytoplasm may be sufficient for genomic integration to occur. Our study provides a plausible explanation for why sequence-conserved transposons, IS elements and integrons can be found disseminated among bacterial species. Moreover, natural transformation of integron harboring populations of competent bacteria revealed that interspecies exchange of gene cassettes can be highly efficient, and independent on genetic relatedness between donor and recipient. In conclusion, natural transformation provides a much broader capacity for horizontal acquisitions of genetic elements and hence, resistance traits from divergent species than previously assumed.

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Section: Discussionmentioning

confidence: 93%

Natural Transformation Facilitates Transfer of Transposons, Integrons and Gene Cassettes between Bacterial Species

et al. 2012

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“…It is well-known that A. baumannii is multidrug resistant, and that prevalence has been recently increasing in ICUs [29][30][31]. It is generally accepted that antibiotic resistance in Acinetobacter mainly develops due to the acquisition of a highly efficient resistance system, known as an integron [32][33][34]. To alleviate the situation, strict control measures and appropriate effective antibiotic therapy should be adopted.…”

Section: Discussionmentioning

confidence: 99%

Ventilator-associated pneumonia in Iranian intensive care units

Japoni

Vazin

Davarpanah

et al. 2011

J Infect Dev Ctries

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Introduction: Nosocomial pneumonia (NP) and ventilator associated pneumonia (VAP) occur most frequently in intensive care units (ICU). This study seeks to determine the etiological agents of NP and VAP along with their antibacterial susceptibility patterns, and to evaluate the factors contributing to patient mortality. The impact of appropriate therapy in terms of three parameters (body temperature, PaO2/FiO2 ratio and leukocyte count) was also assessed. Methodology: This study involved 836 adult patients admitted to ICUs at the Nemazee Hospital, Shiraz, Iran, over nine months during 2008 and 2009. The inclusion criterion was the commencement of infection at least 48 hours following hospital admission. Clinical parameters including core temperature, leukocyte count. and PaO2/FiO2 ratio were evaluated. Antibiotic sensitivities of the isolated bacteria to a panel of antibiotics were determined using E-test. Results: Of 836 cases, only 58 (6.9 %) cases of NP were diagnosed, of which 42 (72 %) were VAP. A. baumannii, MRSA, P. aeruginosa and MSSA were the most prevalent bacteria. Significant correlations between previous antibiotic therapy (p = 0.04), use of corticosteroids (p = 0.02) and attributable mortality were found. A strong correlation between fever abatement and the ratio of PaO2/FiO2 with responses to treatment and outcomes was also evident. Conclusions: Combined treatment with meropenem/imipenem, ciprofloxacin and vancomycin seems to be appropriate and could cover all possible infective agents. To reduce mortality rate, reasonable prescription of antibiotics and corticosteroids could be effective. Furthermore, adopting a strategy to reduce body temperature and PaO2/FiO2 ratio could be beneficial in patients' outcomes.

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“…Integrons contribute significantly to the emergence and dissemination of antibiotic resistance genes in Gram-negative bacteria due to their ability to integrate/excise gene cassettes into or out of themselves via site-specific recombination using self-coded integrases (50,54,56 (20). Efflux pumps have been recognized as a mechanism of antibiotic resistance in Gram-negative bacteria (45,48,71).…”

Section: Discussionmentioning

confidence: 99%

Phenotypic and Molecular Characterization of Acinetobacter Clinical Isolates Obtained from Inmates of California Correctional Facilities

et al. 2011

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Acinetobacter spp. increasingly have been wreaking havoc in hospitals and communities worldwide. Although much has been reported regarding Acinetobacter isolates responsible for nosocomial infections, little is known about these organisms in correctional facilities. In this study, we performed species identification, examined the antibiotic resistance profiles, and determined the mechanisms of resistance and clonal relationships of 123 Acinetobacter isolates obtained from inmates of 20 California correctional facilities (CCFs). We found that 57.7% of the isolates belong to A. baumannii, followed by isolates of Acinetobacter genomic species 3 (gen. sp. 3; 23.6%) and of Acinetobacter gen. sp. 13TU (10.6%). Multidrug-resistant (MDR) CCF isolates were found in only six CCFs. Additionally, DNA sequences of gyrA and parC genes were consistent with fluoroquinolone (FQ) susceptibility phenotypes. Furthermore, the presence of class 1 integrons was detected in 15 CCF isolates, all of which are MDR. Integron-associated gene cassettes encode several aminoglycoside modification enzymes, which correlate with most of the aminoglycoside-resistant phenotypes. Antimicrobial susceptibility testing in the presence of Phe-Arg-␤-naphthylamide dihydrochloride and 1-(1-naphthylmethyl)-piperazine indicated the involvement of efflux pumps in the FQ resistance of only a few CCF isolates. Finally, genetic profiling showed that there was no evidence of A. baumannii outbreaks in CCFs. Instead, our analyses revealed only limited clonal dissemination of mostly non-MDR A. baumannii strains in a few facilities. This study represents the first report to characterize phenotypic and molecular features of Acinetobacter isolates in correctional facilities, which provides a baseline for monitoring the antimicrobial resistance changes and dissemination patterns of these organisms in such specialized institutions.

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Identification of an atypical integron carrying an IS26-disrupted aadA1 gene cassette in Acinetobacter baumannii

Cited by 12 publications

References 14 publications

Natural Transformation Facilitates Transfer of Transposons, Integrons and Gene Cassettes between Bacterial Species

Natural Transformation Facilitates Transfer of Transposons, Integrons and Gene Cassettes between Bacterial Species

Ventilator-associated pneumonia in Iranian intensive care units

Phenotypic and Molecular Characterization of Acinetobacter Clinical Isolates Obtained from Inmates of California Correctional Facilities

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