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Phenotypic and molecular characterization of Acinetobacter baumannii clinical isolates from nosocomial outbreaks in Los Angeles County, California.
J Clin Microbiol. 2008 Aug; 46(8):2499-507.JC

Abstract

Multidrug-resistant Acinetobacter baumannii strains have increasingly resulted in nosocomial outbreaks worldwide, leaving limited options for treatment. To date, little has been reported on the antimicrobial susceptibilities and genomic profiles of A. baumannii strains from hospital outbreaks in the Greater Los Angeles area. In this study, we examined the susceptibilities and genetic profiles of 20 nonduplicate isolates of A. baumannii from nosocomial outbreaks in Los Angeles County (LAC) and determined their mechanisms of fluoroquinolone resistance. Antibiotic susceptibility testing indicated that the majority of these LAC isolates were not susceptible to 14 of the 17 antibiotics tested, with the exception of doxycycline, minocycline, and tigecycline. In particular, all isolates were found to be resistant to ciprofloxacin. Genomic DNA analysis revealed eight epidemiologically distinct groups among these 20 A. baumannii isolates, consistent with antibiotic susceptibility profiles. Sequencing analysis confirmed that concurrent GyrA and ParC amino acid substitutions in the "hot spots" of their respective quinolone resistance-determining regions were primarily responsible for the high-level ciprofloxacin resistance of these isolates. Antibiotic susceptibility testing using two efflux pump inhibitors suggested that the presence of efflux pumps was only a secondary contributor to ciprofloxacin resistance for some of the isolates. In summary, the present study has revealed good correlation between the antibiotic susceptibility profiles and genetic fingerprints of 20 clinical isolates from nosocomial outbreaks in Los Angeles County and has determined their mechanisms of fluoroquinolone resistance, providing an important foundation for continued surveillance and epidemiological analyses of emerging A. baumannii isolates in Los Angeles County hospitals.

Authors+Show Affiliations

California State University, Los Angeles, CA, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural

Language

eng

PubMed ID

18524965

Citation

Valentine, Sonya C., et al. "Phenotypic and Molecular Characterization of Acinetobacter Baumannii Clinical Isolates From Nosocomial Outbreaks in Los Angeles County, California." Journal of Clinical Microbiology, vol. 46, no. 8, 2008, pp. 2499-507.
Valentine SC, Contreras D, Tan S, et al. Phenotypic and molecular characterization of Acinetobacter baumannii clinical isolates from nosocomial outbreaks in Los Angeles County, California. J Clin Microbiol. 2008;46(8):2499-507.
Valentine, S. C., Contreras, D., Tan, S., Real, L. J., Chu, S., & Xu, H. H. (2008). Phenotypic and molecular characterization of Acinetobacter baumannii clinical isolates from nosocomial outbreaks in Los Angeles County, California. Journal of Clinical Microbiology, 46(8), 2499-507. https://doi.org/10.1128/JCM.00367-08
Valentine SC, et al. Phenotypic and Molecular Characterization of Acinetobacter Baumannii Clinical Isolates From Nosocomial Outbreaks in Los Angeles County, California. J Clin Microbiol. 2008;46(8):2499-507. PubMed PMID: 18524965.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Phenotypic and molecular characterization of Acinetobacter baumannii clinical isolates from nosocomial outbreaks in Los Angeles County, California. AU - Valentine,Sonya C, AU - Contreras,Deisy, AU - Tan,Stephanie, AU - Real,Lilian J, AU - Chu,Sheena, AU - Xu,H Howard, Y1 - 2008/06/04/ PY - 2008/6/6/pubmed PY - 2008/10/7/medline PY - 2008/6/6/entrez SP - 2499 EP - 507 JF - Journal of clinical microbiology JO - J Clin Microbiol VL - 46 IS - 8 N2 - Multidrug-resistant Acinetobacter baumannii strains have increasingly resulted in nosocomial outbreaks worldwide, leaving limited options for treatment. To date, little has been reported on the antimicrobial susceptibilities and genomic profiles of A. baumannii strains from hospital outbreaks in the Greater Los Angeles area. In this study, we examined the susceptibilities and genetic profiles of 20 nonduplicate isolates of A. baumannii from nosocomial outbreaks in Los Angeles County (LAC) and determined their mechanisms of fluoroquinolone resistance. Antibiotic susceptibility testing indicated that the majority of these LAC isolates were not susceptible to 14 of the 17 antibiotics tested, with the exception of doxycycline, minocycline, and tigecycline. In particular, all isolates were found to be resistant to ciprofloxacin. Genomic DNA analysis revealed eight epidemiologically distinct groups among these 20 A. baumannii isolates, consistent with antibiotic susceptibility profiles. Sequencing analysis confirmed that concurrent GyrA and ParC amino acid substitutions in the "hot spots" of their respective quinolone resistance-determining regions were primarily responsible for the high-level ciprofloxacin resistance of these isolates. Antibiotic susceptibility testing using two efflux pump inhibitors suggested that the presence of efflux pumps was only a secondary contributor to ciprofloxacin resistance for some of the isolates. In summary, the present study has revealed good correlation between the antibiotic susceptibility profiles and genetic fingerprints of 20 clinical isolates from nosocomial outbreaks in Los Angeles County and has determined their mechanisms of fluoroquinolone resistance, providing an important foundation for continued surveillance and epidemiological analyses of emerging A. baumannii isolates in Los Angeles County hospitals. SN - 1098-660X UR - https://www.unboundmedicine.com/medline/citation/18524965/Phenotypic_and_molecular_characterization_of_Acinetobacter_baumannii_clinical_isolates_from_nosocomial_outbreaks_in_Los_Angeles_County_California_ L2 - https://journals.asm.org/doi/10.1128/JCM.00367-08?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -