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Acinetobacter baumannii Isolated from Lebanese Patients: Phenotypes and Genotypes of Resistance, Clonality, and Determinants of Pathogenicity.

ABSTRACT: Introduction:Acinetobacter baumannii is a nosocomial pathogen that usually affects critically ill patients. High mortality rates have been associated with MDR A. baumannii infections. Carbapenem resistance among these isolates is increasing worldwide and is associated with certain International Clones (ICs) and oxacillinases (OXAs). Moreover, this organism possesses a wide range of virulence factors, whose expression is not yet fully understood. In this study, clinical A. baumannii isolates are characterized in terms of antibiotic resistance, mechanisms of carbapenem resistance, clonality, and virulence. Materials and Methods:A. baumannii clinical isolates (n = 90) where obtained from a tertiary care center in Beirut, Lebanon. API 20NE strips in addition to the amplification of bla_OXA-51-like were used for identification. Antibiotic susceptibility testing by disk diffusion was then performed in addition to PCRs for the detection of the most commonly disseminated carbapenemases. Clonality was determined by tri-locus PCR typing and doubling times were determined for isolates with varying susceptibility profiles. Biofilm formation, hemolysis, siderophore production, proteolytic activity, and surface motility was then determined for all the isolates. Statistical analysis was then performed for the determination of associations. Results and Discussion: 81 (90%) of the isolates were resistant to carbapenems. These high rates are similar to other multi-center studies in the country suggesting the need of intervention on a national level. 74 (91.3%) of the carbapenem resistant isolates harbored bla_OXA-23-like including two that also harbored bla_OXA-24-like. 88.9% of the A. baumannii isolates pertained to ICII and three other international clones were detected, showing the wide dissemination of clones into geographically distinct locations. Virulence profiles were highly diverse and no specific pattern was observed. Nevertheless, an association between motility, siderophore production, and biofilm formation was detected (p < 0.05). Conclusions: A very high rate of carbapenem resistance was detected, showing the need for immediate intervention. IC II and OXA-23-like were the most disseminated, reflecting their international dissemination. No specific associations were made between virulence and resistance, but instead associations among certain virulence factors were found. Investigating a more clonally diverse pool of isolates could help in the determination of associations between virulence and resistance.

SUBMITTER: Dahdouh E

PROVIDER: S-EPMC5122575 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Acinetobacter baumannii Isolated from Lebanese Patients: Phenotypes and Genotypes of Resistance, Clonality, and Determinants of Pathogenicity.

Dahdouh Elias E Hajjar Micheline M Suarez Monica M Daoud Ziad Z

Frontiers in cellular and infection microbiology 20161125

Introduction:Acinetobacter baumannii is a nosocomial pathogen that usually affects critically ill patients. High mortality rates have been associated with MDR A. baumannii infections. Carbapenem resistance among these isolates is increasing worldwide and is associated with certain International Clones (ICs) and oxacillinases (OXAs). Moreover, this organism possesses a wide range of virulence factors, whose expression is not yet fully understood. In this study, clinical A. ...[more]

PMID: 27933276

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Project description:Acinetobacter baumannii is a nosocomial pathogen that is showing increasing rates of carbapenem resistance. Multi-Drug Resistant (MDR) International Clones (ICs), associated with certain oxacillinases, are being reported globally. This organism also harbors numerous virulence determinants. In this study, we aim at characterizing A. baumannii isolated from a Spanish hospital in terms of antimicrobial susceptibility, clonality, carbapenemase genes harbored, and virulence determinants expressed.Fifty nine clinical bloodstream isolates were obtained from 2009 until 2013. Antimicrobial Susceptibility Testing was performed according to the CLSI guidelines. PFGE and tri-locus PCR typing were then performed in order to determine local and international clonality. PCRs for the detection of common carbapenemases were also performed. Production of hemolysis, biofilms, siderophores, surface motility, and proteolysis were determined phenotypically. Doubling times for selected strains were also calculated. Finally, statistical analysis for detecting associations between these factors was conducted.Carbapenem non-susceptibility was 84.75%, suggesting the immediate need for intervention. PFGE showed the distribution of the majority of the isolates among 7 clusters. Although all three ICs were detected, IC II was predominant at 71.19%. blaOXA-24-like was the most prevalent carbapenemase (62.71%), followed by blaOXA-58-like (13.56%), and blaOXA-23-like (11.86%). Strains pertaining to IC II, and those harboring blaOXA-24-like, were positively associated with ?-hemolysis, production of strong biofilms, and siderophore production. Harboring blaOXA-23-like and blaOXA-58-like was associated with attenuated virulence. These associations suggest that an interplay exists between these factors that could be locally exploited.An alarmingly high rate of carbapenem non-susceptibility has been detected in this study. There was a predominance of IC II and blaOXA-24-like, and those factors were associated with heightened expression of virulence determinants. This association could be exploited for modifying treatment regimens and for improving on infection control protocols in this hospital.

Project description:BackgroundAcinetobacter baumannii is a gram-negative bacterium which causes opportunistic infections in immunocompromised hosts. Genome plasticity has given rise to a wide range of strain variation with respect to antimicrobial resistance profiles and expression of virulence factors which lead to altered phenotypes associated with pathogenesis. The purpose of this study was to analyze clinical strains of A. baumannii for phenotypic variation that might correlate with virulence phenotypes, antimicrobial resistance patterns, or strain isolation source. We hypothesized that individual strain virulence phenotypes might be associated with anatomical site of isolation or alterations in susceptibility to antimicrobial interventions.MethodologyA cohort of 17 clinical isolates of A. baumannii isolated from diverse anatomical sites were evaluated to ascertain phenotypic patterns including biofilm formation, hemolysis, motility, and antimicrobial resistance. Antibiotic susceptibility/resistance to ampicillin-sulbactam, amikacin, ceftriaxone, ceftazidime, cefotaxime, ciprofloxacin, cefepime, gentamicin, levofloxacin, meropenem, piperacillin, trimethoprim-sulfamethoxazole, ticarcillin- K clavulanate, tetracyclin, and tobramycin was determined.ResultsAntibiotic resistance was prevalent in many strains including resistance to ampicillin-sulbactam, amikacin, ceftriaxone, ceftazidime, cefotaxime, ciprofloxacin, cefepime, gentamicin, levofloxacin, meropenem, piperacillin, trimethoprim-sulfamethoxazole, ticarcillin- K clavulanate, tetracyclin, and tobramycin. All strains tested induced hemolysis on agar plate detection assays. Wound-isolated strains of A. baumannii exhibited higher motility than strains isolated from blood, urine or Foley catheter, or sputum/bronchial wash. A. baumannii strains isolated from patient blood samples formed significantly more biofilm than isolates from wounds, sputum or bronchial wash samples. An inverse relationship between motility and biofilm formation was observed in the cohort of 17 clinical isolates of A. baumannii tested in this study. Motility was also inversely correlated with induction of hemolysis. An inverse correlation was observed between hemolysis and resistance to ticarcillin-k clavulanate, meropenem, and piperacillin. An inverse correlation was also observed between motility and resistance to ampicillin-sulbactam, ceftriaxone, ceftoxamine, ceftazidime, ciprofloxacin, or levofloxacin.ConclusionsStrain dependent variations in biofilm and motility are associated with anatomical site of isolation. Biofilm and hemolysis production both have an inverse association with motility in the cohort of strains utilized in this study, and motility and hemolysis were inversely correlated with resistance to numerous antibiotics.

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Acinetobacter baumannii Isolated from Lebanese Patients: Phenotypes and Genotypes of Resistance, Clonality, and Determinants of Pathogenicity.

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<i>Acinetobacter baumannii</i> Isolated from Lebanese Patients: Phenotypes and Genotypes of Resistance, Clonality, and Determinants of Pathogenicity.

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