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Integron-Mediated Antibiotic Resistance in Acinetobacter baumannii Isolated from Intensive Care Unit Patients, Babol, North of Iran.

ABSTRACT: We investigated the integron types and their relation with antibiotic resistance among A. baumannii isolates collected from intensive care unit patients, Babol, north of Iran.In this cross-sectional study, a total of 73 bronchoalveolar lavage samples were obtained from patients in ICU. Susceptibility testing was performed by disk diffusion method. Types of integrons were identified by an integrase gene PCR.In total, 47.9% A. baumannii isolates were recovered from the BAL samples. All isolates were resistant to ceftazidime. 91.4% and 58.3% of isolates were MDR and XDR, respectively. The rate of colistin resistance with the E-test was 5.7%. Molecular analysis of class I, II, and III integrons showed that 25.7%, 88.6%, and 28.6% of the isolates carried the intI, intII, and intIII genes, respectively.Our results show that different classes of integrons are commonly spread among A. baumannii strains and these genomic segments can play an important role in the acquisition of MDR and XDR phenotypes. So monitoring drug resistance in A. baumannii isolates with the use of int gene PCR is very important to plan specific infection control measures to prevent the spread of MDR-AB and XDR-AB in Iran's hospitals.

SUBMITTER: Deylam Salehi M

PROVIDER: S-EPMC5540380 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Integron-Mediated Antibiotic Resistance in <i>Acinetobacter baumannii</i> Isolated from Intensive Care Unit Patients, Babol, North of Iran.

Deylam Salehi Mitra M Ferdosi-Shahandashti Elaheh E Yahyapour Yosef Y Khafri Soraya S Pournajaf Abazar A Rajabnia Ramazan R

BioMed research international 20170719

<h4>Background</h4>We investigated the integron types and their relation with antibiotic resistance among <i>A. baumannii</i> isolates collected from intensive care unit patients, Babol, north of Iran.<h4>Methods</h4>In this cross-sectional study, a total of 73 bronchoalveolar lavage samples were obtained from patients in ICU. Susceptibility testing was performed by disk diffusion method. Types of integrons were identified by an integrase gene PCR.<h4>Results</h4>In total, 47.9% <i>A. baumannii< ...[more]

PMID: 28804720

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Project description:This study was conducted in order to assess the acquisition rate of Acinetobacter baumannii by newborn screening, on admission and during the discharge process of neonatal intensive care unit. (NICU). Furthermore, we investigated risk factors for potential colonization and molecular epidemiology of isolated resistant bacteria. This prospective study was conducted in the neonatal unit of Hassan II University Hospital of Fez from February 2013 to July 2015. During this period, all consecutive admitted neonates were screened for A. baumannii intestinal carriage, on admission and during the discharge process. Bacteriological and molecular tests were evaluated according to the international standards. This study examines the screening on admission of 455 newborns, 59% of whom were male. The average gestational age and birth weight were 35.2 weeks and 2612.1 g respectively. In total, 277 patients were included in the acquisition study on admission. The prevalence of multi-drug resistant (MDR) A. baumannii strain carriage was 6.5%, while the acquisition rate during the hospital recovery was 13.7%. In this study, 68 MDR A. baumannii isolates were collected. The resistance rates to different antibiotic classes including, Ceftazidime, Gentamycin and Ciprofloxacin varied between 92 and 100%. Moreover, 13% of MDR A. baumannii isolates were carbapenemase producers and 88% harbored blaOXA-23 gene. On admission, three risk factors were significantly associated with A. baumannii colonization: age (OR, 2.803; IC95%, 1.191-6.596; P = 0.01), gender (OR, 0.382; IC95%, 0.158-0.921; P = 0.03) and the delivery birth at the Maternity of University Hospital (MUH), (OR, 0.196; IC95%, 0.071-0.540; P = 0.002). However during hospitalization, the only risk factor associated with acquisition of A. baumannii was the respiratory distress (OR, 2.270; IC95%, 1.055-4.881; P = 0.03). A high intestinal carriage rate of A. baumannii and multiple antibiotic resistance were found in our NICU. Thus, the spread of MDR A. baumannii should be monitored by an active surveillance strategy.

Project description:We describe a novel genetic mechanism in which tandem amplification of a plasmid-borne integron regulates virulence, opacity variation, and global gene expression by altering levels of a putative small RNA (sRNA) in Acinetobacter baumannii AB5075. Copy number of this amplified locus correlated with the rate of switching between virulent opaque (VIR-O) and avirulent translucent (AV-T) cells. We found that prototypical VIR-O colonies, which exhibit high levels of switching and visible sectoring with AV-T cells by 24 h of growth, harbor two copies of this locus. However, a subset of opaque colonies that did not form AV-T sectors within 24 h were found to harbor only one copy. The colonies with decreased sectoring to AV-T were designated low-switching opaque (LSO) variants and were found to exhibit a 3-log decrease in switching relative to that of the VIR-O. Overexpression studies revealed that the element regulating switching was localized to the 5' end of the aadB gene within the amplified locus. Northern blotting indicated that an sRNA of approximately 300?nucleotides (nt) is encoded in this region and is likely responsible for regulating switching to AV-T. Copy number of the ?300-nt sRNA was also found to affect virulence, as the LSO variant exhibited decreased virulence during murine lung infections. Global transcriptional profiling revealed that >100 genes were differentially expressed between VIR-O and LSO variants, suggesting that the ?300-nt sRNA may act as a global regulator. Several virulence genes exhibited decreased expression in LSO cells, potentially explaining their decreased virulence.IMPORTANCE Acinetobacter baumannii remains a leading cause of hospital-acquired infections. Widespread multidrug resistance in this species has prompted the WHO to name carbapenem-resistant A. baumannii as its top priority for research and development of new antibiotics. Many strains of A. baumannii undergo a high-frequency virulence switch, which is an attractive target for new therapeutics targeting this pathogen. This study reports a novel mechanism controlling the frequency of switching in strain AB5075. The rate of switching from the virulent opaque (VIR-O) to the avirulent translucent (AV-T) variant is positively influenced by the copy number of an antibiotic resistance locus encoded on a plasmid-borne composite integron. Our data suggest that this locus encodes a small RNA that regulates opacity switching. Low-switching opaque variants, which harbor a single copy of this locus, also exhibit decreased virulence. This study increases our understanding of this critical phenotypic switch, while also identifying potential targets for virulence-based A. baumannii treatments.

Project description:Acinetobacter baumannii is a common cause of healthcare-associated infections (HAI) worldwide, mostly occurring in intensive care units (ICUs). Extended-spectrum beta lactamases (ESBL)-positive A. baumannii strains have emerged as highly resistant to most currently used antimicrobial agents, including carbapenems. The most common mechanism for carbapenem resistance in this species is β-lactamase-mediated resistance. Carbapenem-hydrolyzing class D oxacillinases are widespread among multidrug-resistant (MDR) A. baumannii strains. The present study was conducted to determine the presence and distribution of blaOXA genes among multidrug-resistant A. baumannii isolated from ICU patients and genes encoding insertion sequence (IS-1) in these isolates. Additionally, the plasmid DNA profiles of these isolates were determined. A total of 120 clinical isolates of A. baumannii from various ICU clinical specimens of four main Jordanian hospitals were collected. Bacterial isolate identification was confirmed by biochemical testing and antibiotic sensitivity was then assessed. PCR amplification and automated sequencing were carried out to detect the presence of blaOXA-51, blaOXA-23, blaOXA-24, and blaOXA-58 genes, and ISAba1 insertion sequence. Out of the 120 A. baumannii isolates, 95% of the isolates were resistant to three or more classes of the antibiotics tested and were identified as MDR. The most frequent resistance of the isolates was against piperacillin (96.7%), cephalosporins (97.5%), and β-lactam/β-lactamase inhibitor combinations antibiotics (95.8%). There were 24 (20%) ESBL-producing isolates. A co-existence of blaOXA-51 gene and ISAba1 in all the 24 ESBL-producing isolates was determined. In addition, in the 24 ESBL-producing isolates, 21 (87.5%) carried blaOXA-51 and blaOXA-23 genes, 1 (4.2%) carried blaOXA-51 and blaOXA-24, but all were negative for the blaOXA-58 gene. Plasmid DNA profile A and profile B were the most common (29%) in ESBL-positive MDR A. baumannii isolates while plasmid DNA profile A was the most common in the ESBL-negative isolates. In conclusion, there was an increase in prevalence of MDR-A. baumannii in ICU wards in Jordanian hospitals, especially those having an ESBL phenotype. Thus, identification of ESBL genes is necessary for the surveillance of their transmission in hospitals.

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.

Dataset Information

Integron-Mediated Antibiotic Resistance in Acinetobacter baumannii Isolated from Intensive Care Unit Patients, Babol, North of Iran.

Publications

Integron-Mediated Antibiotic Resistance in <i>Acinetobacter baumannii</i> Isolated from Intensive Care Unit Patients, Babol, North of Iran.

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