Oxacillinase Gene Distribution, Antibiotic Resistance, and Their Correlation with Biofilm Formation in <i>Acinetobacter baumannii</i> Bloodstream Isolates

Abstract

<b><i>Objectives:</i></b> The limitations of treatment options in bloodstream infections caused by multidrug-resistant <i>Acinetobacter baumannii</i> (MDRAB) have been related to high morbidity and mortality. The aim of our present study was to determine antimicrobial susceptibility profiles, molecular resistance patterns, and biofilm properties of <i>A. baumannii</i> isolated from bloodstream infections. <b><i>Materials and Methods:</i></b> In the present study, a total of 44 <i>A. baumannii</i> bloodstream isolates were included. Antimicrobial susceptibility profiles and biofilm formation ability were assessed. The distribution of class D carbapenemases, IS<i>Aba1</i>, IS<i>Aba1</i>/<i>bla</i>OXA-23, <i>bla</i>NDM-1, <i>mcr-1</i>, and <i>ompA</i> was investigated by polymerase chain reaction (PCR). Arbitrarily primed-PCR (AP-PCR) was performed to evaluate clonal relationships. <b><i>Results:</i></b> A total of 32 isolates were MDRAB, whereas 6 isolates were also resistant to colistin without <i>mcr-1</i> positivity. All isolates were harboring <i>bla</i>OXA-51 gene, whereas <i>bla</i>OXA-23 positivity was 63.6%. Fifty percent of the isolates had IS<i>Aba1.</i> IS<i>Aba1</i> upstream of <i>bla</i>OXA-23 was determined in 18 isolates. None of the isolates were positive for <i>bla</i>NDM-1 gene. Majority of the strains were strong biofilm producers (86.8%). A total of 56.8% of the isolates were positive for <i>ompA</i> gene with no direct association with strong biofilm formation. However, <i>bla</i>OXA-51 + 23 genotype and trimethoprim-sulfamethoxazole resistance showed a significant relationship with biofilm formation. AP-PCR analysis revealed six distinct clusters of <i>A. baumannii</i>. <b><i>Conclusions:</i></b> Herein, majority of the <i>A. baumannii</i> blood isolates were characterized as <i>bla</i>OXA-51+OXA-23 carbapenemase genotype and were strong biofilm formers. None of the isolates were positive for <i>bla</i>NDM-1, which was promising. Resistant isolates were tended to form strong biofilms. Our results highlight the emergence of oxacillinase-producing MDRAB isolated from bloodstream with high biofilm formation ability.