Molecular characterization of resistance mechanisms to fluoroquinolones of some Acinetobacter baumannii clinical isolates in Upper Egypt

Abstract

Acinetobacter species are free-living microorganisms, present in clinical samples, and different environmental conditions. They are Gram-negative bacteria, strictly aerobic, diplo-coccobacilli, catalase, and citrate utilization positive, oxidase-negative, non-fermenting, and grown easily on common laboratory media. A. baumannii can survive for prolonged periods under a wide range of environmental conditions and on surfaces making it a frequent cause of nosocomial infections and outbreaks especially in ICU, CCU, and inpatients. This organism targets immunocompromised patients and causes a wide spectrum of infections, e.g., bacteremia, respiratory tract, urinary tract, wounds, and associated catheter infections. One of the most striking features of A. baumannii is its unusual ability to develop multiple resistance mechanisms against most of the antibiotic classes, resulting in the emergence and spread of MDR, XDR, and PDR. This study aimed at evaluation of nosocomial infection rates, the antibiotic-resistant profile of A. baumannii recovered from hospitalized patients of two major University Hospitals in Upper Egypt (Al-Azhar and Assiut University Hospitals) followed by studying fluoroquinolone resistance mechanisms. Furthermore, the study aimed to evaluate the use of various CIP or LEV combinations with various antimicrobial and non-antimicrobial agents as an attempt to control this life-threatening pathogen. A total of 1600 Gram-negative isolates were recovered from different clinical specimens. Out of these, 977 isolates (61.06%) were identified as lactose fermenters and 623 isolates (38.94%) were identified as non-lactose fermenters. The clinical isolates were identified as E. coli (667; 41.69%), Klebsiella spp. (310; 19.38%), P. aeruginosa (486; 30.38%), Proteus spp. (22; 1.38%), A. baumannii (100; 6.25%), and Serratia marcescens (15; 0.94%). The recovered A. baumannii isolates represented 6.25% of the total collected isolates. The specimens that showed the highest percentage (61%, 61/100) of A. baumannii contamination were obtained from the respiratory tract (ETT, 29%; nasal, 17%; sputum, 13%; and throat, 2%) while 9% and 12% isolates were recovered from urinary tract (not catheter-associated) and blood infections, respectively. Wounds, skin, urinary tract, and central venous catheter specimens gave 6%, 2%, 8%, and 2% A. baumannii isolates, respectively. The isolates of A. baumannii were isolated from the cardiac care units (CCU), intensive care units (ICU), and wards of inpatient (IP) in two different hospitals. The highest percentage (77%) of isolates was obtained from different types of ICU (general ICU, chest, gyno, neuro, and ortho ICU) followed by IP (14%) and the lowest percentage (9%) was from CCU. Males were