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Antimicrobial susceptibility profile among Enterobacteriaceae strains and detection of Extended-Spectrum β-Lactamase (ESBL) production

Courrol DS, Pereira CBP, Franzolin MR

Laboratório de Bacteriologia, Instituto Butantan, Brasil

Introduction: The family of Enterobacteriaceae is formed by gram-negative bacilli and can be widely found in nature, mostly inhabits the gut of man and animals, either as members of the normal flora or as infection agents. Currently, enterobacteria are commonly isolated bacteria of infectious processes, representing about 70 to 80% of the Gram-negative bacteria strains isolated in laboratory routine. Some complications arising are: urinary tract infection, intestinal infection, sepsis, pneumonia, wound infections, SNC infections, pericarditis, endocarditis, meningitis and otitis. The antimicrobial resistance to some drugs and the production of extended-spectrum beta-lactamases (ESBL) by enterobacteria strains is an increasing problem for public health.  Objectives: This study was carried out to determine the antimicrobial susceptibility pattern of Citrobacter freundii, Providencia sp, Morganella morganii sp, Hafnia alvei, Edwardsiella sp., Serratia sp., and Erwinia sp. strains against 10 antimicrobials drugs, and detect phenotypic production of ESBL using the disk approximation testing.  Methods: The enterobacteria species: Morganella morganii (15 strains), Citrobacter freundii (12), Providencia spp. (5), Edwardsiella (1), Hafnia alvei (1), Serratia spp. (1) and Erwinia spp. (1) of the bacteriological collection of Laboratory of Bacteriology of the Butantan Institute, isolated from patients with and without diarrhea, were tested for antimicrobial susceptibility with the disc diffusion method, using Agar Müller-Hinton and the following antibiotics: Amoxicillin with clavulanic acid (AMC), Cephalothin (CFL), Chloramphenicol (CLO), Imipenem (IPM), Meropenem (MER), Cotrimoxazol (sulfamethoxazole and trimethoprim), Amikacin (AMI), Streptomycin (STR), Ciprofloxacin (CIP) and Tetracycline (TET). The disk approximation testing was done with Agar Müller-Hinton and the following cephalosporins: Ceftazidime (CAZ), Ceftriaxone (CRO), Cefepime (COM) and Aztreonam (ATM), arranged with a distance of 30mm from an Amoxicillin with Clavulanic acid (AMC) disc. Results and Discussion: All of the Enterobacteriaceae isolates showed 100% sensitivity to IPM, MER, AMI and CIP, showing sensitivity to CLO and SUT (86.1% each), STR (77.7%) and TET (63.8 %), as well as resistance to AMC (52.7%) and CFL (77.7%). The enhancement of the zone of inhibition or a so-called ghost zone between some cephalosporin disk and the clavulanate-containing disc indicated the presence of an ESBL in 06/36 (16.7 %) strains. These results show the variability in the susceptibility and resistance pattern, not only among all enterobacteria, as well as strains of the same genus of bacteria, showing the importance of conducting antibiograms in cases of infections caused by Enterobacteria, as well as the monitoring of ESBL production due to its possible spread of ESBL encoding genes on mobile elements to another bacteria.

Supported by FUNDAP

11 - SYSTEMS BIOLOGY 21th Annual Scientific Meeting of Instituto Butantan.