Antimicrobial susceptibility of 3rd generation Cephalosporins-resistant escherichia coli, Klebsiella pneumoniae and Enterobacter spp isolates carried in the gut of patients on admission to Mulago Hospital

Abstract

Background: Resistance to 3rd and 4th generation cephalosporin is on an increase worldwide. These cephalosporins are used in management of severe infections caused by Enterobacteriaceae. The main objective of the study was to determine the susceptibility of third generation cephalosporins-resistant Escherichia coli, Klebsiella pneumoniae and Enterobacter spp isolated from patients at Mulago Hospital. Methods: This was a cross-sectional study that looked at 80 Enterobacteriaceae Isolates, 42 Escherichia coli, 30 Klebsiella pneumoniae and 8 Enterobacter species that were isolated from rectal samples of patients on admission to Mulago Hospital. Antimicrobial susceptibility testing was done using amoxicillin/clavulanate, ampicillin/sulbactam, piperacillin/tazobactam, cefotaxime, ceftriaxone, ceftazidime, aztreonam, ertapenem, imipenem, meropenem, tigecycline, fosfomycin, trimethoprim-sulfamethoxazole, gentamicin, amikacin, nalidixic acid, nitrofurantoin, chloramphenicol, cefoxitin, ciprofloxacin, cefepime,ampicilin and tetracycline discs. The plates were incubated and interpreted according to CLSI guidelines after measuring the zone diameters. For Tigecycline the FDA guidelines were used. Agar dilution method for testing susceptibility of cefoperazone-sulbactam was used on three concentrations (16µg/ml, 32 µg/ml and 64 µg/ml) of cefoperazone/sulbactam dissolved in MHA. Phenotypic ESBL production was detected using the Double Disc Synergy Test. The modified inhibition carbapenamase test was used for detection of carbapenamase production. OXA gene variants were detected using PCR. The PCR products were then sequenced. Results: Results show that 77(96.2 %) were ESBL producers while 3 (3.8 %) were of non-ESBL phenotype. E.coli was the most isolated organism 42(52.5 %), followed by K.pneumoniae 30 (37.5 %) and Enterobacter spp 8(10%).E.coli had the highest percentage of ESBL producers 41(97.6%). Susceptibility was the highest 75(93.8%) to Meropenem and Ertapenem. There was no isolate recorded that produced AmpC and carbapenamase enzymes. 20% of the isolates were positive for OXA-1, 7.5% for OXA-10 and 6.25% for OXA-48. Conclusions: This study reveals a high resistance to drug-inhibitor combinations and cefepime among E. coli, K. pneumoniae and Enterobacter spp that are resistant to 3rd generation cephalosporins isolated from rectal samples of patients on admission to Mulago Hospital.