Detection of extended spectrum beta lactamases genotypes and their association with cephalosporin susceptibility in Community Acquired Enterobacteriaceae Infections
Date of Award
Master of Medicine (MMed)
Pathology (East Africa)
Background: Infections caused by Extended Spectrum Beta-Lactamases (ESBLs) producing enterobacteriaceae have become a global problem. Initially confined to the hospital set-up, they are increasingly being reported in the community.
These infections are often resistant to a wide variety of B- lactams including extended spectrum cephalosporins, with clinical and epidemiological implications for healthcare systems and necessitate surveillance measures based on local data. Local information on the genotypes of ESBLs and their association with cephalosporin resistance in community acquired ESBL-producing Enterobacteriaceae isolates is scanty, hence the need for this study.
Aim: To detect ESBLs genotypes and correlate these with susceptibility to cephalosporins among ESBL producing Escherichia coli (E.coli) and Klebsiella pneumoniae (K.pneumoniae) isolates acquired in the community.
Materials and Methods: This was a cross-sectional study in which 52 ESBL producing bacterial isolates chosen through consecutive sampling were analyzed for ESBLs genotypes by polymerase chain reaction (PCR) and gel electrophoresis. The isolates were from various clinical specimens submitted in the outpatient setting. The genotypes of interest were SHV, CTX-M, and TEM. Cephalosporin susceptibility was determined by Minimum inhibitory concentrations (MICs) using E-tests and classified into three categories; sensitive, intermediate, and resistant. I also determined association between the genotypes and MICs categories.
Results:Forty six (88.5%) of the isolates expressed CTX-M, 13(25%) had SHV, and 18(34.6%) had TEM. Nineteen (36.5%) isolates had more than one genotype. Urine specimens provided most of the ESBL producing isolates (71%) followed by respiratory specimens (11%).
The MICs for the cepharosporins were elevated with MIC50 for cefotaxime, ceftazidime, and ceftriaxone being 60ug/ml, 13ug/ml, and 139ug/ml, respectively. There was a statistically significant association (p-value= 0.017) between SHV genotype and resistance to Ceftazidime. Though other trends could be discerned between the remaining genotypes and susceptibility profiles of the three dugs, they were not statistically significant.
Interpretation and conclusion: CTX-M is the predominant ESBL genotype in community acquired Enterobacteriaceae infections, majority of which tend to be urinary tract infections. Though the presence of ESBL genes resulted in elevated MICs for the cephalosporins, only the SHV genotype could predict resistance to Ceftazidime. This information of the genotypes present in our locality could form a basis for surveillance of ESBL spread and antibiotic resistance in community isolates.
Maina, D. W. (2010). Detection of extended spectrum beta lactamases genotypes and their association with cephalosporin susceptibility in Community Acquired Enterobacteriaceae Infections (Unpublished master's dissertation). .