PHENOTYPIC DETECTION OF EXTENDED SPECTRUM BETA LACTAMASES PRODUCING ORGANISM AMONG GODFREY OKOYE UNIVERSITY STUDENTS

ABSTRACT

Extended-spectrum beta-lactamases (ESBL) are enzymes that confer resistance to most beta-lactam antibiotics, including penicillin, cephalosporin, and the aztreonams. The aim of this present study is to phenotypically identify and establish the presence of ESBL-producing organism among students in the university community. Within the University community of Godfrey Okoye University, Enugu, early morning urine samples of midstream-catch were collected into sterile bottles from sixty (60) students between ages 18 and 25years from the 2^ndMay to 31^st May. Thirty (30) male students and thirty (30) female students were sampled. Eighteen (18) isolates were identified after the following biochemical test were carried out: Gram staining, IMViC test (Indole test, methyl red test, Vogesproskauer test and citrate utilization test), and coagulase test. Twelve (12) isolates were from female students and six (6) isolates were from male students. The organisms identified were: Streptococcus spp,Corynebacteriumspp, Staphylococcus spp, and Escherichia coli. All theisolates were Gram positive except for one which was Gram negative. The double disc synergy test (DDST) was also carried out to phenotypically confirm the presence of ESBL producing organisms. All isolates were sensitive to the test drugs in the antimicrobial susceptibility test but there was no obvious DDST zones of inhibition. The result of the study suggests the absence of ESBL producing organisms among the students involved in this study.

CHAPTER ONE

1.1 Introduction

Extended-spectrum beta-lactamases (ESBL) are enzymes that confer resistance to most beta-lactam antibiotics, including penicillin, cephalosporin, and aztreonams (Bush and Jacoby, 2010).

Extended-spectrum Beta(β)-lactamases (ESBLs) are a group which are mostly plasmid-mediated, diverse, complex and rapidly evolving enzymes that are posing a major therapeutic challenge today in the treatment of hospitalized and community-based patients. Infections due to ESBL producers range from uncomplicated urinary tract infections (UTI) to life-threatening sepsis. These enzymes share the ability to hydrolyze third-generation cephalosporin and aztreonam and yet, are inhibited by clavulanic acid. In addition, ESBL-producing organisms exhibit co-resistance to many other classes of antibiotics, resulting in limitation of therapeutic option. Because of inoculum effect and substrate specificity, their detection is also a major challenge (Deepthiet al 2010).

Numerous studies have barbed towards high incidence rate of UTI associated with Escherichia coli (E. coli) and antibiotic resistance. The emergence of Multi Drug Resistant (MDR) variant of E. coli has been accounted. MDR is defined as resistance to at least two antibiotics of different classes including aminoglycosides, chloramphenicol, tetracycline and/or erythromycin. MDR in many bacteria is due to the action of multi-drug efflux pumps and by the accumulation on Resistance (R) plasmids or transposons of genes with each coding for resistance to a specific agent. Nowadays, in UTIs, ESBL -expressing Gram-Negative Bacilli (ESBL-GNB) generally cause community-acquired infections. The resistance of Gram-negative bacteria is typically owed to plasmid mediated enzymes of ESBL. ESBL producing bacteria are typically associated with multi-drug resistance (MDR) and antibacterial choice is often complicated by multi-drug resistance (Prakash and Yadav, 2017).

1.2 CLASSIFICATION OF ESBL

There are two major classification systems for β-lactamases:

1. 1. Molecular classification is based on the amino acid sequence and divides β-lactamases Ambler classes into A (serine penicillinases), C (cephalosporinases), and D (oxa-cillinases) enzymes which utilize serine for β-lactam hydrolysis and class B metalloenzymes which require divalent zinc ions for substrate hydrolysis (Bush and Jacoby, 2010).
   2. Functional classification scheme was initially proposed by Bush in 1989 and then expanded in 1995. It takes into account substrate and inhibitor profiles in an attempt to group the enzymes in ways that can be correlated with their phenotype in clinical isolates (Bush and Jacoby, 2010).

The first plasmid-mediated beta-lactamase in gram-negative bacteria was discovered in Greece in the 1960s. It was named TEM after the patient from whom it was isolated (Temoniera).   Although TEM-type beta-lactamases are most often found in Escherichia coli and Klebsiellapneumoniae, they are also found in other species of Gram-negative bacteria with increasing frequency (Clark et al., 1990).

SHV beta-lactamases

Sulfhydryl variable, (SHV) shares 68 percent of its amino acids with TEM and has a similar overall structure. The SHV beta-lactamase is most commonly found in Klebsiellapneumoniae and is responsible for up to 20% of the plasmid-mediated ampicillin resistance in this species. ESBLs in this family also have amino acid changes around the active site. More than 60 SHV varieties are known  (Chow et al., 2010).

CTX-M beta-lactamases

Cefotaximase Munich (CTX-M), these enzymes were named for their greater activity against cefotaxime than other oxyimino-beta-lactam substrates (e.g., ceftazidime, ceftriaxone, or cefepime). Rather than arising by mutation, they represent examples of plasmid acquisition of beta-lactamase genes normally found on the chromosome of Kluyveraspecies, a group of rarely pathogenic commensal organisms. These enzymes are not very closely related to TEM or SHV beta-lactamases in that they show only approximately 40% identity with these two commonly isolated beta-lactamases. More than 80 CTX-M enzymes are currently known. Despite their name, a few are more active on ceftazidime than cefotaxime. They have mainly been found in strains of Salmonella entericaserovartyphimuriumand E. coli, but have also been described in other species of Enterobacteriaceae(Chow et al., 2010).