EXTENDED SPECTRUM BETA LACTAMASES AND METALLOBETA-LACTAMASES: AN UPDATE FROM LAHORE, PAKISTAN

Noor Ul Ain, Samyyia Abrar, Kiran Nazeer and Saba Riaz*

ABSTRACT

The objectives of the presented study were to update knowledge of the resistance burden in isolates from clinical settings in Pakistan, and assess the prevalence of ESBLs and MBLs in them. A total of 642 samples were processed in regional diagnostic center during October 2014 to December 2014. All the samples were subjected to Antimicrobial susceptibility testing (AST) by Kirby-Bauer disc diffusion method. Extended spectrum beta lactamases were screened by double disc synergism test (DDST) and Combination disc test (CDST). Strains resistant to carbapenems were further screened for metallo-β-lactamases (MBLs) using EDTA- imipenem disc synergism test and modified Hodge test. 498 Gram negative strains were obtained, most frequently from urine samples (61%), followed by pus (19%) and wound (6%) samples. There were 30% more infected samples from female patients than from male patients. The pathogens most frequently detected were Escherichia coli (50%) followed by Klebsiella spp. (18%), Pseudomonas spp. (11%) and Citrobacter spp. (11%). All of the E. coli and Klebsiella strains showed resistance to ampicillin and cefuroxime, and 97-98% of them showed resistance to cephradine, ceftrioxone, azeotrenum and amoxicillin. However, 85-92 and 82% of them were susceptible to carbapenems and amikacin, respectively. The DDSTs indicated that 58% of the strains carried ESBLs, and they were most prevalent in isolates from neonates (<1-year-old) followed by 21-40 year-olds. The commonest ESBL-carrying strains were Escherichia coli (54%) followed by Klebsiella spp. (23%) and Citrobacter spp. (11%). CDSTs detected ESBLs in more strains (73%) than the DDSTs. In addition, 57 and 85% of the carbapenem-resistant strains possessed MBL activity according to EDTA-imipenem CDST and EDTA-imipenem disc synergism tests. Use of ESBL- and MBL-phenotypic detection tests and antimicrobial susceptibility tests in routine screening may be a good strategy for managing infections in a country like Pakistan.

Keywords: ESBLs, MBLs, AST and antibiotics resistance.