Department of Biomaterial Sciences
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Item Phenotypic and Molecular Characterization of Extended-Spectrum Βeta-Lactamases in Klebsiella Pneumoniae and Escherichia Coli Isolates in Accra, Ghana(University of Ghana, 2015-06) Hackman, H. K.; Twum-Danso, K.; Brown, C. A.; University of Ghana, College of Health Sciences, School of Medicine and Dentistry Department of Biomaterial SciencesExtended-spectrum beta-lactamases (ESBLs) are plasmid-mediated enzymes capable of hydrolysing beta-lactams except carbapenems and cephamycins but are inhibited by beta-lactamase inhibitors. Most of these ESBL plasmids also carry genes conferring resistance to several non-beta-lactam antimicrobials. Hence, ESBL-producing isolates limit therapeutic options, contribute to treatment failure, increase morbidity and mortality, prolong hospitalization and increase cost of healthcare. There is no published work on the genetic characterization of ESBL producing strains, the characteristic antimicrobial resistance profile of CTX-M and TEM ESBL producers and the occurrence of AmpC beta-lactamases among ESBL and non-ESBL phenotypes in Accra. This work determined the phenotypic and molecular characterization of ESBLs in K. pneumoniae and E. coli isolates and their antimicrobial resistance profile in Accra. Four hundred (400) K. pneumoniae and E. coli non-duplicate isolates were collected at Korle Bu Teaching Hospital and Advent Clinical Laboratories. The species identification, ESBL detection, MIC and antimicrobial susceptibility testing were concurrently determined using Vitek 2 Compact System. The Combined Disc Synergy Method (CDM) was used to confirm ESBL-producing strains. The isolates were screened for AmpC beta-lactamase phenotypes using disc synergy testing. The genotypes of the ESBL-coding genes were determined by PCR using already published primers. The results showed that 202 (50.5%) of the bacterial isolates were ESBL-producers with high co-resistance to beta-lactams, beta-lactam/beta-lactamase inhibitors and non-beta-lactams. The sensitivity (98.5%), specificity (98.9%), positive predictive value (99%) and negative predictive value (98.5%) of Vitek 2 Compact system confirmed it as a rapid and reliable system for accurate detection of ESBL strains in Accra. The findings of this current study showed a low rate of AmpC beta-lactamase phenotypes which might not to interfere with the detection of ESBL producers. There were significant differences (p<0.05) between the resistance of ESBL producers and non-ESBL producers to beta-lactams, beta-lactam/beta-lactamase inhibitors and non-beta-lactams. Of a 100 randomly selected ESBL producers based on the MIC of cefotaxime, CTX-M (90%) and CTX-M-1group (78%) were the dominant ESBL genes, 2% were positive for CTX-M-9 group ESBL genes and 25% had TEM genes. None of the ESBL producers possessed SHV genes. CTX-M-type ESBLs are more efficient in hydrolysing cefotaxime with typical cefotaxime MIC of ≥64μg/ml. TEM-type ESBL producers appeared to be more efficient in hydrolysing ceftazidime than CTX-M-types ESBL producers and hydrolysed both ceftazidime and cefotaxime. The CTX-M-type and TEM-type ESBLs showed co-resistances to beta-lactams, beta-lactam/beta-lactamase inhibitors and non-beta-lactams and hydrolysed cefepime with less efficiency. Imipenem and amikacin were the drugs of choice for managing CTX-M and TEM-type ESBL producers. It is vital to routinely detect ESBL-phenotypes and implement appropriate antimicrobial stewardship programs in health facilities. Further studies into the sequencing of ESBL genes is recommended to determine specific ESBL gene present in a strain.