Prevalence of blaCTX-M, blaTEM, and blaSHV Genes among Extended-spectrum β-lactamases-producing Clinical Isolates of Enterobacteriaceae in Different Regions of Sudan


Background: This study aimed to characterize blaCTX-M, blaTEM, and blaSHV genes among extended-spectrum beta-lactamases (ESBLs)-producing Enterobacteriaceae species in different regions of Sudan.

Methods: In this cross-sectional study, different clinical samples (n = 985) were collected randomly from symptomatic patients from four geographical regions of Sudan and cultured on chromogenic media. Following bacterial identification, phenotypic screening of ESBLs was done according to CLSI guidelines using cefotaxime (30 μg), ceftazidime (30 μg), and cefepime (30 μg) discs with and without clavulanic acid. The DNA was extracted by guanidine hydrochloride protocol, and then conventional PCR was used to detect blaCTX-M, blaTEM, and blaSHV genes. The presence of genes’ subtypes was characterized by DNA Sanger sequencing for selected samples. 

Results: Enterobacteriaceae represented 31% (305/985) of all isolates, 42 (128/305) of which were ESBLs producer, confirmed by phenotypic confirmatory test (75% [96/128] of them were positive for blaCTX-M genes, 61% [78/128] for blaTEM genes, and 38% [48/128] for blaSHV genes). Fourteen isolates (11%) were negative for all genes. Forty-eight percent (63/75) of Escherichia coli isolates were positive for blaCTX-M, while in Klebsiella pneumoniae, the dominant gene was blaTEM (82%) and had a low amount of blaSHV (59%). There was a significant association (P-value = 0.001 for all except for chloramphenicol, P = 0.014, and amikacin, P = 0.017) between resistance to third-generation cephalosporins and ciprofloxacin, nalidixic acid, meropenem, chloramphenicol, and amikacin.  Forty-two percent (40/96) of CTX-M-positive isolates were in Gizera State, 33% (32.96) in Sinnar, 24% (23/96) in Khartoum, and 1% (1/96) in White Nile. 

Conclusion: We conclude that blaCTX-M genes are the most dominant genes in ESBLs-producing isolates and are more prevalent in big cities than in rural areas.

Keywords: phenotypic, blaCTX-M, blaTEM, and blaSHV ESBLs genes, Enterobacteriaceae, Sudan

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