Abstract
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
Highlights
Extended-spectrum beta-lactamases (ESBLs) are the types of enzymes that cause resistance to most beta-lactam ring containing antibiotics [1]
A dramatic increase has been reported in the frequency of blaCTX-M types β-lactamases-producing bacteria, which replaced the predominant types in the past, such as blaTEM and blaSHV [4]. blaCTX-M carrier, E. coli, can disseminate these genes in the community and hospitals from intestinal flora and cause infection [5]
More than 45% (139/305) of all Enterobacteriaceae isolates were resistant to cefotaxime, 39.3% (120/305) to ceftazidime, and 13.4% (41/305) to cefepime
Summary
Extended-spectrum beta-lactamases (ESBLs) are the types of enzymes that cause resistance to most beta-lactam ring containing antibiotics [1]. Resistance to cephalosporins and production of ESBLs genes in hospitals and environment have been reported in previous studies [9,10,11]. This study aimed to detect blaCTX-M, blaSHV, and blaTEM genes and their subtypes among ESBLs-producing Enterobacteriaceae in different regions of Sudan. 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. 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). 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%). Conclusion: We conclude that blaCTX-M genes are the most dominant genes in ESBLsproducing isolates and are more prevalent in big cities than in rural areas
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