Salmonella is the leading cause of typhoidal and non-typhoidal infections in the world. The entry of Salmonella into the bloodstream causes an invasive disease state, resulting to high morbidity and mortality rates, especially in children. Owing to the misuse of antibiotics, certain Salmonella serovars are multi-drug resistant and do not respond to traditional antibiotics, such as ampicillin and trimethoprim-sulphamethoxazole, presenting a significant challenge for healthcare practitioners in treating and controlling the spread of this disease. Therefore, expensive third-generation cephalosporins, such as ceftriaxone, are currently used to treat Salmonella infection. However, a novel serovar of Salmonella that resists ceftriaxone was recently identified in Saudi Arabia, indicating wide spread Salmonella resistance. A comprehensive literature review on ceftriaxone resistance in Salmonella is therefore necessary to reflect upon current challenges. In this report, we provide a summary of Salmonella incidence, mechanisms of ceftriaxone resistance in Salmonella, and current treatment options.

The rapidly increasing prevalence and spread of antibiotic-resistant Salmonella worldwide have become a thorny problem that poses a serious threat to human health. It is speculated that antibiotic abuse, frequent traveling, and mass gatherings accelerate this threat. To explore this hypothesis, we investigated 13 Salmonella isolates from Medina, Saudi Arabia and 15 from China as the control group using typical methods of serotype identification, antibiotic resistance tests, pulsed-field gel electrophoresis (PFGE), and multi-locus sequence typing (MLST). Our results indicated that the isolates from China showed greater serotype diversity and a higher antimicrobial resistance rate, which was consistent with results from other studies in China. In contrast, the Saudi Arabian isolates were mainly identified as Serovar Bredeney and were resistant to a limited number of antibiotics. Interestingly, two of the Bredeney isolates was resistant to third-generation cephalosporins but sensitive to all other tested antibiotics. To confirm the results and understand the underlying molecular mechanisms of these isolates, whole-genome sequencing (WGS) was performed. We discovered that several cephalosporin resistance-associated genes were shared with other strains, but one gene (LEN-23) was unique. Therefore, to the best of our knowledge, we concluded that this study is the first to report the emergence of Salmonella Bredeney resistant to third-generation cephalosporins in Saudi Arabia.