Serotypes, antibiotic resistance, and molecular characterization of non-typhoidal salmonella isolated from diarrheic patients in Guangxi Zhuang Autonomous Region, China, 2014–2017

The serotype, antimicrobial resistance, and molecular typing of 843 Salmonella isolates recovered from diarrheic patients in Guangxi Zhuang Autonomous Region (Guangxi), China from 2014 to 2017 were investigated. Among these 843 isolates, a total of 67 Salmonella serotypes and four un-typable isolates were detected by the slide agglutination method. The most prevalence serotype was Salmonella 1,4,[5],12:i:- (27.4%, 231/843), followed by S. Enteritidis (20.8%) and S. Typhimurium (16.1%). Many of these isolates (86.2%, 727/843) were resistant to more than one antibiotic. The rate of resistance to early generation antimicrobial agents was high (AMP [73.8%], TET [65.5%], and NAL [43.2%]). Moreover, the rate of resistance to clinically important antimicrobial agents was of great concern (CIP [21.6%], CTX [12.9%], and AZM [5.7%]). Importantly, 34 (4.0%) isolates of nine serovars were resistant to both CIP and CTX, which included 14 (1.7%) that were also resistant to AZM. In addition, 74.9% (631/843) of nontyphoidal Salmonella isolates demonstrated decreased susceptibility to ciprofloxacin with S. Enteritidis as the dominant serovar. Overall, 393 (46.6%) isolates were identified as multidrug resistance (MDR) with resistance to three or more classes of antimicrobials, of which MDR S. 1,4,[5],12:i:- accounted for the highest proportion (31.6%, 124/393). Genotypic analyses by pulsed-field gel electrophoresis of 447 isolates containing the three most common serotypes revealed a high diversity, suggesting that the majority human salmonellosis cases are attributed to sporadic events. These results highlighted the diversity of Salmonella serotypes and the high prevalence of emerging MDR Salmonella. 1,4,[5],12:i:- isolates in Guangxi. Therefore, surveillance of these emerging MDR isolates should be enhanced to monitor antimicrobial resistant Salmonella in the food chain and to inform risk-based decisions to protect public health.