Characterization and Source Investigation of Multidrug-Resistant Salmonella Anatum from a Sustained Outbreak, Taiwan

Abstract

Memorial Hospital (CGMH) is a main referral hospital for cities in northern Taiwan, including Taipei, New Taipei, and Taoyuan. The population in this region is approximately seven million. The Clinical Microbiology Laboratory has launched a program to monitor the serovars of NTS causing human infections since 2012. All Salmonella isolates from patients were collected and serotyped. Antimicrobial susceptibility testing was performed using the disc diffusion method specified in the Clinical and Laboratory Standards Institute (CLSI) guidelines (1). S. Anatum is a relatively uncommonly recorded serovar for human infections.

Changing Antimicrobial Resistance and Epidemiology of Non-Typhoidal Salmonella Infection in Taiwanese Children

“…Such infections have also been reported in central Taiwan, indicating that this outbreak has already spread throughout the island ( Chiou et al, 2019 ). Coresistance to ceftriaxone and ciprofloxacin is the main feature of the outbreak clone ( Feng et al, 2020 ).…”

“…Parents may have more often touched, rinsed, and cooked contaminated meat before feeding other foods to their infants. Moreover, these parents were more willing to purchase meat from traditional markets rather than supermarkets ( Feng et al, 2020 ). One possibility is that parents bought meat from traditional markets, and then, their frequent rinsing spread the Salmonella from the surface of the meats to cutting boards, knives, sinks, and finally onto fresh vegetables, fruit, and other ready-to-eat foods that were cross-contaminated and reached the infants through parents or other caregivers.…”

Prevalence, Serotypes, and Antimicrobial Resistance Patterns of Non-Typhoid Salmonella in Food in Northern Taiwan

“…In this study, high AMR was common in some Salmonella serotypes detected in pork samples, particularly the Anatum and Goldcoast serotypes. A human outbreak of MDR S. Anatum emerged in Taiwan in 2015 [11]. This serotype is virulent in humans, and children became ill more frequently due to contamination from meat.…”

“…According to whole-genome sequencing, the clone responsible for the clinical outbreak shared its genealogy with an S. Goldcoast strain detected in a retail meat isolate [12]. The antimicrobial-resistant isolates of serotypes Anatum and Goldcoast from Taiwan, which harbor conjugatable plasmids (such as pSal-3973_DHA_CMY and pSal-5364) with qnrB4 (or qnrS1) and bla DHA-1 (or bla CMY-2 ) genes conferring resistance to ciprofloxacin and ceftriaxone, respectively, show high genetic similarity to Anatum isolates from the UK and Goldcoast isolates from the UK (strain 296839) and Germany (strain SAL_IB6386AA) [11,12]. Notably, very few MDR isolates were verified before 2015 [11,12,35,36].…”

“…According to Taiwanese research, antimicrobial resistance (AMR) is a serious problem in clinical Salmonella isolates [10]. The antimicrobial-resistant Salmonella spreads through the food chain, especially the MDR serotypes Anatum and Goldcoast in Taiwan [11,12], and it has been making the treatment of Salmonella infections in clinical practice more difficult [13].…”