Salmonella in Retail Food and Wild Birds in Singapore—Prevalence, Antimicrobial Resistance, and Sequence Types

Abstract

Non-typhoidal salmonellosis is a leading cause of foodborne zoonosis. To better understand the epidemiology of human salmonellosis, this study aimed to determine the prevalence, antimicrobial resistance and sequence types of Salmonella in retail food and wild birds (proximity to humans) in Singapore. We analyzed 21,428 cooked and ready-to-eat food and 1,510 residual faecal samples of wild birds collected during 2010–2015. Thirty-two Salmonella isolates from food and wild birds were subjected to disc diffusion and multi-locus sequence typing (MLST). Salmonella was isolated from 0.08% (17/21,428) of food and 0.99% (15/1510) of wild birds. None of the isolates from wild birds (n = 15) exhibited phenotypic resistance, while the isolates from food (47.1%, 8/17) showed a high prevalence of phenotypic resistance to, at least, one antimicrobial. These findings suggested that the avian Salmonella isolates had been subjected to less antimicrobial selection pressure than those from food samples. MLST revealed specific sequence types found in both food and wild birds. The study can guide future studies with whole-genome analysis on a larger number of isolates from various sectors for public health measures.

Distribution of Salmonella Serovars in Humans, Foods, Farm Animals and Environment, Companion and Wildlife Animals in Singapore

“…The serovar has been isolated from a wide variety of sources including poultry, reptiles, fish, mushrooms and turtles [27]. Two monophasic strains belonging to the MLST sequence types ST42 and ST423 were isolated in Singapore from local wild birds (black bittern and crow) in 2012 [28]. In 2018, the serovar 4,5,12:b:-(dT+) was reported to be responsible for a multistate outbreak of Salmonella infection due to consumption of products containing Kratom, a tropical plant native to Southeast Asia [29].…”

Analysis of Salmonella enterica serovar Enteritidis isolates from chickens and chicken meat products in Malaysia using PFGE, and MLST

“…While ST11 had been reported in humans, poultry, food, and some wild animal species, including reptiles in many countries from Asia, Africa, South America, and European countries (enterobase). Notably, ST1925 has been reported to be a single cell variant of ST11, and both sequence types are known to be geographically widespread and have previously been reported in foods, humans and animals [23,24]. The detection of these STs from different sources may also indicate their ability to adapt to, and persist in different hosts or types of samples.…”

“…The detection of these STs from different sources may also indicate their ability to adapt to, and persist in different hosts or types of samples. The detection of ST11 in foods may imply possible transmission from neighboring countries like Singapore and China, where the ST type prevails [24]. In this study, the Whole-Genome Sequencing platform was used for the MLST analysis against the traditional PCR based MLST, followed by Sanger sequencing.…”

Association between non-typhoidal Salmonella urinary tract infection and Klebsiella pneumoniae lung empyema

“…15 Ciprofloxacin has previously been suggested as first-line treatment of NTS infections, as this antibiotic accumulates intracellularly where Salmonella pathogens tend to grow. 15 However, a Singaporebased study 16 demonstrated a 35.3% resistance to quinolones among NTS isolates versus a 5.9% resistance to co-amoxiclav. Hence, the use of co-amoxiclav as first-line treatment of NTS infections may be preferred in a Singaporean population.…”