Phenotypic and genotypic characterization of antibiotic-resistant Salmonella isolated from humans, aquaculture, and poultry in Sri Lanka: A retrospective study.

BACKGROUND: In Sri Lanka, foodborne diseases caused by nontyphoidal Salmonella are of increasing concern. We therefore aimed to characterize the dominant Salmonella serovars in humans, poultry, and aquaculture through a One Health approach. METHODS: We collected isolates from different sectors, confirmed their identities using PCR, screened their antibiotic resistance profiles, and determined their antibiotic resistance genes based on whole-genome sequencing. RESULTS: Of the 75 Salmonella isolates identified, the majority of serotypes were unidentified. Both Salmonella enterica serovar Enteritidis (S. Enteritidis) and Salmonella enterica serovar Typhimurium (S. Typhimurium) could be isolated from human sources and were also found prevalent in the poultry sector. ST36, ST11 and ST1541 were the dominant serotypes of S. Typhimurium and S. Enteritidis, respectively. Alarmingly, 4% (1/25) of poultry Salmonella isolates were resistant to ciprofloxacin, suggesting an emergence of this phenotype. Moreover, virulence genes were very diverse among S. Enteritidis and S. Typhimurium isolates. CONCLUSIONS: With the diversity of unidentified serotypes found and the detection of emerging resistances, our study highlights the importance of a One Health approach to monitoring antibiotic resistance. For public health initiatives in Sri Lanka to be successful in mitigating salmonellosis, all three sectors - humans, aquaculture, and poultry - must be tackled concomitantly in a coordinated manner under the One Health approach because antibiotic resistance genes, and even specific sequence types, may be able to spread across the aforementioned sectors. We anticipate that our results will inform public health policies in Sri Lanka to tackle foodborne illnesses.

Serotyping of invasive and colonizing group B Streptococcus (GBS) isolates at selected hospitals in Sri Lanka: a multicenter study.

Background: Group B Streptococcus (GBS) causes significant morbidity and mortality in neonates, pregnant women and patients with underlying comorbidities. Intrapartum antibiotic prophylaxis (IAP) is currently the mainstay of prevention and effective vaccine against invasive GBS disease is under clinical trial. Objectives: To describe the serotype distribution of invasive and colonizing GBS isolates in Sri Lanka. Methods: Probable GBS isolates from high vaginal swabs (HVS) and sterile body sites were collected from eight selected hospital laboratories. Following confirmation of the identification as group B Streptococcus by phenotypic methods including Lancefield grouping test (Plasmatic UK), isolates were tested for serotyping by latex agglutination test kit (STATEN serum institute, Denmark). Results: Out of the 145 probable GBS isolates only 100 from HVS and 37 from sterile body sites were confirmed as GBS. Serotype III was the most predominant in invasive GBS isolates followed by Ia, Ib, VI, II and V in the descending order of frequency. Serotype VI was the most predominant in HVS isolates followed by serotype III, V, Ia, II, Ib and IV. Difference of GBS serotype distribution between the invasive and HVS group was statistically significant (P value = 0.038). Conclusion: Serotype distribution pattern of the study isolates was comparable to most of the other developing and developed countries and hence will be beneficial in future vaccine introduction. GBS vaccine which is currently under clinical trial (Ia, Ib and III) is potentially effective for preventing 68% of the early onset disease in neonates in this study setting.

Salmonella enterica serovar Paratyphi A isolated from a hard-to-heal diabetic ulcer: a case report.

Chronically infected diabetic wounds have a polymicrobial aetiology. However, Salmonella Paratyphi A is a very rare cause of wound infection. A 76-year-old female patient with type II diabetes presented with a wound on the left leg of two months' duration. The wound was painful, erythematous and a thick, foul-smelling discharge was present. There was a history of delayed wound healing. Salmonella Paratyphi A and Pseudomonas aeruginosa were isolated from the wound tissue. The patient was treated with cefuroxime and cloxacillin empirically and following the antibiotic susceptibility testing (ABST) report, ciprofloxacin was given for 10 days. The wound was treated with multiple debridements and topical antiseptic. On follow-up, the patient remained afebrile with subsiding discharge from the ulcer. This is the first reported case of Salmonella Paratyphi A from an infected diabetic ulcer in Sri Lanka and it serves to further define the spectrum of illnesses caused by this uncommon pathogen.

Whole-Genome Sequencing Analysis of Nontyphoidal Salmonella enterica of Chicken Meat and Human Origin Under Surveillance in Sri Lanka.

A total of 73 nontyphoidal Salmonella enterica isolates, 33 from raw chicken meat and 40 from routine clinical specimens, were collected between 2015 and 2017 from eight cities in Sri Lanka for a pilot study of whole-genome sequencing for Salmonella surveillance. The isolates were characterized by conventional serotyping and whole-genome sequencing. The raw sequenced data were assembled and analyzed to predict Salmonella serotypes, determine sequence type (ST) profiles of genome and plasmid, and identify plasmid replicon sequences and antimicrobial resistance (AMR) genes. The most common serovar isolated from chicken meat was Salmonella enterica serovar Agona of ST13 (n = 16), in contrast to Salmonella enterica serovar Enteritidis of ST11 (n = 21) in human. Salmonella enterica serovar Corvallis is the only serovar that was overlapping between human and chicken meat. The level of agreement between serotyping and serotype prediction results was 100%. Among the 33 chicken isolates, multidrug resistance (MDR) was observed in five isolates, including two Salmonella enterica serovar Kentucky ST314, which harbored six different classes of AMR determinants. Among the 40 human isolates, MDR was detected in two Salmonella enterica serovar Chester (ST2063) isolates containing five different antibiotic classes of AMR determinants. Out of 73 isolates, the only human Salmonella enterica serovar Typhimurium strain of ST36 was found to possess extended-spectrum beta-lactamase (ESBL) gene, blaCTX-M-15, and it was positive for ESBL production. In summary, this study identified S. enterica serovars that were dominating in chicken meat and human and showed the genomic differences among the chicken meat and human strains. It should be noted that the limited number of isolates and sampling at a different time period means that thorough source attribution is not possible. To the best of our knowledge, this is the first report on the use of whole-genome sequencing analysis of nontyphoidal S. enterica isolated from chicken meat and human in Sri Lanka.