RESUMEN
Field investigations were conducted after a small cluster of food poisoning involving six cases was reported. While no stool samples were available from the cases for microbiological testing, Salmonella species was found to be present in the stools of food handlers with gastroenteritis symptoms. Four Salmonella isolates recovered from the food handlers were retrospectively investigated at the genome level using whole-genome sequencing (WGS). WGS showed that S. Anfo (antigenic formulae 39:y:1,2), a rarely isolated serovar, caused infections in the food handlers. S. Anfo analysed in this study contained virulence factors required for causing disease. They did not contain any antibiotic resistance genes or plasmid. The epidemiologically related isolates differed to each other by a maximum of one single nucleotide polymorphism. WGS was useful in identifying rare Salmonella serovars and it is potentially more cost-effective than traditional serotyping methods. It can also confidently group epidemiologically related isolates belonging to S. Anfo.
Asunto(s)
Manipulación de Alimentos , Intoxicación Alimentaria por Salmonella/diagnóstico , Salmonella enterica/genética , Secuenciación Completa del Genoma , Heces/microbiología , Industria de Alimentos , Genoma Bacteriano , Humanos , Enfermedades Profesionales/microbiología , Polimorfismo de Nucleótido Simple , Estudios Retrospectivos , Salmonella enterica/aislamiento & purificación , Serogrupo , Serotipificación , Singapur , Factores de Virulencia/genéticaRESUMEN
The number of salmonellosis cases in Singapore has increased over the years. Salmonella enterica serovar Enteritidis has always been the most predominant serovar in the last five years. The National Public Health Laboratory assisted outbreak investigations by performing multilocus variable number tandem repeat analysis (MLVA) on isolates that were collected at the time of the investigations. Isolates were defined as belonging to a particular cluster if they had identical MLVA patterns. Whilst MLVA has been instrumental in outbreak investigations, it may not be useful when outbreaks are caused by an endemic MLVA type. In this study, we analysed 67 isolates from 12 suspected outbreaks with known epidemiological links to explore the use of next-generation sequencing (NGS) for defining outbreaks. We found that NGS can confidently group isolates into their respective outbreaks. The isolates from each suspected outbreak were closely related and differed by a maximum of 3 single nucleotide polymorphisms (SNPs). They were also clearly separated from isolates that belonged to different suspected outbreaks. This study provides an important insight and further evidence on the value of NGS for routine surveillance and outbreak detection of S. Enteritidis.
Asunto(s)
Brotes de Enfermedades/estadística & datos numéricos , Infecciones por Salmonella/epidemiología , Infecciones por Salmonella/microbiología , Salmonella enteritidis/genética , ADN Bacteriano/genética , Estudio de Asociación del Genoma Completo , Secuenciación de Nucleótidos de Alto Rendimiento , Humanos , Filogenia , Polimorfismo de Nucleótido Simple/genética , Estudios Retrospectivos , Salmonella enteritidis/clasificación , Singapur/epidemiologíaRESUMEN
Singapore is situated in the tropics where the seasonality of influenza is not as well defined as that of temperate countries. We examined the circulation of influenza viruses in the community in terms of the characteristics of influenza activity. We reviewed laboratory-confirmed virological data collected between 2010 and 2014 under the national influenza surveillance programme. Influenza activity was measured by the proportion of specimens from outpatients with influenza-like illness tested positive for influenza virus based on 4-weekly moving interval. Seasonal epidemics occurred around the end of previous year or the beginning and middle of the year. Increases in influenza positivity were more pronounced when there was a change in the predominant circulating influenza virus type/subtype to influenza A(H3N2). Influenza epidemics lasted about 12 weeks on average, with longer duration when there was a change in the predominant influenza type/subtype and especially when it was associated with influenza A(H3N2). Continuous influenza surveillance is important as it could provide early warning of imminent surges in virus transmission, and allow for timely implementation of public health prevention and control interventions to minimize influenza-associated disease burden. J. Med. Virol. 88:2069-2077, 2016. © 2016 Wiley Periodicals, Inc.
Asunto(s)
Monitoreo Epidemiológico , Subtipo H3N2 del Virus de la Influenza A/aislamiento & purificación , Virus de la Influenza A/aislamiento & purificación , Virus de la Influenza B/aislamiento & purificación , Gripe Humana/epidemiología , Epidemias/prevención & control , Humanos , Subtipo H3N2 del Virus de la Influenza A/inmunología , Virus de la Influenza A/inmunología , Virus de la Influenza B/inmunología , Gripe Humana/prevención & control , Gripe Humana/transmisión , Gripe Humana/virología , Investigación Cualitativa , Estudios Retrospectivos , Estaciones del Año , Singapur/epidemiología , Factores de Tiempo , Clima Tropical , Virosis/epidemiología , Virosis/prevención & control , Virosis/virologíaRESUMEN
INTRODUCTION: This paper describes the epidemiology and control of a community outbreak of novel influenza A (H1N1-2009) originating from a dance club in Singapore between June and July 2009. MATERIALS AND METHODS: Cases of novel influenza A (H1N1-2009) were confirmed using in-house probe-based real-time polymerase chain reaction (PCR). Contact tracing teams from the Singapore Ministry of Health obtained epidemiological information from all cases via telephone. RESULTS: A total of 48 cases were identified in this outbreak, of which 36 (75%) cases were patrons and dance club staff, and 12 (25%) cases were household members and social contacts. Mathematical modelling showed that this outbreak had a reproductive number of 1.9 to 2.1, which was similar to values calculated from outbreaks in naïve populations in other countries. CONCLUSION: This transmission risk occurred within an enclosed space with patrons engaged in intimate social activities, suggesting that dance clubs are places conducive for the spread of the virus.