A retrospective investigation of the population structure and geospatial distribution of Salmonella Paratyphi A in Kathmandu, Nepal.

Salmonella Paratyphi A, one of the major etiologic agents of enteric fever, has increased in prevalence in recent decades in certain endemic regions in comparison to S. Typhi, the most prevalent cause of enteric fever. Despite this increase, data on the prevalence and molecular epidemiology of S. Paratyphi A remain generally scarce. Here, we analysed the whole genome sequences of 216 S. Paratyphi A isolates originating from Kathmandu, Nepal between 2005 and 2014, of which 200 were from patients with acute enteric fever and 16 from the gallbladder of people with suspected chronic carriage. By exploiting the recently developed genotyping framework for S. Paratyphi A (Paratype), we identified several genotypes circulating in Kathmandu. Notably, we observed an unusual clonal expansion of genotype 2.4.3 over a four-year period that spread geographically and systematically replaced other genotypes. This rapid genotype replacement is hypothesised to have been driven by both reduced susceptibility to fluoroquinolones and genetic changes to virulence factors, such as functional and structural genes encoding the type 3 secretion systems. Finally, we show that person-to-person is likely the most common mode of transmission and chronic carriers seem to play a limited role in maintaining disease circulation.

Genetic diversity of Salmonella Paratyphi A isolated from enteric fever patients in Bangladesh from 2008 to 2018.

BACKGROUND: The proportion of enteric fever cases caused by Salmonella Paratyphi A is increasing and may increase further as we begin to introduce typhoid conjugate vaccines (TCVs). While numerous epidemiological and genomic studies have been conducted for S. Typhi, there are limited data describing the genomic epidemiology of S. Paratyphi A in especially in endemic settings, such as Bangladesh. PRINCIPAL FINDINGS: We conducted whole genome sequencing (WGS) of 67 S. Paratyphi A isolated between 2008 and 2018 from eight enteric disease surveillance sites across Bangladesh. We performed a detailed phylogenetic analysis of these sequence data incorporating sequences from 242 previously sequenced S. Paratyphi A isolates from a global collection and provided evidence of lineage migration from neighboring countries in South Asia. The data revealed that the majority of the Bangladeshi S. Paratyphi A isolates belonged to the dominant global lineage A (67.2%), while the remainder were either lineage C (19.4%) or F (13.4%). The population structure was relatively homogenous across the country as we did not find any significant lineage distributions between study sites inside or outside Dhaka. Our genomic data showed presence of single point mutations in gyrA gene either at codon 83 or 87 associated with decreased fluoroquinolone susceptibility in all Bangladeshi S. Paratyphi A isolates. Notably, we identified the pHCM2- like cryptic plasmid which was highly similar to S. Typhi plasmids circulating in Bangladesh and has not been previously identified in S. Paratyphi A organisms. SIGNIFICANCE: This study demonstrates the utility of WGS to monitor the ongoing evolution of this emerging enteric pathogen. Novel insights into the genetic structure of S. Paratyphi A will aid the understanding of both regional and global circulation patterns of this emerging pathogen and provide a framework for future genomic surveillance studies.

Drug-resistant enteric fever worldwide, 1990 to 2018: a systematic review and meta-analysis.

BACKGROUND: Antimicrobial resistance (AMR) is an increasing threat to global health. There are > 14 million cases of enteric fever every year and > 135,000 deaths. The disease is primarily controlled by antimicrobial treatment, but this is becoming increasingly difficult due to AMR. Our objectives were to assess the prevalence and geographic distribution of AMR in Salmonella enterica serovars Typhi and Paratyphi A infections globally, to evaluate the extent of the problem, and to facilitate the creation of geospatial maps of AMR prevalence to help targeted public health intervention. METHODS: We performed a systematic review of the literature by searching seven databases for studies published between 1990 and 2018. We recategorised isolates to allow the analysis of fluoroquinolone resistance trends over the study period. The prevalence of multidrug resistance (MDR) and fluoroquinolone non-susceptibility (FQNS) in individual studies was illustrated by forest plots, and a random effects meta-analysis was performed, stratified by Global Burden of Disease (GBD) region and 5-year time period. Heterogeneity was assessed using the I2 statistics. We present a descriptive analysis of ceftriaxone and azithromycin resistance. FINDINGS: We identified 4557 articles, of which 384, comprising 124,347 isolates (94,616 S. Typhi and 29,731 S. Paratyphi A) met the pre-specified inclusion criteria. The majority (276/384; 72%) of studies were from South Asia; 40 (10%) articles were identified from Sub-Saharan Africa. With the exception of MDR S. Typhi in South Asia, which declined between 1990 and 2018, and MDR S. Paratyphi A, which remained at low levels, resistance trends worsened for all antimicrobials in all regions. We identified several data gaps in Africa and the Middle East. Incomplete reporting of antimicrobial susceptibility testing (AST) and lack of quality assurance were identified. INTERPRETATION: Drug-resistant enteric fever is widespread in low- and middle-income countries, and the situation is worsening. It is essential that public health and clinical measures, which include improvements in water quality and sanitation, the deployment of S. Typhi vaccination, and an informed choice of treatment are implemented. However, there is no licenced vaccine for S. Paratyphi A. The standardised reporting of AST data and rollout of external quality control assessment are urgently needed to facilitate evidence-based policy and practice. TRIAL REGISTRATION: PROSPERO CRD42018029432.

Molecular mechanism of azithromycin resistance among typhoidal Salmonella strains in Bangladesh identified through passive pediatric surveillance.

BACKGROUND: With the rise in fluoroquinolone-resistant Salmonella Typhi and the recent emergence of ceftriaxone resistance, azithromycin is one of the last oral drugs available against typhoid for which resistance is uncommon. Its increasing use, specifically in light of the ongoing outbreak of extensively drug-resistant (XDR) Salmonella Typhi (resistant to chloramphenicol, ampicillin, cotrimoxazole, streptomycin, fluoroquinolones and third-generation cephalosporins) in Pakistan, places selective pressure for the emergence and spread of azithromycin-resistant isolates. However, little is known about azithromycin resistance in Salmonella, and no molecular data are available on its mechanism. METHODS AND FINDINGS: We conducted typhoid surveillance in the two largest pediatric hospitals of Bangladesh from 2009-2016. All typhoidal Salmonella strains were screened for azithromycin resistance using disc diffusion and resistance was confirmed using E-tests. In total, we identified 1,082 Salmonella Typhi and Paratyphi A strains; among these, 13 strains (12 Typhi, 1 Paratyphi A) were azithromycin-resistant (MIC range: 32-64 µg/ml) with the first case observed in 2013. We sequenced the resistant strains, but no molecular basis of macrolide resistance was identified by the currently available antimicrobial resistance prediction tools. A whole genome SNP tree, made using RAxML, showed that the 12 Typhi resistant strains clustered together within the 4.3.1.1 sub-clade (H58 lineage 1). We found a non-synonymous single-point mutation exclusively in these 12 strains in the gene encoding AcrB, an efflux pump that removes small molecules from bacterial cells. The mutation changed the conserved amino acid arginine (R) at position 717 to a glutamine (Q). To test the role of R717Q present in azithromycin-resistant strains, we cloned acrB from azithromycin-resistant and sensitive strains, expressed them in E. coli, Typhi and Paratyphi A strains and tested their azithromycin susceptibility. Expression of AcrB-R717Q in E. coli and Typhi strains increased the minimum inhibitory concentration (MIC) for azithromycin by 11- and 3-fold respectively. The azithromycin-resistant Paratyphi A strain also contained a mutation at R717 (R717L), whose introduction in E. coli and Paratyphi A strains increased MIC by 7- and 3-fold respectively, confirming the role of R717 mutations in conferring azithromycin resistance. CONCLUSIONS: This report confirms 12 azithromycin-resistant Salmonella Typhi strains and one Paratyphi A strain. The molecular basis of this resistance is one mutation in the AcrB protein at position 717. This is the first report demonstrating the impact of this non-synonymous mutation in conferring macrolide resistance in a clinical setting. With increasing azithromycin use, strains with R717 mutations may spread and be acquired by XDR strains. An azithromycin-resistant XDR strain would shift enteric fever treatment from outpatient departments, where patients are currently treated with oral azithromycin, to inpatient departments to be treated with injectable antibiotics like carbapenems, thereby further burdening already struggling health systems in endemic regions. Moreover, with the dearth of novel antimicrobials in the horizon, we risk losing our primary defense against widespread mortality from typhoid. In addition to rolling out the WHO prequalified typhoid conjugate vaccine in endemic areas to decrease the risk of pan-resistant Salmonella Typhi strains, it is also imperative to implement antimicrobial stewardship and water sanitation and hygiene intervention to decrease the overall burden of enteric fever.

The epidemiology of typhoid fever in the Dhulikhel area, Nepal: A prospective cohort study.

INTRODUCTION: Typhoid fever (TF) continues to cause considerable morbidity and mortality in Nepal, but only limited epidemiologic data is available about TF outside Kathmandu. METHODS: As part of an interventional trial, we performed a prospective cohort study of bacteremic TF patients in Dhulikhel Hospital between October 2012 and October 2014. Demographic, epidemiological, clinical, and microbiologic data were recorded. RESULTS: 116 bacteremic typhoid patients were included in the study. Most were young, healthy, adults (mean age 27.9±12 years), 41.4% of whom were female. More than 70% of patients were employed in non-manual services or were university students. Salmonella Typhi accounted for 64/115 (55.7%) of all isolates, while Salmonella Paratyphi accounted for 51/115 (44.3%), of which 42 were Paratyphi A and 9 Paratyphi B. A significant proportion of TF cases occurred also during the dry season (48/116, 41.6%). The clinical presentation of Salmonella Typhi and Paratyphi infections was similar, except for a greater proportion of arthralgia in patients with Salmonella Typhi. Most Salmonella Typhi and Paratyphi isolates were resistant to nalidixic acid and susceptible to older antibiotics. One Salmonella Paratyphi isolate was resistant to ceftriaxone. CONCLUSIONS: TF remains common in the Dhulikhel area, even among those with a high level of education. Public health measures aimed at reducing the incidence of TF in the Dhulikhel area are warranted. The relative burden of TF caused by Salmonella Paratyphi is rising; a vaccine with activity against Salmonella Paratyphi is needed. Since Salmonella Paratyphi B was more prevalent in this cohort than in large cohorts of patients from Kathmandu, it is likely that there are significant regional variations in the epidemiology of TF outside Kathmandu.

[Antimicrobial resistance and molecular subtypes of Salmonella typhi and Salmonella paratyphoid isolates from Jiangsu province, 2012-2015].

Objective: To retrospectively analyze the antimicrobial resistance phenotype and molecular typing characteristics of Salmonella (S.) typhi and S. paratyphi in Jiangsu province from 2012 to 2015. Methods: The samples were collected from typhoid and paratyphoid patients in Jiangsu province. The biochemical identification and serotyping were carried out after isolation and culture. Kirby-Bauer (K-B) testing was used to detect the drug susceptibility of the strains. The molecular typing characteristics of S. typhi and S. paratyphi were analyzed by pulsed field gel electrophoresis (PFGE). Results: The resistant rates of 134 S. typhi and S. paratyphi A strains to nalidixic acid were highest (61.2% and 86.7%), while the resistant rates to remaining antibiotics were less than 15.0%. Most of S. typhi and S. paratyphi A strains were resistant to only one antibiotic. Multidrug-resistant (MDR) strains of S. typhi and S. paratyphi A accounted for 2.6% and 13.3% respectively. The composition of the all-sensitive strains of S. typhi increased by 44.3% in 2015, at the same time, there were also MDR S. paratyphi A strains, which were resistant to 5 and 6 antibiotics. S. paratyphi A could be divided into eight molecular patterns by PFGE, showing that the similarity between the MDR strains and other strains was relatively low. The S. paratyphi A strains with same pattern were resistant to same antibiotics. S. typhi could be divided into 68 molecular patterns by PFGE, with large variability between different patterns. There was no corresponding relationship between the patterns and the drug resistance characteristics. Conclusions: The overall antibiotic resistance of S. typhi and S. paratyphi A strains showed a decreasing trend, but the number of antibiotics to which they were resistant increased. PFGE patterns of S. typhi showed diversity without correspondence to antibiotic characteristics. PFGE patterns of S. paratyphi A were less with correspondence to antibiotic characteristics. We should pay more attention to key patterns in key areas.

The clinical and microbiological characteristics of enteric fever in Cambodia, 2008-2015.

BACKGROUND: Enteric fever remains a major public health problem in low resource settings and antibiotic resistance is increasing. In Asia, an increasing proportion of infections is caused by Salmonella enterica serovar Paratyphi A, which for a long time was assumed to cause a milder clinical syndrome compared to Salmonella enterica serovar Typhi. METHODOLOGY: A retrospective chart review study was conducted of 254 unique cases of blood culture confirmed enteric fever who presented at a referral adult hospital in Phnom Penh, Cambodia between 2008 and 2015. Demographic, clinical and laboratory data were collected from clinical charts and antibiotic susceptibility testing was performed. Whole genome sequence analysis was performed on a subset of 121 isolates. RESULTS: One-hundred-and-ninety unique patients were diagnosed with Salmonella Paratyphi A and 64 with Salmonella Typhi. In the period 2008-2012, Salmonella Paratyphi A comprised 25.5% of 47 enteric fever cases compared to 86.0% of 207 cases during 2013-2015. Presenting symptoms were identical for both serovars but higher median leukocyte counts (6.8 x 109/L vs. 6.3 x 109/L; p = 0.035) and C-reactive protein (CRP) values (47.0 mg/L vs. 36 mg/L; p = 0.034) were observed for Salmonella Typhi infections. All but one of the Salmonella Typhi isolates belonged to haplotype H58 associated with multidrug resistance (MDR) (i.e. resistance to ampicillin, chloramphenicol and co-trimoxazole).;42.9% actually displayed MDR compared to none of the Salmonella Paratyphi A isolates. Decreased ciprofloxacin susceptibility (DCS) was observed in 96.9% (62/64) of Salmonella Typhi isolates versus 11.5% (21/183) of Salmonella Paratyphi A isolates (all but one from 2015). All isolates were susceptible to azithromycin and ceftriaxone. CONCLUSIONS: In Phnom Penh, Cambodia, Salmonella Paratyphi A now causes the majority of enteric fever cases and decreased susceptibility against ciprofloxacin is increasing. Overall, Salmonella Typhi was significantly more associated with MDR and DCS compared to Salmonella Paratyphi A.

Regional Transmission of Salmonella Paratyphi A, China, 1998-2012.

To explore transmission patterns and genetic relationships of Salmonella enterica serovar Paratyphi A in China, we conducted a genome-wide single-nucleotide polymorphism analysis on the strains in the 4 provinces in which incidence was highest during 1998-2012. Markedly phylogeographic clustering suggested regional virus circulation after introduction from areas in southeastern China.

[Taq Man probe-based quadruple real-time PCR for detection of Salmonella paratyphi A/B/C and Salmonella typhi].

OBJECTIVE: Establishment and application of Taq Man probe-based quadruple real-time PCR for detection of Salmonella paratyphi A/B/C and Salmonella typhi. Primers specific to Salmonella paratyphi A( SPAP), Salmonella paratyphi B( SPBP), Salmonella paratyphi C( SPCP), and Salmonella typhi( STP) were designed. METHODS: A method of Taq Man probe-based quadruple real-time PCR was established according to the distinction of the 5'end of the probe mark of TET, ROX, FAM and HEX. 5 strains of SPA, 4 strains of SPB, 7 strains of SPC and 11 strains of ST were identified by amplification from SPAP, SPBP, SPCP and STP. RESULTS: While other serotypes of salmonella and17 strains of non-salmonella got negative results of amplification. Amplification rate of SPAP, SPBP, SPCP, and STP were 84. 5%, 101. 8%, 92. 4% and 90. 9%, respectively. The linear correlation coefficient( R~2) were 0. 996, 0. 975, 0. 996 and 0. 984, respectively. CONCLUSION: The PCR system is specific and sensitive for the identification of SPA, SPB, SPC and ST.

Typhoidal Salmonellae: Use of Multi-Locus Sequence Typing to Determine Population Structure.

Enteric fever is an invasive infection predominantly caused by Salmonella enterica serovars Typhi and Paratyphi A. The pathogens have evolved from other nontyphoidal salmonellaeto become invasive and host restricted. Emergence of antimicrobial resistance in typhoidal salmonellae in some countries is a major therapeutic concern as the travelers returning from endemic countries carry resistant strains to non endemic areas. In order to understand the epidemiology and to design disease control strategies molecular typing of the pathogen is very important. We performed Multilocus Sequence Typing (MLST) of 251 S. Typhi and 18 S. Paratyphi strains isolated from enteric fever patients from seven centers across India during 2010-2013to determine the population structure and prevalence of MLST sequence types in India. MLST analysis revealed the presence of five sequence types (STs) of typhoidal salmonellae in India namely ST1, ST2 and ST3 for S. Typhi and ST85 and ST129 for S. Paratyphi A.S. Typhi strains showed monophyletic lineage and clustered in to 3 Sequence Types-ST1, ST2 and ST3 and S. Paratyphi A isolates segregated in two sequence types ST85 and ST129 respectively. No association was found between antimicrobial susceptibility and sequence types. This study found ST1 as the most prevalent sequence type of S. Typhi in India followed by ST2, which is in concordance with previous studies and MLST database. In addition a rare sequence type ST3 has been found which is reported for the first time from the Indian subcontinent. Amongst S. Paratyphi A, the most common sequence type is ST129 as also reported from other parts of world. This distribution and prevalence suggest the common spread of the sequence types across the globe and these findings can help in understanding the disease distribution.

Emerging enteric fever due to switching biotype of Salmonella (paratyphi A) in Eastern Odisha.

BACKGROUND: Typhoid fever is classically caused by Salmonella enterica serotype typhi.Recently the frequency of isolation of S. paratyphi A (SPA) has been increased in comparison to S. typhi in Indian scenario. AIM: To observe the rate of isolation and antimicrobial susceptibility pattern of SPA from suspected enteric fever cases attending tertiary care centres of Eastern Orissa. SETTINGS AND DESIGN: Retrospective study Materials and Methods: 1488 blood samples were collected during different duration of fever and cultured in BACTEC blood culture system and bottles showing signal for growth were subcultured and identified as Salmonella spp. by standard procedure and mini API (Biomeriux) and antimicrobial susceptibility by disc diffusion method. STATISTICAL ANALYSIS: Chi square test. RESULTS: 167 Salmonella spp. were isolated including 83.8% Salmonella paratyphi A and 16.6% S. typhi. Among them 102 were males and 65 were females with mean age of 22.7 yrs. S. paratyphi A was the predominant spp. each year but during 2008 - 2011, there was a dramatic rise (significant P value- 0.034). Multidrug resistance was noticed in 10.2% of the isolates. 98% of S. paratyphi A were resistant to nalidixic acid and 41% to ciprofloxacin, but the MIC of ciprofloxacin was raised between 1-2 µgm/dl showing the relation between nalidixic acid resistance and raised MIC of ciprofloxacin. CONCLUSION: Nalidixic acid should be tested along with ciprofloxacin disc while testing for susceptibility and MIC of ciprofloxacin is mandatory before advocating therapy to prevent treatment failure.

Outbreak of enteric fever due to Salmonella Paratyphi A variety durazzo (2,12:a:-) in a hilly region of North India: A report of 43 cases.

Enteric fever due to Salmonella Paratyphi A (SPA) is a global problem occurring as outbreaks at times. An unusual SPA (2,12:a:-) variety durazzo has been reported rarely. We report an outbreak of enteric fever due to this variety affecting 43 individuals. The blood samples grew unusual mucoid, lactose non-fermenting colonies with atypical biochemical reactions in sugar fermentation and amino acid decarboxylation. Isolates had sensitivity to ceftriaxone, chloramphenical, cotrimoxazole, intermediate susceptibility to ciprofloxacin and resistance to ampicillin and nalidixic acid. Identification was confirmed as SPA (2,12:a:-) at the National Salmonella Centre.

[Characteristics of drug resistance and molecular type of Salmonella typhi and Salmonella paratyphi isolated in Henan province, 2009-2011].

OBJECTIVE: To investigate the antibiotic resistance and pulsed field gel electrophoresis (PFGE) patterns of clinical isolates of Salmonella (S.) typhi and S. paratyphi in Henan province during 2009-2011. METHODS: According to molecular typing and Salmonella K-B drug susceptibility test method published by international PulseNet bacterial infectious disease monitoring network and USA Clinical and Laboratory Standards Institute (CLSI), the drug susceptibility and PFGE molecule characteristics of 78 S. typhi and S. paratyphi strains isolated from sentinel hospitals in Henan were analyzed. RESULTS: The 78 strains of S. typhi and S. paratyphi were resistant to 13 kinds of antibiotics, in which 62 were multidrug resistant (79.5%), 4 were resistant to 2-3 kinds of antibiotics (5.1%), 41 were resistant to 5-8 kinds of antibiotics (52.6%), 14 were resistant to 9-10 kinds of antibiotics (17.9%), 3 were resistant to 11-12 kinds of antibiotics (3.8%). The resistant rate to cephalosporins, quinolones and other 3 kinds of antibiotic showed an increase trends. Seventy two strains of S. typhi and S. paratyphi could be divided 14 molecular patterns by digestion with XbaⅠ and PFGE, each pattern contains 1-47 strains which shared the similarity of 66.03%-100.00%. CONCLUSIONS: The drug resistance of clinical isolates of S. typhi and S. paratyphi was serious in Henan. The PFGE patterns showed diversity, but the predominant patterns could be still found. The PFGE patterns of some strains were associated with their drug resistance.

Increase in paratyphoid fever cases in Japanese travellers returning from Cambodia in 2013.

In 2013, an unusual increase of paratyphoid fever cases in travellers returning from Cambodia was reported in Japan. From December 2012 to September 2013, 18 cases of Salmonella Paratyphi A infection were identified. Microbiological analyses revealed that most isolates had the same clonal identity, although the epidemiological link between these cases remains unclear. It was inferred that the outbreak was caused by a common and persistent source in Cambodia that was likely to have continued during 2014. The information of surveillance and laboratory data from cases arising in travellers from countries with limited surveillance systems should be timely shared with the country of origin.

Genomic analysis of Salmonella enterica serotype Paratyphi A during an outbreak in Cambodia, 2013-2015.

In 2013, an unusual increase in the number of Salmonella enterica serotype Paratyphi A (Salmonella Paratyphi A) infections was reported in patients in Phnom Penh, Cambodia, and in European, American and Japanese travellers returning from Cambodia. Epidemiological investigations did not identify a common source of exposure. To analyse the population structure and genetic diversity of these Salmonella Paratyphi A isolates, we used whole-genome sequencing on 65 isolates collected from 1999 to 2014: 55 from infections acquired in Cambodia and 10 from infections acquired in other countries in Asia, Africa and Europe. Short-read sequences from 80 published genomes from around the world and from 13 published genomes associated with an outbreak in China were also included. Pulsed-field gel electrophoresis (PFGE) was performed on a subset of isolates. Genomic analyses were found to provide much more accurate information for tracking the individual strains than PFGE. All but 2 of the 36 isolates acquired in Cambodia during 2013-2014 belonged to the same clade, C5, of lineage C. This clade has been isolated in Cambodia since at least 1999. The Chinese outbreak isolates belonged to a different clade (C4) and were resistant to nalidixic acid, whereas the Cambodian outbreak isolates displayed pan-susceptibility to antibiotics. Since 2014, the total number of cases has decreased, but there has been an increase in the frequency with which nalidixic acid-resistant C5 isolates are isolated. The frequency of these isolates should be monitored over time, because they display decreased susceptibility to ciprofloxacin, the first-choice antibiotic for treating paratyphoid fever.

Molecular characteristics of Salmonella enterica Paratyphi A in Yunnan Province, southwest China.

Previously, the prevalence of Salmonella enterica Paratyphi A in Yunnan was high; and recently Yunnan was the predominant endemic province in China. To identify the molecular epidemiology, antibiotic resistance profile and genotypic diversity of the S. Paratyphi A isolates from 1995 to 2013 in Yunnan, we performed the study. Antibiotic susceptibility tests, pulse-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used to identify the characteristics of the bacterial isolates. The results showed from 1995 to 2013, 366 S. Paratyphi A were isolated: 295 isolates (80.6%) from Yuxi and 68 isolates (18.58%) from Honghe. All of the strains were resistant to nalidixic acid, and some were resistant to ampicillin and trimethoprim/sulfamethoxazole in different years. All the isolates were sensitive to cefotaxime and ciprofloxacin. Identical PFGE with two enzyme digestion patterns were found for 339 isolates. Some environmental isolates in different years were homologous with the strains isolated from food and patients. MLST showed 349 strains were ST85, only 17 isolates were ST129. S. Paratyphi A isolates from Yunnan showed a high similarity, and we found the pathogen isolated from patients, the environment and food had the close epidemiological relationship, forming a transmission circulation. These findings have important implications for paratyphoid-control strategies.

Phenotyping of Salmonella serotypes isolated from natural sources of water in rural areas of East Sikkim.

The objective of the study was to conduct bacteriological analysis of water with special reference to Salmonella spp from natural sources of rural habitations of East Sikkim. A total of 28 Salmonella serovars isolated were biotyped, phage typed and tested for their anti-microbial susceptibility. All the isolates of Salmonella enterica serovar Typhi belonged to Biotype I. Four isolates of S. typhi belonged to phage type A. All S. paratyphi A isolates belong to phage 2. All the isolates were sensitive to chloramphenicol, cefixime and amikacin. Untreated natural water sources are unsafe for human consumption.

Multiple-locus variable number of tandem repeats analysis of Salmonella enterica serotype paratyphi A from Yuxi and comparison with isolates from the Chinese Medical Culture Collection Center.

The aim of the present study was to genotype Salmonella enterica serotype paratyphi A (SPA) isolated from Yuxi, China, in a multiple-locus variable number of tandem repeats (VNTRs) analysis (MLVA) and to compare them with isolates from the Chinese Medical Culture Collection Center (CMCC). Potential VNTRs were screened from the genomes of ATCC9150 and AKU_12601 using the Tandem Repeats Finder program. Nine VNTRs were established for MLVA typing of 195 SPA isolates from Yuxi and 20 isolates from CMCC. The dendogram for MLVA profiles and minimum spanning tree (MST) were drawn using the categorical coefficient calculated by BioNumerics software. A total of 23 MLVA types were identified in 215 SPA isolates and were grouped into six distinct cluster groups A, B, C, D, E and F. A total of 195 Yuxi SPA isolates were exclusively grouped into cluster C with nine MLVA genotypes. A total of 20 CMCC isolates were grouped in clusters A B, D, E and F with the other 14 MLVA types. The MLVA with nine VNTR loci, which was exploited in the present study, represents a successful strategy for genotyping SPA. Furthermore, the 195 Yuxi isolates appear to be closely related to each other and distinct from the 20 CMCC strains.

A large outbreak of Salmonella Paratyphi A infection among israeli travelers to Nepal.

BACKGROUND: In Asia, Salmonella Paratyphi A is an emerging infection, and travelers are increasingly at risk. During October 2009-November 2009, an outbreak in S. Paratyphi A infection was noted in Israeli travelers returning from Nepal. METHODS: An outbreak investigation included a standardized exposure questionnaire admitted to all patients and medical chart abstraction. Isolates were tested for antimicrobial susceptibility and pulsed-field gel electrophoresis (PFGE). RESULTS: During 1 October 2009-30 November 2009, 37 Israeli travelers returning from Nepal were diagnosed with S. Paratyphi A bacteremia. All 37 case isolates had an identical pattern on PFGE, and all were nalidixic acid resistant. Only 1 food venue was frequented by all the outbreak cases, with the largest number of exposures occurring around the Jewish New Year. All patients recovered without complications. Time to defervescence in 17 patients treated with ceftriaxone and azithromycin combination was 3.2 days (± 1.7), whereas in 13 cases treated with ceftriaxone monotherapy, the time to defervescence was 6.6 days (± 1.8; P < .001). CONCLUSIONS: A point-source, "Paratyphoid Mary"-like outbreak was identified among Israeli travelers to Nepal. Combination Ceftriaxone-Azithromycin therapy may provide a therapeutic advantage over monotherapy, and merits further clinical trials.

Optimization of pulsed-field gel electrophoresis protocols for Salmonella Paratyphi A subtyping.

Salmonella enterica serovar Paratyphi A infection has caused public health problems in some countries in recent years. Pulsed-field gel electrophoresis (PFGE) has been used for the subtyping and epidemiological investigations of some serotypes of Salmonella, mainly in outbreaks caused by non-typhoidal Salmonella. In this study, different restriction endonucleases and electrophoresis parameters were compared for the PFGE subtyping by using Salmonella Paratyphi A strain panels. Two protocols for the enzymes SpeI and XbaI showed higher discriminatory power, which may facilitate epidemiological analysis for more accurate case definition, and clonality study of Salmonella Paratyphi A.