A recurring outbreak of Shigella sonnei among traditionally observant Jewish children in New York City: the risks of daycare and household transmission

Shigella sonnei: epidemiology, evolution, pathogenesis, resistance and host interactions

Shigella sonnei is a major cause of diarrhoea globally and is increasing in prevalence relative to other Shigella because of multiple demographic and environmental influences. This single-serotype species has traditionally received less attention in comparison to Shigella flexneri and Shigella dysenteriae, which were more common in low-income countries and more tractable in the laboratory. In recent years, we have learned that Shigella are highly complex and highly susceptible to environmental change, as exemplified by epidemiological trends and increasing relevance of S. sonnei. Ultimately, methods, tools and data generated from decades of detailed research into S. flexneri have been used to gain new insights into the epidemiology, microbiology and pathogenesis of S. sonnei. In parallel, widespread adoption of genomic surveillance has yielded insights into antimicrobial resistance, evolution and organism transmission. In this Review, we provide an overview of current knowledge of S. sonnei, highlighting recent insights into this globally disseminated antimicrobial-resistant pathogen and assessing how novel data may impact future vaccine development and implementation.

The genomic epidemiology of shigellosis in South Africa

Shigellosis, a leading cause of diarrhoeal mortality and morbidity globally, predominantly affects children under five years of age living in low- and middle-income countries. While whole genome sequence analysis (WGSA) has been effectively used to further our understanding of shigellosis epidemiology, antimicrobial resistance, and transmission, it has been under-utilised in sub-Saharan Africa. In this study, we applied WGSA to large sub-sample of surveillance isolates from South Africa, collected from 2011 to 2015, focussing on Shigella flexneri 2a and Shigella sonnei. We find each serotype is epidemiologically distinct. The four identified S. flexneri 2a clusters having distinct geographical distributions, and antimicrobial resistance (AMR) and virulence profiles, while the four sub-Clades of S. sonnei varied in virulence plasmid retention. Our results support serotype specific lifestyles as a driver for epidemiological differences, show AMR is not required for epidemiological success in S. flexneri, and that the HIV epidemic may have promoted Shigella population expansion.

Risk factors for contracting watery diarrhoea in Mzilikazi, Bulawayo City, Zimbabwe, 2020: a case control study

Introduction

Mzilikazi clinic had an upsurge of diarrhoea cases with 41 cases from the 28^th to the 30^th of September 2020, against a threshold of 11. We therefore, investigated the risk factors associated with this outbreak to recommend prevention and control measures.

Methods

we conducted a 1:1 unmatched case-control study. A case was any person who suffered from diarrhoea, and was resident in the clinic´s catchment since the 21^st of September 2020. Demographic data, knowledge and practices related to diarrhoea were collected using a standard questionnaire for both cases and controls. Environmental assessment, water quality and stool testing was also done. We conducted univariate and multivariate analysis at 95% confidence interval, to determine factors independently associated with contracting diarrhoea.

Results

the median age was 30 years (Q1=12, Q3=46) for cases and 30 years (Q1=22, Q3=48) for controls. The dominant gender was female for cases and male for controls. The independent risk factors were: drinking borehole water [adjusted Odds Ratio (aOR)=2.66; 95%CI=(1.41-5.00)], storing water in open container [aOR=2.76; 95%CI=(1.38-5.53)] and being under-five years old [aOR=5.73; 95%CI=(2.06-15.89)]. Boiling drinking water [aOR=0.39; 95%CI=(0.20-0.75)] was protective. Coliforms were detected from boreholes and stored water samples, and Shigella flexneri was isolated from 2 of the 13 stool specimens collected. Residents accessed water from decommissioned boreholes due to severe municipal water rationing.

Conclusion

being under-five years old, drinking borehole water and storing water in open containers were independent risk factors. Health education on home water treatment, distribution of water storage containers, and Aquatabs was done.

A shigellosis outbreak associated with a sports festival at a kindergarten in Kitakyushu City, Japan

INTRODUCTION

Shigellosis cases have decreased gradually in Japan in recent years, but indigenous shigellosis outbreaks sometimes occur in childcare facilities. From national surveillance data, we identified a shigellosis outbreak involving a kindergarten.

METHODS

After detecting Shigella sonnei in Kitakyushu City, we conducted active case finding and epidemiological investigation in Kindergarten Z, including stool specimen collection and interviews. The stool specimens were cultured, and isolated strains were subjected to pulsed-field gel electrophoresis (PFGE) and multiple-locus variable-number tandem-repeat analysis (MLVA).

RESULTS

Between September 1 and December 31, 2014, we identified 19 cases: 14 confirmed, 2 suspected, and 3 asymptomatic. Of the 19 cases, 16 were epidemiologically associated with Kindergarten Z (10 pupils, 5 family members, and 1 teacher). On October 19, a pupil with gastrointestinal illness participated in the kindergarten's sports festival, in which the pupils were split into "red" and "white" teams; the pupil in question belonged to the red team. Attack rates of the red and white teams were 8% (7/82) and 0% (0/108), respectively (relative risk, 10.5; 95% confidence interval, 1.3-82.1). PFGE patterns were identical or similar for the isolates in all 17 cases; 7 isolates were identical, and the others had one locus difference on MLVA.

CONCLUSIONS

We concluded that contact during the sports festival could have been responsible for spread of the shigellosis outbreak at the kindergarten, although the infection source was not determined. It is vital to inform guardians immediately after detection of shigellosis cases that symptomatic pupils should not participate in activities such as sports festivals.

Disparities in Shigellosis Incidence by Census Tract Poverty, Crowding, and Race/Ethnicity in the United States, FoodNet, 2004-2014

BACKGROUND

Shigella causes an estimated 500 000 enteric illnesses in the United States annually, but the association with socioeconomic factors is unclear.

METHODS

We examined possible epidemiologic associations between shigellosis and poverty using 2004-2014 Foodborne Diseases Active Surveillance Network (FoodNet) data. Shigella cases (n = 21 246) were geocoded, linked to Census tract data from the American Community Survey, and categorized into 4 poverty and 4 crowding strata. For each stratum, we calculated incidence by sex, age, race/ethnicity, and FoodNet site. Using negative binomial regression, we estimated incidence rate ratios (IRRs) comparing the highest to lowest stratum.

RESULTS

Annual FoodNet Shigella incidence per 100 000 population was higher among children <5 years old (19.0), blacks (7.2), and Hispanics (5.6) and was associated with Census tract poverty (incidence rate ratio [IRR], 3.6; 95% confidence interval [CI], 3.5-3.8) and household crowding (IRR, 1.8; 95% CI, 1.7-1.9). The association with poverty was strongest among children and persisted regardless of sex, race/ethnicity, or geographic location. After controlling for demographic variables, the association between shigellosis and poverty remained significant (IRR, 2.3; 95% CI, 2.0-2.6).

CONCLUSIONS

In the United States, Shigella infections are epidemiologically associated with poverty, and increased incidence rates are observed among young children, blacks, and Hispanics.

Recommendations for ‘The City in Need’

As the body first deteriorates and then reaches immunity against a disease, the city also first suffers and then becomes more resilient by the end of an outbreak event. The city may not become fully immune, but will be more experienced and prepared with a much enhanced resilience for the future.

Serum IgG antibodies to Shigella lipopolysaccharide antigens - a correlate of protection against shigellosis

Shigella is a leading cause of diarrhea among children globally and of diarrheal deaths among children under 5 years of age in low- and middle-income countries. To date, no licensed Shigella vaccine exists. We review evidence that serum IgG antibodies to Shigella LPS represent a good correlate of protection against shigellosis; this could support the process of development and evaluation of Shigella vaccine candidates. Case-control and cohort studies conducted among Israeli soldiers serving under field conditions showed significant serotype-specific inverse associations between pre-exposure serum IgG antibodies to Shigella LPS and shigellosis incidence. The same serum IgG fraction showed a dose-response relationship with the protective efficacy attained by vaccine candidates tested in phase III trials of young adults and children aged 1-4 years and in Controlled Human Infection Model studies and exhibited mechanistic protective capabilities. Identifying a threshold level of these antibodies associated with protection can promote the development of an efficacious vaccine for infants and young children.

Burden and risk factors of Shigella sonnei shigellosis among children aged 0-59 months in hyperendemic communities in Israel

OBJECTIVES

Ultraorthodox Jewish populations living in towns with good sanitary infrastructure but with conditions of crowding have been the epicenter of Shigella sonnei shigellosis outbreaks. In this study, the incidence and risk factors of S. sonnei shigellosis in children living in an ultraorthodox community were determined.

METHODS

Data for the years 2000-2013 for all reported culture-proven S. sonnei shigellosis cases in children aged 0-59 months in the city of Elad were compared with data for the rest of the sub-district. Environmental factors obtained through parental interviews were evaluated for 78 incident cases of S. sonnei shigellosis and 141 community controls, matched by age, sex, and neighborhood. Conditional logistic regression models were performed.

RESULTS

Cyclic epidemics of S. sonnei shigellosis occurred every 2 years. The mean annual incidence was 10.0 per 1000 children in Elad (95% confidence interval 7.9-12.6) vs. 3.8 per 1000 children (95% confidence interval 3.3-4.4) in the sub-district (p<0.001). Concurrent diarrheal disease in family members, having the same person in the daycare center responsible for food handling and changing diapers, and more rooms and sinks in the center, were positively associated with S. sonnei shigellosis, while children's hand-washing before meals was inversely associated.

CONCLUSIONS

The burden of S. sonnei shigellosis in ultraorthodox communities is high. Enhanced hygiene interventions are required for epidemic control.

Evaluation of the impact of shigellosis exclusion policies in childcare settings upon detection of a shigellosis outbreak

Background

In the event of a shigellosis outbreak in a childcare setting, exclusion policies are typically applied to afflicted children to limit shigellosis transmission. However, there is scarce evidence of their impact.

Methods

We evaluated five exclusion policies: Children return to childcare after: i) two consecutive laboratory tests (either PCR or culture) do not detect Shigella, ii) a single negative laboratory test (PCR or culture) does not detect Shigella, iii) seven days after beginning antimicrobial treatment, iv) after being symptom-free for 24 h, or v) 14 days after symptom onset. We also included four treatments to assess the policy options: i) immediate, effective treatment; ii) effective treatment after laboratory diagnosis; iii) no treatment; iv) ineffective treatment. Relying on published data, we calculated the likelihood that a child reentering childcare would be infectious, and the number of childcare-days lost per policy.

Results

Requiring two consecutive negative PCR tests yielded a probability of onward transmission of < 1%, with up to 17 childcare-days lost for children receiving effective treatment, and 53 days lost for those receiving ineffective treatment.

Conclusions

Of the policies analyzed, requiring negative PCR testing before returning to childcare was the most effective to reduce the risk of shigellosis transmission, with one PCR test being the most effective for the least childcare-days lost.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-3796-7) contains supplementary material, which is available to authorized users.

Whole-genome sequencing revealed concurrent outbreaks of shigellosis in the English Orthodox Jewish Community caused by multiple importations of Shigella sonnei from Israel

In December 2013, Public Health England (PHE) observed an increase in the number of cases of Shigella sonnei linked to the Orthodox Jewish Community (OJC). Ultimately, 52 cases of S. sonnei phage type (PT) P and PT7 were notified between November 2013 and July 2014. Whole-genome sequencing (WGS) was performed on a HiSeq 2500 platform (Illumina) on isolates of S. sonnei submitted to PHE during the investigation. Quality trimmed sequence reads were mapped to a reference genome using BWA-MEM, and single-nucleotide polymorphisms (SNPs) were identified using GATK2. Analysis of the core genome SNP positions (>90 % consensus, minimum depth 10×, MQ≥30) revealed that isolates linked to the outbreak could be categorized as members of distinct monophyletic clusters (MPCs) representing concurrent regional outbreaks occurring in the OJCs across the United Kingdom. A dated phylogeny predicted the date of the most recent common ancestor of the MPCs to be approximately 3.1 years previously [95 % highest posterior density (HPD), 2.4-3.4]. Isolates of S. sonnei from cases from the OJCs in Israel included in the phylogeny, branched from nodes basal to the UK OJC outbreak clusters, indicating they were ancestral to the UK OJC isolates, and that the UK isolates represented multiple importations of S. sonnei into the UK population from Israel. The level of discrimination exhibited by WGS facilitated the identification of clusters of isolates within the closely related bacterial populations circulating in the OJC that may be linked to a unique point sources or transmission routes, thus enabling a more appropriate public health response and targeted interventions.

Daily Reportable Disease Spatiotemporal Cluster Detection, New York City, New York, USA, 2014-2015

Each day, the New York City Department of Health and Mental Hygiene uses the free SaTScan software to apply prospective space–time permutation scan statistics to strengthen early outbreak detection for 35 reportable diseases. This method prompted early detection of outbreaks of community-acquired legionellosis and shigellosis.

Travel- and Community-Based Transmission of Multidrug-Resistant Shigella sonnei Lineage among International Orthodox Jewish Communities

Shigellae are sensitive indicator species for studying trends in the international transmission of antimicrobial-resistant Enterobacteriaceae. Orthodox Jewish communities (OJCs) are a known risk group for shigellosis; Shigella sonnei is cyclically epidemic in OJCs in Israel, and sporadic outbreaks occur in OJCs elsewhere. We generated whole-genome sequences for 437 isolates of S. sonnei from OJCs and non-OJCs collected over 22 years in Europe (the United Kingdom, France, and Belgium), the United States, Canada, and Israel and analyzed these within a known global genomic context. Through phylogenetic and genomic analysis, we showed that strains from outbreaks in OJCs outside of Israel are distinct from strains in the general population and relate to a single multidrug-resistant sublineage of S. sonnei that prevails in Israel. Further Bayesian phylogenetic analysis showed that this strain emerged approximately 30 years ago, demonstrating the speed at which antimicrobial drug-resistant pathogens can spread widely through geographically dispersed, but internationally connected, communities.

Summary of Notifiable Infectious Diseases and Conditions - United States, 2015

The Summary of Notifiable Infectious Diseases and Conditions - United States, 2015 (hereafter referred to as the summary) contains the official statistics, in tabular and graphical form, for the reported occurrence of nationally notifiable infectious diseases and conditions in the United States for 2015. Unless otherwise noted, data are final totals for 2015 reported as of June 30, 2016. These statistics are collected and compiled from reports sent by U.S. state and territories, New York City, and District of Columbia health departments to the National Notifiable Diseases Surveillance System (NNDSS), which is operated by CDC in collaboration with the Council of State and Territorial Epidemiologists (CSTE). This summary is available at https://www.cdc.gov/MMWR/MMWR_nd/index.html. This site also includes summary publications from previous years.

Outbreak of Shigella sonnei in Montréal's ultra-Orthodox Jewish community, 2015

An outbreak of Shigella sonnei that occurred in the ultra-Orthodox Jewish community (UOJC) was the subject of an investigation and response by the Montréal Regional Public Health Department (DRSP), who collaborated with several health and community partners. A total of 27 confirmed cases were reported in this outbreak, which lasted from February to June 2015. The epidemic curve was compatible with a point source with secondary person-to-person transmission. In 11 of the 27 cases, pulsed-field gel electrophoresis (PFGE) analysis of strains found a single PFGE pattern newly identified in Quebec. Almost all strains tested showed resistance to ampicillin and trimethoprim-sulfamethoxazole (TMP/SMX). All the cases resided in Montréal Centre-West. Most of the cases were under 5 years old and attended a daycare centre, an environment recognized to be conducive to the transmission of enteric diseases. DRSP sent timely information to families, daycare and school stakeholders, community partners and synagogues in the UOJC, which helped reduce the transmission of shigellosis in the community.

[Shigella sonnei outbreak in a school in Northern Spain]

In October 2012, an outbreak of acute gastroenteritis caused by Shigella sonnei was detected in a nursery and primary school in the north of Spain affecting 112 people: 63.7% were pupils and teachers and 35.7% their co-habitants. The source was a sick child who had travelled to an endemic country, and the key trigger factor was inadequate hygiene in one of the toilets of the school. The enforcement of strict hygiene measures was essential for controlling the outbreak.

Development of an Aotus nancymaae model for Shigella Vaccine immunogenicity and efficacy studies

Several animal models exist to evaluate the immunogenicity and protective efficacy of candidate Shigella vaccines. The two most widely used nonprimate models for vaccine development include a murine pulmonary challenge model and a guinea pig keratoconjunctivitis model. Nonhuman primate models exhibit clinical features and gross and microscopic colonic lesions that mimic those induced in human shigellosis. Challenge models for enterotoxigenic Escherichia coli (ETEC) and Campylobacter spp. have been successfully developed with Aotus nancymaae, and the addition of a Shigella-Aotus challenge model would facilitate the testing of combination vaccines. A series of experiments were designed to identify the dose of Shigella flexneri 2a strain 2457T that induces an attack rate of 75% in the Aotus monkey. After primary challenge, the dose required to induce an attack rate of 75% was calculated to be 1 × 10(11) CFU. Shigella-specific immune responses were low after primary challenge and subsequently boosted upon rechallenge. However, preexisting immunity derived from the primary challenge was insufficient to protect against the homologous Shigella serotype. A successive study in A. nancymaae evaluated the ability of multiple oral immunizations with live-attenuated Shigella vaccine strain SC602 to protect against challenge. After three oral immunizations, animals were challenged with S. flexneri 2a 2457T. A 70% attack rate was demonstrated in control animals, whereas animals immunized with vaccine strain SC602 were protected from challenge (efficacy of 80%; P = 0.05). The overall study results indicate that the Shigella-Aotus nancymaae challenge model may be a valuable tool for evaluating vaccine efficacy and investigating immune correlates of protection.

Recent trends in the epidemiology of shigellosis in Israel

We provide an update on the epidemiology of shigellosis in Israel using data generated by a sentinel laboratory-based surveillance network for the period 1998-2012. The average annual incidence of culture-proven shigellosis was 97/100 000. We estimated that each case of shigellosis accounted for 25 cases in the community indicating the high burden of disease. Orthodox Jewish communities, living in highly crowded conditions and with a high number of children aged <5 years were the epicentre of country-wide biennial propagated epidemics of S. sonnei shigellosis. S. flexneri was the leading Shigella serogroup in Israeli Arabs. S. flexneri 2a and S. flexneri 6 alternated as the most common serotypes. Both S. sonnei and S. flexneri isolates showed high rates of resistance to ampicillin and trimethoprim/sulfamethoxazole and very low rates of resistance to quinolones and third-generation cephalosporins. Shigellosis due to S. sonnei conferred 81% (95% confidence interval 69-89) protection against the homologous Shigella serotype when epidemic exposure re-occurred 2 years later. These data are of value in the process of Shigella vaccine development.

Retrospective analysis of whole genome sequencing compared to prospective typing data in further informing the epidemiological investigation of an outbreak of Shigella sonnei in the UK

The aim of this study was to retrospectively assess the value of whole genome sequencing (WGS) compared to conventional typing methods in the investigation and control of an outbreak of Shigella sonnei in the Orthodox Jewish (OJ) community in the UK. The genome sequence analysis showed that the strains implicated in the outbreak formed three phylogenetically distinct clusters. One cluster represented cases associated with recent exposure to a single strain, whereas the other two clusters represented related but distinct strains of S. sonnei circulating in the OJ community across the UK. The WGS data challenged the conclusions drawn during the initial outbreak investigation and allowed cases of dysentery to be implicated or ruled out of the outbreak that were previously misclassified. This study showed that the resolution achieved using WGS would have clearly defined the outbreak, thus facilitating the promotion of infection control measures within local schools and the dissemination of a stronger public health message to the community.

Risk factors for community-based reports of gastrointestinal, respiratory, and dermal symptoms: findings from a cohort study in Australia

Background

Although gastrointestinal (GI), respiratory, and dermal symptoms are common, few studies have conducted concurrent and comparative prospective analyses of risk factors for these 3 morbidity outcomes.

Methods

We used data from a community-based randomized controlled trial among 277 South Australian families to analyze GI (diarrhea, vomiting), respiratory (sore throat, runny nose, cough) and dermal (rash, generalized itch, dermal infection) symptoms.

Results

Log-binomial regression analysis revealed similar risks of GI (adjusted risk ratio [RR], 1.65; 95% CI, 1.05–2.58) and respiratory (RR, 1.68; 95% CI, 1.31–2.15) symptoms among childcare/kindergarten attendees. Swimming in public pools/spas in the current or previous week was associated with all 3 symptom complexes, conferring similar risk for each (RR for GI: 1.33; 95% CI, 0.99–1.77; respiratory: 1.20; 95% CI, 1.04–1.38; dermal: 1.41; 95% CI, 1.08–1.85). Pet ownership was not associated with symptoms. Household clustering of GI and respiratory symptoms was common, and clustering of respiratory symptoms correlated with number of individuals per household.

Conclusions

This simultaneous examination of risk factors for 3 health outcomes yielded new comparative data that are useful for developing prevention strategies.

Enterococcus spp on fomites and hands indicate increased risk of respiratory illness in child care centers

BACKGROUND

Surface-mediated transmission is a potential route for respiratory disease in child care centers, but evidence of its importance relative to other routes (eg, airborne) is limited.

METHODS

We tracked respiratory disease and monitored bacteria contamination on hands and fomites over 4 months during 64 visits at 2 child care centers. Staff monitored health daily by recording respiratory symptoms. We measured concentrations of Escherichia coli, Enterococcus spp, and fecal coliform in hand rinses and on select fomites.

RESULTS

We demonstrated that symptomatic respiratory illness was positively associated with microbial contamination on hands and fomites, as measured using Enterococcus spp. Enterococcus spp were 0.28 (95% confidence interval: 0.08-0.48)-log10 (colony-forming units per 2 hands) higher when an individual had symptomatic respiratory illness. Susceptible individuals were 1.62 (95% confidence interval: 1.06-2.46) times more likely to develop respiratory illness within 4 days with every log10 increase of Enterococcus spp on hands.

CONCLUSION

The findings imply that hand contamination as measured using Enterococcus spp is a risk factor for onset of respiratory illness and highlight the utility of fecal indicator bacteria as a metric for hand and fomite contamination.

Infrequent cross-transmission of Shigella flexneri 2a strains among villages of a mountainous township in Taiwan with endemic shigellosis

BACKGROUND

Shigellosis is rare in Taiwan, with an average annual incidence rate of 1.68 cases per 100,000 persons in 2000-2007. However, the incidence rate for a mountainous township in eastern Taiwan, Zhuoxi, is 60.2 times the average rate for the entire country. Traveling between Zhuoxi's 6 villages (V1-V6) is inconvenient. Disease transmission among the villages/tribes with endemic shigellosis was investigated in this study.

METHODS

Demographic data were collected in 2000-2010 for epidemiological investigation. Thirty-eight Shigella flexneri 2a isolates were subjected to pulsed-field gel electrophoresis (PFGE) genotyping and antimicrobial susceptibility testing (AST).

RESULTS

Fifty-five shigellosis cases were identified in 2000-2007, of which 38 were caused by S. flexneri 2a from 2000-2007, 16 cases were caused by S. sonnei from 2000-2003, and 1 case was caused by S. flexneri 3b in 2006. S. flexneri 2a caused infections in 4 of the 6 villages of Zhuoxi Township, showing the highest prevalence in villages V2 and V5. PFGE genotyping categorized the 38 S. flexneri 2a isolates into 2 distinct clusters (clones), 1 and 2. AST results indicated that most isolates in cluster 1 were resistant to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole and trimethoprim-sulfamethoxazole (ACSSuX); all isolates in cluster 2 were resistant to ACSSuX and tetracycline. Genotypes were primarily unique to different villages or tribes. Tribe V2-1 showed the highest endemic rates. Eighteen isolates recovered from V2-1 tribe members fell into 6 genotypes, where 5 were the same clone (cluster 1). An outbreak (OB2) in 2004 in village V2 was caused by different clonal strains; cases in tribe V2-1 were caused by 2 strains of clone 1, and those in tribe V2-2 were infected by a strain of clone 2.

CONCLUSIONS

From 2000-2007, 2 S. flexneri 2a clones circulated among 4 villages/tribes in the eastern mountainous township of Zhuoxi. Genotyping data showed restricted disease transmission between the villages and tribes, which may be associated with difficulties in traveling between villages and limited contact between different ethnic aborigines. Transmission of shigellosis in this township likely occurred via person-to-person contact. The endemic disease was controlled by successful public health intervention.

Estimates of illnesses, hospitalizations and deaths caused by major bacterial enteric pathogens in young children in the United States

BACKGROUND

Many enteric pathogens disproportionately affect young children. However, higher incidences of laboratory-confirmed illness may be explained, at least in part, by higher rates of medical care-seeking and stool sample submission in this age group. We estimated the overall number of bacterial enteric illnesses among children <5 years old in the United States caused by Campylobacter, Escherichia coli O157, nontyphoidal Salmonella, Shigella and Yersinia enterocolitica.

MATERIALS AND METHODS

We used a statistical model that scaled counts of laboratory-confirmed illnesses from the Foodborne Diseases Active Surveillance Network up to an estimated number of illnesses in the United States, adjusting for the surveillance steps needed for an illness to be laboratory diagnosed (medical care sought, stool sample submitted, bacterial culture performed, laboratory tested for pathogen, laboratory test sensitivity).

RESULTS

We estimated that 5 bacterial enteric pathogens caused 291,162 illnesses each year among children <5 years old, resulting in 102,746 physician visits, 7830 hospitalizations and 64 deaths. Nontyphoidal Salmonella caused most illnesses (42%), followed by Campylobacter (28%), Shigella (21%), Y. enterocolitica (5%) and E. coli O157 (3%). The estimated annual number of physician visits ranged from 3763 for E. coli O157 to 44,369 for nontyphoidal Salmonella. Nontyphoidal Salmonella was estimated to cause most hospitalizations (4670) and deaths (38).

CONCLUSIONS

Bacterial enteric infections cause many illnesses in US children. Compared with the general population, enteric illnesses among children <5 years old are more likely to be diagnosed. However, overall rates of illness remain higher in children after adjusting for underdiagnosis in both groups.

Foodborne outbreaks of shigellosis in the USA, 1998-2008

We examined reported outbreaks of foodborne shigellosis in the USA from 1998 to 2008 and summarized demographic and epidemiological characteristics of 120 confirmed outbreaks resulting in 6208 illnesses. Most reported foodborne shigellosis outbreaks (n = 70, 58%) and outbreak-associated illnesses (n = 3383, 54%) were restaurant-associated. The largest outbreaks were associated with commercially prepared foods distributed in multiple states and foods prepared in institutional settings. Foods commonly consumed raw were implicated in 29 (24%) outbreaks and infected food handlers in 28 (23%) outbreaks. Most outbreaks (n = 86, 72%) were caused by Shigella sonnei. Targeted efforts to reduce contamination during food handling at multiple points in the food processing and distribution system, including food preparation in restaurants and institutional settings, could prevent many foodborne disease outbreaks and outbreak-related illnesses including those due to Shigella.

Transmission and strain variation of Shigella flexneri 4a after mass prophylaxis in a long-stay psychiatric centre

Shigella flexneri 4a caused sustained outbreaks in a large long-stay psychiatric centre, Taiwan, 2001-2006. Trimethoprim-sulphamethoxazole (SXT) prophylaxis was administered in 2004. We recovered 108 S. flexneri 4a isolates from 83 symptomatic (including one caregiver) and 12 asymptomatic subjects (11 contacts, one caregiver). The isolates were classified into eight antibiogram types and 15 genotypes (six clusters) by using antimicrobial susceptibility testing and pulsed-field gel electrophoresis of NotI-digested DNA, respectively. These characteristics altered significantly after SXT prophylaxis (P < 0·05), with concomitant emergence of SXT-resistant isolates in two antibiogram types. P01 (n = 71), the predominant epidemic genotype, caused infection in two caregivers and five patients under their care; two P01 isolates were recovered from the same patient 6 months apart. These results indicate the importance of sustained person-to-person transmission of S. flexneri 4a by long-term convalescent, asymptomatic or caregiver carriers, and support the emergence of SXT-resistant strains following selective pressure by SXT prophylaxis.

How we didn't clean up until we washed our hands: shigellosis in an elementary and middle school in North Texas

BACKGROUND

Shigella outbreaks often continue for months and are linked frequently to poor hygiene and hand washing. Such outbreaks are found often in day care facilities, but rarely are reported in schools. We present the investigation of an outbreak in autumn 2007 at a building that housed an elementary school and a middle school in separate wings in a small Texas city north of Dallas-Fort Worth.

METHODS

We canvassed local hospitals, school attendance records, and physician offices for cases. Ill individuals were interviewed using a standard questionnaire for symptoms, disease onset, and the presence of the illness in an ill person's household.

RESULTS

A music teacher was the index case for this outbreak of gastrointestinal illness caused by S. sonnei. Ten percent of the students in the school building were ill, and 15 households had secondary cases. Installing liquid soap in dispensers in student restrooms was the initial control measure, followed by sustained instruction in hand washing, scheduled hand washing times, and monitored cleaning and disinfection procedures for surfaces and inanimate objects. Enhanced surveillance detected no new cases in the school district.

CONCLUSIONS

Appropriate soap supplies and repeated instruction in hand washing and its monitoring were needed to control the outbreak.

Infectious agents of food- and water-borne illnesses

Food- and water-borne infections have afflicted mankind since the earliest days of human development and preceded the emergence of civilization. Despite current knowledge of microbial pathogenicity, modern methods of food production and rigorous industrial hygiene, these infections are still commonplace and exact significant health and economic tolls on human populations in all parts of the globe. This review uses data derived from new surveillance networks to survey the current epidemiology of bacterial, protozoan and viral pathogens transmitted by food and water. In addition, we will discuss clinical features of human disease caused by pathogens of current and emerging relevance.

Antimicrobial resistance trends of Shigella serotypes in New York City, 2006-2009

Shigellosis is the third most common enteric bacterial infection in the United States. Although infection is typically self-limiting, empiric treatment is often prescribed. Because of increasing antimicrobial resistance to Shigella, empiric treatment options are decreasing. Identifying resistance patterns can inform empiric treatment recommendations. The goals of our study were to examine risk factors associated with antimicrobial resistance of Shigella and examine issues related to empiric treatment and antimicrobial resistance of Shigella. During June 2006-February 2009, we attempted to interview all New York City patients reported to have shigellosis. Their Shigella isolates were tested for antimicrobial susceptibility to examine the level of resistance and identify risk factors for resistance. Analysis was conducted on two groups distinguished by a large outbreak that was documented during the data collection period. Of the 477 nonoutbreak patients, 333 (70%) patients reported taking an antibiotic for shigellosis and 36 (11%) were treated with an antibiotic to which their Shigella infection was resistant. Among this group, high levels of antimicrobial resistance were detected to amoxicillin-clavulanate (66%), ampicillin (68%), and trimethoprim-sulfamethoxazole (66%). Non-travel-associated ciprofloxacin-resistant Shigella (five patients) and ciprofloxacin-resistant Shigella sonnei (four patients) were reported for the first time to our knowledge. Antimicrobial resistance is significantly higher in New York City residents compared with national data. Some patients were treated with therapies that were not effective and to which the patient's Shigella infection was resistant. Shigella infections should not be treated with antibiotics unless the patient presents with severe or underlying illness and is at risk for systemic illness. When treatment is indicated, local monitoring of Shigella for antimicrobial resistance will provide local clinicians with the best guidance for effective empiric treatments.

Characterization of WRSs2 and WRSs3, new second-generation virG(icsA)-based Shigella sonnei vaccine candidates with the potential for reduced reactogenicity

Live, attenuated Shigella vaccine candidates, such as Shigella sonnei strain WRSS1, Shigella flexneri 2a strain SC602, and Shigella dysenteriae 1 strain WRSd1, are attenuated principally by the loss of the VirG(IcsA) protein. These candidates have proven to be safe and immunogenic in volunteer trials and in one study, efficacious against shigellosis. One drawback of these candidate vaccines has been the reactogenic symptoms of fever and diarrhea experienced by the volunteers, that increased in a dose-dependent manner. New, second-generation virG(icsA)-based S. sonnei vaccine candidates, WRSs2 and WRSs3, are expected to be less reactogenic while retaining the ability to generate protective levels of immunogenicity seen with WRSS1. Besides the loss of VirG(IcsA), WRSs2 and WRSs3 also lack plasmid-encoded enterotoxin ShET2-1 and its paralog ShET2-2. WRSs3 further lacks MsbB2 that reduces the endotoxicity of the lipid A portion of the bacterial LPS. Studies in cell cultures and in gnotobiotic piglets demonstrate that WRSs2 and WRSs3 have the potential to cause less diarrhea due to loss of ShET2-1 and ShET2-2 as well as alleviate febrile symptoms by loss of MsbB2. In guinea pigs, WRSs2 and WRSs3 were as safe, immunogenic and efficacious as WRSS1.

Transmission risk factors and treatment of pediatric shigellosis during a large daycare center-associated outbreak of multidrug resistant Shigella sonnei: implications for the management of shigellosis outbreaks among children

BACKGROUND

Shigellosis outbreaks in daycare centers result in substantial disease and economic burdens in the United States. The emergence of multidrug resistant Shigella strains raises questions regarding control of transmission within daycare centers and treatment for children. From May to October 2005, 639 Shigella sonnei cases were reported in northwest Missouri, mostly among persons exposed to daycare centers.

METHODS

We conducted a case-control investigation among licensed daycare centers (LDCs) in northwest Missouri to determine transmission risk factors, tested isolates for antimicrobial resistance, and described treatment practices. Case LDCs had secondary attack rates of shigellosis>or=2% (range, 2%-25%) and control LDCs<or=2% (range, 0%-1.3%). We interviewed LDC staff and performed on-site inspections. Thirty-one outbreak isolates were tested for antimicrobial resistance. We interviewed physicians and reviewed health department outbreak-related treatment data.

RESULTS

We enrolled 18 case and 21 control LDCs. LDCs with >or=1 sink in every room (odds ratio [OR]: 0.1; 95% confidence interval [CI]: 0.02-0.5) or a diapering station in every room (OR: 0.1; 95% CI: 0.01-0.6) were less likely to be case-LDCs. Resistance to ampicillin and trimethoprim-sulfamethoxazole was found in 90% of the outbreak strains. Among 210 children treated with antimicrobial agents, azithromycin was used in 92 (44%) while a fluoroquinolone was used in 11 (5%) children.

CONCLUSIONS

During a large daycare center-associated shigellosis outbreak, strains were highly resistant to ampicillin and trimethoprim-sulfamethoxazole. Children were frequently treated with azithromycin and occasionally fluoroquinolones. Appropriate handwashing and diapering infrastructure are necessary to minimize spread of shigellosis within daycare centers, and could reduce use of antimicrobial agents.

Biennial hyperepidemic shigellosis in an observant Jewish community

We aimed to study patterns of shigellosis in a large observant Jewish community in Israel and to describe local interventions during outbreaks. Surveillance data from the Ministry of Health were used to calculate incidence rates in 1998-2006, both in the city of Bene Beraq and the Tel Aviv district. Information on isolates was collected from the bacteriological laboratory of a community hospital. Public notices and educational conferences conveyed a message to increase personal hygiene and keep ill children at home. During a 9-year period, a clear biennial pattern of outbreaks was noticed. Annual incidence rates ranged between 18 and 353/100,000 population. Shigellosis outbreaks tended to occur in the winter and were attributed to clonally related Shigella sonnei strains. Outbreaks in Bene Beraq preceded those in the other cities of Tel Aviv district, suggesting propagation of disease. In this population with highly endemic as well as superimposed outbreaks of shigellosis, short-term interventions had no lasting effect on prevention; future studies should focus on community-based programmes to avoid anticipated outbreaks.

The changing panorama of bacterial enteric infections

We studied the age-specific population-based incidence of bacterial enteric infections caused by Shigella, Salmonella and Campylobacter, in Jerusalem. During 1990–2008, 32 408 cases were reported (incidence rate 232·1/100 000 per annum). The patterns of Shigella (47·4% of cases), Salmonella (34·4%) and Campylobacter (18·2%) infections evolved noticeably. Campylobacter rates increased from 15·0 to 110·8/100 000 per annum. Salmonella rates increased from 74·2 to 199·6/100 000 in 1995 then decreased to 39·4/100 000. Shigella showed an endemic/epidemic pattern ranging between 19·7 and 252·8/100 000. Most patients (75%) were aged <15 years; children aged <5 years comprised 56·4% of cases, despite accounting for only 12·9% of the population. Campylobacter was the predominant organism in infants aged <1 year and Shigella in the 1–4 years group. The hospitalization rates were: Shigella, 1·8%; Campylobacter, 2·3%; Salmonella, 6·9%. Infants were 2·2 times more likely to be hospitalized than children aged 1–14 years (P=0·001). Household transmission occurred in 21·2% of Shigella cases compared with 5% in the other bacteria.

Macrolide-resistant Shigella sonnei

Shigella sonnei UCN59, isolated during an outbreak of S. sonnei in January 2007, was resistant to azithromycin (MIC 64 mg/L). The isolate contained a plasmid-borne mph(A) gene encoding a macrolide 2′-phosphotransferase that inactivates macrolides. Emergence of the mph(A) gene in S. sonnei may limit usefulness of azithromycin for treatment of shigellosis.