Multistate shigellosis outbreak and commercially prepared food, United States

Proteome based mapping and molecular docking revealed DnaA as a potential drug target against Shigella sonnei

Shigella sonnei is one of the major causes of diarrhea and remained a critical microbe responsible for higher morbidity and mortality rates resulting from dysentery every year across the world. Antibiotic therapy of Shigella diseases plays a critical role in decreasing the prevalence as well as the fatality rate of this infection. However, the management of these diseases remains challenging, owing to the overall increase in resistance against many antimicrobials. The situation necessitates the rapid development of effective and feasible S. sonnei treatments. In the present study, the subtractive genomics approach was utilized to find the potential drug targets for S. sonnei strain Ss046. Various tools of bioinformatics were implemented to remove the human-specific homologous and pathogen-specific paralogous sequences from the bacterial proteome. Then, metabolic pathway and subcellular location analysis were performed of essential bacterial proteins to describe their role in various cellular processes. Only one essential protein i-e Chromosomal replication initiator protein DnaA was found in the proteome of the pathogen that could be used as a potent target for designing new drugs. 3D structure prediction of DnaA protein was carried out using Phyre 2. Molecular docking of 5000 phytochemicals was performed against DnaA to identify four top-ranked phytochemicals (Riccionidin A, Dothistromin, Fustin, and Morin) based on scoring functions and interaction with the active site. This study suggests that these phytochemicals could be used as antibacterial drugs to treat S. sonnei infections in the future. To confirm their efficacy and evaluate their drug potency, further in vitro analyses are required.

Shigella sonnei: virulence and antibiotic resistance

Shigella sonnei is the emerging pathogen globally, as it is the second common infectious species of shigellosis (bloody diarrhoea) in low- and middle-income countries (LMICs) and the leading one in developed world. The multifactorial processes and novel mechanisms have been identified in S. sonnei, that are collectively playing apart a substantial role in increasing its prevalence, while replacing the S. flexneri and other Gram-negative gut pathogens niche occupancy. Recently, studies suggest that due to improvement in sanitation S. sonnei has reduced cross-immunization from Plesiomonas shigelliodes (having same O-antigen as S. sonnei) and also found to outcompete the two major species of Enterobacteriaceae family (Shigella flexneri and Escherichia coli), due to encoding of type VI secretion system (T6SS). This review aimed to highlight S. sonnei as an emerging pathogen in the light of recent research with pondering aspects on its epidemiology, transmission, and pathogenic mechanisms. Additionally, this paper aimed to review S. sonnei disease pattern and related complications, symptoms, and laboratory diagnostic techniques. Furthermore, the available treatment reigns and antibiotic-resistance patterns of S. sonnei are also discussed, as the ciprofloxacin and fluoroquinolone-resistant S. sonnei has already intensified the global spread and burden of antimicrobial resistance. In last, prevention and controlling strategies are briefed to limit and tackle S. sonnei and possible future areas are also explored that needed more research to unravel the hidden mysteries surrounding S. sonnei.

Relative transmissibility of shigellosis among male and female individuals: a modeling study in Hubei Province, China

BACKGROUND

Developing countries exhibit a high disease burden from shigellosis. Owing to the different incidences in males and females, this study aims to analyze the features involved in the transmission of shigellosis among male (subscript m) and female (subscript f) individuals using a newly developed sex-based model.

METHODS

The data of reported shigellosis cases were collected from the China Information System for Disease Control and Prevention in Hubei Province from 2005 to 2017. A sex-based Susceptible-Exposed-Infectious/Asymptomatic-Recovered (SEIAR) model was applied to explore the dataset, and a sex-age-based SEIAR model was applied in 2010 to explore the sex- and age-specific transmissions.

RESULTS

From 2005 to 2017, 130 770 shigellosis cases (including 73 981 male and 56 789 female cases) were reported in Hubei Province. The SEIAR model exhibited a significant fitting effect with the shigellosis data (P <  0.001). The median values of the shigellosis transmission were 2.3225 × 10⁸ for SAR_mm (secondary attack rate from male to male), 2.5729 × 10⁸ for SAR_mf, 2.7630 × 10^-8 for SAR_fm, and 2.1061 × 10^-8 for SAR_ff. The top five mean values of the transmission relative rate in 2010 (where the subscript 1 was defined as male and age ≤ 5 years, 2 was male and age 6 to 59 years, 3 was male and age ≥ 60 years, 4 was female and age ≤ 5 years, 5 was female and age 6 to 59 years, and 6 was male and age ≥ 60 years) were 5.76 × 10^-8 for β₆₁, 5.32 × 10^-8 for β₃₁, 4.01 × 10^-8 for β₃₄, 7.52 × 10^-9 for β₆₂, and 6.04 × 10^-9 for β₆₄.

CONCLUSIONS

The transmissibility of shigellosis differed among male and female individuals. The transmissibility between the genders was higher than that within the genders, particularly female-to-male transmission. The most important route in children (age ≤ 5 years) was transmission from the elderly (age ≥ 60 years). Therefore, the greatest interventions should be applied in females and the elderly.

In-flight transmission of foodborne disease: How can airlines improve?

Food contamination during air travel presents unique risks to those affected. Foodborne pathogens can cause serious illness among all on board, and potentially jeopardize flight safety. These risks are likely to increase with current trends of "densification" and a predicted massive expansion of air travel. While aircraft are being equipped with ever newer designs with a focus on efficiency and comfort, regulations remained largely unmodified in terms of basic hygiene requirements. Strict guidelines for food hygiene exist for on-ground food settings and catering kitchens. There is uncertainty about hygiene standards on board commercial aircraft, and little regulatory oversight of what happens to food in-flight. In two hypothetical scenarios we indicate the potential risks associated with poor food handling practice onboard aircraft, with the ultimate aim of bringing aviation food safety in line with on-ground regulations. Changes in cabin design alongside adequate training in safe food handling have the potential to increase public health protection. We urge a review of existing in-flight hygiene protocols to better direct the development of regulation, prevention, and intervention measures for aviation food safety.

A Brief History of Shigella

The history of Shigella, the causative agent of bacillary dysentery, is a long and fascinating one. This brief historical account starts with descriptions of the disease and its impact on human health from ancient time to the present. Our story of the bacterium starts just before the identification of the dysentery bacillus by Kiyoshi Shiga in 1898 and follows the scientific discoveries and principal scientists who contributed to the elucidation of Shigella pathogenesis in the first 100 years. Over the past century, Shigella has proved to be an outstanding model of an invasive bacterial pathogen and has served as a paradigm for the study of other bacterial pathogens. In addition to invasion of epithelial cells, some of those shared virulence traits include toxin production, multiple-antibiotic resistance, virulence genes encoded on plasmids and bacteriophages, global regulation of virulence genes, pathogenicity islands, intracellular motility, remodeling of host cytoskeleton, inflammation/polymorphonuclear leukocyte signaling, apoptosis induction/inhibition, and "black holes" and antivirulence genes. While there is still much to learn from studying Shigella pathogenesis, what we have learned so far has also contributed greatly to our broader understanding of bacterial pathogenesis.

Bacteriophage preparation lytic for Shigella significantly reduces Shigella sonnei contamination in various foods

ShigaShield™ is a phage preparation composed of five lytic bacteriophages that specifically target pathogenic Shigella species found in contaminated waters and foods. In this study, we examined the efficacy of various doses (9x105-9x107 PFU/g) of ShigaShield™ in removing experimentally added Shigella on deli meat, smoked salmon, pre-cooked chicken, lettuce, melon and yogurt. The highest dose (2x107 or 9x107 PFU/g) of ShigaShield™ applied to each food type resulted in at least 1 log (90%) reduction of Shigella in all the food types. There was significant (P<0.01) reduction in the Shigella levels in all phage treated foods compared to controls, except for the lowest phage dose (9x105 PFU/g) on melon where reduction was only ca. 45% (0.25 log). The genomes of each component phage in the cocktail were fully sequenced and analyzed, and they were found not to contain any "undesirable genes" including those listed in the US Code for Federal Regulations (40 CFR Ch1). Our data suggest that ShigaShield™ (and similar phage preparations with potent lytic activity against Shigella spp.) may offer a safe and effective approach for reducing the levels of Shigella in various foods that may be contaminated with the bacterium.

Comparative assessment of antimicrobial efficacy of different hand sanitizers: An in vitro study

Background:

To evaluate the antimicrobial efficacy of four different hand sanitizers against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecalis as well as to assess and compare the antimicrobial effectiveness among four different hand sanitizers.

Materials and Methods:

The present study is an in vitro study to evaluate antimicrobial efficacy of Dettol, Lifebuoy, PureHands, and Sterillium hand sanitizers against clinical isolates of the aforementioned test organisms. The well variant of agar disk diffusion test using Mueller-Hinton agar was used for evaluating the antimicrobial efficacy of hand sanitizers. McFarland 0.5 turbidity standard was taken as reference to adjust the turbidity of bacterial suspensions. Fifty microliters of the hand sanitizer was introduced into each of the 4 wells while the 5^th well incorporated with sterile water served as a control. This was done for all the test organisms and plates were incubated in an incubator for 24 h at 37΀C. After incubation, antimicrobial effectiveness was determined using digital caliper (mm) by measuring the zone of inhibition.

Results:

The mean diameters of zones of inhibition (in mm) observed in Group A (Sterillium), Group B (PureHands), Group C (Lifebuoy), and Group D (Dettol) were 22 ± 6, 7.5 ± 0.5, 9.5 ± 1.5, and 8 ± 1, respectively. Maximum inhibition was found with Group A against all the tested organisms. Data were statistically analyzed using analysis of variance, followed by post hoc test for group-wise comparisons. The difference in the values of different sanitizers was statistically significant at P < 0.001.

Conclusion:

Sterillium was the most effective hand sanitizer to maintain the hand hygiene.

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.

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.

Alternative hand contamination technique to compare the activities of antimicrobial and nonantimicrobial soaps under different test conditions

Antimicrobial hand soaps provide a greater bacterial reduction than nonantimicrobial soaps. However, the link between greater bacterial reduction and a reduction of disease has not been definitively demonstrated. Confounding factors, such as compliance, soap volume, and wash time, may all influence the outcomes of studies. The aim of this work was to examine the effects of wash time and soap volume on the relative activities and the subsequent transfer of bacteria to inanimate objects for antimicrobial and nonantimicrobial soaps. Increasing the wash time from 15 to 30 seconds increased reduction of Shigella flexneri from 2.90 to 3.33 log(10) counts (P = 0.086) for the antimicrobial soap, while nonantimicrobial soap achieved reductions of 1.72 and 1.67 log(10) counts (P > 0.6). Increasing soap volume increased bacterial reductions for both the antimicrobial and the nonantimicrobial soaps. When the soap volume was normalized based on weight (approximately 3 g), nonantimicrobial soap reduced Serratia marcescens by 1.08 log(10) counts, compared to the 3.83-log(10) reduction caused by the antimicrobial soap (P < 0.001). The transfer of Escherichia coli to plastic balls following a 15-second hand wash with antimicrobial soap resulted in a bacterial recovery of 2.49 log(10) counts, compared to the 4.22-log(10) (P < 0.001) bacterial recovery on balls handled by hands washed with nonantimicrobial soap. This indicates that nonantimicrobial soap was less active and that the effectiveness of antimicrobial soaps can be improved with longer wash time and greater soap volume. The transfer of bacteria to objects was significantly reduced due to greater reduction in bacteria following the use of antimicrobial soap.

Effect of hand wash agents on controlling the transmission of pathogenic bacteria from hands to food

The goals of this study were to evaluate the effectiveness of two hand wash regimens in reducing transient bacteria on the skin following a single hand wash and the subsequent transfer of the bacteria to a ready-to-eat food item, freshly cut cantaloupe melon. The number of bacteria recovered from hands and the quantity transferred to the melon were significantly less following the use of an antibacterial soap compared with plain soap. The antimicrobial soap achieved > 3-log reductions versus Escherichia coli and 3.31- and 2.83-log reductions versus Shigella flexneri. The plain soap failed to achieve a 2-log reduction against either organism. The bacteria recovered from the melon handled by hands treated with antimicrobial hand soap averaged 2 log. Melon handled following hand washing with plain soap had > 3 log bacteria in the experiments. Based on previously published feeding studies, an infection rate in the range of approximately 15 to 25% would be expected after ingesting melon containing 2 log CFU compared with ingesting greater than the 3 log transferred from hands washed with plain soap, which would result in a higher infection attack rate of 50 to 80%. The data thus demonstrate there is a greater potential to reduce the transmission and acquisition of disease through the use of an antimicrobial hand wash than through the use of plain soap.

Multilocus variable-number tandem-repeat analysis for molecular typing of Shigella sonnei

A multilocus variable-number tandem-repeat (VNTR) analysis (MLVA) method was developed and evaluated for the subtyping of Shigella sonnei isolates. A total of 26 VNTR loci were identified by exploring the repeat sequence loci in the genomic sequences of S. sonnei strains Ss046 and 53G and by testing 536 isolates that had previously been characterized by pulsed-field gel electrophoresis (PFGE). The discriminatory power of MLVA (Simpson's index of diversity [D], 0.9524; 95% confidence interval [CI], 0.9373 to 0.9564) for the 536 isolates was significantly higher than that of PFGE (D, 0.8882; CI, 0.8667 to 0.9097). MLVA typing with the four and eight most variable loci had D values of 0.9468 and 0.9481, respectively, results approaching that of 26 loci. The usefulness of MLVA for outbreak investigation was evaluated using 151 isolates from 10 shigellosis outbreaks and 22 PFGE-indistinguishable isolates collected from nine epidemiologically unrelated events in five different countries. The evaluations indicated that MLVA was a powerful typing tool to distinguish isolates for outbreak investigation and that it exhibited a good discrimination of the 22 PFGE-indistinguishable isolates. Single-locus variants did occur during the outbreak; therefore, S. sonnei isolates with MLVA profiles differing at no more than a single locus should be considered part of the same outbreak. The present study suggests that MLVA has the potential to replace PFGE as a standard method of typing S. sonnei isolates for disease surveillance and outbreak investigation.

Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 2. Description of outbreaks by size, severity, and settings

This article is the second in a series of several by members of the Committee on the Control of Foodborne Illness of the International Association of Food Protection, and it continues the analysis of 816 outbreaks where food workers were implicated in the spread of foodborne disease. In this article, we discuss case morbidity and mortality and the settings where the 816 outbreaks occurred. Some of the outbreaks were very large; 11 involved more than 1,000 persons, 4 with more than 3,000 ill. The larger outbreaks tended to be extended over several days with a continuing source of infections, such as at festivals, resorts, and community events, or the contaminated product had been shipped to a large number of customers, e.g., icing on cakes or exported raspberries. There were five outbreaks with more than 100 persons hospitalized, with rates ranging from 9.9 to 100%. However, overall, the hospitalization rate was low (1.4%), and deaths were rare (0.11% of the 80,682 cases). Many of the deaths were associated with high-risk persons (i.e., those who had underlying diseases, malnutrition, or both, as in a refugee camp, or young children), but a few occurred with apparently healthy adults. An analysis of the settings for the food worker-related events showed that most of the outbreaks came from food service facilities (376 outbreaks [46.1%]), followed by catered events (126 outbreaks [15.4%]), the home (83 outbreaks [10.2%]), schools and day care centers (49 [6.0%]), and health care institutions (43 outbreaks [5.3%]). However, many cases resulted from relatively few outbreaks (< 30 each) associated with community events (9,726), processing plants (8,580), mobile/temporary service (5,367), and camps/ armed forces (5,117). The single most frequently reported setting was restaurants, with 324 outbreaks and 16,938 cases. Improper hygienic practices in homes, on picnics, or at community events accounted for 89 of the 816 outbreaks. There were 18 outbreaks associated with commercial travel in air flights, trains, and cruise ships over several decades, although only the last seems to be a major concern today. Sixteen outbreaks occurred where food, primarily produce, was harvested and shipped from one country to another. Sometimes the presence of an infected worker preparing food was only one of several factors contributing to the outbreak.

Shigellaas a Foodborne Pathogen and Current Methods for Detection in Food

Shigella, the causative agent of shigellosis or "bacillary dysentery," has been increasingly involved in foodborne outbreaks. According to the Centers for Disease Control and Prevention's Emerging Infections Program, Foodborne Diseases Active Surveillance Network (FoodNet), Shigella was the third most reported foodborne bacterial pathogen in 2002. Foods are most commonly contaminated with Shigella by an infected food handler who practices poor personal hygiene. Shigella is acid resistant, salt tolerant, and can survive at infective levels in many types of foods such as fruits and vegetables, low pH foods, prepared foods, and foods held in modified atmosphere or vacuum packaging. Survival is often increased when food is held at refrigerated temperatures. Detection methods for Shigella include conventional culture methods, immunological methods, and molecular microbiological methods. Conventional culture of Shigella in foods is often problematic due to the lack of appropriate selective media. Immunological methods for Shigella have been researched, yet there is only one commercially available test kit. Molecular microbiological methods such as PCR, oligonucleotide microarrays, and rep-PCR have also been developed for the detection and identification of Shigella. This manuscript reviews the general characteristics, prevalence, growth and survival, and methods for detection of Shigella in food.

Short report: analysis of clonal relationship among Shigella sonnei isolates circulating in Argentina

Thirty-five isolates of Shigella sonnei from patients with diarrhoea in three geographic regions of Argentina were examined for genetic diversity by pulsed-field gel electrophoresis (PFGE) and plasmid profile. PFGE of XbaI and BlnI DNA digests confirmed the occurrence of outbreaks in two regions caused by two separate predominant clones of S. sonnei. The third region was characterized by three circulating clones, one of which was possibly associated with an outbreak. Similar plasmids were found in distinct clones and in one outbreak clone five different plasmid profiles were identified. Antimicrobial resistance of the isolates varied from fully susceptible to the agents tested, to resistance to cotrimoxazole, ampicillin and ciprofloxacin. Antibiotic resistance did not correlate with plasmid content. This information will form the basis for active surveillance of shigellosis in Argentina and elsewhere in the region through the PulseNet International Network.

A Bayesian approach to acute infectious diarrhea in adults

Acute infectious diarrhea is a yearly occurrence for most Americans, and is associated with 1 million hospitalizations and about 6000 deaths in the United States annually. Up to 80% of acute infectious diarrhea is caused by noroviruses, which produce a clinically mild illness with a predictable short course and good outcome that make laboratory testing and antimicrobial treatment unnecessary. Most diarrhea-causing bacteria and protozoa can cause a clinical illness "like norovirus"; when they do so in healthy adults neither specialized testing nor antimicrobials is required. The presence or absence of epidemiologic evidence (such as travel, hospitalization, antibiotic use, other exposures)and clinical evidence (such as diarrhea frequency and duration, severity of abdominal pain and fever, character of stool, presence of chronic illness or immune deficiency) can change the probability of "not norovirus" from as low as 8% to as high as 100%. Such probabilities guide the use of laboratory testing and antimicrobial therapy in patients who have acute infectious diarrhea.

Locus-specific mutational events in a multilocus variable-number tandem repeat analysis of Escherichia coli O157:H7

Multilocus variable-number tandem repeat analysis (MLVA) is a validated molecular subtyping method for detecting and evaluating Escherichia coli O157:H7 outbreaks. In a previous study, five outbreaks with a total of 21 isolates were examined by MLVA. Nearly 20% of the epidemiologically linked strains were single-locus variants (SLV) of their respective predominant outbreak clone. This result prompted an investigation into the mutation rates of the seven MLVA loci (TR1 to TR7). With an outbreak strain that was an SLV at the TR1 locus of the predominant clone, parallel and serial batch culture experiments were performed. In a parallel experiment, none (0/384) of the strains analyzed had mutations at the seven MLVA loci. In contrast, in the two 5-day serial experiments, 4.3% (41/960) of the strains analyzed had a significant variation in at least one of these loci (P < 0.001). The TR2 locus accounted for 85.3% (35/41) of the mutations, with an average mutation rate of 3.5 x 10(-3); the mutations rates for TR1 and TR5 were 10-fold lower. Single additions accounted for 77.1% (27/35) of the mutation events in TR2 and all (6/6) of the additions in TR1 and TR5. The remaining four loci had no slippage events detected. The mutation rates were locus specific and may impact the interpretation of MLVA data for epidemiologic investigations.

Use of a prospective space-time scan statistic to prioritize shigellosis case investigations in an urban jurisdiction

OBJECTIVE

A prospective space-time scan statistic was applied to Chicago's 2002 shigellosis surveillance data to evaluate its utility in objectively describing clusters and assisting in the prioritization of investigations.

METHODS

The prospective space-time module of SaTScan, a free software available online, was used to identify "live" clusters of disease, meaning cases that were current as of the date of the analysis and strongly associated in place and time. Fifty-two separate space-time analyses were run; one simulation for each week of 2002. Identified clusters were described in terms of space, time, risk factors reported by involved case-patients, and cases' links to venue-associated outbreaks.

RESULTS

Twelve live clusters were detected at the p < 0.05 significance level: two single-household clusters and 10 community clusters. The community clusters ranged in size from 194 to 367 census tracts (median = 294), and in disease burden from 21 to 41 cases (median = 29). Geographically, all of the community clusters were located in the west-central part of the city and had a temporal span of 28 days. Within the 10 community clusters, 15 different day care centers were identified as potential exposure settings for case-patients or their close contacts.

CONCLUSIONS

The prospective space-time scan statistic offers local health departments an objective way of describing clusters of shigellosis cases. The method used in this study could help prioritize the assignment and investigation of cases, particularly when overall shigellosis incidence exceeds expected numbers or when an agency's resources are stressed by other events, such as outbreaks.