Molecular epidemiology of Shigella flexneri in a diarrhoea-endemic area of Lima, Peru

Toward a Shigella Vaccine: Opportunities and Challenges to Fight an Antimicrobial-Resistant Pathogen

Shigellosis causes more than 200,000 deaths worldwide and most of this burden falls on Low- and Middle-Income Countries (LMICs), with a particular incidence in children under 5 years of age. In the last decades, Shigella has become even more worrisome because of the onset of antimicrobial-resistant strains (AMR). Indeed, the WHO has listed Shigella as one of the priority pathogens for the development of new interventions. To date, there are no broadly available vaccines against shigellosis, but several candidates are being evaluated in preclinical and clinical studies, bringing to light very important data and information. With the aim to facilitate the understanding of the state-of-the-art of Shigella vaccine development, here we report what is known about Shigella epidemiology and pathogenesis with a focus on virulence factors and potential antigens for vaccine development. We discuss immunity after natural infection and immunization. In addition, we highlight the main characteristics of the different technologies that have been applied for the development of a vaccine with broad protection against Shigella.

Efficacy and potential of phage therapy against multidrug resistant Shigella spp

Shigella-infected bacillary dysentery or commonly known as Shigellosis is a leading cause of morbidity and mortality worldwide. The gradual emergence of multidrug resistant Shigella spp. has triggered the search for alternatives to conventional antibiotics. Phage therapy could be one such suitable alternative, given its proven long term safety profile as well as the rapid expansion of phage therapy research. To be successful, phage therapy will need an adequate regulatory framework, effective strategies, the proper selection of appropriate phages, early solutions to overcome phage therapy limitations, the implementation of safety protocols, and finally improved public awareness. To achieve all these criteria and successfully apply phage therapy against multidrug resistant shigellosis, a comprehensive study is required. In fact, a variety of phage-based approaches and products including single phages, phage cocktails, mutated phages, genetically engineered phages, and combinations of phages with antibiotics have already been carried out to test the applications of phage therapy against multidrug resistant Shigella. This review provides a broad survey of phage treatments from past to present, focusing on the history, applications, limitations and effective solutions related to, as well as the prospects for, the use of phage therapy against multidrug resistant Shigella spp. and other multidrug resistant bacterial pathogens.

The changing epidemiology of bacillary dysentery and characteristics of antimicrobial resistance of Shigella isolated in China from 2004-2014

Background

Bacillary dysentery caused by bacteria of the genus Shigella is a significant public health problem in developing countries such as China. The objective of this study was to analyze the epidemiological pattern of bacillary dysentery, the diversity of the causative agent, and the antimicrobial resistance patterns of Shigella spp. for the purpose of determining the most effective allocation of resources and prioritization of interventions.

Methods

Surveillance data were acquired from the National Infectious Disease Information Reporting System (2004–2014) and from the sentinel hospital-based surveillance system (2005–2014). We analyzed the spatial and temporal distribution of bacillary dysentery, age and sex distribution, species diversity, and antimicrobial resistance patterns of Shigella spp.

Results

The surveillance registry included over 3 million probable cases of bacillary dysentery during the period 2004–2014. The annual incidence rate of bacillary dysentery decreased from 38.03 cases per 100,000 person-years in 2004 to 11.24 cases per 100,000 person-years in 2014. The case-fatality rate decreased from 0.028% in 2004 to 0.003% in 2014. Children aged <1 year and 1–4 years were most affected, with higher incidence rates (228.59 cases per 100,000 person-years and 92.58 cases per 100,000 person-years respectively). The annual epidemic season occurred between June and September. A higher incidence rate of bacillary dysentery was found in the Northwest region, Beijing and Tianjin during the study period. Shigella flexneri was the most prevalent species that caused bacillary dysentery in China (63.86%), followed by Shigella sonnei (34.89%). Shigella isolates were highly resistant to nalidixic acid (89.13%), ampicillin (88.90%), tetracycline (88.43%), and sulfamethoxazole (82.92%). During the study period, isolates resistant to ciprofloxacin and cefotaxime increased from 8.53 and 7.87% in 2005 to 44.65 and 29.94% in 2014, respectively.

Conclusions

The incidence rate of bacillary dysentery has undergone an obvious decrease from 2004 to 2014. Priority interventions should be delivered to populations in northwest China and to individuals aged <5 years. Antimicrobial resistance of Shigella is a serious public health problem and it is important to consider the susceptibility profile of isolates before determining treatment.

Shigella Infections in Household Contacts of Pediatric Shigellosis Patients in Rural Bangladesh

To examine rates of Shigella infections in household contacts of pediatric shigellosis patients, we followed contacts and controls prospectively for 1 week after the index patient obtained care. Household contacts of patients were 44 times more likely to develop a Shigella infection than were control contacts (odds ratio 44.7, 95% CI 5.5–361.6); 29 (94%) household contacts of shigellosis patients were infected with the same species and serotype as the index patient’s. Pulsed-field gel electrophoresis showed that 14 (88%) of 16 with infected contacts had strains that were indistinguishable from or closely related to the index patient’s strain. Latrine area fly counts were higher in patient households compared with control households, and 2 patient household water samples were positive for Shigella. We show high susceptibility of household contacts of shigellosis patients to Shigella infections and found environmental risk factors to be targeted in future interventions.

Virulence factors and mechanisms of antimicrobial resistance in Shigella strains from periurban areas of Lima (Peru)

The study was aimed to describe the serotype, mechanisms of antimicrobial resistance, and virulence determinants in Shigella spp. isolated from Peruvian children. Eighty three Shigella spp. were serogrouped and serotyped being established the antibiotic susceptibility. The presence of 12 virulence factors (VF) and integrase 1 and 2, along with commonly found antibiotic resistance genes was established by PCR. S. flexneri was the most relevant serogroup (55 isolates, 66%), with serotype 2a most frequently detected (27 of 55, 49%), followed by S. boydii and S. sonnei at 12 isolates each (14%) and S. dysenteriae (four isolates, 5%). Fifty isolates (60%) were multi-drug resistant (MDR) including 100% of S. sonnei and 64% of S. flexneri. Resistance levels were high to trimethoprim-sulfamethoxazole (86%), tetracycline (74%), ampicillin (67%), and chloramphenicol (65%). Six isolates showed decreased azithromycin susceptibility. No isolate was resistant to nalidixic acid, ciprofloxacin, nitrofurantoin, or ceftriaxone. The most frequent resistance genes were sul2 (95%), tet(B) (92%), cat (80%), dfrA1 (47%), blaOXA-1like (40%), with intl1 and intl2 detected in 51 and 52% of the isolates, respectively. Thirty-one different VF profiles were observed, being the ipaH (100%), sen (77%), virA and icsA (75%) genes the most frequently found. Differences in the prevalence of VF were observed between species with S. flexneri isolates, particularly serotype 2a, possessing high numbers of VF. In conclusion, this study highlights the high heterogeneity of Shigella VF and resistance genes, and prevalence of MDR organisms within this geographic region.

Serotype distribution and characteristics of antimicrobial resistance in Shigella isolated from Henan province, China, 2001–2008

The serotype distribution and susceptibility to 14 antimicrobial agents of 526 isolates ofShigellaspp. from four hospitals in Sun county, Henan province, China during 2001–2008, were analysed to identify associations of serotypes with resistance trends.S.flexneriwas the most frequent species (92·4%), the remainder wasS.sonnei. The prevalent serotype ofS.flexneriwas 2a (26·7%). Almost all (>99%) isolates were resistant to tetracycline, nalidixic acid and pipemidic acid; >80% were resistant to chloramphenicol, amoxicillin and co-trimoxazole but less than 5% were resistant to polymyxin B, furazolidone, cefotaxime and gentamicin.S.flexnerishowed statistically significant higher resistance thanS.sonneito amoxicillin, ampicillin, chloramphenicol and ciprofloxacin but resistance to co-trimoxazole was more common inS.sonneithan inS.flexneri. These results emphasize that monitoring of emerging resistance inShigellaisolates is essential for timely and appropriate recommendations for antimicrobial therapy.

Detection of intra-familial transmission of shigella infection using conventional serotyping and pulsed-field gel electrophoresis

Pulsed-field gel electrophoresis (PFGE) is commonly used in molecular epidemiology. However, this technique has never been used in studying intra-family spread of enteric diseases in Bangladesh. Our objective was to evaluate the intra-familial transmission of shigella infection using PFGE. Children of either sex, less than 10 years old, who were family contacts of shigella-infected index cases were the study population. PFGE was applied if the same serotypes/sub-serotypes of shigella were isolated from both the index case and the family contact children. In total, 227 index cases were studied. Shigella was isolated from 61 (27%) contact children on day 1 of enrolment, among which Shigella flexneri (41%) and S. boydii (41%) were dominant, followed by S. dysenteriae (10%), S. sonnei (3%), and shigella-like organisms (5%). Seventeen (28%) of the asymptomatic infections in contact children were caused by the same serotype of shigella as that found in the index case. The intra-familial shigella transmission rate was 8% (17/227). Of the 227 contact children, eight (4%) developed diarrhoea during a 10-day follow-up and shigella was isolated from five (2%) of these children, and three of them (S. flexneri 3a, 1b, and 3a) were identical to the strains from their respective index cases. Compared to children without asymptomatic carriage of shigella (2/166), the risk (odds ratio) of developing diarrhoea for the children with asymptomatic carriage of shigella identical to their cases (3/17) was 9.0 (95% CI 1.5-49.0, P=0.01). The attributable risk for symptomatic shigella infection by intra-familial transmission was 50%. Results of this study demonstrated that intra-familial transmission of shigella carries a higher risk for diarrhoea.