Multidrug-resistant Shigella Strains Research Articles

Bacterial diarrhoea.

This review describes recent findings about the burden of bacterial diarrhoea and its potential complications, newer diagnostics, the emerging threat of multidrug resistance, and the promise of vaccines in development. Introduction of rotavirus vaccines in over 110 countries has changed the landscape of diarrheal pathogens. In upper middle and high-income countries, the incidence of rotavirus-specific and all-cause gastroenteritis has declined substantially, and norovirus has become the major pathogen in many settings. Bacterial pathogens cause approximately 10-15% of episodes, most often Shigella, nontyphoidal Salmonella (NTS) Campylobacter and Shiga toxin-producing Escherichia coli (STEC). In lower income countries, bacterial pathogens remain a major cause of medically attended diarrhoea with Shigella, Campylobacter and enterotoxigenic Escherichia coli (ETEC) predominating. Multidrug-resistant strains of Shigella, NTS and, Campylobacter have emerged globally requiring judicious use of antibiotics according to current guidance. Management of bacterial diarrhoea includes standard fluid and electrolyte therapy, vigilance for potential complications, and use of antibiotics for children who have moderate-severe illness due to pathogens for which efficacy has been demonstrated, or for those at high risk for severe disease. The threat of multiply resistant strains provides impetus for preventive strategies such as development of vaccines.

Shigellosis Among Gay and Bisexual Men: A Qualitative Assessment to Examine Knowledge, Attitudes, and Practices.

Shigellosis is a highly contagious enteric bacterial disease transmitted through the fecal-oral route. It is primarily transmitted through person-to-person contact and via contaminated food and water. Outbreaks of shigellosis among men who have sex with men (MSM) attributed to sexual person-to-person contact have been reported. These outbreaks are of concern because they are often caused by multidrug-resistant strains of Shigella. Little is known about shigellosis-related knowledge, attitudes, and practices among gay, bisexual, and other MSM. Six focus groups were conducted among self-identified gay or bisexual men in Atlanta, GA, in Fall 2017. Participants were asked about shigellosis-related knowledge, attitudes, and practices. Focus groups were audio recorded, and the transcribed audio was analyzed using inductive and deductive thematic coding. Among the 24 focus group participants, most perceived that diarrheal illness was caused by contaminated food. Knowledge of shigellosis and Shigella was low, with most never having heard of the disease or bacteria. Participants did not perceive shigellosis to be a serious health concern, especially when compared with HIV; however, they did perceive gay and bisexual men to be at risk of Shigella infection. Participants reported mixed intentions to change sexual behaviors to prevent shigellosis or talk with sexual partners about diarrhea. Health communication and education efforts could be used to increase knowledge about shigellosis and shift perceptions about the severity of shigellosis among gay, bisexual, and other MSM. Additional work is needed to identify effective ways to promote shigellosis-related prevention behaviors among gay, bisexual, and other MSM.

Genomic and Proteomic Characterizations of Sfin-1, a Novel Lytic Phage Infecting Multidrug-Resistant Shigella spp. and Escherichia coli C.

Shigellosis is a public health threat in developed as well as developing countries like “India.” While antibiotic therapy is the mainstay of treatment for shigellosis, current emergence of multidrug-resistant strains of Shigella spp. has posed the problem more challenging. Lytic bacteriophages which destroy antibiotic resistant Shigella spp. have great potential in this context and hence their identification and detailed characterization is necessary. In this study we presented the isolation and a detailed characterization of a novel bacteriophage Sfin-1, which shows potent lytic activity against multidrug-resistant isolates of Shigella flexneri, Shigella dysenteriae, Shigella sonnei obtained from clinical specimens from shigellosis patients. It is also active against Escherichia coli C. The purified phage is lytic in nature, exhibited absorption within 5–10 min, a latent period of 5–20 min and burst size of ∼28 to ∼146 PFU/cell. The isolated phage shows stability in a broad pH range and survives an hour at 50°C. Genome sequencing and phylogenetic analyses showed that Sfin-1 is a novel bacteriophage, which is very closely related to T1-like phages (89.59% identity with Escherichia virus T1). In silico analysis indicates that Sfin-1 genome consists of double stranded linear DNA of 50,403 bp (GC content of 45.2%) encoding 82 potential coding sequences, several potential promoters and transcriptional terminators. Under electron microscopy, Sfin-1 shows morphology characteristics of the family Siphoviridae with an isometric head (61 nm) and a non-contractile tail (155 nm). This is most likely the first report of a lytic bacteriophage that is active against three of the most virulent multidrug-resistant Shigella species and therefore might have a potential role in phage therapy of patients infected with these organisms.

Resistant Plasmid Profile Analysis of <i>Shigella spp</i> Isolated from Stool Samples of School Children from Selected Communities in Odeda Local Government, Ogun State

Shigellosis is a worldwide health concern especially in developing countries with poor sanitation, lack of personal hygiene and use of contaminated water supplies especially for young children. The emergence of multidrug-resistant Shigella strains incidence imply that shigellosis is an unsolved global health problem causing diarrhoea. This study therefore was carried out to determine the resistant plasmids of multidrug resistant serotypes of Shigella species isolated from stool samples of school children among selected communities in Odeda Local government with their biodata. A total of 10 Shigella spp isolates were obtained from stool samples collected from school children. Antibiotics susceptibility was performed and multi-drug resistant isolates were selected for plasmid profiling. Plasmid profiling of multi-drug resistant Shigella isolates was done by alkaline lysis method. Molecular characterization for identification of the bacterial isolates was carried out using 16S rRNA gene sequencing method. Data obtained were analyzed using One-way Analysis of Variance (ANOVA). Somatic serotyping characterized the isolates to be Shigella flexneri (2.02%), Shigella boydii (1.2%) and Shigella sonnei (0.81%). Plasmid profile analysis showed detectable plasmids with estimated sizes between 100bp to 1200bp. Genomic characterization revealed the isolates belonging to Shigella sonnei strain M-X2D, Shigella flexneri strain MHW4.1 and Shigella boydii strain 3052-94. This study confirmed the emergence of multidrug resistant R-plasmids among Shigella spp causing diarrhoea amongst school children in Abeokuta environs, Nigeria.

Bacteriophage application for biocontrolling Shigella flexneri in contaminated foods.

Shigellosis (bacillary dysentery) is an acute enteric infection caused by members of Shigella genus. It causes annual deaths of approximately five million children in developing countries. Among Shigella spp., S. flexneri causes more serious forms of dysentery than other Shigella species. Due to the appearance of multidrug-resistant strains of Shigella spp., it is necessary to find alternative antimicrobial agents. The aims of this study were the isolation of a novel species-specific phage against S. flexneri and to evaluate its potential and efficacy for biocontrolling of S. flexneri in foods. Shigella flexneri PTCC 1234 was used as the host strain for bacteriophage isolation from waste water. A lytic phage of the Siphoviridae family was isolated and designated as vB_SflS-ISF001. The phage activity remained at high levels after 1h of incubation at -20 to 50°C and was fairly stable for 1h at pH values ranging from 7 to 9. The latent period and burst size were approximately 20min and 53±4 phages per host cell, respectively. Raw and cooked chicken breast were inoculated with a predetermined amount of S. flexneri and subjected to biocontrol test. The results showed that using vB_SflS-ISF001 phage led to more than two logs reduction in the count of viable S. flexneri. It was demonstrated that using vB_SflS-ISF001 phage is of high potential for developing an alternative strategy against S. flexneri contamination in foodstuffs.

The importance of integrons for development and propagation of resistance in Shigella: the case of Latin America.

In Latin America, the disease burden of shigellosis is found to coexist with the rapid and rampant spread of resistance to commonly used antibiotics. The molecular basis of antibiotic resistance lies within genetic elements such as plasmids, transposons, integrons, genomic islands, etc., which are found in the bacterial genome. Integrons are known to acquire, exchange, and express genes within gene cassettes and it is hypothesized that they play a significant role in the transmission of multidrug resistance genes in several Gram-negative bacteria including Shigella. A few studies have described antibiotic resistance genes and integrons among multidrug resistant Shigella isolates found in Latin America. For example, in Brazil, Bolivia, Chile, Costa Rica and Peru, class 1 and class 2 integrons have been detected among multidrug resistant strains of Shigella; this phenomenon is more frequently observed in S. flexneri isolates that are resistant to trimethoprim, sulfamethoxazole, streptomycin, ampicillin, chloramphenicol, and tetracycline. The gene cassette sul2, which is frequently detected in Shigella strains resistant to the sulfonamides, suggests that the sulfonamide-resistant phenotype can be explained by the presence of the sul2 genes independent of the integron class detected. It is to be noted that sul3 was negative in all isolates analyzed in these studies.The high frequency of sulfonamide (as encoded by sul2) and trimethoprim resistance is likely to be a result of the recurrent use of trimethoprim sulfamethoxazole as a popular regimen for the treatment of shigellosis. The observed resistance profiles of Shigella strains confirm that ampicillin and trimethoprim-sulfamethoxazole are ineffective as therapeutic options. In-depth information regarding antibiotic resistance mechanism in this pathogen is needed in order to develop suitable intervention strategies. There is a pressing need for regional and local antimicrobial resistance profiling of Shigella to be included as a part of the public health strategy.

Plasmid Profile Analysis and Antibiotic Resistance Patterns of Shigella Isolates from Kwale County, Kenya

Shigellosis caused by multidrug-resistant (MDR) Shigella strains is an important cause of morbidity and mortality in developing countries. Shigella strains usually harbour heterogeneous population of plasmids which can confer resistance to different antibiotics. A hospital based survey was conducted to determine the pattern of antimi- crobial resistance and plasmid profiles in Shigella species from diarrheal patients in Kwale county. Twenty nine (8.1%) Shigella spp were obtained from 360 stool samples collected and each strain screened for antimicrobial resistance to common antimicrobial agents and presence of plasmids. High antibiotic resistance was found to Sulfamethoxazole-tri- methoprim (79%), Ampicillin (75.9%) and Streptomycin (75.9%). All isolates were sensitive to ciprofloxacin, ceph- alosporins and Aztreonam antibiotics. Ninety seven percent of the isolates screened contained one or more plasmids ranging from 1-6. Majority were small plasmids. Species specific plasmids of 3.2kb, 9.0kb, and 3.8kb were found in Shigella flexneri, Shigella dysenteriae and Shigella sonnei respectively, while 34.5% and 79.3% MDR strains harbored large (>100kb) and middle range self-transmissible plasmids (10-100kb). In all species, no association was found be- tween specific plasmid profile and antibiotic resistance patterns. Significant association was found between carriage of 80kb plasmid in S. dysenteriae (P<0.001), combined 48kb and 80kb plasmids in S. flexneri (P=0.002) and S. sonnei (P=0.041) and MDR phenotype. The middle range plasmids specified resistance to Sulfamethoxazole-trimethoprim, Ampicillin, Streptomycin and Tetracycline. This study reports the usefulness of plasmid profiling in detection and discrimination of Shigella strains in Kenya. The study also shows that middle range self-transferable R-plasmids are widespread among the circulating MDR Shigella strains indicating the important role of these genetic elements in the development and dissemination of multidrug resistance.

Structural Analyses of &lt;i&gt;Shigella&lt;/i&gt; Invasion Proteins Reveals Non-Conserved; Intrinsically Unstructured Regions

Shigella is one of the most common bacterial pathogens that are isolated from patients with diarrhea. Various attempts are being made worldwide with encouraging observations; still the emergence of multidrug-resistant Shigella strains and a continuous high disease incidence imply that shigellosis is an unsolved global health problem which can probably be solved only by developing a proper vaccine and a vaccine regime for the disease. The need of the hour is to foster the development of an effective vaccine which should not only serve to improve hygiene but also should be able to curb infections by the pathogen. This goal can only be achieved by gaining proper detailed knowledge underlying Shigella pathogenesis. The analyses of the Shigella invasion proteins which have been long been targeted to be potential candidate vaccines remains an open ended problem and forms the core of this present computational study which identifies the fact that long regions in the structure of the proteins are disordered having no distinct structural conformation; multiple alignments however, did not show any conserved stretches in the disordered regions. The results probably explain the ability of these proteins to interact with multiple cellular proteins and perform a diverse array of functions leading to successful pathogenesis.

Structural Analyses of &lt;i&gt;Shigella&lt;/i&gt; Invasion Proteins Reveals Non-Conserved; Intrinsically Unstructured Regions

Shigella is one of the most common bacterial pathogens that are isolated from patients with diarrhea. Various attempts are being made worldwide with encouraging observations; still the emergence of multidrug-resistant Shigella strains and a continuous high disease incidence imply that shigellosis is an unsolved global health problem which can probably be solved only by developing a proper vaccine and a vaccine regime for the disease. The need of the hour is to foster the development of an effective vaccine which should not only serve to improve hygiene but also should be able to curb infections by the pathogen. This goal can only be achieved by gaining proper detailed knowledge underlying Shigella pathogenesis. The analyses of the Shigella invasion proteins which have been long been targeted to be potential candidate vaccines remains an open ended problem and forms the core of this present computational study which identifies the fact that long regions in the structure of the proteins are disordered having no distinct structural conformation; multiple alignments however, did not show any conserved stretches in the disordered regions. The results probably explain the ability of these proteins to interact with multiple cellular proteins and perform a diverse array of functions leading to successful pathogenesis.

Shigellosis in Bay of Bengal Islands, India: clinical and seasonal patterns, surveillance of antibiotic susceptibility patterns, and molecular characterization of multidrug-resistant Shigella strains isolated during a 6-year period from 2006 to 2011

This study aims to determine the clinical features and seasonal patterns associated with shigellosis, the antimicrobial resistance frequencies of the isolates obtained during the period 2006-2012 for 22 antibiotics, and the molecular characterization of multidrug-resistant strains isolated from endemic cases of shigellosis in the remote islands of India, with special reference to fluoroquinolone and third-generation cephalosporins resistance. During the period from January 2006 to December 2011, stool samples were obtained and processed to isolate Shigella spp. The isolates were evaluated with respect to their antibiotic resistance pattern and various multidrug resistance determinants, including resistance genes, quinolone resistance determinants, and extended-spectrum β-lactamase (ESBL) production. Morbidity for shigellosis was found to be 9.3 % among children in these islands. Cases of shigellosis occurred mainly during the rainy seasons and were found to be higher in the age group 2-5 years. A wide spectrum of resistance was observed among the Shigella strains, and more than 50 % of the isolates were multidrug-resistant. The development of multidrug-resistant strains was found to be associated with various drug-resistant genes, multiple mutations in the quinolone resistance-determining region (QRDR), and the presence of plasmid-mediated quinolone-resistant determinants and efflux pump mediators. This report represents the first presentation of the results of long-term surveillance and molecular characterization concerning antimicrobial resistances in clinical Shigella strains in these islands. Information gathered as part of the investigations will be instrumental in identifying emerging antimicrobial resistance, for developing treatment guidelines appropriate for that community, and to provide baseline data with which to compare outbreak strains in the future.

High prevalence of atypical class 1 integrons and class 2 integrons in multi-drug resistance Shigella flexneri isolated from China

Shigella flexneri is an important cause of bacterial dysentery in the developing world. Treatment with most widely used and inexpensive antimicrobial drugs became limited due to globally emerging antimicrobial resistance. Integron-associated antibiotic resistance was observed in S. flexneri. This study described the antimicrobial susceptibility and the characteristic of classes 1 and 2 integrons in S. flexneri in China. 90.5% (48/53) S. flexneri strains accounted for multi-drug resistance and carried integrons of class 1 (90.5%), class 2 (86.8%), or both (86.8%). The gene cassettes of typical class 1 integrons, dfrV and dfrA17-aadA5, were detected in 6 strains and 2 strains, respectively. Atypical class 1 integrons with gene cassettes blaOXA-30-aadA1 were detected in 45 (84.9%) strains. The typical and atypical class 1 integrons coexisted in 6 strains; 46 (86.8%) strains carried class 2 integrons with gene cassettes dfrA1-sat1-aadA1. No intI3was detected. The PFGE profiles showed spread of integrons among different serotypes in S. flexneri. The majority of Shigella strains are resistant to ampicillin, chloramphenicol, tetracycline, streptomycin and trimethoprim-sulfamethoxazole. Atypical class 1 and class 2 integrons are widely present in these Shigella strains. Typical and atypical class 1 integrons coexist among some multi-drug resistant Shigella strains. Key words: Shigella flexneri, integrons, multi-drug resistance, pulsed-field gel electrophoresis.

Plasmid-mediated streptomycin and sulfamethoxazole resistance in Shigella flexneri 3a

Shigellosis is a major cause of diarrhoea-related morbidity and mortality, especially in children in developing countries such as India. Recently, it was estimated that 91 million individuals worldwide contract shigellosis each year. The emergence and dissemination of multidrug-resistant strains of Shigella is now an emerging global health problem. During the past two decades, much attention was given to re-evaluation of treatment recommendations. In the present study, we investigated a clinical strain of Shigella flexneri 3a with multiple drug resistance. This strain was resistant to ampicillin, chloramphenicol, co-trimoxazole (trimethoprim/sulfamethoxazole), nalidixic acid, streptomycin, sulfamethoxazole, tetracycline and trimethoprim. However, it was susceptible to 46.7% of drugs tested, i.e. azithromycin, ceftriaxone, ciprofloxacin, gentamicin, kanamycin, norfloxacin and ofloxacin. A 6.3-kb plasmid was cured from this strain using acridine orange. Following curing, it was observed that 87% of drug resistance loci of S. flexneri 3a are chromosomal and 13% are plasmid-encoded. This 6.3-kb plasmid was involved in streptomycin and sulfamethoxazole resistance in S. flexneri 3a strain, which was confirmed by the disk diffusion method. Clonality was confirmed by pulse-field gel electrophoresis (PFGE). This study contributes to our knowledge on acquired drug resistance in one of the most common Shigella spp., S. flexneri 3a, which will enable better understanding of effective clinical management of shigellosis.

High-Throughput Screening of the Virulence Regulator VirF: A Novel Antibacterial Target for Shigellosis

Shigella flexneri is a human enteropathogen that infects about 165 million people and claims more than 1 million lives per year worldwide. Although shigellosis has been considered a disease of the "Third World," like many other contagious diseases, it does occur in developed countries. The emergence of drug and multidrug-resistant strains of Shigella emphasizes the need for novel antibiotic development. VirF, an AraC-type transcriptional regulator, is responsible for the expression of all downstream virulence factors that control intracellular invasion and cell-to-cell spread of Shigella. Gene knockout studies have validated that inhibition of VirF expression is sufficient to block the normal life cycle of Shigella in the host and thereby increase susceptibility to the host immune system. The authors have developed a high-throughput, cell-based assay to monitor inhibition of VirF using beta-galactosidase as a reporter protein. Using an avirulent strain of Shigella, they have screened libraries containing approximately 42,000 small molecules. Following confirmation and dose-response analysis, they have identified 7 compounds that demonstrate VirF inhibition in vivo >or=55% in comparison with the controls and little general antibacterial activity (measured by cell growth, OD(600)). The authors are in the process of confirming these "hits" in several secondary assays to assess the mechanism of action.

Transmission Risk Factors and Treatment of Pediatric Shigellosis During a Large Daycare Center-Associated Outbreak of Multidrug Resistant Shigella sonnei

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. 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. 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. 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.

Alteration in the GyrA Subunit of DNA Gyrase and the ParC Subunit of Topoisomerase IV in Quinolone-Resistant Shigella dysenteriae Serotype 1 Clinical Isolates from Kolkata, India

Alteration in the GyrA Subunit of DNA Gyrase and the ParC Subunit of Topoisomerase IV in Quinolone-Resistant <i>Shigella dysenteriae</i> Serotype 1 Clinical Isolates from Kolkata, India