Shigella dysenteriae type 1 with reduced susceptibility to fluoroquinolones

Isolation, phenotypic characterization and comparative genomic analysis of 2019SD1, a polyvalent enterobacteria phage

Shigella has the remarkable capability to acquire antibiotic resistance rapidly thereby posing a significant public health challenge for the effective treatment of dysentery (Shigellosis). The phage therapy has been proven as an effective alternative strategy for controlling Shigella infections. In this study, we illustrate the isolation and detailed characterization of a polyvalent phage 2019SD1, which demonstrates lytic activity against Shigella dysenteriae, Escherichia coli, Vibrio cholerae, Enterococcus saccharolyticus and Enterococcus faecium. The newly isolated phage 2019SD1 shows adsorption time < 6 min, a latent period of 20 min and burst size of 151 PFU per bacterial cell. 2019SD1 exhibits considerable stability in a wide pH range and survives an hour at 50 °C. Under transmission electron microscope, 2019SD1 shows an icosahedral capsid (60 nm dia) and a 140 nm long tail. Further, detailed bioinformatic analyses of whole genome sequence data obtained through Oxford Nanopore platform revealed that 2019SD1 belongs to genus Hanrivervirus of subfamily Tempevirinae under the family Drexlerviridae. The concatenated protein phylogeny of 2019SD1 with the members of Drexlerviridae taking four genes (DNA Primase, ATP Dependent DNA Helicase, Large Terminase Protein, and Portal Protein) using the maximum parsimony method also suggested that 2019SD1 formed a distinct clade with the closest match of the taxa belonging to the genus Hanrivervirus. The genome analysis data indicate the occurrence of putative tail fiber proteins and DNA methylation mechanism. In addition, 2019SD1 has a well-established anti-host defence system as suggested through identification of putative anti-CRISPR and anti-restriction endonuclease systems thereby also indicating its biocontrol potential.

Prevalence and antimicrobial profile of Shigella isolates in a tertiary care hospital of North Karnataka: A 12-year study

Context

Shigella is a common cause of bacillary dysentery. Although it is reported worldwide, the majority of the infections are seen in developing countries with Shigella flexneri being the most common isolate. Prevalence of Shigella species and their antibiotic susceptibility profiles vary according to geographic area and season.

Aims

In the present study, the epidemiology and antimicrobial profile of Shigella from stool samples received at our hospital for a period of 12 years (January 2006 to December 2017) was evaluated.

Subjects and Methods

A total of 4578 stool samples were collected from the cases of acute gastroenteritis and diarrhoea. Samples were processed for culture and sensitivity according to standard microbiological techniques. The presumptive identification of Shigella species was done using standard conventional biochemical tests and confirmed using antisera.

Results

A total of 189 (4.2%) samples yielded Shigella spp. Isolation of Shigella spp. were more frequent from males (58.2%). S. flexneri was the commonest species isolated (47.6%) followed by Shigella sonnei(11.6%), Shigella dysenteriae (4.2%) and Shigella boydii (2.1%). Non-typeable Shigella was commonly recovered. The isolates showed high resistance to ampicillin (76.7%) and co-trimoxazole (75%) while highest susceptibility was observed to ceftriaxone (79.2%).

Conclusions

S. flexneri was the most prevalent species isolated at this centre. Shigella isolates from the study showed alarming resistance to recommended antibiotics. Non-typeable Shigella accounted for 34.4% isolates. Molecular discrimination between Shigella and Escherichia coli is essential.

Shigellosis: Epidemiology in India

Shigellosis is one of the major causes of diarrhoea in India. The accurate estimates of morbidity and mortality due to shigellosis are lacking, though it is endemic in the country and has been reported to cause many outbreaks. The limited information available indicates Shigella to be an important food-borne pathogen in India. S. flexneri is the most common species, S. sonnei and non-agglutinable shigellae seem to be steadily surfacing, while S. dysenteriae has temporarily disappeared from the northern and eastern regions. Antibiotic-resistant strains of different Shigella species and serotypes have emerged all over the world. Especially important is the global emergence of multidrug resistant shigellae, notably the increasing resistance to third generation cephalosporins and fluoroquinolones, and also azithromycin. This calls for a continuous and strong surveillance of antibiotic resistance across the country for periodic updation of the local antibiograms. The prevention of shigellosis is desirable as it will substantially reduce the morbidity associated with diarrhoea in the country. Public health measures like provision of safe water and adequate sanitation are of immense importance to reduce the burden of shigellosis, however, the provision of resources to develop such an infrastructure in India is a complex issue and will take time to resolve. Thus, the scientific thrust should be focused towards development of a safe and affordable multivalent vaccine. This review is focused upon the epidemiology, disease burden and the therapeutic challenges of shigellosis in Indian perspective.

Intracellular and membrane-damaging activities of methyl gallate isolated from Terminalia chebula against multidrug-resistant Shigella spp

Shigella spp. (Shigella dysenteriae, Shigella flexneri, Shigella boydii and Shigella sonnei) cause bacillary dysentery (shigellosis), which is characterized by bloody mucous diarrhoea. Although a variety of antibiotics have been effective for treatment of shigellosis, options are becoming limited due to globally emerging drug resistance. In the present study, in vitro antibacterial activity of methyl gallate (MG) isolated from Terminalia chebula was determined by performing MIC, minimal bactericidal concentration (MBC) and time-kill kinetic studies. Bacterial membrane-damaging activity of MG was determined by membrane perturbation and transmission electron microscopy (TEM). Cellular drug accumulation, cell infection and assessment of intracellular activities of MG and reference antibiotics were performed using HeLa cell cultures. The bactericidal activity of MG against multidrug-resistant (MDR) Shigella spp. in comparison with other commonly used drugs including fluoroquinolone was demonstrated here. TEM findings in the present study revealed that MG caused the total disintegration of inner and outer membranes, and leakage of the cytoplasmic contents of S. dysenteriae. The level of accumulation of MG and tetracycline in HeLa cells incubated for 24  h was relatively higher than that of ciprofloxacin and nalidixic acid (ratio of intracellular concentration/extracellular concentration of antibiotic for MG and tetracycline>ciprofloxacin and nalidixic acid). The viable number of intracellular S. dysenteriae was decreased in a time-dependent manner in the presence of MG (4 × MBC) and reduced to zero within 20  h. The significant intracellular activities of MG suggested that it could potentially be used as an effective antibacterial agent for the treatment of severe infections caused by MDR Shigella spp.

Options for treating resistant Shigella species infections in children

Infection due to Shigella species remains an important public health problem, especially in developing countries where it remains the most common cause of bloody diarrhea. In the United States (US), 10,000 to 15,000 cases of shigellosis are reported each year in both children and adults. US surveillance data from 2004 has demonstrated increased resistance in Shigella species to first-line antibiotics such as ampicillin and trimethoprim-sulfamethoxazole, with approximately 37% of isolates demonstrating resistance to both ampicillin and trimethoprim-sulfamethoxazole. Since approximately 69% of Shigella infections occur in children younger than 5 years of age, it is important that alternative antibiotics other than typical first-line agents such as ampicillin and trimethoprim-sulfamethoxazole be available to treat Shigella infections in this population. The American Academy of Pediatrics (AAP) recommends cefixime, ceftriaxone, azithromycin, and fluoroquinolones as alternative antibiotics for the treatment of Shigella species infections in children. This paper will review the microbiology, susceptibility, efficacy and safety data of these alternative antibiotics with regard to the treatment of Shigella species infections in children, and will attempt to define the role of each of these agents in the pediatric population.

Lactobacillus plantarum lipoteichoic acid down-regulated Shigella flexneri peptidoglycan-induced inflammation

Bacterial peptidoglycans (PGNs) are recognized by the host's innate immune system. This process is mediated by the NOD/CARD family of proteins, which induces inflammation by activating nuclear factor (NF)-κB. Excessive activation of monocytes by Shigella flexneri PGN (flexPGN) leads to serious inflammatory diseases such as intestinal bowel diseases (IBD) and Crohn's disease. In this study, we examined whether Lactobacillus plantarum lipoteichoic acid (pLTA) could attenuate the pro-inflammatory signaling induced by flexPGN in human monocytic THP-1 cells. Compared to control THP-1 cells, pLTA-tolerant cells showed a significant reduction in TNF-α and IL-1β production in response to flexPGN. We also examined the inhibition of NF-κB and the activation of mitogen-activated protein kinase (MAPK) in pLTA-tolerant cells. We found that the expression of NOD2 in pLTA-tolerant cells was down-regulated at the mRNA and protein levels, suggesting that pLTA is a potent modulator of the pro-inflammatory NOD2-related signaling pathways induced by flexPGN. Together, these data indicate that pLTA induces cross-tolerance against flexPGN. Notably, these effects are related not only to IL-1 signaling, which is known to play a role in LPS tolerance, but also to NOD-Rick signaling. This study provides insight into how commensal microflora may contribute to homeostasis of the host intestinal tract.

Antibiotic therapy for Shigella dysentery

BACKGROUND

Shigella dysentery is a relatively common illness and occasionally causes death, worldwide. Mild symptoms are self-limiting but in more severe cases, antibiotics are recommended for cure and preventing relapse. The antibiotics recommended are diverse, have regional differences in sensitivity, and have side effects.

OBJECTIVES

To evaluate the efficacy and safety of antibiotics for treating Shigella dysentery.

SEARCH STRATEGY

In June 2009 we identified all relevant trials from the following databases: Cochrane Infectious Diseases Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, issue 4), MEDLINE, EMBASE, LILACS and the metaRegister of Controlled Trials (mRCT). We also checked conference proceedings for relevant abstracts, and contacted researchers, organizations, and pharmaceutical companies.

SELECTION CRITERIA

Randomized controlled trials of antibiotics for Shigella dysentery.

DATA COLLECTION AND ANALYSIS

Four authors, working in pairs, independently assessed trial eligibility, methodological quality, and extracted data. We calculated risk ratios (RR) with 95% confidence intervals (CI) for dichotomous data, and used the random-effects model for significant heterogeneity. We explored possible sources of heterogeneity, when present, in subgroup analyses of participant age and percentage of participants with confirmed Shigella infection.

MAIN RESULTS

Sixteen trials (1748 participants), spanning four decades and with differing sensitivity to Shigella isolates, met the inclusion criteria. Seven were judged to be at risk of bias due to inadequate allocation concealment or blinding, and 12 due to incomplete reporting of outcome data. Limited data from one three-armed trial of people with moderately severe illness suggest that antibiotics reduce the episodes of diarrhoea at follow-up (furazolidone versus no drug RR 0.21, 95% CI 0.09 to 0.48, 73 participants; cotrimoxazole versus no drug RR 0.30, 95% CI 0.15 to 0.59, 76 participants).There was insufficient evidence to consider any class of antibiotic superior in efficacy in treating Shigella dysentery, but heterogeneity for some comparisons limits confidence in the results. All the antibiotics studied were safe. There was inadequate evidence regarding the role of antibiotics in preventing relapses.

AUTHORS' CONCLUSIONS

Antibiotics reduce the duration of Shigella dysentery.Regularly updated local or regional antibiotic sensitivity patterns to different species and strains of Shigella are required to guide empiric therapy. More trials adhering to standard guidelines are required to evaluate the role of antibiotics in the treatment of severe forms of Shigella dysentery and in groups who are at high risk of complications.

Changing species distribution and antimicrobial susceptibility pattern of Shigella over a 29-year period (1980-2008)

We studied changes in species distribution and antimicrobial resistance patterns of Shigella during 1980-2008, using the Diarrhoeal Diseases Surveillance system of Dhaka Hospital of ICDDR,B. In hospitalized patients Shigella prevalence decreased steadily from 8-12% in the 1980s to 3% in 2008. Endemic S. flexneri was the most commonly isolated species (54%). Epidemic S. dysenteriae type 1 had two peaks in 1984 and 1993, but was not found after 2000, except for one case in 2004. The therapeutic options are now limited: in 2008 a total of 33% of S. flexneri were resistant to ciprofloxacin and 57% to mecillinam. In the <5 years age group, severely underweight, wasted and stunted children were more at risk of shigellosis compared to well-nourished children (P<0·001). Although hospitalization for Shigella diarrhoea is decreasing, the high levels of antimicrobial resistance and increased susceptibility of malnourished children continue to pose an ongoing risk.

Antibiotic therapy for Shigella dysentery

BACKGROUND

Shigella dysentery is a relatively common illness and occasionally causes death, worldwide. Mild symptoms are self-limiting but in more severe cases, antibiotics are recommended for cure and preventing relapse. The antibiotics recommended are diverse, have regional differences in sensitivity, and have side effects.

OBJECTIVES

To evaluate the efficacy and safety of antibiotics for treating Shigella dysentery.

SEARCH STRATEGY

In June 2009 we identified all relevant trials from the following databases: Cochrane Infectious Diseases Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, issue 4), MEDLINE, EMBASE, LILACS and the metaRegister of Controlled Trials (mRCT). We also checked conference proceedings for relevant abstracts, and contacted researchers, organizations, and pharmaceutical companies.

SELECTION CRITERIA

Randomized controlled trials of antibiotics for Shigella dysentery.

DATA COLLECTION AND ANALYSIS

Four authors, working in pairs, independently assessed trial eligibility, methodological quality, and extracted data. We calculated risk ratios (RR) with 95% confidence intervals (CI) for dichotomous data, and used the random-effects model for significant heterogeneity. We explored possible sources of heterogeneity, when present, in subgroup analyses of participant age and percentage of participants with confirmed Shigella infection.

MAIN RESULTS

Sixteen trials (1748 participants), spanning four decades and with differing sensitivity to Shigella isolates, met the inclusion criteria. Seven were judged to be at risk of bias due to inadequate allocation concealment or blinding, and 12 due to incomplete reporting of outcome data. Limited data from one three-armed trial of people with moderately severe illness suggest that antibiotics reduce the episodes of diarrhoea at follow-up (furazolidone versus no drug RR 0.21, 95% CI 0.09 to 0.48, 73 participants; cotrimoxazole versus no drug RR 0.30, 95% CI 0.15 to 0.59, 76 participants).There was insufficient evidence to consider any class of antibiotic superior in efficacy in treating Shigella dysentery, but heterogeneity for some comparisons limits confidence in the results. All the antibiotics studied were safe. There was inadequate evidence regarding the role of antibiotics in preventing relapses.

AUTHORS' CONCLUSIONS

Antibiotics reduce the duration of Shigella dysentery.Regularly updated local or regional antibiotic sensitivity patterns to different species and strains of Shigella are required to guide empiric therapy. More trials adhering to standard guidelines are required to evaluate the role of antibiotics in the treatment of severe forms of Shigella dysentery and in groups who are at high risk of complications.

Antibiotic therapy for Shigella dysentery

BACKGROUND

Shigella dysentery is a relatively common illness and occasionally causes death, worldwide. Mild symptoms are self-limiting but in more severe cases, antibiotics are recommended for cure and preventing relapse. The antibiotics recommended are diverse, have regional differences in sensitivity, and have side effects.

OBJECTIVES

To evaluate the efficacy and safety of antibiotics for treating Shigella dysentery.

SEARCH STRATEGY

In June 2009 we identified all relevant trials from the following databases: Cochrane Infectious Diseases Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, issue 4), MEDLINE, EMBASE, LILACS and the metaRegister of Controlled Trials (mRCT). We also checked conference proceedings for relevant abstracts, and contacted researchers, organizations, and pharmaceutical companies.

SELECTION CRITERIA

Randomized controlled trials of antibiotics for Shigella dysentery.

DATA COLLECTION AND ANALYSIS

Four authors, working in pairs, independently assessed trial eligibility, methodological quality, and extracted data. We calculated risk ratios (RR) with 95% confidence intervals (CI) for dichotomous data, and used the random-effects model for significant heterogeneity. We explored possible sources of heterogeneity, when present, in subgroup analyses of participant age and percentage of participants with confirmed Shigella infection.

MAIN RESULTS

Sixteen trials (1748 participants), spanning four decades and with differing sensitivity to Shigella isolates, met the inclusion criteria. Seven were judged to be at risk of bias due to inadequate allocation concealment or blinding, and 12 due to incomplete reporting of outcome data. Limited data from one three-armed trial of people with moderately severe illness suggest that antibiotics reduce the episodes of diarrhoea at follow-up (furazolidone versus no drug RR 0.21, 95% CI 0.09 to 0.48, 73 participants; cotrimoxazole versus no drug RR 0.30, 95% CI 0.15 to 0.59, 76 participants).There was insufficient evidence to consider any class of antibiotic superior in efficacy in treating Shigella dysentery, but heterogeneity for some comparisons limits confidence in the results. All the antibiotics studied were safe. There was inadequate evidence regarding the role of antibiotics in preventing relapses.

AUTHORS' CONCLUSIONS

Antibiotics reduce the duration of Shigella dysentery.Regularly updated local or regional antibiotic sensitivity patterns to different species and strains of Shigella are required to guide empiric therapy. More trials adhering to standard guidelines are required to evaluate the role of antibiotics in the treatment of severe forms of Shigella dysentery and in groups who are at high risk of complications.

Purification and characterization of an immunogenic outer membrane protein of Shigella flexneri 2a

In the present study we purified 34 kDa major outer membrane protein (MOMP) of Shigella flexneri 2a for the first time, which was cross-reactive and antigenically conserved among Shigella spp. and the epitope was surface exposed on the intact bacterium. The purified antigen was found to be glycosylated, which aids in binding to macrophages and up-regulated the production of nitric oxide, granulocyte-colony stimulating factor and IL-12p70, indicating that the MOMP is immunogenic and has the ability to commence protective immune responses against intracellular pathogens, thereby it may be considered as a potential vaccine candidate.

Part II. Analysis of data gaps pertaining to Shigella infections in low and medium human development index countries, 1984-2005

The global incidence of Shigella infection has been estimated at 80-165 million episodes annually, with 99% of episodes occurring in the developing world. To identify contemporary gaps in the understanding of the global epidemiology of shigellosis, we conducted a review of the English-language scientific literature from 1984 to 2005, restricting the search to low and medium human development countries. Our review yielded 11 population-based studies of Shigella burden from seven countries. No population-based studies have been conducted in sub-Saharan Africa or in low human development countries. In studies done in all age groups, Shigella incidence varied from 0.6 to 107 episodes/1000 person-years. S. flexneri was the most commonly detected subgroup in the majority of studies. Case-fatality rates ranged from 0% to 2.6% in population-based studies and from 0% to 21% in facility-based studies. This review highlights the large gaps in data on the burden of Shigella infections for low human development index countries and, more specifically, for sub-Saharan Africa.

Antimicrobial resistance of Vibrio cholerae O1 serotype Ogawa isolated in Manhiça District Hospital, southern Mozambique

OBJECTIVES

To describe the antimicrobial susceptibility profile of isolated Vibrio cholerae O1 serotype Ogawa recovered from patients admitted to the cholera facility in the Manhiça District Hospital (MDH), Mozambique.

METHODS

Rectal swabs were collected from patients with complaints symptomatic of cholera admitted to the MDH cholera facility. Samples were processed for V. cholerae isolation at the Centro de Investigação em Saúde da Manhiça (CISM) and identified by biochemical reaction. Serotypes were determined by slide-agglutination antisera. Susceptibilities were determined by disc diffusion.

RESULTS

Seventy-seven isolates were examined for their resistance profile. High incidences of antimicrobial resistance were found for chloramphenicol (57.9%), co-trimoxazole (96.6%) and tetracycline (97.3%). Quinolone resistance remained low (4.2%).

CONCLUSIONS

Although V. cholerae infections in Africa do not usually require antimicrobial treatment, strains in rural Mozambique show high incidences of resistance to readily available drugs. When appropriate, quinolones or third-generation cephalosporins can be used as treatment options.

Using European travellers as an early alert to detect emerging pathogens in countries with limited laboratory resources

Background

The volume, extent and speed of travel have dramatically increased in the past decades, providing the potential for an infectious disease to spread through the transportation network. By collecting information on the suspected place of infection, existing surveillance systems in industrialized countries may provide timely information for areas of the world without adequate surveillance currently in place. We present the results of a case study using reported cases of Shigella dysenteriae serotype 1 (Sd1) in European travellers to detect "events" of Sd1, related to either epidemic cases or endemic cases in developing countries.

Methods

We identified papers from a Medline search for reported events of Sd1 from 1940 to 2002. We requested data on shigella infections reported to the responsible surveillance entities in 17 European countries. Reports of Sd1 from the published literature were then compared with Sd1 notified cases among European travellers from 1990 to 2002.

Results

Prior to a large epidemic in 1999–2000, no cases of Sd1 had been identified in West Africa. However, if travellers had been used as an early warning, Sd1 could have been identified in this region as earlier as 1992.

Conclusion

This project demonstrates that tracking diseases in European travellers could be used to detect emerging disease in developing countries. This approach should be further tested with a view to the continuous improvement of national health surveillance systems and existing European networks, and may play a significant role in aiding the international public health community to improve infectious disease control.

Molecular epidemiology of multidrug-resistant Shigella dysenteriae type 1 causing dysentery outbreaks in Central African Republic, 2003–2004

Shigella dysenteriae type 1 (Sd1) represents a particular threat in developing countries because of the severity of the infection and its epidemic potential. Antimicrobial susceptibility testing and molecular subtyping by pulsed-field gel electrophoresis (PFGE) and plasmid profiling (PP) of Sd1 isolates collected during two dysentery outbreaks (2013 and 445 cases of bloody diarrhoea) in Central African Republic (CAR) during the period 2003-2004 were reported. Eleven Sd1 comparison strains (CS) acquired by travellers or residents of Africa (n=10) or Asia (n=1) between 1993 and 2003 were also analysed. The 19 Sd1 isolates recovered from CAR outbreaks were multidrug resistant, although susceptible to quinolones and fluoroquinolones. Molecular subtyping by PFGE was more discriminatory than PP. The PFGE using XbaI and NotI restriction enzymes indicated that the two outbreaks were due to two different clones and also revealed a genetic diversity among the CS recovered from outbreak or sporadic cases between 1993 and 2003. This study was the result of a fruitful collaboration between field physicians and microbiologists. The data collected will serve as the basis for establishing long-term monitoring of Sd1 in CAR.

Current status of anti-diarrheal and anti-secretory drugs in the management of acute childhood diarrhea

Each year 1.8 million children die due to diarrheal diseases. Indiscriminate use of antibiotics has resulted in increasing resistance to commonly used antibiotics. Moreover the recent outbreaks of shigella and cholera have revealed multi-drug resistance strains. There is a need for review of recommended antibiotics for shigellosis. From recent data it emerges that fluoroquinolones should be the first line of therapy and cephalosporins to be used as the second line. Among the anti-cholera antibiotics, tetracyclines which were the drug of choice for adults, has the advantage of high sensitivity and low cost. Single dose doxycycline would have minimal side effects, hence can be the drug of choice even in children. We should not allow the business pressures to force usage of probiotics and racecadotril as their role in the management of acute diarrhea is yet to be established. Nitazoxanide has high efficacy against Cryptosporodial diarrhea only. Strict adherence to the recommendations for the management of acute childhood diarrhea is needed or else we dilute the effect of standard management.

Frequency of serovars and antimicrobial resistance in Shigella spp. from Brazil

A total of 296 Shigella spp. were received from State Public Health Laboratories, during the period from 1999 to 2004, by National Reference Laboratory for Cholera and Enteric Diseases (NRLCED)--IOC/Fiocruz, Rio de Janeiro, Brazil. The frequency of Shigella spp. was: S. flexneri (52.7%), S. sonnei (44.2%), S. boydii (2.3%), and S. dysenteriae (0.6%). The most frequent S. flexneri serovars were 2a and 1b. The highest incidence rates of Shigella isolation were observed in the Southeast (39%) and Northeast (34%) regions and the lowest rate in the South (3%) of Brazil. Strains were further analyzed for antimicrobial susceptibility by disk diffusion method as part of a surveillance program on antimicrobial resistance. The highest rates of antimicrobial resistance were to trimethoprim-sulfamethozaxole (90%), tetracycline (88%), ampicillin (56%), and chloramphenicol (35%). The patterns of antimicrobial resistance among Shigella isolates pose a major difficulty in the determination of an appropriate drug for shigellosis treatment. Continuous monitoring of antimicrobial susceptibilities of Shigella spp. through a surveillance system is thus essential for effective therapy and control measures against shigellosis.

High prevalence of antimicrobial resistance among Shigella isolates in the United States tested by the National Antimicrobial Resistance Monitoring System from 1999 to 2002

Shigella spp. infect approximately 450,000 persons annually in the United States, resulting in over 6,000 hospitalizations. Since 1999, the National Antimicrobial Resistance Monitoring System (NARMS) for Enteric Bacteria has tested every 10th Shigella isolate from 16 state or local public health laboratories for susceptibility to 15 antimicrobial agents. From 1999 to 2002, NARMS tested 1,604 isolates. Among 1,598 isolates identified to species level, 1,278 (80%) were Shigella sonnei, 295 (18%) were Shigella flexneri, 18 (1%) were Shigella boydii, and 7 (0.4%) were Shigella dysenteriae. Overall, 1,251 (78%) were resistant to ampicillin and 744 (46%) were resistant to trimethoprim-sulfamethoxazole (TMP-SMX). Prevalence of TMP-SMX- or ampicillin- and TMP-SMX-resistant Shigella sonnei isolates varied by geographic region, with lower rates in the South and Midwest regions (TMP-SMX resistance, 27% and 30%, respectively; ampicillin and TMP-SMX resistance, 25% and 22%, respectively) and higher rates in the East and West regions (TMP-SMX resistance, 66% and 80%, respectively; ampicillin and TMP-SMX resistance, 54% and 65%, respectively). Nineteen isolates (1%) were resistant to nalidixic acid (1% of S. sonnei and 2% of S. flexneri isolates); 12 (63%) of these isolates had decreased susceptibility to ciprofloxacin. One S. flexneri isolate was resistant to ciprofloxacin. All isolates were susceptible to ceftriaxone. Since 1986, resistance to ampicillin and TMP-SMX has dramatically increased. Shigella isolates in the United States remain susceptible to ciprofloxacin and ceftriaxone.

Development and evaluation of a Shigella flexneri 2a and S. sonnei bivalent invasin complex (Invaplex) vaccine

Over 160 million cases of shigellosis occur annually worldwide, with the two most prevalent species being Shigella flexneri and S. sonnei. Protective immunity against Shigella infection is primarily directed at the lipopolysaccharide (LPS) of the homologous serotype, so it may be necessary to combine monovalent vaccines for multiple Shigella serotypes to construct a multivalent vaccine against predominant serotypes. Recently, we described a subcellular vaccine isolated from virulent S. flexneri, consisting of proteins (including the invasins IpaB and IpaC) and LPS, that protected mice and guinea pigs from homologous challenge. In the present study, a bivalent Invaplex vaccine consisting of S. flexneri 2a and S. sonnei Invaplex was used to intranasally immunize mice and guinea pigs to determine the bivalent vaccine's immunogenicity and protective capacity against challenge with either strain. Mice and guinea pigs immunized with the bivalent S. flexneri 2a/S. sonnei Invaplex vaccine produced serum IgA and IgG antibodies to S. flexneri LPS, S. sonnei LPS, the homologous Invaplex and the water extract antigens (invasins) as determined by ELISA. The immune responses in animals immunized with the bivalent vaccine were similar to responses in animals immunized with the monovalent Invaplex vaccines. Mice and guinea pigs immunized with the bivalent vaccine were protected from a lethal lung challenge (mice, P<0.001) or severe keratoconjunctivitis (guinea pigs, P< or = 0.002) after challenge with either S. flexneri 2a or S. sonnei. Animals immunized with monovalent Invaplex vaccines were protected (P<0.001) against the homologous agent at levels comparable to the bivalent vaccine. After challenge, immunized animals demonstrated boosts in antibody titers to LPS, water extract antigens and Invaplex. These studies indicate that the subcellular Invaplex vaccine will be readily adaptable to a multivalent vaccine approach for shigellosis.

Infectious diarrhea in developed and developing countries

Diarrhea from gastrointestinal infection remains a common problem. In industrialized countries, management is aimed at reducing morbidity and defining groups that may benefit from further investigation. Most infectious diarrhea is self-limiting and only requires supportive management. Viral agents are increasingly recognized as causative agents of epidemic and sporadic diarrhea. In developing countries, diarrhea is a major cause of mortality in children. Oral rehydration therapy, guided by a clinical assessment of the degree of dehydration, is cheap, simple, and effective and remains the mainstay of management of infant diarrhea. Controversies focus on the optimal formulation of oral rehydration solution. A vaccine against rotavirus has the potential to save millions of lives worldwide.

Shigella infections in children: new insights

Shigellosis , the acute enteric infection caused by bacteria of the genus Shigella , has a worldwide distribution with an estimated annual incidence of 164.7 million cases, of which 163.2 million occur in developing countries, and 1.1 million deaths. Sixty-nine percent of all episodes and 61 percent of all Shigella -related deaths involve children younger than 5 years old. In the United States, 10,000 to 15,000 cases of shigellosis are reported each year. Although usually confined to the colonic mucosa, shigellosis sometimes can cause extraintestinal complications. Recent publications have shed light on the clinical characteristics of Shigella -induced bacteremia, surgical complications, urogenital symptoms, and neurologic manifestations, and on the unique manifestations in the neonatal period. The mainstay of treatment of shigellosis in children is correction of the fluid and electrolyte loss, which often is achieved by the administration of oral rehydration solutions. Appropriate antibiotic therapy shortens the duration of both clinical symptoms and fecal excretion of the pathogen. However, the increasing antimicrobial resistance of shigellae worldwide constitutes a major problem. Regarding the pathophysiology of shigellosis and its complications, recent data not only elucidated the molecular mechanisms involved but also linked manifestations of disease to the interplay of bacterial virulence factors and host responses. The improved understanding of the pathophysiology is hoped to lead to innovative therapeutic approaches against shigellosis and new generations of vaccine candidates.

Case management of a multidrug-resistant Shigella dysenteriae serotype 1 outbreak in a crisis context in Sierra Leone, 1999-2000

From December 1999 to the end of February 2000, 4218 cases of dysentery were reported in Kenema district, southeastern Sierra Leone, by a Médecins Sans Frontières team operating in this region. Shigella dysenteriae serotype 1 was isolated from the early cases. The overall attack rate was 7.5% but higher among children under 5 years (11.2%) compared to the rest of the population (6.8%) (RR = 1.6; 95% CI 1.5-1.8). The case fatality ratio was 3.1%, and higher for children under 5 years (6.1% vs. 2.1%) (RR = 2.9; 95% CI 2.1-4.1). A case management strategy based on stratification of affected cases was chosen in this resource-poor setting. Patients considered at higher risk of death were treated with a 5 day ciprofloxacin regimen in isolation centres. Five hundred and eighty-three cases were treated with a case fatality ratio of 0.9%. Patients who did not have signs of severity when seen by health workers were given hygiene advice and oral rehydration salts. This strategy was effective in this complex emergency.

Shigella dysenteriae serotype 1, Kolkata, India

Since July 2002, bacteriologically confirmed shigellosis cases have increased, and multidrug-resistant Shigella dysenteriae serotype 1 strains have reemerged in patients hospitalized with diarrhea in Kolkata, India. The isolated strains of S. dysenteriae 1 showed resistance to chloramphenicol (80%), ampicillin (100%), tetracycline (100%), co-trimoxazole (100%), nalidixic acid (100%), norfloxacin (100%), and ciprofloxacin (100%). Emergence of fluoroquinolone resistance in S. dysenteriae 1 strains complicated treatment of shigellosis patients. Six strains belonging to provisional serovars of S. dysenteriae were also identified for the first time in patients hospitalized with diarrhea in Kolkata, India.