Ag impregnated sub-micrometer crystalline jute cellulose particles: Catalytic and antibacterial properties.

This work discussed the preparation of Ag nanoparticles (AgNPs) and AgNPs impregnated sub-micrometer crystalline jute cellulose (SCJC) particles using a green synthetic bioreduction method. The ultimate nanocomposite particles were named as SCJC/Ag. The crystalline structure of AgNPs was maintained in SCJC/Ag nanocomposte particles. The catalytic efficiency of SCJC/Ag nanocomposite particles were evaluated for the degradation of congo red (CR) and methylene blue (MB) using NaBH4 as reducing agent. A complete degradation of 20 mL of each CR (0.1 mM) and MB (0.05 mM) dye solution was achieved within 14 min when 0.005 mg mL-1 of SCJC/Ag nanocomposite particles was employed. SCJC/Ag nanocomposite particles also exhibited moderate antibacterial activities against Staphylococcus aureus, Escherichia coli, Shigella dysenteriae and Shigella boydii and the results were comparable with those of the reference AgNPs. SCJC/Ag nanocomposite particles were the most effective against Escherichia coli (E. coli) with minimum inhibitory concentration of 0.014 mg mL-1.

Evaluation of antimicrobial, antibiofilm and carbonic anhydrase inhibition profiles of 1,3-bis-chalcone derivatives.

A series of 1,3-bis-chalcone derivatives (3a-i, 6a-i and 8) were synthesized and evaluated antimicrobial, antibiofilm and carbonic anhydrase inhibition activities. In this evaluation, 6f was found to be the most active compound showing the same effect as the positive control against Bacillus subtilis and Streptococcus pyogenes in terms of antimicrobial activity. Biofilm structures formed by microorganisms were damaged by compounds at the minimum inhibitory concentration value between 0.5% and 97%.1,3-bis-chalcones ( 3a-i, 6a-i and 8) showed good inhibitory action against human (h) carbonic anhydrase (CA) isoforms I and II. hCA I and II were effectively inhibited by these compounds, with K i values in the range of 94.33 ± 13.26 to 787.38 ± 82.64 nM for hCA I, and of 100.37 ± 11.41 to 801.76 ± 91.11 nM for hCA II, respectively. In contrast, acetazolamide clinically used as CA inhibitor showed K i value of 1054.38 ± 207.33 nM against hCA I, and 983.78 ± 251.08 nM against hCA II, respectively.

Histochemical localization of N-acetylhexosamine-binding lectin HOL-18 in Halichondria okadai (Japanese black sponge), and its antimicrobial and cytotoxic anticancer effects.

We studied localization and physiological activities of a lectin showing specific binding to N-acetylhexosamines, termed HOL-18, purified from Japanese black sponge (Halichondria okadai). Antiserum against the lectin was generated in rabbit and applied for immunohistochemical analyses. HOL-18 was expressed specifically around water pores and on spicules of sponge tissues. It showed strong binding to a variety of N-acetylhexosamines: N-acetyl D-glucosamine, N-acetyl D-galactosamine, N-acetyl mannosamine, N-acetyl muramic acid, and N-acetyl neuraminic acid. Hemagglutination induced by the lectin was inhibited by lipopolysaccharides and a peptidoglycan. HOL-18 inhibited growth of a gram-positive bacterium (Listeria monocytogenes), gram-negative bacteria (Escherichia coli, Shigella boydii, Pseudomonas aeruginosa), and a fungus (Aspergillus niger). It displayed anti-biofilm activity against P. aeruginosa. HOL-18 was internalized into conidiophores of A. niger, and displayed notable antifungal activity. Fluorescence microscopy revealed binding and incorporation of the lectin into human cancer cell lines HeLa, MCF-7, and T47D, but not Caco-2. HOL-18 displayed dose-dependent cytotoxic effects against HeLa, MCF-7, and T47D, with respective IC50 values 40, 52, and 63 µg/mL. In HeLa cells, it activated phosphorylation of MAPK pathway molecule (ERK1/2) and activated caspase-3 to trigger apoptosis. HOL-18 thus has the potential to upregulate metabolic pathways in higher animal cells through binding to N-acetylhexosamines.

Antimicrobial potentials of Catharanthus roseus by disc diffusion assay.

The present research work investigates the in vitro antimicrobial activity of different solvent extracted samples from the aerial parts (stem, leaf, fruit and flower) of C. roseus against different microbial species using disc diffusion assay at two different concentrations of 1 and 2 mg disc-1. Hexane extracted samples inhibited the growth of all tested microbial strains except S. typhi. Similarly, ethyl acetate extracted samples was effective to control the activity of all the tested microbial strains. E. coli and S. typhi showed resistance to chloroform extracted samples and the remaining eight microbial strains were susceptible to the same extract. Butanol extracted samples did not inhibit the growth of K. pneumonia and S. typhi at low concentration, however, at higher concentration the same extract reduced the growth of different microbes. Methanol extracted samples effectively controlled the growth of all tested microbes at both concentrations except for S. typhi. Water extracted samples did not inhibit the growth at low concentration except E. coli, K. pneumonia and S. aureus and were ineffective against P. aeroginosa at both concentration. C. albicans, showed resistance against chloroform and water extracted samples at low concentration and susceptible to other solvent extracted samples at both concentration. All fractions were effective against plant pathogens i.e. E. carotovora and A. tumefaciens.

In vitro development and analysis of Escherichia coli and Shigella boydii azithromycin-resistant mutants.

The aim of this study was to develop and analyze in vitro azithromycin (AZM)-resistant mutants of Escherichia coli and Shigella boydii. Three clinical isolates of E. coli and one S. boydii isolated from feces samples collected from children under 5 years of age with diarrhea in Lima, Peru were inoculated onto Mueller-Hinton plates containing increasing serial dilutions of AZM ranging from their specific minimal inhibitory concentration (2 or 4 mg/l) to 64 mg/l. From these plates, 16 AZM-resistant mutants were selected to determine the stability of the resistance and the presence of cross resistance with other antibiotics. The role of Phe-Arg-ß-Naphthylamide (PAßN)-inhibitible efflux pumps as well as the presence of mutations in the rplV, rplD, and rrlH (23S rRNA) genes and alterations in the outer membrane profiles were determined in these 16 mutants. The rate of mutation ranged from < 2.70×10(-10) to 2.17×10(-7) for E. coli and from < 9.58×10(-10) to 1.05×10(-8) for S. boydii. E. coli mutants showed an increase in the AZM-MIC up to sixfold with one strain achieving a MIC >256 mg/l. In contrast, S. boydii only presented increases of up to twofold in MIC levels. All the strains obtained, but one showed stable AZM resistance. In the presence of PAßN, the AZM MICs decreased to parental levels in Shigella mutants, while no MIC returned to parental levels among the E. coli mutants. No cross resistance to other classes of antibiotics was found. These results show the relevance of PAßN-inhibitible efflux pumps in the basal levels and development of AZM resistance. Further studies to characterize the remaining unidentified mechanisms of AZM resistance are needed.

Genetic diversity and antibiotic resistance in Shigella dysenteriae and Shigella boydii strains isolated from children aged <5 years in Egypt.

Diversity within Shigella dysenteriae (n=40) and Shigella boydii (n=30) isolates from children living in Egypt aged <5 years was investigated. Shigella-associated diarrhoea occurred mainly in summer months and in children aged <3 years, it commonly presented with vomiting and fever. Serotypes 7 (30%), 2 (28%), and 3 (23%) accounted for most of S. dysenteriae isolates; 50% of S. boydii isolates were serotype 2. S. dysenteriae and S. boydii isolates were often resistant to ampicillin, chloramphenicol and tetracycline (42%, 17%, respectively), although resistance varied among serotypes. Pulsed-field gel electrophoresis separated the isolates into distinct clusters correlating with species and serotype. Genetic differences in trimethoprim/sulfamethoxazole and ß-lactam-encoding resistance genes were also evident. S. dysenteriae and S. boydii are genetically diverse pathogens in Egypt; the high level of multidrug resistance associated with both pathogens and resistance to the most available inexpensive antibiotics underlines the importance of continuing surveillance.

Effect of NaCl on the biofilm formation by foodborne pathogens.

This study was designed to evaluate the effect of NaCl on the biofilm formation of Listeria monocytogenes, Staphylococcus aureus, Shigella boydii, and Salmonella Typhimurium. The biofilm cells were cultured in media containing different NaCl concentrations (0% to 10%) for 10 d of incubation at 37 °C using a 24-well polystyrene microtiter plate, collected by swabbing methods, and enumerated using plate count method. The attachment and detachment kinetic patterns were estimated according to the modified Gompertz model. The cell surface hydrophobicity and auto-aggregation were observed at different NaCl concentrations. Most strains showed 2 distinctive phases at lower than 6% NaCl, while the numbers of adhered cells gradually increased throughout the incubation period at 4% to 10% NaCl. At 0% NaCl, the numbers of adhered L. monocytogenes, S. aureus, S. boydii, and S. Typhimurium cells rapidly increased up to 7.04, 6.47, 6.39, and 7.27 log CFU/cm(2), respectively, within 4 d of incubation. The maximum growth rate (k(A)) and specific growth rate (µ(A)) of adherent pathogenic cells were decreased with increasing NaCl concentration. Noticeable decline in the numbers of adherent cells was observed at low concentration levels of NaCl (<2%). The adherence abilities of foodborne pathogens were influenced by the physicochemical surface properties. The hydrophobicity and auto-aggregation enhanced the biofilm formation during the incubation periods. Therefore, this study could provide useful information to better understand the adhesion and detachment capability of foodborne pathogens on food contact surfaces.

Antimicrobial resistance in Shigella species isolated in Dakar, Senegal (2004-2006).

From May 2004 to October 2006, a prospective study was carried out in Dakar, Senegal, to update information about the antimicrobial susceptibility of Shigella spp. isolated from stool specimens. Among the 165 non-duplicate strains collected, 81 (49%) were identified as Shigella flexneri, 75 (45%) as Shigella sonnei, 5 (3%) as Shigella boydii, and 4 (2%) as Shigella dysenteriae. Disk diffusion testing revealed that the majority of isolates were resistant to sulphonamides, trimethoprim-sulfamethoxazole, streptomycin, and tetracycline (respective overall resistance rates: 90, 90, 96, and 94%). More than half of the S. flexneri isolates were resistant to amoxicillin, amoxicillin-clavulanic acid, and chloramphenicol (respective resistance rates: 59, 58, and 52%), and almost all of the S. sonnei isolates were susceptible to these antimicrobials (respective resistance rates: 4, 1, and 4%). Only one isolate (belonging to the species S. sonnei) was resistant to nalidixic acid and displayed reduced susceptibility to ciprofloxacin.

Synthesis and structure-activity relationship of 7-(substituted)-aminomethyl-4-quinolone-3-carboxylic acid derivatives.

Gram-positive organisms have re-emerged as the major hospital pathogens, which make the unmet medical needs for antibacterial therapy even worse. In searching for potent agents against Gram-positive pathogens, novel 7-(substituted)-aminomethyl-quinolone-3-carboxylic acids were designed, synthesized, and evaluated for their antibacterial activities in vitro. Many 7-monoarylaminomethyl derivatives exhibited high potency against Gram-positive organisms compared to reference agents: vancomycin and pazufloxacin. Additionally, a few 7-monoalkylaminomethyl derivatives exhibited good activities against both Gram-positive and Gram-negative organisms.

Identification of a group of shigella-like isolates as Shigella boydii 20.

Infections by Shigella species are an important cause of diarrhoeal disease worldwide. Of 4198 Shigella isolates received by the French National Reference Centre for Escherichia coli and Shigella, 180 from patients with diarrhoea and dysentery in 2000-2004 did not react with any available polyclonal rabbit antisera used to identify the established Shigella serogroups. This study describes the molecular and phenotypic characteristics of these isolates in seroagglutination tests, molecular serotyping (rfb-RFLP and fliC-RFLP), ribotyping, detection of invasivity and enterotoxins genes, and antibiotic sensitivity. All isolates gave biochemical reactions typical of Shigella boydii, were mannitol-positive and indole-negative. They all carried invasion-associated genes, enterotoxin 2 [ShET-2] and an IS630 sequence. They had a unique ribotype that was distinct from all other Shigella and E. coli patterns. Further characterization by rfb-RFLP clearly distinguished this serogroup from all other Shigella or E. coli O-groups. The fliC-RFLP pattern corresponded to P4, an F-pattern which is associated with 10 different serogroups of S. boydii. A new antiserum prepared against strain 00-977 agglutinated all 180 isolates and cross-agglutination and absorption studies with anti-00-977 serum and anti-CDC 99-4528 (reference for the newly described S. boydii serogroup 20) serum showed identical antigenic structure. Furthermore, strains 00-977 and CDC 99-4528 had the same molecular serotype, ribotype and virulence genes.

Shigella antibiotic resistance in central Turkey: comparison of the years 1987-1994 and 1995-2002.

BACKGROUND: The epidemiology and antibiotic susceptibility of Shigella species changes over time. Updated susceptibility knowledge is necessary for appropriate empirical antibiotic treatment. METHODS: In this study the clinical characteristics and the antibiotic susceptibility test results of Shigella species isolated from patients admitted to Hacettepe University Ihsan Dogramac Children's Hospital Diarrheal Diseases Training and Treatment Unit between 1995-2002 (n = 218) were evaluated. The results were compared with the results of 1987-1994 from the same center (n = 618). RESULTS: The predominant species was S. sonnei in both periods with increasing prevalence in the later period (64% and 71.5% respectively, P < 0.05). Although the prevalence of bloody diarrhea among Shigella cases did not change between periods, the prevalence of mild to moderate dehydration (11% and 20.6%) increased. Approximately 40% of cases were prescribed antibiotics on the suspicion of shigellosis. When the two periods were compared, Shigella resistance to trimethoprim/sulfamethoxazole increased from 39% to 70% (P < 0.0001), whereas resistance to ampicillin decreased from 41% to 23% (P < 0.0001). However, the resistance of S. flexneri to ampicillin was found to be quite high (72.9%) between 1995-2002. No Shigella species resistant to ciprofloxacin was detected. Multi-drug resistance was present in 52 (24%) of the cases, of which 10 were S. sonnei (6.3%) and 42 S. flexneri (26.4%) (P < 0.0001). CONCLUSION: The need to treat all Shigella cases in areas where S. sonnei is predominant should be reevaluated, as should the appropriate empirical antibiotic.

Catecholamines and in vitro growth of pathogenic bacteria: enhancement of growth varies greatly among bacterial species.

The purpose of this study was to examine the effects of catecholamines on in vitro growth of a range of bacterial species, including anaerobes. Bacteria tested included: Porphyromonas gingivalis, Bacteriodes fragilis, Shigella boydii, Shigella sonnie, Enterobacter Sp, and Salmonella choleraesuis. The results of the current study indicated that supplementation of bacterial cultures in minimal medium with norepinephrine or epinephrine did not result in increased growth of bacteria. Positive controls involving treatment of Escherichia coli with catecholamines did result in increased growth of that bacterial species. The results of the present study extend previous observations that showed differential capability of catecholamines to enhance bacterial growth in vitro.

[Antimicrobial resistance of Shigella spp. in Córdoba, Argentina, during the period 1990-1997]. / Resistencia de Shigella spp. a los antimicrobianos en Córdoba, Argentina, durante el período 1990-1997.

This study analyzed the evolution of antimicrobial resistance in 771 isolates of Shigella spp. obtained from a total of 9,195 feces cultures done between 1990 and 1997 in a children's hospital in Córdoba, Argentina. S. flexneri, which was responsible for 73% of the Shigella infections, was the species with the greatest resistance. The frequency of S. flexneri resistance to the three antibiotics most used (ampicillin, trimethoprim-sulfamethoxazole, and chloramphenicol) increased from 10% in 1990 to 58% in 1997 (P < 0.001). Considering each of the drugs individually, the resistance to ampicillin increased from 60% to 100% (P < 0.001), the resistance to chloramphenicol from 13% to 71% (P < 0.001), and the resistance to trimethoprim-sulfamethoxazole from 79% to 84% (P = 0.22). For S. sonnei, the increase in resistance to ampicillin (from 36% in 1990 to 54% in 1997) was not statistically significant (P = 0.20), nor was the reduction in resistance to trimethoprim-sulfamethoxazole, which went from 82% in 1990 to 55% in 1997 (P = 0.08). Only two S. sonnei isolates were found that were resistant to chloramphenicol, one in 1995 and another in 1997; two S. sonnei isolates were found with resistance to all three antibiotics. We consider it essential to carry out susceptibility tests of each Shigella clinical isolate, to detect changes in the resistance profile and thus modify empiric treatment.

Increasing incidence of antibiotic resistance in shigellas from humans in England and Wales: recommendations for therapy.

Since 1983 the incidence of resistance to ampicillin in Shigella dysenteriae, Sh. flexneri, and Sh. boydii infections in England and Wales has increased from 42% to 65% and the incidence of resistance to trimethoprim, from 6% to 64%. Furthermore, of 1524 strains received in 1995-1996, 46% were resistant to both of these antimicrobials. For Sh. sonnei almost 50% of isolates were resistant to ampicillin or trimethoprim and 15% were resistant to both of these antimicrobials. These results demonstrate that if antibiotic therapy had been indicated for infections with Sh. dysenteriae, Sh. flexneri, and Sh. boydii, then treatment with either ampicillin or trimethoprim may have been ineffective in almost 50% of cases and for Sh. sonnei, in 15% of cases. It is concluded that if it is necessary to commence treatment before the results of laboratory-based sensitivity tests are available, the best options would be to use nalidixic acid for children and a fluoroquinolone antibiotic such as ciprofloxacin or ofloxacin, for adults.

Severe shigellosis in childhood.

A prospective study was performed on 20 bacteriologically proven pediatric cases of severe shigellosis admitted to the Department of Pediatrics, Chulalongkorn Hospital during March 1989 to March 1990. Fourteen patients were male and six were female. Shigella B was found in 85% and Shigella D in 15% of cases. The major indications for admission were convulsions and dehydration. Fifteen per cent of cases had underlying malignancies and 42.1% had malnutrition. Most patients had a peak of fever between 39.5 and 40.5 degrees C, serum sodium between 128-144 mEq/l. Mild acidosis was detected in 45% and moderate acidosis in 30% of cases. There were no statistical differences in peak of fever and serum sodium between patients who had convulsion and who did not. Shigellemia was found in one case who also had underlying neuroblastoma. One patient died due to necrotizing enterocolitis, septic shock and renal failure. Most of the organisms found resisted to ampicillin and trimethoprim-sulfamethoxazole (TMP-SMX). However, TMP-SMX was prescribed in most immunocompetent patients and they recovered well. All of three patients with underlying malignancy responded well to ceftriaxone.

[Studies on bacillary dysentery cases of overseas travellers--during 1979 to 1995].

A total of 36,780,440 overseas travellers during 1979-1995 (17 years) were quarantined at Osaka and Kansai Airport Quarantine Station, 84,777 travellers reported themselves suffer from diarrhoea. Stools from 29,587 persons were bacteriologically examined. Various enteropathogenic bacteria were isolated from 9,766 (33.0%) patients of the stools examined. Isolated species were as follows: Plesiomonas shigelloides (3,234 cases); Salmonella spp. (2,236 cases); enterotoxgenic Escherichia coli (1,621 cases); Vibrio parahaemolyticus (1,959 cases); and Shigella spp. (1,242 cases). 1,278 different Shigella strains were isolated from 1,242 cases who were thus diagnosed as bacillary dysentery patients. The suspected regions or countries for infection of these cases were analysed. The serovars and antibiotic-sensitivities of the isolated strains were examined. Colicine typing of S. sonnei strains were also done. The results can be summarized as follows. 1) The most cases (53.4%) were infected in India. 2) The percentage distribution of sub-species of the strains was as follows; S. sonnei (57.8%), S flexneri (29.8%), S. boydii (8.4%), and S. dysenteriae (4.0%), respectively. 3) The major colicine type of S. sonnei strains were type 6 and 0. 4) The percentage of Antibiotic-resistant strains of each sub-species was S. dysenteriae (92.2%), S. sonnei (89.4%), S. flexneri (87.1%), and S. boydii (84.9%), respectively. The percentage of Antibiotic-resistant strains of S. flexneri were increased annually.

Antimicrobial resistance and serotypes of Shigella isolates in Kigali, Rwanda (1983 to 1993): increasing frequency of multiple resistance.

The serotype distribution and susceptibility to nine antibiotics was determined for 2491 Shigella isolates cultured in the medical laboratory of the Centre Hospitalier de Kigali, Rwanda, during 1983 to 1993. Overall, Shigella flexneri was the most frequent species, ranking before Shigella sonnei, Shigella boydii, and Shigella dysenteriae. However, the relative frequency of the different Shigella spp. showed an important variability over time. S flexneri increased from 40% in 1983 to 68% of the isolates in 1993 whereas S. dysenteriae Type 1 decreased gradually from 30 to 0.5% of the isolates in 1992. After the outbreak of severe civil unrest, which caused the displacement of many people to the capital, a new epidemic of dysentery started in the Kigali area and S. dysenteriae Type 1 accounted again for 24% of the isolates in 1993. In 1983, resistance to tetracycline, streptomycin, and sulfonamides was common among the endemic Shigella spp. Resistance to chloramphenicol was observed in 17% (30/182) of the isolates. Only 10% were resistant to ampicillin and an equal proportion to trimethoprim, whereas 5% of the isolates showed resistance to both products. By 1993, 66% (195/295) of the isolates were resistant to chloramphenicol (for comparison with 1983, p < 0.001), 70% (207/295) to ampicillin (p < 0.001), 67% to trimethoprim (p < 0.001), and 58% had combined resistance to the latter two drugs (p < 0.001). Resistance patterns differed strongly by species, S. flexneri being more frequently resistant than S. sonnei. In 1983, all S. dysenteriae Type 1 isolates were resistant to ampicillin, chloramphenicol, tetracycline, and sulfonamides. Trimethoprim resistance increased from 31% (25/80) in 1983 to 96% (26/27) of the isolates in 1986 (p < 0.001). After the introduction of nalidixic acid as an alternative for trimethoprim-sulfamethoxazole, trimethoprim resistance decreased to 87%, during 1987 to 1992, and subsequently to 68% of the isolates in 1993. However, 20% of the isolates became resistant to nalidixic acid in 1993. Ampicillin and trimethoprim-sulfamethoxazole are no longer useful for the empirical treatment of shigellosis in Rwanda.

The molecular epidemiology of trimethoprim-sulphamethoxazole- resistance of Shigella flexneri in the Trakya region of Turkey.

Trimethoprim-sulphamethoxazole (SXT) resistance increased among Shigella flexneri isolates in 1995 relative to previous years, in the Trakya region, the European part of Turkey. Since this region is the entrance to Turkey from northern countries, a heavy traffic of travellers passing through should have been importing or exporting the resistant isolates. We studied the genetic basis and epidemiology of this resistance and monitored the clonal changes which have taken place in the meanwhile. During the study period, a total of 70 Shigella spp. were isolated. Of these 58 were S. flexneri, 10 were S. sonnei and two were S. boydii. S. dysenteriae was not isolated. Of S. flexneri isolates 32 were SXT, ampicillin, chloramphenicol and tetracycline resistant (pattern I), while two isolates were found to be resistant only to SXT (Pattern II). Transconjugation experiments revealed that an approximately 80 Kbp self-transmissible plasmid carried the SXT resistance genes in both groups. However, EcoRI and HindIII restriction patterns of the plasmids from resistance pattern I and resistance pattern II were different. Ribotypes of three randomly selected isolates from pattern I were identical and were distinguishable from the ribotype of the isolate from pattern II. We concluded that at least two different clones with different plasmids and resistance patterns were spreading in our territory.

Microbiological screening of Indian medicinal plants with special reference to enteropathogens.

The World Health Organisation (WHO) has recommended that all member states actively promote native medicines in their country. Ten Indian medicinal plants were screened for antibacterial activity specific to enteropathogens. Diffusion and dilution methods were used to measure the antibacterial activity. Allium sativum, Camellia sinensis, and Chamaesyce hirta showed higher activity when compared to the rest. They had a minimum bactericidal concentration (MBC) of < 100 micrograms/ml and gave inhibition zones of more than 2 cm. Among the pathogens studied, Vibrio cholerae and Shigella flexneri were found to be highly susceptible to the plant extracts.

Epidemiology of shigellosis among children exposed to cases of Shigella dysentery: a multivariate assessment.

We followed 1,756 young, rural Bangladeshi children less than five years of age for one month after identification of sentinel Shigella patients in their neighborhoods. Two hundred nineteen (12%) children developed Shigella diarrhea (shigellosis) and 227 (13%) developed culture-negative dysentery. Shigella flexneri (60%) and S. dysenteriae, type 1 (15%) were the most common isolates among shigellosis cases. Within individual neighborhoods, there was poor agreement (Kappa = 0.21) between Shigella species isolated from sentinel patients and from additional cases detected during surveillance. The risk of shigellosis increased substantially after infancy and peaked in the second year of life. Severe stunting, as assessed by height-for-age, was associated with an increased risk of shigellosis (adjusted odds ratio [ORa] = 1.67, 95% confidence interval [CI] = 1.09-2.57, P < 0.05), while breast-feeding was protectively associated (ORa = 0.40, 95% CI = 0.24-0.69, P < 0.001). Only 43% of the shigellosis cases reported bloody stools; frank dysentery occurred more frequently in S. dysenteriae 1 infections than in S. flexneri infections (ORa = 5.04, 95% CI = 1.76-14.48, P < 0.01), and was also associated with severe stunting (ORa = 2.16, 95% CI = 1.01-4.58, P < 0.05). Our findings show that the high risk of shigellosis in residentially exposed Bangladeshi children results from multiple Shigella strains circulating concurrently within the same neighborhood; demonstrate that the risk is notably modified by host age, nutritional status, and dietary patterns; and illustrate that the classic picture of dysentery is relatively infrequent and is correlated with the infecting species and with host nutritional status.