Antimicrobial susceptibility of Shigella from a rural community in Bangladesh

Of the 63 Shigella strains isolated from stool cultures from 200 patients who attended a district hospital in Bangladesh with bloody diarrhoea, 37 (59%) were S. dysenteriae type 1, 25 (39%) were S. flexneri and only one (2%) was S. sonnei. Over half (54%) of the Shigella isolates came from children aged < 10 years. Most (89%) of the isolates of S. dysenteriae type 1 were resistant to ampicillin, cotrimoxazole, nalidixic acid, tetracycline and chloramphenicol. Although many (60%) of the isolates of S. flexneri were resistant to ampicillin and cotrimoxazole, only 4% of them were resistant to nalidixic acid. However, all of the S. dysenteriae and S. flexneri were sensitive to ciprofloxacin. The need for periodic monitoring to determine the resistance pattern in remote areas is emphasised.     

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.     

Recognition and management of catheter-induced pulmonary artery rupture

The use of PCR to amplify a specific virA gene fragment serves as a highly specific and sensitive method to detect virulent bacteria of the genus Shigella and enteroinvasive Escherichia coli. Amplification of a 215-bp DNA band was obtained by using isolated genomic DNA of Shigella, individual cells of Shigella dysenteriae, and mayonnaise contaminated with S. dysenteriae. Moreover, a multiplex PCR with specific (virA) and bacterium-restricted (16S ribosomal DNA) primers generated an amplification product of approximately 755 bp for all bacteria tested and an additional 215-bp product for Shigella and enteroinvasive E. coli.     

Structure of the Shigella dysenteriae haem transport locus and its phylogenetic distribution in enteric bacteria

The ability to transport and use haemin as an iron source is frequently observed in clinical isolates of Shigella spp. and pathogenic Escherichia coli. We found that many of these haem-utilizing E. coli strains contain a gene that hybridizes at high stringency to the S. dysenteriae type 1 haem receptor gene, shuA. These shuA-positive strains belong to multiple phylogenetic groups and include clinical isolates from enteric, urinary tract and systemic infections. The distribution of shuA in these strains suggests horizontal transfer of the haem transport locus. Some haem-utilizing pathogenic E. coli strains did not hybridize with shuA, so at least one other haem transport system is present in this group. We also characterized the chromosomal region containing shuA in S. dysenteriae. The shuA gene is present in a discrete locus, designated the haem transport locus, containing eight open reading frames. Several of the proteins encoded in this locus participate with ShuA in haem transport, as a Salmonella typhimurium strain containing the entire haem transport locus used haem much more efficiently than the same strain containing only shuA. The haem transport locus is not present in E. coli K-12 strains, but the sequences flanking the haem transport locus in S. dysenteriae matched those at the 78.7 minute region of E. coli K-12. The junctions and flanking sequences in the shuA-positive pathogenic E. coli strains tested were nearly identical to those in S. dysenteriae, indicating that, in these strains, the haem transport locus has an organization similar to that in S. dysenteriae, and it is located in the same relative position on the chromosome.     

High percentage of antibiotic resistance in Shigella infections in children in Cura?ao

OBJECTIVE: To evaluate antimicrobial treatment and resistance in clinical childhood shigellosis. DESIGN: Retrospective. SETTING: St. Elisabeth Hospital, Willemstad, Cura?ao, Dutch Antilles. METHOD: From September 1991 through August 1995 shigellosis was diagnosed in 93 children out of 456 hospitalised with gastroenteritis (S. flexneri in 60, S. sonnei in 32, S. dysenteriae in 1). From hospital and laboratory records, the clinical presentation, antibiotic treatment and duration of hospitalization were indexed as well as the antibacterial resistance pattern of shigellae. RESULTS: Of the hospitalised children 52 (56%) were treated with antibiotics. Ampicillin was given most frequently (71%), followed by the combination trimethoprim-sulfamethoxazole (25%). Isolated shigellae were resistant to ampicillin in 52% and to trimethoprim-sulfamethoxazole in 34%; 42% of the antibiotic treatments were in accordance with susceptibility of the isolated Shigella. CONCLUSION: A high percentage of shigellae isolated on Cura?ao was resistant to the most frequently used antibiotics ampicillin and trimethoprim-sulfamethoxazole.     

Impact of either elevated or decreased levels of cytochrome bd expression on Shigella flexneri virulence

Shigella spp. are the major cause of bacillary dysentery worldwide. The pathogenic process involves bacterial invasion and lysis of the phagocytic vacuole, followed by replication and movement within the cell cytoplasm and, ultimately, spread directly into adjacent cells. This study demonstrates that S. flexneri cytochrome bd expression is necessary for normal intracellular survival and virulence. Cytochrome bd is one of two terminal oxidases in the bacterial respiratory chain that reduce molecular oxygen to water, utilizing intermediates shuttled through the electron transport chain. S. flexneri mutants that contain a disruption in the cydC locus, which leads to defective cytochrome bd expression, or in the riboflavin (ribE) or ubiquinol-8 (ubiH) biosynthetic pathway, which leads to elevated cytochrome bd expression, were evaluated in intracellular survival and virulence assays. The cydC mutant formed significantly smaller plaques, had significantly decreased intracellular survival, and had a 100-fold increase in lethal dose for mice compared with the wild type. The ribE and ubiH mutants each formed significantly larger plaques and had a 10-fold decrease in lethal dose for mice compared with the wild type. The data indicate that expression of cytochrome bd is required for S. flexneri intracellular survival and virulence.     

Antitumor activity of bacterial endotoxins and their subunits in in vitro test

The tumoricidal effect of endotoxins and their subunits of Shigella dysenteriae serovar 1 of both growth forms and certain other representatives of the Enterobacteriaceae family was tested against Németh-Kellner mouse lymphoma cells using an in vitro assay based on the use of sodium chromate solution yielding labelled hexavalent 51Cr ions. The most effective in vitro activity was evidenced in both growth forms by S. dysenteriae 1 lipopolysaccharide-protein complex (LPSP) (76-92%), lipid A and lipoid B isolated from LPS (77-82%) and lipid A and lipoid B from LPSP (53-70%). A direct dependence of the level of the Limulus test and pyrogenicity on the tumoricidal activity of a preparation was not demonstrated. The influence of selected cations (Cu, Fe, Ca, Mg, Zn) bound to selected substances on antitumor activity was monitored. The method of probit analysis is recommended as it enables estimation, based on a number of concentrations, of the regression line of probable effectiveness of a given preparation.     

Strategy for cross-protection among Shigella flexneri serotypes

Based upon the lipopolysaccharide (LPS) structure and antigenicity of Shigella group B, a strategy for broad cross-protection against 14 Shigella flexneri serotypes was designed. This strategy involves the use of two S. flexneri serotypes (2a and 3a), which together bear the all of the major antigenic group factors of this group. The novel attenuated strains used in these studies were S. flexneri 2a strain CVD 1207 (DeltaguaB-A DeltavirG Deltaset1 Deltasen) and S. flexneri 3a strain CVD 1211 (DeltaguaB-A DeltavirG Deltasen). Guinea pigs were immunized with an equal mixture of these strains and later challenged (Sereny test) with a wild-type S. flexneri serotype 1a, 1b, 2b, 4b, 5b, Y, or 6 strain of demonstrated virulence in the same model. Guinea pigs that were immunized with these two vaccine strains produced serum and mucosal antibodies that cross-reacted with all the S. flexneri serotypes tested (except of S. flexneri serotype 6) as assessed by enzyme-linked immunosorbent assay, immunoblotting, and slide agglutination. Furthermore, the combination vaccine conferred significant protection against challenge with S. flexneri serotypes 1b, 2b, 5b, and Y but not with serotypes 1a, 4b, or (as predicted) 6.     

Isolation of Shigella dysenteriae serotypes 11, 12, and 13 from patients with diarrhea in Bangladesh

Nine isolates of bacteria biochemically resembling Shigella dysenteriae but not belonging to the 10 recognized serotypes were isolated from patients with diarrhea in Bangladesh. Further studies suggested that two, one, and six isolates belonged to the recently recognized S. dysenteriae serotypes 11, 12, and 13, respectively.     

Aplasia cutis congenita: report of one case

CONTEXT: Shigella dysenteriae type 2 is rare in the United States, and outbreaks associated with this pathogen are uncommon. OBJECTIVE: To determine the magnitude and source of an outbreak of S dysenteriae type 2. DESIGN: Retrospective cohort. SETTING: Laboratory of a large medical center. PATIENTS: Case patients were identified as laboratory workers who had diarrhea on or after October 28 and a positive stool culture or temperature greater than 37.8 degrees C. Laboratory workers with diarrhea only were probable case patients. MAIN OUTCOME MEASURES: We interviewed laboratory staff and performed identification, serotyping, and pulsed-field gel electrophoresis on isolates from case patients, implicated food, and laboratory stock culture. RESULTS: From October 29 through November 1, a total of 12 (27%) of 45 laboratory staff developed severe, acute diarrheal illness; 8 had S dysenteriae isolated from stool and 4 were hospitalized. All case patients reported having eaten muffins or doughnuts placed in the staff break room on October 29. Pulsed-field gel electrophoresis showed stool isolates from 9 case patients were indistinguishable from S dysenteriae type 2 recovered from an uneaten muffin and from the laboratory's stock strain, a portion of which was missing. CONCLUSIONS: The source of the outbreak was most likely the laboratory's stock culture, which was used to contaminate the pastries. Results of this investigation underscore the need for adequate precautions to prevent inadvertent or intentional contamination from highly pathogenic laboratory specimens.     

"Black holes" and bacterial pathogenicity: a large genomic deletion that enhances the virulence of Shigella spp. and enteroinvasive Escherichia coli

Plasmids, bacteriophages, and pathogenicity islands are genomic additions that contribute to the evolution of bacterial pathogens. For example, Shigella spp., the causative agents of bacillary dysentery, differ from the closely related commensal Escherichia coli in the presence of a plasmid in Shigella that encodes virulence functions. However, pathogenic bacteria also may lack properties that are characteristic of nonpathogens. Lysine decarboxylase (LDC) activity is present in approximately 90% of E. coli strains but is uniformly absent in Shigella strains. When the gene for LDC, cadA, was introduced into Shigella flexneri 2a, virulence became attenuated, and enterotoxin activity was inhibited greatly. The enterotoxin inhibitor was identified as cadaverine, a product of the reaction catalyzed by LDC. Comparison of the S. flexneri 2a and laboratory E. coli K-12 genomes in the region of cadA revealed a large deletion in Shigella. Representative strains of Shigella spp. and enteroinvasive E. coli displayed similar deletions of cadA. Our results suggest that, as Shigella spp. evolved from E. coli to become pathogens, they not only acquired virulence genes on a plasmid but also shed genes via deletions. The formation of these "black holes," deletions of genes that are detrimental to a pathogenic lifestyle, provides an evolutionary pathway that enables a pathogen to enhance virulence. Furthermore, the demonstration that cadaverine can inhibit enterotoxin activity may lead to more general models about toxin activity or entry into cells and suggests an avenue for antitoxin therapy. Thus, understanding the role of black holes in pathogen evolution may yield clues to new treatments of infectious diseases.     

Resistance to antibiotics of Shigella strains isolated in Somalia

The resistance to antibiotics of 240 Shigella strains isolated in Somalia from 1973 to 1976 was studied. Many strains, particularly those of Shigella dysenteriae type 1, were found to be resistant to more than one drug. In view of their resistance to ampicillin, chloramphenicol, streptomycin, tetracycline, and sulfonamides, it is suggested that polymyxin B or M sulfate - which have proved to be effective in vivo - should be used for the treatment of clinically typical cases of bacillary dysentery.     

Comparative studies on activities of antimicrobial agents against causative organisms isolated from patients with urinary tract infections (1995). II. Background of patients

Clinical background was investigated on patients with urinary tract infections (UTIs) from whom 785 bacterial strains were isolated in 11 hospitals during the period from June, 1995 through May, 1996. 1. Distributions of age and sex of patients and type of infections. Among the patients examined, those with ages 50 years or older were the most frequent (males: 80.5%, females: 69.7%), and, among females, those with ages in the 20's were 12.6%. With regard to types of infections, more than a half of infections among males were of complicated types, but most of infections among females were of uncomplicated types, especially among females of ages less than 60 years. 2. Ages of patients and types of pathogens. The higher the ages of patients, the lesser became the isolation frequencies of Proteus spp. and Serratia spp., but the higher were those of Klebsiella spp. and Pseudomonas spp. 3. Effect of antibiotic use on isolation frequencies of pathogens. Use of antibiotics decreased pathogens isolated from patients with uncomplicated UTIs drastically (237 isolates before antibiotics compared to 33 after). Even isolated pathogens from patients with complicated UTIs decreased drastically with the use of antibiotics when indwelling catheters were not in use (200 isolates before antibiotics compared to 83 after), but when indwelling catheters were in use, antibiotics apparently failed to decrease the isolation frequency. 4. Surgical procedures and types of causative organisms for UTIs. Escherichia coli was the most frequently isolated organism from uncomplicated cases of UTIs. From cases of complicated UTIs without indwelling catheters, Enterococcus faecalis was the most frequently isolated, followed by E. coli, P. aeruginosa and Klebsiella spp. When a surgical procedures were not done, E. coli was isolated most frequently. From cases of complicated UTIs with indwelling catheters, P. aeruginosa, E. faecalis and S. aureus were the organisms that were mainly isolated, with isolation frequencies of 23.9%, 17.3% and 12.7%, respectively. When no surgical procedures were used, isolation frequencies of P. aeruginosa, Klebsiella spp. and E. faecalis were 25.7%, 14.3% and 14.3%, respectively.     

Xylose lysine deoxycholate agar for the isolation of Salmonella and Shigella from clinical specimens

Xylose lysine deoxycholate (XLD) agar was more efficient for the detection of Shigella sonnei than Salmonella-Shigella (SS) agar and Drigalski agar, XLD was slightly more efficient for the detection of Salmonellae by direct plating than SS agar. Xylose lysine deoxycholate agar is proposed as the second selective plating medium for Shigellae isolation. It is also a useful second selecting plating medium for the isolation of Salmonellae serotypes, which form non-characteristic colonies on Bismuth-Sulfite agar. Efficiency comparisons between 4 direct plating media and one enrichment medium were made during the period of 3 years by analysing 21793 fresh clinical stool specimens. In that time 1394 Salmonella and 519 Shigella strains were isolated.     

Identification of Shigella flexneri subserotype 1c in rural Egypt

In a population-based study of diarrhea in rural, northern Egypt, 60 Shigella flexneri strains were identified, of which 10 could not be definitively serotyped. Serological analysis with commercial reagents suggested that they were serotype 1, but the strains failed to react with subserotype 1a- or 1b-specific antibodies. All 10 strains reacted with MASF 1c, a monoclonal antibody specific for a provisional S. flexneri subserotype, 1c, first identified in Bangladesh and not previously detected outside of that region. Our results show that S. flexneri subserotype 1c is not unique to Bangladesh and that the inability to detect it may reflect both the limited use of suitable screening methods and the rarity of this subserotype.     

Recognition of three epitopic regions on invasion plasmid antigen C by immune sera of rhesus monkeys infected with Shigella flexneri 2a

The invasive ability of Shigella spp. is correlated with the expression of several plasmid-encoded proteins, including invasion plasmid antigen C (IpaC). By characterizing the antigenic structure of IpaC with monoclonal antibodies and convalescent-phase sera, it may be possible to determine the physical location of specific epitopes as well as the involvement of epitopes in a protective immune response or the host's susceptibility to disease. By using overlapping octameric synthetic peptides, which together represent the entire IpaC protein, the precise linear sequence of four surface-exposed epitopes was defined for four IpaC monoclonal antibodies. Furthermore, 17 unique peptide epitopes of IpaC were mapped by using 9-day-postinfection serum samples from 13 rhesus monkeys challenged with Shigella flexneri 2a. Each individual recognized a somewhat different array of IpaC peptide epitopes after infection with shigellae. However, the epitopes were clustered within three regions of the protein: region I (between amino acid residues 1 and 61), region II (between amino acid residues 177 and 258), and region III (between amino acid residues 298 and 307). Region II was recognized by 92% of S. flexneri-infected individuals and was considered to be a highly immunogenic region. Animals asymptomatic for shigellosis after challenge with S. flexneri recognized peptide epitopes within all three epitopic regions of IpaC, whereas symptomatic animals recognized peptides in only one or two of the epitopic regions. Antibody from monkeys challenged with S. sonnei recognized IpaC peptide epitopes which fell within and outside the three S. flexneri epitopic regions. While numerous potential epitopes exist on the IpaC protein, the identification of three regions in which epitopes are clustered suggests that these regions are significant with respect to the immune response and to subsequent pathogenesis postinfection.     

Infectious etiology of diarrheal morbidity in a Senegalese region of high exposure to Schistosoma mansoni

Endemic schistosomiasis due to Schistosoma mansoni has been observed in Richard-Toll (The Senegal River basin) in Senegal since 1990. Because of its high prevalence, schistosomiasis is assumed to be the cause of most cases of diarrhea observed in the region. The purpose of the present study carried out within the framework of the ESPOIR program for control of bilharziasis in the Senegal River region was to confirm the exact etiology of diarrhea in the region. A total of 109 subjects presenting diarrhea including 57 children under the age of 5 years were included in the study. In all cases, stool examination using appropriate techniques was performed to detect bacterial, viral, and parasitic agents. Schistosoma mansoni was identified in 47 cases (43.1%). Stool cultures were positive in 28 cases (25.6%) for Escherichia coli (n = 9), Shigella spp. (n = 18), and Salmonella spp. (n = 1). With regard to Shigella, a predominance of the Shigella dysenteriae type I stereotype (10/18) and a high incidence of co-infection involving Shigella spp. and Schistosoma was noted. Rotavirus infection was observed in 6 cases involving subjects under the age of 5 years. The relative incidence of the different infectious agents varied widely in function of age. This study in an endemic area of bilharziasis in Senegal demonstrates that Schistosoma mansoni should not be assumed to account for all cases of diarrhea occurring in the area.     

Shigellae isolated in 1997--plasmid profiles and antibiotic resistance

INTRODUCTION: Shigella spp is one of the most frequently isolated bacteria causing acute diarrhea with us. Genetics of pathogenicity of Shigella spp. includes chromosomal and plasmid genes. Most virulence factors are coded by invasion plasmid antigen genes residing on a 180-230 MDa plasmid. There is a big problem with multiple resistance of Shigella spp. strains, which is mostly plasmid-borne. Genetic analysis of bacterial cells, that is plasmid profile analysis, is important for investigation of sources and ways of spreading of the infection. All isolates originating from the same clone have identical plasmid profiles, i.e. number and size of plasmids. The aim of the investigation was: comparing the type of resistance to antimicrobical agents found in epidemic and nonepidemic. Shigella strains isolated in 1997, analyzing plasmid profiles of these isolates and confirming their epidemic connection. MATERIAL AND METHODS: Susceptibility to antibiotics was examined by a standard disc-diffusion method. Plasmid profiles of 40 strains (20 from the outbreak and 20 from sporadic cases) were tested using a method of alkaline lysis by Birnboim and Doly followed by electrophoresis in agarose gel. RESULTS: Shigella strains were resistant to antimicrobial agents which are most commonly used. Epidemic isolates shared the same resistance type, they were resistant to cephalexin, streptomycin and co-trimoxazole. The dominant type of resistance of nonepidemic strains was to ampicillin, streptomycin and co-trimoxazole. Strains isolated during the outbreak had identical plasmid profiles (2 plasmid bands of 55 and 1.5 MDa). Non-epidemic isolates had different plasmid profiles as well as type of resistance. CONCLUSION: Strains of Shigella spp. isolated during an outbreak had the same type of resistance and the same plasmid profiles, which indicated their origin from the same clone. The plasmid profile analysis is a reliable and precise method for determination of epidemic connection of Shigella isolates.     

Serum antibody to lipopolysaccharide antigens of Shigella species among U.S. military personnel deployed to Saudi Arabia and Kuwait during Operations Desert Shield and Desert Storm

During Operations Desert Shield and Desert Storm, U.S. troops were at high risk of diarrheal disease due to Shigella spp., particularly Shigella sonnei. In order to better understand the serologic response to Shigella infection, 830 male U.S. combat troops were evaluated before and after the deployment to Saudi Arabia and Kuwait for immunoglobulin A (IgA) and IgG anti-Shigella lipopolysaccharide (LPS) (antibody to S. sonnei form I and Shigella flexneri serotypes 1a, 2a, and 3a) in serum. Just before deployment, 10.3% of the subjects were seropositive for IgA and 18.3% were positive for IgG anti-Shigella LPS. IgA and IgG anti-LPS antibody levels in serum prior to deployment were significantly associated with nonwhite race and ethnicity, birth outside the United States, and antibody to hepatitis A virus and Helicobacter pylori. During the deployment, which lasted for a mean of 131 days, 60% of the subjects reported at least one episode of diarrhea and 15% reported an episode of diarrhea with feverishness; also, 5.5% of the subjects exhibited IgA seroconversion to Shigella LPS and 14.0% exhibited IgG seroconversion. A significant association between the development of diarrheal symptoms and either positive predeployment anti-LPS antibody or seroconversion was not found. These data indicate that in this population of U.S. Desert Storm troops who were at high risk of Shigella infection, there was no apparent relation between IgA or IgG anti-Shigella LPS in serum and diarrheal disease.