Fecal carriage of vancomycin- and ampicillin-resistant Enterococci observed in Swedish adult patients with diarrhea but not among healthy subjects.

During a 1-y prospective study between 1 October 1996 and 30 September 1997, fecal samples from 786 adult patients with diarrhea and 203 healthy control subjects were screened for vancomycin-resistant Enterococci (VRE) and ampicillin-resistant Enterococci (ARE). The carriage rates of VRE and ARE were 0.4% and 6%, respectively among patients and 0% among controls. The 3 VRE isolates were all VanA and were obtained from patients who had been abroad (Thailand, Spain, France) within the previous 3 months. Thirteen of the 45 patients with ARE (29%) had been abroad within 2 weeks of the onset of diarrhea. These findings suggest a potential risk of introduction of antibiotic-resistant Enterococci in Swedish hospitals by patients receiving treatment for diarrhea after traveling abroad.

Enteropathogens in adult patients with diarrhea and healthy control subjects: a 1-year prospective study in a Swedish clinic for infectious diseases.

A 1-year prospective study was conducted to identify enteropathogens in adults with diarrhea (n=851) and in healthy control subjects (n=203) by use of conventional laboratory methods. Virulence factor genes for diarrheagenic Escherichia coli were detected by polymerase chain reaction. Enteropathogens were identified in 56% of patients and 16% of control subjects. The isolation rate was 65% for patients with symptoms for <1 week and for travelers; >1 pathogen was found in 11% of patients. The most frequent enteropathogens were Campylobacter (13% of patients), Clostridium difficile (13%), enterotoxigenic Escherichia coli (8%), Salmonella (7%), Shigella (4%), Blastocystis hominis (4%), calicivirus (3%), rotavirus (3%), enteroaggregative E. coli (2%), Aeromonas (2%), Giardia intestinalis (2%), Cryptosporidium (2%), and astrovirus (2%). Less frequently isolated (< or =1% of patients) were verotoxigenic E. coli, enteropathogenic E. coli, enteroinvasive E. coli, Entamoeba histolytica/Entamoeba dispar, microsporidia, and adenovirus. Fifty percent of the patients were hospitalized, and 43% needed intravenous fluids. The median duration of diarrhea was 14 days. Clinical features were not helpful for predicting the etiology of diarrhea.

New species-related MIC breakpoints for early detection of development of resistance among gram-negative bacteria in Swedish intensive care units.

The frequency of decreased antibiotic susceptibility among 534 Gram-negative aerobic bacilli from patients admitted to intensive care units at eight hospitals in Sweden during 1997 was evaluated. MICs of cefepime, ceftazidime, ceftriaxone, ciprofloxacin, gentamicin, imipenem and piperacillin-tazobactam were determined using Etest. Reduced susceptibility (resistant and intermediate/indeterminate susceptible strains) was defined according to the MIC breakpoints of the British Society for Antimicrobial Chemotherapy (BSAC), the National Committee for Clinical Laboratory Standards (NCCLS) and the new species-related breakpoints of the Swedish Reference Group for Antibiotics (SRGA). The BSAC/NCCLS/SRGA breakpoints for susceptible category (mg/L) of Enterobacteriaceae are: cefepime, not available (NA)/8/0.5; ceftazidime, 2/8/2; ceftriaxone, NA/8/0.5; ciprofloxacin, 1/1/0.12; gentamicin, 1/4/2; imipenem, 4/4/1; and piperacillin-tazobactam, NA/16/16. The most frequently isolated organisms were Escherichia coli (n = 160; 30%), Klebsiella spp. (n = 84; 16%), Enterobacter spp. (n = 77; 14%), Pseudomonas aeruginosa (n = 64; 12%) andProteus spp. (n = 28; 5%). Decreased susceptibility among E. coliusing the BSAC/NCCLS/SRGA respective breakpoints (%) were: cefepime, NA/0/2; ceftazidime, 2/2/2; ceftriaxone, NA/1/2; ciprofloxacin, 2/2/8; gentamicin, 21/0/3; imipenem, 0/0/2; and piperacillin-tazobactam, NA/4/4. Corresponding levels of decreased susceptibility (%) among Klebsiellaspp. were: cefepime, NA/0/5; ceftazidime, 2/1/2; ceftriaxone, NA/1/10; ciprofloxacin, 4/4/19; gentamicin, 25/2/5; imipenem, 0/0/0; and piperacillin-tazobactam, NA/10/10; and among Enterobacter spp. were: cefepime, NA/1/19; ceftazidime, 30/29/30; ceftriaxone, NA/30/36; ciprofloxacin, 3/3/15; gentamicin,18/0/0; imipenem, 0/0/5; and piperacilllin-tazobactam, NA/27/27. In conclusion, the species-related SRGA breakpoints detected Gram-negative isolates with decreased susceptibility in comparison with the native population with higher frequency than did the NCCLS breakpoints. The BSAC breakpoints for susceptible organisms were similar to NCCLS for ciprofloxacin and imipenem, and similar to SRGA for ceftazidime but lower than both NCCLS and SRGA for gentamicin, causing a much higher frequency of decreased susceptibility to gentamicin.

Prevalence of enterotoxigenic Bacteroides fragilis in adult patients with diarrhea and healthy controls.

Enterotoxigenic strains of Bacteroides fragilis (ETBF) have been associated with diarrheal diseases in animals and humans. The enterotoxin of ETBF induces fluid changes in ligated intestinal segments and a cytotoxic response in HT29/C1 cells. An assay based on immunomagnetic-beads separation in combination with PCR was used to detect ETBF in fecal samples from patients with diarrhea and healthy Swedish adults. A total of 922 fecal samples were analyzed in this study, including 728 samples from patients with diarrhea and 194 samples from controls. ETBF was detected in 195 of 728 patients (26.8%) and 24 of 194 healthy controls (12.4%). The difference between the two groups was statistically significant (P<.01). ETBF was the only potential diarrheal agent in 91 (12.5%) of 728 patients. All ETBF-positive samples from patients and controls were also positive in the HT29/C1 assay. The data show high carriage of ETBF in Swedish adults, which might be associated with diarrheal disease.

Age-related prevalence of Shigella and Salmonella antibodies and their association with diarrhoeal diseases in Peruvian children.

Shigella and Salmonella antibodies in relation to diarrhoea were studied in a cohort of 413 children between 2 and 27 months of age in peri-urban Lima, Peru. Blood samples were obtained at 2, 3 and 12 months of age. Antibody titres against lipopolysaccharide from Shigella flexneri serotype Y, Shigella dysenteriae serotype 1, Shigella sonnei, Salmonella serogroups AO, BO, DO, and Shigella Ipa and Salmonella typhi Vi antigens were measured by enzyme immunoassay. IgG titres against S. flexneri and Shigella Ipa were higher at 2 than at 3 or 12 months of age (p=0.001), while the changes in IgG titres against S. dysenteriae, S. sonnei and Salmonella were not pronounced. IgA and IgM titres against S. flexneri, Shigella Ipa, S. dysenteriae, S. sonnei and Salmonella were significantly higher at 12 than at 2 or 3 months of age (p=0.001). Stool samples were obtained from children in 64% of all diarrhoeal episodes. Shigella spp. were isolated from 20% of the children during the first 2 y of life and Salmonella in 3%. Most isolates were from children at 13-24 months of age (78%). IgG antibodies at 12 months of age did not protect against shigellosis during the second year of life.

Construction and characterization of a live attenuated vaccine candidate against Shigella dysenteriae type 1.

Vaccine candidates against Shigella dysenteriae type 1, which is associated with the most severe cases of bacillary dysentery, were constructed. The rfp and rfb gene clusters, which code for S. dysenteriae 1 O antigen biosynthesis, were randomly integrated into either the chromosome or the virulence plasmid of the rough attenuated Shigella flexneri aroD strain SFL124-27 with a minitransposon carrying an arsenite resistance selection marker. The recombinant clones efficiently expressed the recombinant O antigen, exhibited a normal growth pattern, were able to invade and survive within eukaryotic cells to the same extent as the parental strain, and expressed the recombinant antigen within invaded cells. A clone was selected as the vaccine candidate, which was demonstrated to be immunogenic and safe in animal models, leading to 47% full protection and 53% partial protection against challenge with the wild-type strain.

Safety and immunogenicity study of the auxotrophic Shigella flexneri 2a vaccine SFL1070 with a deleted aroD gene in adult Swedish volunteers.

The live auxotrophic Shigella flexneri 2a vaccine strain SFL1070 with a deleted aroD gene was given orally to 37 adult Swedish volunteers who received three doses within 5 days. Each dose comprised 1 x 10(5) (n = 9), 1 x 10(7) (n = 10), 1 x 10(8) (n = 9) or 1 x 10(9) (n = 9) c.f.u. S. flexneri SFL1070. One volunteer vaccinated with 1 x 10(7) and three vaccinated with 1 x 10(8) c.f.u. reported mild gastrointestinal symptoms after the first dose. Vaccination with 1 x 10(9) c.f.u. caused abdominal pain and watery diarrhoea in four volunteers who all recovered spontaneously within 72 h. S. flexneri SFL1070 was not recovered from volunteers given 1 x 10(5) c.f.u., but was shed in faeces by six volunteers vaccinated with 1 x 10(7), by all nine vaccinated with 1 x 10(8), and by seven volunteers vaccinated with 1 x 10(9) c.f.u. The mean excretion time was 2.6 (range 0-4) days in the 1 x 10(8) and the 1 x 10(9) groups. Serum antibody responses against either S. flexneri 2a and Y lipopolysaccharides (LPSs) or Shigella invasion plasmid antigens (Ipa) were seen in eight volunteers vaccinated with 1 x 10(9) (p < 0.01 to p < 0.05 for mean relative titres of IgA and IgG against S. flexneri 2a and Y LPSs), in four vaccinated with 1 x 10(8), and in two and one volunteers each vaccinated with 1 x 10(7) and 1 x 10(5) c.f.u. of S. flexneri SFL1070. Intestinal sIgA responses to the same antigens were elicited in all volunteers in the 1 x 10(9) and the 1 x 10(8) groups, and in six and one volunteers vaccinated with 1 x 10(7) and 1 x 10(5) c.f.u., respectively. The sIgA responses against S. flexneri 2a and Y LPSs were significant in all but the 1 x 10(5) group (p < 0.01 to p < 0.05). Significant antibody-secreting cell (ASC) responses specific to S. flexneri 2a LPS were seen in peripheral blood from eight volunteers each in the 1 x 10(9) and 1 x 10(8) groups and from five volunteers vaccinated with 1 x 10(7) c.f.u. (p < 0.01 to p < 0.05). The number of volunteers showing anti-Shigella Ipa ASC responses in these groups were five (p < 0.01 to p < 0.05), three and one, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunopathological patterns in the rectal mucosa of patients with shigellosis: expression of HLA-DR antigens and T-lymphocyte subsets.

Expression of HLA-DR antigens and infiltration of T-lymphocyte subsets (CD4, CD8), cell activation marker (CD25), B cells (CD20), macrophages (CD68 and Ber-Mac 3) and natural killer cells (CD56) in the rectal mucosa of patients with bacillary dysentery and in healthy controls were studied in an effort to interpret the immunopathological changes taking place in the rectal mucosa during the acute phase of shigellosis. The epithelium of the rectal mucosa from 21 of 32 patients was HLA-DR+. Conventional histology showed acute inflammation in 16 of these patients, chronic inflammation in 3, and in 2 histology was normal. In 7 of 20 controls the epithelium was HLA-DR+; 4 of these 7 were found to suffer from chronic inflammation, whilst in 3 the mucosa was normal. The number of HLA-DR+ intraepithelial lymphocytes in biopsies from patients with Shigella infection was significantly higher (p = 0.005) than in controls. The infiltration of CD8+ cells in the surface epithelium and in the lamina propria, and of CD4+ cells in the lamina propria alone, was significantly higher (p < 0.001) in patients than in controls. The results demonstrate that infiltration of T cells with suppressor/cytotoxic or helper/inducer phenotype in the epithelium and in the lamina propria in Shigella-infected patients may be related to the induction of HLA-DR expression in non-lymphoid cells during acute Shigella infection.

Safety and immunogenicity of the live oral auxotrophic Shigella flexneri SFL124 in adult Vietnamese volunteers.

The live, auxotrophic dependent Shigella flexneri Y vaccine strain SFL124 with a deleted aroD gene was tested in 30 healthy adult male Vietnamese volunteers. A single dose of 2 x 10(9) live bacteria was given orally to 15 volunteers, whereas 15 received three doses every other day. None of the volunteers reacted with fever or diarrhoea and SFL124 was excreted by all for a mean of 2.8 (single dose) and 2.6 (three doses) days. A total of 27 of 30 (90%) and 26 of 30 (87%) responded with significantly (0.001 < p < 0.01) increased antibody-secreting cell (ASC) numbers against Shigella flexneri Y lipopolysaccharide (LPS) and invasion plasmid-coded antigens (Ipa). A faecal IgA antibody response to LPS and Ipa was seen in 20 of the 30 (67%) volunteers against both antigens. Serum antibody responses were seen in 23 of 30 (77%) against the LPS and in 17 of the 30 against Ipa. The three-dose schedule elicited only somewhat stronger immune responses than the single-dose schedule. A booster dose of 2 x 10(9) live bacteria was given to half of the volunteers in each group after 6 months, the other half received the same dose after 12 months. Following the booster at 6 or 12 months (i) the excretion of SFL124 was significantly shorter (p < 0.05) than after primary vaccination; (ii) the anti-S. flexneri LPS and anti-Ipa faecal sIgA titres were significantly higher (p < 0.05 to p < 0.01) than after primary vaccination; (iii) the anti-LPS and anti-Ipa ASC responses were significantly lower (p < 0.05) and of shorter duration than after primary vaccination, and (iv) the serum anti-LPS and anti-Ipa responses were significantly elevated (p < 0.05) and similar to those seen after primary vaccination. The results indicate that SFL124 is a safe, live vaccine strain with a negligible reactogenicity in adults living in a Shigella endemic area. SFL124 induces specific immune responses against LPS and Ipa with a mucosal memory lasting for at least 1 year.

AroD deletion attenuates Shigella flexneri strain 2457T and makes it a safe and efficacious oral vaccine in monkeys.

The aromatic-dependent live Shigella flexneri 2a vaccine strain SFL1070, with a deleted aroD gene, had a much reduced intracellular growth in HeLa cells compared with its parent strain S. flexneri 2457T. S. flexneri SFL1070 gave no adverse effects in eight Macaca fascicularis monkeys orally vaccinated with four doses of 1 x 10(11) live bacteria within a 5-week period, whereas S. flexneri 2457T caused dysentery in all eight non-vaccinated monkeys. Thus the aromatic dependency rendered S. flexneri SFL1070 significantly attenuated (p = 0.00008). Significant intestinal S. flexneri lipopolysaccharide (LPS)-specific sIgA responses were seen in seven of eight vaccinated monkeys (p < 0.01) after four doses with SFL1070. However, serum IgG or IgA responses to various S. flexneri LPS antigens and the invasion plasmid antigens (Ipa-s) were seen in only four of eight vaccinated monkeys. The serum IgG titre increases against S. flexneri Y and 2a LPS reached significant levels (p < or = 0.05). All but one of the vaccinated monkeys were protected against oral challenge with 1 x 10(10) or 1 x 10(11) live S. flexneri 2457T given 2 weeks after the last vaccination. The protection was highly significant (p = 0.0007) as all non-vaccinated monkeys challenged with equal doses of strain 2457T developed dysentery. Three of them succumbed. Challenge infection of vaccinated monkeys elicited serum IgA and IgG responses to the homologous S. flexneri 2a LPS in three monkeys each (0.005 < or = p < or = 0.025). Serum IgA and IgG responses to the Ipa-s were seen in five and four monkeys each (0.01 < p < or = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Auxotrophic live oral Shigella flexneri vaccine protects monkeys against challenge with S. flexneri of different serotypes.

The aromatic-dependent live Shigella flexneri Y strain SFL114, attenuated by a Tn10-inactivated aroD gene, was given as an oral vaccine to 14 Macaca fascicularis monkeys. A significant clinical attenuation of SFL114 was seen (p = 0.0058) as all vaccinated monkeys tolerated 2 x 10(10)-1 x 10(11) bacteria of SFL114, whereas four out of seven monkeys orally given 1 x 10(11) of the virulent parent strain SFL1 developed shigellosis. The average excretion time for SFL114 and SFL1 were 2 and 18 days, respectively. As seen endoscopically SFL1 caused colonic lesions, whereas SFL114 did not. Histopathologic examination of colonic biopsies showed that SFL114 induced only slight acute inflammation, whereas SFL1 caused severe acute inflammation (p less than 0.01). The vaccine strain SFL114 elicited significant species-specific serum immune responses (p less than 0.005) as seen in enzyme immune assays using lipopolysaccharides from S. flexneri serotypes Y, 1b, and 2a and Escherichia coli K-12 as antigens. The titres were comparable to those seen in monkeys given virulent S. flexneri strains. Western blot analyses showed that many prevaccination sera contained antibodies directed against the invasion plasmid-coded polypeptides. However, after vaccination with SFL114 increased amounts of such anti-polypeptide antibodies were seen, particularly in sera from monkeys having a low prevaccination antibody level. SFL114 also elicited a significant species-specific (p less than 0.025) local intestinal sIgA response against the homologous lipopolysaccharide antigen. Vaccinated monkeys were clinically protected against an oral challenge with 1-2 x 10(11) live, virulent S. flexneri strains of any of serotypes Y (strain SFL1), 1b (strain SFL27), or 2a (strain M4243).(ABSTRACT TRUNCATED AT 250 WORDS)

Live oral auxotrophic Shigella flexneri SFL124 vaccine with a deleted aroD gene: characterization and monkey protection studies.

Shigella flexneri SFL124, with a deletion encompassing all, or nearly all, of the coding sequence of gene aroD was obtained after selection on a fusaric acid medium supplemented with 2,3-dihydroxybenzoic acid for tetracycline-sensitive mutants of S. flexneri SFL114 which is an aroD::Tn10 transductant. Two of 20 tetracycline-sensitive mutants tested in colony hybridization with a 32P-labelled DNA probe of approximately 1400 base pairs (comprising all except the 75 N-terminal base pairs of the coding region of gene aroD) did not hybridize. The selected mutant SFL124 is Congo-red positive, invades and shows a limited multiplication in HeLa cells and does not cause keratoconjunctivitis in guinea-pigs. It is well tolerated by Macaca fascicularis monkeys, is excreted for up to 4 days, elicits a slight inflammatory reaction in the colonic mucosa, stimulates significant secretory IgA responses in the intestine and serum IgA and IgG responses against the S. flexneri cell envelope lipopolysaccharide. The immune response conferred a complete protection against challenge with 1 x 10(11) (equivalent to a 100 LD50 dose) live S. flexneri SFL1.

Shigella flexneri infection: a histopathologic study of colonic biopsies in monkeys infected with virulent and attenuated bacterial strains.

Macaca fascicularis monkeys were orally infected with live virulent Shigella flexneri wild-type strains of either serotype Y (S. flexneri SFL1), 2a (S. flexneri M4243) or 1b (S. flexneri SFL27). Clinical signs of shigellosis varied from mild watery diarrhea (SFL1) to dysentery (M4243, SFL27), with a fatal outcome in two monkeys (SFL27). Colonoscopy showed slight pathologic changes in monkeys infected with SFL1, and pronounced changes in monkeys infected with SFL27. In colonic biopsies the most severe acute inflammation, with surface epithelial erosions and ulcerations, was seen after infection with SFL27, followed by SFL1, and M4243. The live S. flexneri serotype Y vaccine strain SFL114, derived from SFL1 and attenuated because of an inactivated aroD gene and hence auxotrophic for p-aminobenzoic acid, caused no diarrheal illness in 14 monkeys. In colonic biopsies, SFL114 only elicited a slight acute inflammatory reaction. Vaccinated monkeys were protected against clinical disease when challenged with any one of the three virulent S. flexneri wild-type strains. Histopathologically, the acute inflammation was of less intensity than that seen in non-vaccinated monkeys. A good correlation between clinical signs, endoscopic findings and the degree of acute inflammation was demonstrated for monkeys vaccinated with SFL114 and challenged with either SFL1 or SFL27.

Shigellosis in Vietnam: seroepidemiologic studies with use of lipopolysaccharide antigens in enzyme immunoassays.

The performance of enzyme immunoassays (EIAs) with use of O-antigen-containing lipopolysaccharides (LPSs) extracted with phenol-water from Shigella dysenteriae type 1, Shigella flexneri serotypes 1a-5b, and Shigella sonnei for determination of the serum antibody responses after onset of bacillary dysentery is reviewed. For the purpose of several studies, serum samples from a total of 175 Vietnamese and 47 Swedish patients, for whom Shigella species had been isolated from fecal specimens, were obtained at various intervals until less than or equal to 1 year after the onset of infection. Titers of antibodies in serum samples from infected patients were compared with those in serum samples from healthy control subjects; the combined control population of all studies comprised 426 Vietnamese and 154 Swedes. The sensitivity of the EIAs ranged from 78% to 100% for patients whose fecal culture was positive for Shigella. For diagnosis of S. flexneri, a species-specific but no serotype-specific assay based on LPS antigens is possible. Among Vietnamese patients the EIA with use of S. flexneri was sensitive and diagnostic only for children less than 3 years of age, most likely because healthy older Vietnamese children and adults have high titers of antibody to the O-antigens of S. flexneri. Among Swedish patients the same EIA was diagnostic for adults as well as children. Increased titers of IgA in the early phase and of IgG in the convalescent phase, as determined by EIA, were the best indicators of infection due to Shigella species.

An auxotrophic live oral Shigella flexneri vaccine: development and testing.

Through transduction, a wild-type strain of Shigella flexneri serotype Y (SFL1) was rendered auxotrophic and dependent on aromatic metabolites that are not available in mammalian tissues. Monkeys that were orally vaccinated with 10(11) bacteria of the transductant strain SFL114 remained healthy when challenged with 10(11) bacteria of wild-type strains of S. flexneri serotypes Y, 1b, and 2a. The safety and immunogenicity of SFL114 were next studied in volunteers who were given either 10(9) or 10(10) SFL114 bacteria orally. Mild intestinal discomfort that lasted for 1-2 days was reported by three (12%) of 25 volunteers given 10(9) live SFL114 bacteria and by 13 (54%) of 24 volunteers given 10(10) live SFL114 bacteria. A local intestinal secretory IgA response to the S. flexneri O-antigen was recorded. The in vitro and in vivo results suggest that the aroD transductant SFL114 possesses properties that are desirable in an oral live candidate vaccine.

The lipopolysaccharide of Shigella bacteria as a virulence factor.

The virulence factors of the lipopolysaccharide of Shigella species bacteria include the endotoxic activities of the lipid A component of the molecule and the ability of the polysaccharide chain--the core and the O-antigenic polysaccharide--to provide the bacterium with resistance to host defense mechanisms such as opsonization, phagocytosis, and intracellular killing. Structural features of the lipopolysaccharides of four Shigella species-S. dysenteriae, S. flexneri, S. boydii, and S. sonnei--are described.

Early antibiotic treatment of reactive arthritis associated with enteric infections: clinical and serological study.

OBJECTIVE: To find out whether a 10-14 days' course of antibiotics early in the course of reactive arthritis associated with enteric infections could reduce the severity and duration of the disease and whether the antibody response in patients with reactive arthritis associated with yersinia infection differed between those treated and those not treated with the antibiotics. DESIGN: Prospective multicentre trial in which patients were randomised to treatment or no treatment with antibiotics. Patients were seen at three and six weeks and three, six, nine, 12, and 18 months after their first visit. SETTING: Departments of infectious diseases in three hospitals in Linköping, Malmö, and Stockholm, Sweden. PATIENTS: 40 Consecutive patients who had had symptoms of reactive arthritis associated with enteric infection for less than four weeks. INTERVENTIONS: 20 Patients were allocated to treatment with antibiotics and 20 patients did not receive antibiotics. All patients received non-steroidal anti-inflammatory drugs, and four also received intra-articular steroid injections after at least six weeks' observation. MAIN OUTCOME MEASURES: Arthritic symptoms assessed clinically and by using Ritchies' index; blood measurements reflecting inflammatory activity; serum IgG, IgM, and IgA antibody titres; HLA tissue type. RESULTS: No difference was observed concerning duration of arthritis, grade of inflammation, and number of joints affected between patients treated and those not treated with antibiotics. Furthermore, there was no significant difference between the two groups in erythrocyte sedimentation rate and haptoglobin, IgG, and IgA concentrations. All values had returned to normal within three months. No patient developed chronic arthritis, but sustained slight arthralgia occurred in three patients. The HLA-B27 antigen was found in 23 (58%) of the patients, and its presence did not affect clinical outcome. The IgG, IgM, and IgA antibody responses were similar in patients treated with antibiotics and those not treated. CONCLUSION: Short term antibiotic treatment has no beneficial effect on the clinical outcome of reactive arthritis associated with enteric infection.

Construction of an auxotrophic Shigella flexneri strain for use as a live vaccine.

A virulent Shigella flexneri serotype Y strain, SFL1, was made auxotrophic for aromatic metabolites, including p-aminobenzoic acid, which is not available in mammalian tissues, by transduction of a Tn10-inactivated aroD gene from Escherichia coli K-12 NK5131. One transductant, SFL114, selected for further studies, had the same biochemical and serological characteristics as the parent strain and the O-antigen patterns of the two strains were identical in SDS-PAGE and Western blot experiments. SFL114 was as invasive for cultured epithelial cells as SFL1, and both strains could escape from the phagocytic vacuole into the cytoplasm of the infected cells. However, the ability of SFL114 to multiply intracellularly was considerably reduced. When applied to the conjunctival sac of guinea pigs, the parent strain gave rise to keratoconjunctivitis, i.e. was Serény-positive, in 13 of 16 animals. By contrast, SFL114 was Serény-negative in all 11 guinea pigs tested. These in vitro and in vivo results suggest that the aromatic-dependent transductant S. flexneri SFL114 is attenuated and possesses properties desirable for a live vaccine.

The pathology of Shigella flexneri infection in rhesus monkeys: an endoscopic and histopathological study of colonic lesions.

Twenty-two Rhesus monkeys were orally fed 1 x 10(11) live virulent Shigella flexneri of either serotypes 1b, 2a, 4a or Y. On the basis of colonoscopic findings they were classified into: group A - normal endoscopic picture (10 monkeys), and group B - pathological endoscopic picture (12 monkeys). Pathological findings, distributed over the entire colon, were seen as either red patches (+/- erosions) or diffuse lesions, i.e. fragile red mucosa, mucosal bleeding and broad edemas. Histopathological examination of concomitant biopsies showed an acute inflammation restricted to the mucosa in 8/12 of group B as compared to 2/10 of group A. The Shigellae were most commonly demonstrated in the surface epithelium and more rarely in the deep layer of the lamina propria. Immunohistochemical staining, using monoclonal antibodies directed against Shigella flexneri O-antigenic polysaccharide, showed a high correlation with histopathological findings. Clinically all 10 monkeys in group A remained healthy, whereas 7/12 (all displaying histopathological signs of acute inflammation) in group B developed dysenteric symptoms. Colonoscopy should be combined with histopathological and immunohistochemical examinations of biopsies to study the pathological events taking place in the colon tissue during the course of a Shigella infection and will be of great value to assess the protective efficacy of S. flexneri vaccine candidates.