Characterization of Shiga toxin producing E. coli and O157 serotype E. coli isolated in France from healthy domestic cattle.

A study was carried out in France in collaboration with the meat industry to investigate the occurrence and characteristics of Shiga toxin-producing E. coli (STEC) and O157 E. coli in a population of healthy bovines representative of French livestock. A total of 851 animals belonging to three bovine classes (106 young bulls, 374 dairy cows and 371 meat cows) were included in the study. Samples of feces and of the corresponding carcasses were collected from March 97 to August 97 in seven abattoirs spread throughout the national territory. STEC cultures from the 1702 samples were screened using PCR for the presence of stx genes. Positive samples were further subjected to colony blot hybridization and to O157-specific immunomagnetic separation. Probe-positive colonies and O157 colonies were then analyzed for the presence of virulence genes and phenotypic characters (serotype, Stx production). In 154 (18.1%) feces and 91 (10.7%) carcass samples stx genes were detected. Two hundred and twenty-two STEC colonies were isolated from 67 (7.9%) feces and 16 (1.9%) carcass samples, with 183 STEC isolated from feces and 39 from carcasses. Only eight O157 isolates were collected from feces samples. None of these O157 E. coli isolates presented stx genes and thus could not be considered as pathogenic regarding hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS). In 3.2% of STEC isolated from feces and in 10.2% of STEC from carcasses eae genes were detected. In 17% of STEC from feces and in 30.7% from carcasses ehx genes were detected. Using these data, the 222 STEC colonies could be classified in 11 different 'virulence patterns' (presence/absence of stx1, stx2, eae and ehx genes), showing that more than 77% of isolates presented only one virulence factor. Only three STEC on 222 colonies (1.3%) presented the three virulence factors stx, eae and ehx in association, none of them reacting with antisera specific for enterohemorrhagic E. coli. (EHEC). These data, together with the fact that only five isolates on the 222 (2.2%) reacted with such antisera (three O111 and two O26 isolates) demonstrated that the natural bacterial populations isolated during this study were clearly distinct from EHEC.

Sex-dependent neutralizing humoral response to Schistosoma mansoni 28GST antigen in infected human populations.

The reduction of Schistosoma fecundity observed after experimental vaccination with the Schistosoma mansoni 28-kDa glutathione S-transferase (Sm28GST) antigen has been related to the inhibition of glutathione S-transferase (GST) enzymatic activity by specific antibody. The humoral immune response to the protective antigen Sm28GST and to the epitopes involved in the enzymatic site (amino acid ¿aa sequences 10-43 and 190-211) was evaluated in infected individuals before chemotherapy treatment. The capacity of the serum samples to inhibit GST enzymatic activity was assessed. Specific IgG3 response was predominant in the male population with a low intensity of infection and was associated with maximal GST inhibition. In contrast, the neutralizing activity of serum samples from women with a low intensity of infection was correlated with high specific IgA response specifically directed toward the 190-211 epitope. These results strongly support the hypothesis that GST-neutralizing IgG3 and IgA isotypes are sex dependent. The relationship of this specific acquired immune response with the level of intensity of infection is discussed.

Cellular immune responses of a Senegalese community recently exposed to Schistosoma mansoni: correlations of infection level with age and inflammatory cytokine production by soluble egg antigen-specific cells.

A recently reported epidemic of Schistosoma mansoni infection in Senegal provided an opportunity to study the dynamics of the development of immunity to human schistosomiasis. We report here on the cell-mediated immune response in a population of 99 females and 95 males, with particular emphasis on the relationship between intensity of infection and age. We found that the intensity of infection correlated negatively with age in females but not in males. In men and women, both Th1- and Th2-type cytokines were detected upon in vitro stimulation of PBMCs with soluble egg antigen (SEA) or soluble adult worm antigens (SWAP). In the female group, SEA-induced PBMC proliferation was associated with the production of IFN-gamma, IL-2 and IL-5, all of which correlated negatively with intensity of infection. Most cytokine production correlated positively with age. Spontaneous production of TNF-alpha, IL-6 and IL-10 was higher in the infected population than in an uninfected control group. Our results suggest that immunity to infection could be more pronounced in the female population and associated with a Th0/1 + 2 pattern of cytokine secretion mediated by soluble egg antigen (SEA).

Influence of cold stress on the preliminary enrichment time needed for detection of enterohemorrhagic Escherichia coli in ground beef by PCR.

The influence of cold stress at 4 and 0 degree C on the detection time as assessed by impedance technology (Bactometer; Biomérieux, Marcy l'Etoile, France) of different enterohemorrhagic Escherichia coli (EHEC) strains was determined. Although there is some variation in susceptibility among EHEC strains, prolonged exposure of EHEC to cold stress, i.e., 4 and 5 days at 4 and 0 degree C, respectively, in general significantly increased their detection time. This reflects an increase of the lag-phase time caused by cold stress. Two EHEC strains were selected to determine the minimum preliminary enrichment time that would ensure a positive PCR detection of low numbers of verotoxin-producing E. coli (VTEC; 2 to 2 x 10(5) CFU/25 g) inoculated into ground beef (25 g) and stored at 4 or -20 degrees C for 8 and 14 days, respectively. Incubation times of 6 and 9 h of 1 to 10 CFU/g and 1 to 10 CFU/25 g, respectively, were sufficient for PCR detection of VTEC in ground beef when analysis was performed immediately after inoculation (no cold stress). When cells are exposed to cold stress (4 or -20 degrees C) a 24-h enrichment period is recommended. Restriction of enrichment time to 9 h under these circumstances decreases the sensitivity of PCR detection to 80 CFU/g. Hence, to obtain maximum sensitivity, PCR detection of VTEC in naturally contaminated ground beef should be performed after 24 h of enrichment.

Organometric investigations of the spleen and liver by ultrasound in Schistosoma mansoni endemic and nonendemic villages in Senegal.

With the intention of ultrasonographically assessing hepatosplenic morbidity in Schistosoma mansoni infection and of validating the grading system applied (Cairo classification), 191 subjects in a schistosomiasis endemic village and 247 controls from a nonendemic village in northern Senegal underwent sonographic examination of the liver and spleen. Measurements of the diameters of the peripheral periportal vein branches, the main portal vein stem, liver size (left lobe and right lobe), and spleen length in the endemic village were compared with those in the nonendemic village to evaluate the much discussed influence of S. mansoni infection on those variables. To subtract this presumed influence from reference values for the named variables, they are given as measured in the nonendemic village, stratified by body weight, enabling future investigators on schistosomiasis-induced morbidity to refer to these reference values. The 95th percentile regarding peripheral periportal vein branch diameter in the control groups was exceeded in 24% of the subjects in the endemic group. It was exceeded by 6% for the main portal vein stem diameter, 13% for the left liver lobe, 12% for the right liver lobe, and 14% for the spleen length. According to the Cairo classification, 97% of the endemic population and 81% of the controls had periportal thickening of the liver, mostly grade I. We conclude that 1) hepatic morbidity in the S. mansoni endemic area was low, despite strikingly high intensities of infection; 2) the Cairo classification in its present form overestimates periportal thickening, especially in the case of mild morbidity; and 3) body height-dependent reference values, obtained from endemic controls, must be applied for organometric parameters.

[Infectious etiology of diarrheal morbidity in a Senegalese region of high exposure to Schistosoma mansoni]. / Etiologie infectieuse de la morbidité diarrheique dans un foyer sénégalais fortement exposé à 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.

[Salmonella bacteremia and generalized cryptococcosis, a double indicator of African AIDS]. / Bactériémie à Salmonella et cryptococcose généralisée, double indicateur du S.I.D.A. africain.

A male Rwandese adult with proven A.I.D.S. died from generalized cryptococcosis six months after episodes of recurrent fever with isolation of Salmonella enteritidis from the blood culture. The authors discuss the frequent and precocious appearance of Salmonella septicaemia in patients with A.I.D.S. They propose the inclusion of nontyphoidal Salmonella bacteraemia in the provisional W.H.O. case definition of adult A.I.D.S. in countries with limited diagnostic resources.

PIP: This work argues that nontyphoidal Salmonella bacteremia should be included in the provisional World Health Organization case definition of adult AIDS for countries with limited diagnostic resources. The case is described of a 50-year-old-man from Rwanda with proven AIDS who died from generalized cryptococcosis 6 months after episodes of recurrent fever during which Salmonella enteritidis was isolated from blood cultures. 3 months after the initial hospitalization with Salmonella bacteremia a positive hemoculture for Cryptococcus neoformans was obtained, and subsequent ELISA and immunofluorescence tests for AIDS were positive. Adult nontyphoidal Salmonella septicemia affects weakened subjects suffering from deficits of cellular immunity: leukemia, lymphoma, malignant tumors, or treatment with corticoid or other immunosuppressive medications. Numerous publications have drawn attention to the association of Salmonellosis and AIDS. Most of the authors observed the salmonelloses in AIDS patients were recurrent, and some recommended uninterrupted antibacterial treatment for such cases. Several authors mentioned the early character of Salmonella, which often appeared before the 4 opportunistic infections recognized in the WHO definition of AIDS.

[Analytical study of an epidemic of bacillary dysentery in Rwanda. Epidemiologic and bacteriologic aspects]. / Etude analytique d'une épidémie de dysenterie bacillaire au Rwanda. Aspects épidémiologiques et bactériologiques.

From january 1985 to march 1985, an epidemic of bacillary dysentery stroke one of the region in north Rwanda. The area struck, only 160 km2, is densely populated (720 inhabitants/km2). Multiresistant Shigella dysenteriae n. 1 is the only responsible factor. The study of this epidemic shows that, from an endemic disease, burst out can occur in a narrow area and in a short interval of time (7 weeks). The main risk factors have been identified on individual as well as collective level. The authors demonstrate the interest of a Public Health Laboratory as technical support of an Epidemiology Monitoring Department.

Comparison of norfloxacin and nalidixic acid for treatment of dysentery caused by Shigella dysenteriae type 1 in adults.

A severe epidemic of dysentery began late in 1979 in northeast Zaire and spread to Rwanda, Burundi, and Tanzania. The epidemic strain is a multiply resistant Shigella dysenteriae type 1, which acquired resistance against trimethoprim and more recently against nalidixic acid in the course of the epidemic. A comparative open trial in Rwandan adults with Shiga dysentery involved 18 patients treated with norfloxacin at 400 mg twice daily and 12 patients treated with nalidixic acid at 1 g three times daily for 5 days. All isolates showed in vitro susceptibility to both drugs. Though norfloxacin eliminated Shigella organisms from stools more rapidly than nalidixic acid, its clinical superiority did not reach the level of significance. Norfloxacin is a promising drug and is more effective than nalidixic acid in the treatment of multiresistant shigellosis.

[Bacteriological study of shigellosis in the Lake Kivu area (Central Africa). Developments in the last 15 years (1968-1983)]. / Etude bactériologique des shigelloses dans la région du lac Kivu (Afrique centrale). Evolution au cours des quinze dernières années (1968-1983).

1913 Shigella strains were isolated from 1968 to 1983 in lake Kivu area (Central Africa). Distribution and evolution of serotypes, biotypes and antibiotypes were studied. The majority of serotypes and biotypes were stable. However, few of these strains showed variations, among them Shigella dysenteriae serotype 1, causing epidemic dysenteriae since 1981. Epidemiologic survey of shigellosis in Kivu seems to be rather underdeveloped (4 bacteriology laboratories for an area of 10 million inhabitants) and the number of registered cases is probably underestimated. This problem is threatening the public health and coordination of laboratory activities, either local or regional, should be improved.

[3-year study of shigellosis epidemic in Rwanda, Central Africa. Problems of public health and bacteriological aspects]. / Etude sur trois ans d'une épidémie de shigellose au Rwanda--Afrique centrale. Problèmes de santé publique et aspects bactériologiques.

Since 1979, the Lakes region (Kivu in Zaïre, Western Uganda, Rwanda, Burundi) has been stricken by a bacillary dysentery epidemic at S. dysenteriae type 1. Supposed to be extinct since the 1950s., this bacillus has revealed a very noticeable virulence as well by the number of registered cases (524/100.000 in 1983 at Ruhengeri-Rwanda) as its fast break through. Demographic density (from 400 to 600/km2) has played an important role and has facilitated the transition toward epidemicity. Systematic bacteriological exams on the spot has allowed prompt identification of the involved germ, antibiotics to be used, and resistance variations during the period under consideration. The role of a regional laboratory to monitor diarrheal diseases has been demonstrated as of prime importance to set up a fighting strategy at regional level.

[Epidemic of Neisseria meningitidis cerebrospinal meningitis in the Ruhengeri health district (Rwanda)]. / Epidémie de méningite cérébrospinale à Neisseria meningitidis dans la région sanitaire de Ruhengeri (Rwanda).

Rwanda is a central african country where mean altitude is high (1,800 m), dwelling scattered, and population density important (372/km2). In 1978, a CSM epidemic broke out and raged for 4 years. Death incidence was very noticeable: 223/100 000. Treatment by an unique doses of chloramphenicol proved to be effective. As a consequence of an experimental immunization campaign, limited to one township, local population immunity is still solid after three years.