Evaluación de técnicas moleculares e inmunoenzimáticas para la detección de escherichia coli enterohemorrágico en brotes de toxi infecciones alimentarias / Evaluation of molecular and immunoenzymatic assays for detecting enterohemorrhagic escherichia coli in food borne outbreaks

Background: Enterohemorrhagic Escherichia coli (EHEC), is an emergent pathogen that causes sporadic infections and outbreaks of gastroenteritis associated with consumption of contaminated food products. Because detection of EHEC in diarrhea patients is not routinely performed, infection is most probably underestimated. Aim: To compare three techniques to detect EHEC: Colony hybridization with DNA probes, polymerase chain reaction (PCR) for the detection of stx1 and stx2 genes and immunoenzymatic detection by ELISA (Premier EHEC) of Stx1 and Stx2 toxins. Material and methods: Four outbreaks of food-borne gastroenteritis were studied including 16 patients and 78 strains of E coli. Twenty one (26,9 percent) strains, hybridized with the stx1 probe, 1 (1,3 percent) hybridized only with the stx2 probe and 36 (46,1 percent) with both probes. PCR amplification for cytotoxin genes was observed in 6 strains (7,7 percent) from the second outbreak studied. The immunoenzimatic assay detected the cytotoxins in 18 (23,0 percent), of the 78 studied strains. Agreement between probes and ELISA was 44,8 percent, between PCR and probes 34,7 percent and 82,4 percent between ELISA and PCR. Conclusions: These results indicate a variable yield among different EHEC detection techniques. Considering PCR as the gold standard, ELISA technique showed a better sensitivity and specificity than probes

Situación epidemiológica de las enfermedades transmitidas por alimentos en Santiago de Chile: período 1999-2000 / Survey of foodborne diseases in the Metropolitan Area of Chile

Background: Foodborne diseases are becoming an important cause of morbidity in Chile. In the Metropolitan Region of Chile, the Environmental Health Service started a surveillance program for foodborne diseases in 1994. In 2000, this program was complemented with an etiologic study of individuals involved in outbreaks. Aim: To report the incidence of foodborne outbreaks in the Metropolitan Region of Chile and its causative agents. Results: One hundred ninety outbreaks of foodborne diseases were reported in 1999 and 260 in 2000. The Southern Metropolitan health service had the higher incidence rates (7.5 in 1999 and 8.2 in 2000). The mean attack rates were 25 percent in both periods, affecting 1248 individuals in 1999 and 1774 in 2000. In 18 percent of outbreaks, a pathogen was identified; the most frequent agents were Salmonella Spp, Staphylococcus aureus and Shigella. In 15 percent of subjects, the cause was histamine or chemical agents. In the rest of the cases, the cause was not identified. The foods with higher risk of causing foodborne diseases were hot prepared dishes, home made goat cheese and meats. Conclusions: The incidence rates of foodborne disease in Metropolitan Area of Chile are high and maybe underestimate, only in a low rate of outbreaks was possible to have samples for etiologic studies. For a better understanding of this problem, timely notification of foodborne diseases must be encouraged and educational campaigns about the proper manipulation of food items must be implemented

Brote de shigellosis en una escuela de educación básica / Shigella outbreak in an elementary school

Se analiza un brote de gastroenteritis por shigella sonnei, ocurrido en una escuela básica de una comuna de Santiago, en marzo de 1997. En esta escuela, con una matricula de 1470 niños entre 5 y 14 años de edad, 350 se beneficiaban con el programa de alimentación escolar (pae) y almorzaban en el establecimiento. Treinta y cinco de los 350 niños del pae presentaron simultáneamente gastroenteritis que motivó consulta en un servicio de emergencia, 2 de los cuales presentaron diarrea con sangre requiriendo hospitalización. Durante los cinco días posteriores se registraron 189 nuevos casos en la escuela. Frente a la notificación, se efectuó visita epidemiológica a la escuela, obteniéndose muestras de deposición para estudio de bacterias y virus enteropatógenos en 65 niños sintomáticos y en los tres manipuladores de alimentos. Se identificó s. sonnei en 20,5 porciento de los coprocultivos y todas las cepas tenían el mismo antibiotipo. La búsqueda de virus entéricos (rotavirus, calcivirus) dio resultados negativos. En los manipuladores de alimentos no se detectó enteropatógenos bacterianos ni virales. La presentación del brote plantea una toxiinfección por s. sonnei, iniciada probablemente por ingestión de alimentos (tasa de ataque primario 10 porciento) y luego transmisión persona a persona (tasa de ataque secundario 16,9 porciento) Para controlar el brote se reforzaron medidas de higiene personal y de saneamiento ambiental a través de educación a toda la comunidad escolar y el control sanitario del establecimiento. A partir del quinto día de iniciado el primer caso, se administró cotrimoxazol, durante cinco días, sólo a los casos sintomáticos. El brote se controló al noveno día

Multirresistencia antimicrobiana en cepas de shigella sp en una comuna semi rural del área norte de Santiago / Antimicrobial multiresistance of shigella sp strains in a semi rural community of north Santiago

Appropriate antimicrobial therapy shortens the duration of Shigellosis and significantly reduces the risk of transmission. Shigella strains resistant to common antimicrobials have increased during the past years, determining the need for a periodic surveillance, to guide effective therapy. Aim: To report the results of a surveillance program in a rural community near Santiago (Colina), for Shigella infections. Material and methods: Between 1995 and 1997, stool samples from 3,534 episodes of diarrhoea, that occurred in Colina, were obtained. Two hundred twenty six Shigella strains were isolated and studied for susceptibility to ampicilin (AM), amoxicillin/clavulanic acid (AMC), cotrimoxazole (STX), chloramphenicol (CAF), tetracycline (TET), furazolidine (FU), ciprofloxacine (CIPR), nalidixic acid (AC NAL), gentamycin (GENT) and cefotaxime (CFTX). Results: Shigella flexnerii represented 134 of 226 Shigella strains isolated. All strains were susceptible to CIPR, AC NAL, GENT and CFTX. Yearly variation of resistance patterns to other antimicrobials were observed for these strains. Resistance to AM varied from 56 to 76 percent, to AMC from 25 to 56 percent, to STX from 21 to 47 percent, to CAF from 36 to 39 percent, to TET from 44 to 78 percent and to FU from 9 to 18 percent. Overall resistance was higher during 1997. All 85 strains of S sonnei were susceptible to CIPR, AC NAL and CFTX. Resistance throughout the years varied from 56 to 88 percent for AM, from 0 to 28 percent for AMC, from 44 to 53 percent for STX, from 11 to 40 percent for CAF, from 11 to 42 percent for TET and from 5 to 11 percent for FU. Overall resistance was also higher during 1997, except for AM and STX. Seven S boydii strains were isolated, only during 1995. All seven were resistant to AM and TET and none were resistant to FU, CIPR, AC NAL and CFTX. One strain was resistant to AMC, STX and CAF. Conclusions: Antimicrobial resistance patterns of Shigella sp isolated in Colina have increased from 1995 to 1997, specially for commonly used antimicrobials. Resistance remains low for furazolidine and all strains remain susceptible to quinolones

Variación temporal de genotipos y serogrupos de E coli enterohemorrágicos aislados en niños chilenos con infecciones intestinales o síndrome hemolítico urémico / Temporal variation of genotypes and serogroups of enterohemorrhagic E coli isolated from chilean children with intestinal infections or hemolytic-uremic syndrome

Thirty six strains isolated from chilean children with hemolytic-uremic syndrome (8 obtained in 1988-1989, 15 obtained in 1990-1993 and 13 obtained in 1995-1996), 33 strains from asymptomatic children, obtained in similar periods and 30 strains from children with bloody diarrhea, obtained in 1995-1996 were studied. Virulence factors were investigated with a colony hybridization technique using probes that identify virulence genes. Serotypes were identified with commercial antisera. Both SLTI and SLTII genes predominated in strains obtained from children with hemolytic uremic syndrome in 1988-1989 and 1995-1996 and SLTI gene predominated in strains obtained in 1990-1993. Similar temporal variations in virulence genes of strains obtained from asymptomatic children were observed. SLTI/SLTII pattern predominated in strains obtained from children bloody diarrhea and the frequency of 0157 serogroup was lower, compared to strains obtained from children with hemolytic uremic syndrome. There was a temporal variation in toxigenic genotypes of enterohemorrhagic E coli strains, but no association between these genotypes and the risk for hemolitic uremic syndrome was observed

Susceptibilidad in vitro de escherichia coli enterohemorrágicas frente a 11 antimicrobianos: relación entre resistencia antibiótica y genotipos toxigénicos / In vitro susceptibility of enterohemorrhagic escherichia coli to 11 antimicrobials: relation between antibiotical resistance and toxicogenic genotypes

Enterohemorrhagic escherichia coli (EHEC) has been recognized as the main etiologic agent of hemorrhagic colitis and hemolytic uremic syndrome (HUS). The usefulness of antibiotic treatment in patients with EHRC infections is a matter of current debate. Knowledge on EHEC antimicrobial susceptibility patterns in different geographic areas is important for both treatment considerations and for strain characterization. We studied by diffusion disk agar technique the antibiotic susceptibility of 83 EHEC strains obtained from stools of patients with HUS or diarrhea. Eleven antimicrobials were tested (ampicillin, cotrimoxazole, tetracycline, chloramphenicol, furazolidone, gentamycin, amikacin, ciprofloxacin, erythromycin, vancomycin and metronidazol). Resistant strains by disk diffusion were tested for MIC (mg/ml) by agar dilution. SLT-I and SLT-II were detected with specific biotinylated gene probes. All 83 strains were susceptible to furazolidone, ciprofloxacin, gentamycin and amikacin. Resistance was detected to tetracycline 4 percent, chloramphenicol 5 percent, cotrimoxazole 24 percent and ampicillin 25 percent. As expected for EHEC strains all were resistant to erythromycin, vancomycin and metronidazol. Resistant strains were significantly more common in non toxigenic and SLT-I producing strains (p=0.01). Resistant strains were similarly distributed among patients who had diarrhea only and those who developed HUS (p=0.3). In Chile, resistant EHEC strains seem to be more common and of different genotypes than those reported in more developed countries. Regional differences of EHEC antibiotic susceptibility patterns indicate a need for continious monitoring, specially if antibiotic prove to be useful in disease prevention

Escherichia coli enterohemorrágica en el síndrome hemolítico urémico, en niños chilenos: evaluación de diferentes técnicas de diagnóstico de infección / Enterohemorrhagic escherichia coli in hemolytic uremic syndrome, in chilean children: evaluation of different technics of infection diagnosis

Enterohemorrhagic escherichia coli (EHEC), have been associated with pathogenesis of hemolytic uremic syndrome (HUS) worldwide. Our aim was to determine the association of EHEC ing¿fection and HUS in chilean children. During may 1991 and october 1993, 34 children HUS and 33 age matched controls (children with diarrhea that did not develop HUS) were enrolled in a case/control study. For each child a stool and serum sample were obtained at admission. Stools were processed for common enteropathogen and for EHEC identification. EHEC were identified in stools by gene probes for different virulence factors (EHEC plasmid-associated fimbria, Shiga-like toxin I, Shiga-like toxin II and eae adherence factor) and by detection of free fecal toxin by neutralization assay in Vero cells. Sera were processed for anti-cytotoxin antibodies also by an assay in Vero cells. Enteropathogens were isolated in 20.6 percent and 15.5 percent of HUS and control children respectively (p=NS). 91 percent of the HUS children and 73 percent of the control children were EHEC positive by one or more of the techniques used (p=0.05). Of the 3 detection methods used for EHEC, only free fecal cytotoxin was significantly more common in HUS children than controls (45.5 percent vs 9 percent p=0.007). Genotype patterns of HUS and controls strains were similar except for a trend towards a higher frequency of non-toxigenic strains in the control group. Serogroup 0157 was more common in HUS children than in controls (9 percent vs 0 percent p=0.036). In Chile as in other countries, EHEC infection is common and significantly associated with occurrence of HUS. Infection with EHEC strains 0157 seems to be important risk factor for HUS