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

Caracterización molecular de mecanismos de resistencia a cloranfenicol en cepas de shigella flexneri aisladas en niños chilenos con diarrea aguda / Molecular characterization of resistance mechanisms to chloramphenicol in shigella flexneri strains isolated from chilean children with acute diarrhea

Background: Chloramphenicol is one of the therapeutic options for shigellosis, but resistance to this antimicrobial is increasing. Aim: To characterize molecular mechanisms conferring resistance to chloramphenicol (CmR) in Shigella flexneri strains isolated from Chilean children with acute diarrhea. Material and methods: Thirty one Shigella filexneri strains, including 22 with the CmR phenotype were analyzed. Strains were tested for antimicrobial susceptibility by plate dilution and for the presence of an internal fragment of the cat gene encoding for chloramphenicol o-acetyl-transferase, by polymerase chain reaction and Southern blot analysis. Results: All CmR strains had a minimal inhibitory concentration over 64 µg/ml and amplified the internal fragment of the cat gene. Southern blot analyses indicated that this gene was located in the bacterial chromosome. Conclusions: Resistance to chloramphenicol in this group of Shigella flexneri strains was mediated by a chromosomally located cat gene

Red de vigilancia de resistencia antimicrobiana PRONARES: informe primer semestre 2001 / PRONARES antimicrobial surveillance network on antimicrobial agents resistance: report of the first semester 2001

En el transcurso de los años hemos sido testigos de un creciente problema de resistencia antimicrobiana, fenómeno que involucra cada día mayor número de cepas, nuevas especies y nuevos mecanismos. En noviembre de 1997 iniciamos una red de vigilancia de resistencia antimicrobiana PRONARES (Programa Nacional de Resistencia), en diferentes hospitales del país, que trabajando un protocolo común (20 cepas por síndrome clínico por mes) y utilizando un programa computacional WHONET (diseñado para vigilancia), nos permitiera detectar y monitorear el problema de la resistencia bacteriana en Chile. Los resultados del primer semestre de este año reportan 5.251 cepas de diferentes síndromes clínicos. En ITU, Escherichia coli (1.088 cepas) demostró alta susceptibilidad a todos los antimicrobianos, Klebsiella (1.000 cepas) demostró un perfil de resistencia más elevado, en cepas de Enterococcus spp se observó 30 por ciento de resistencia a ciprofloxacina y 2 por ciento a nitrofurantoína. Entre 899 cepas procedentes de infecciones invasoras, Staphylococcus aureus (555 cepas), mostró elevado perfil de resistencia a cloxacilina 40 por ciento superior -40 por ciento (21 por ciento) al observado en cepas aisladas de piel y tejido blandos (550). Shigella spp, (137 cepas) presentó 80 por ciento de resistencia ampicilina y 32 por ciento a cloranfenicol; ciprofloxacina y furazolidona demostraron muy buena actividad in vitro frente a este enteropatógeno. Al comparar cepas nosocomiales y de la comunidad, las primeras mostraron un perfil de mayor resistencia. Mantener una red nacional de vigilancia de resistencia se hace cada vez más necesario para orientar el uso adecuado de antibacterianos y evitar así que el fenómeno aumente

Perfil de resistencia a los antimicrobianos en agentes causantes de infección del tracto urinario en niños chilenos: programa de vigilancia PRONARES / Antimicrobial susceptibility of agents causing urinary tract infections in chilean children: PRONARES surveillance program

Background: PRONARES (Programa Nacional de Vigilancia de Resistencia) is a national surveillance program for antimicrobial susceptibility, focused in different syndromes and among these, urinary tract infections. The work is done in a laboratory net that uses common protocols and whose data are centrally analyzed using the WHONET program. Aim: To analyze the pattern of antimicrobial susceptibility of agents causing urinary infections in children in the period 1997-1999. Material and methods: In the study period, 5,525 strains were analyzed. Of these, 2,307 came from pediatric patients (1,495 hospitalized and 803 ambulatory). Results: The most common causative agent was E. coli in 74,2 percent of cases, followed by Klebsiella spp in 8,2 percent and other agents in a lower frequency. Of E. coli strains, 74 percent were resistant to ampicillin, 52 percent to clotrimoxazole and 30 percent to first generation cephalosporins. These strains were sensitive to second and third generation cephalosporins, aminoglycosides, ciprofloxacin and nitrofurantoin. Strains from nosocomial or community infections had similar antimicrobial susceptibility. Klebsiella spp had a high rate of antimicrobial resistance (over 40 percent), that was even higher among nosocomial strains. It was 90 percent susceptible to ciprofloxacin and 100 percent to imipenem. All centers from which strains came had a similar pattern of susceptibility, with the exception of a pediatric center that had significantly higher resistance levels. Conclusions: The current therapeutic recommendations for urinary tract infections in children caused by E coli, are still pertinent, but the use of first generation cephalosporins must be cautious. The treatment of Klebsiella spp requires an individual antibiogram

Tendencias en la etiología de la meningitis bacteriana aguda en niños chilenos período 1989-1998: impacto de la vacuna anti-H influenzae tipo b Hib / Etiology of acute bacterial meningitis in chilean children from 1989 to 1998: impact of anti H influenzae type b vaccine

Background: Acute bacterial meningitis still has a high mortality and rate of complications. Aim: To assess the impact of anti H influenzae vaccination on the epidemiology of acute bacterial meningitis in Chilean children. Material and methods: A retrospective study of hospital discharge records of patients with acute bacterial meningitis. Causative agents were studied globally, by hospital and by age group. The changes in etiology from 1989 to 1995 were also assessed. Between 1996 and 1998, only those patients with acute bacterial meningitis caused by H influenzae were recollected. Results: In the period prior to vaccination (1989-1995), 1000 cases were registered. The main causative agents were N meningitidis in 33.8 percent, H influenzas type b in 21.9 percent and S pneumoniae in 15.4 percent. The incidence of H influenzae decreased in the period from 36.4 to 9.9 percent (p<0.001) and the incidence of N meningitidis increased from 22.9 to 52.1 percent (p <0.001). The incidence of S pneumoniae did not change significantly. H influenzae predominated in children between 4 and 24 months of age and N meningitidis predominated in children over 25 months of age. In the period after the introduction of vaccination (1995-1998), there was a further decrease in the incidence of H influenzae from 10 to 2 percent (p <0.001). Until 1997, there was a considerable increase in the incidence of N meningitidis, specially in children over 25 months of age. It declined in 1998 to 38 percent. Conclusions: There was a reduction in the incidence of acute bacterial meningitis caused by H influenzae prior to the introduction of the vaccine against H influenzae type b. The decrease was more pronounced after the introduction of the vaccine

Actividad comparativa in vitro de moxifloxacina y otros antimicrobianos frente a patógenos respiratorios / Comparative in vitro activity of moxifloxacin and other antimicrobials against respiratory pathogens

Background: Respiratory pathogens are becoming increasingly resistant to antimicrobials. A new group of drugs, called respiratory quinolones have been synthesized to overcome this problem. Aim: To study the in vitro susceptibility of respiratory pathogens to old and new antimicrobials. Material and methods: Forty five strains of S pneumoniae, 44 strains of H influenzae, 21 strains of M catarrhalis, 10 strains of methicillin susceptible S aureus and 20 strains of methicillin resistant S aureus were studied. All were isolated from community acquired respiratory infections during 1999. Minimal inhibitory concentrations of moxifloxacin, amoxicilin, amoxicilin/clavulanic acid, clarithromycin, azithromycin, ciprofloxacin and levofloxacin were determined using the Etest method. Betalactamase production by H influenzae and M catarrhalis was also studied. Results: S pneumoniae strains were 100 percent susceptible to quinolones and cotrimoxazole, 2 percent were resistant to macrolides, 11 percent were resistant to amoxicilin/clavulanic acid and 47 percent were resistant to cefuroxime. H influenzae was 100 percent susceptible to quinolones, azithromycin and amoxicilin/clavulanic acid. There was a 53 percent resistance to cotrimoxazole, 21 percent to amoxicilin, 9 percent to clarithromycin and 7 percent to cefuroxime. M catarrhalis was 100 percent susceptible to quinolones and 100 percent resistant to amoxicilin, 5 percent resistant to macrolides, 14 percent resistant to amoxicilin/clavulanic acid, 20 percent to cefuroxime and 30 percent to cotrimoxazole. Methicilline susceptible S aureus was susceptible to all antimicrobials and methicillin resistant S aureus was resistant to all. Conclusions: Moxifloxacin and the new respiratory quinolones can be useful in the treatment of respiratory infections

Prevalencia de eschericia coli enterohemorrágico en una zona ganadera de Argentina: caracterización genotípica de las cepas de origen animal / Animal reservoir and genotipic characterization of enterohemorrhagic escherichia coli in Argentina

Background: There is a high prevalence of infection by Enterohemorrhagic Escherichia coli (EHEC) and patients with hemolytic uremic syndrome (HUS) in Argentina. Aim: To study cattle and pigs as a possible reservoir of EHEC in Argentina. Material and methods: One hundred two healthy animals (68 cattles and 31 pigs) from a livestock in Argentina, were studied. Stool samples were obtained with a rectal swab. The strains were identified by DNA hybridization with specific gene probes detecting Shiga-like toxin 1 and 2 (Stx1, Stx2), and hly gen related to fimbrial adhesin-associated plasmid. EHEC strains were serogrouped using comercial antisera. Results: EHEC was isolated from 30 out of 68 bovines cultures (44.1 percent) and from 25 out of 31 pigs (58.1 percent). Isolates carrying genes codifying both Stx1 and Sxt2, were observed in 50 percent of cattle and 63.9 percent of pigs. The gene which codifies for hemolysin (associated to fimbrial adhesin) was observed in about 41 percent of EHEC isolates. Strains belonging to serogroups O26, O111, and O157 were isolated from cattle, and O111, and O157 from pigs. Conclusions: The high percentage of EHEC in both cattle and pigs and the presence of human infection-associated serogroups, suggests that these animals are a reservoir of EHEC associated with disease in humans

Prevalencia de chlamdia trachomatis en conjuntivitis neonatal determinada mediante las técnicas de inmuno-fluorescencia y amplificación génica / Indirect fluorescence and genic amplification for the determination of chlamydia trachomatis prevalence in neonatal conjunctivitis

Backgrund: Chlamydia trachomatis is one of the most common identifiable infectious agents in neonatal conjunctivitis. It also causes pneumonitis, that is preceded by conjunctivitis in one third of cases. Aim: To asses the prevalence of Chlamydia trachomatis in newborns with conjunctivitis. Patients and methods: In 162 newborns, coming from 14 Primary Health Centers from Santiago de Chile, C. trachomatis was detected by indirect fluorescence and two polymerase chain reaction (PCR 1 and 2), wich amplified different sequences from the common endogenous plasmid. Those patients with positive indirect fluorescence and PCR 2 were definedas infected: Results: The prevalence of C. trachomatis was 8 percent, and the distribution of the positive cases was similar in the different Health Centers. Other isolates were: S. aureus (9.8 percent), S. pneumoniae (8 percent), S. viridans (6.2 percent) y H. influenzae (5.5 percent). Conclusions: The prevalence of C. trachomatis in neonatal conjunctivitis in Chile is similar to that of developed countries. Therefore, C. trachomatis should be considered in the election of antimicrobials for the treatment of neonatal conjunctivitis, to avoid ocular and respiratory complications

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

Emergencia de resistencia a macrólidos en streptococcus pyogenes / Emergence of macrolide resistant streptococcus pyogenes strains

Background: Diseases produced by Streptoccocus pyogenes are still a problem in Chile, as in the rest of the world. It exhibits in vitro susceptibility to different antimicrobials, but penicillin continues to be the treatment of choice. Alternative drugs have been developed for allergic patients, such as erythromycin, new macrolides and cephalosporins. Nevertheless, resistant strains are appearing due to the indiscriminate use of macrolides. Aim: To assess present antimicrobial susceptibility of S Pyogenes strains isolated from chilean patients. Material and Methods: The susceptibility to penicillin, macrolides, clindamycin, cephalotin and vancomycin of 153 S Pyogenes strains, obtained from different health centers of the Metropolitan Region and isolated between 1996 and 1998, was assessed using the Kirby-Bauer method. Agar dilution minimal inhibitory concentration was then determined to macrolide resistant strains. Results: All strains were susceptible to penicillin. There was a 7.2 percent cross-resistance to macrolides. Conclusions: These results confirm that S Pyogenes resistance to macrolides has increased considerably in the Metropolitan Region of Chile during the last years

Resistencia a los antimicrobianos en agentes causantes de infección del tracto urinario en 11 hospitales chilenos: proyecto PRONARES / Antimicrobial resistance of agents causing urinary tract infections in 11 chilean hospitals: PRONARES project

Background: the computer program WHONET generates a common database to analyze local or general antimicrobial resistance of bacteria. A surveillance of agents causing urinary tract infections in Chile has been performed using this program. Aim: to report the results after 12 months of urinary tract infection agent surveillance. Material and methods: since november, 1997, a surveillance of in vitro antimicrobial resistance, using agar diffusion techniques, has been performed in 20 to 40 bacterial strains per month, isolated from 11 hospitals in the country. Results have been analyzed using WHONET program. Results: in first 12 months, 3144 strains, 1625 coming from outpatients, have been studied. Seventy four percent of isolated strains were E. coli, 19 percent were other enterobacteria, 4.1 percent were non fermenting bacilli and 2.1 percent were Gram (+) cocci. Sixty five percent of E coli strains were resistant to ampicillin, 11 percent to cefazolin, 2.5 percent to cefuroxime, 19 percent to ceftriaxone, 9 percent to ceftazidime, 4.2 percent to gentamicin 1.3 percent to amikacin, 5.6 percent to ciprofloxacin, 8.4 percent to grepafloxacin, 4.3 percent to nitrofurantoin and 43 percent to trimeproprim/sulphamethoxazole. Eighty two percent of other enterobacteria strains were resistant to ampicillin, 45.5 percent to cefazolin, 33.5 percent to cefuroxime, 26.6 percent to ceftriaxone, 21.5 percent to ceftazidime, 30.3 percent to gentamicin 17.2 percent to amikacin, 21 percent to ciprofloxacin, 16.3 percent to grepafloxacin, 48.2 percent to nitrofurantoin and 44.6 percent to trimeproprim/sulphamethoxazole. There were differences in betalactamic resistance among hospitals. Conclusions: noteworthy is the high resistance rates to third generation cephalosporins, evidenced when the new cutoff values for E coli and klebsiella spp are used. This national surveillance provides updated information on antimicrobial resistance of agents causing urinary tract infections

Eficacia de una monodosis de azitromicina para el tratamiento de la uretritis aguda masculina / Efficacy of azithromycin monodose for treatment of male acute urethritis

La uretritis aguda es causa frecuente de consulta en nuestro medio en centros de enfermedades de transmisión sexual y los principales agentes etiológicos son Neisseria gonorrhoeae y Chlamydia trachomatis. Un problema para el manejo de esta patología, es la emergencia de resistencia en N. gonorrhoeae; datos de 1991 mostraban una resistencia en cepas chilenas de N. gonorrhoeae de 30,3 por ciento a penicilina y 39,8 por ciento a tetraciclina, los antibióticos que se utilizaban empíricamente. Estas cifras se mantienen con tendencia al ascenso en algunas regiones. En estas situaciones, la OMS recomienda usar ceftriaxona intramuscular, una dosis de 125 mg, lo cual resulta costoso y poco práctico para nuestra realidad y no cubre a C. trachomatis. Para evaluar otras alternativas terapéuticas con un enfoque sindromático, se estudió la eficacia y seguridad de una dosis de 1 gramo oral de azitromicina en 61 pacientes masculinos que consultaron por uretritis aguda. A cada paciente que accedió a ingresar al estudio se le efectuaron tres controles clínicos y bacteriológicos: el día 1, entre 7 a 10 y 21 a 38 días, después del tratamiento. En estos pacientes, la etiología de la uretritis correspondió a N. gonorrohoeae en 67 por ciento, a C. trachomatis en 3 por ciento, en 11,5 por ciento a una coinfección por estos dos agentes y en 18 por ciento no se detectó el agente causal. Se observó curación clínica en 85,2 por ciento a los 7-10 días y 91,5 por ciento a los 21-28 días. La erradicación bacteriológica fue del 95 por ciento. Dos pacientes (3,2 por ciento) presentaron efectos adversos y de corta duración que se manifestaron por vómitos, hipotermia y epigastralgia. En conclusión, azitromicina resultó una alternativa eficaz, segura y práctica para el tratamiento de pacientes con uretritis aguda; la eficacia fue excelente para los dos agentes más frecuentemente observados