[Review and guidelines for treatment of diarrhea caused by Vibrio parahaemolyticus]. / Revisión y recomendaciones para el manejo de diarrea por Vibrio parahaemolyticus.

In Chile Vibrio parahaemolyticus has been detected in 3 gastroenteritis outbreaks since 1998. The most recent outbreak occurred during the summer of 2005, affecting over 10,000 people of whom one died. Affected individuals presented with one or more of the following symptoms: diarrhea, nausea, vomiting, abdominal pain and/or fever. Fecal white blood cells were detected in only 6% of patients. The predominant serotype in the 3 outbreaks was the pandemic O3:K6 strain. Diagnosis was confirmed by isolation and identification of V. parahaemolyticus in stool cultures and/or by establishing an epidemiological link. V. parahaemolyticus isolates were 100% susceptible to tetracycline, ciprofloxacin and chloramphenicol, and universally resistant to ampicillin. Due to the public health impact of the 2005 outbreak, the Ministry of Health called for a National Task Force mandated to review epidemiological, clinical and microbiological features of the outbreak and to propose management guidelines.

Population-based surveillance for hospitalized and ambulatory pediatric invasive pneumococcal disease in Santiago, Chile.

BACKGROUND: Nine- and 11-valent pneumococcal conjugate vaccines under development may control pediatric pneumococcal disease in nonindustrialized countries. Because these vaccines are expensive, population-based surveillance of pneumococcal disease in children <36 months of age was undertaken in Santiago, Chile to provide health authorities with reliable data on the burden of invasive pneumococcal disease and causative serotypes, including those in outpatients with high fever. METHODS: Automated blood culture machines were introduced into 9 hospitals that admit 85% of all hospitalized children in Santiago. Acutely ill pediatric febrile ambulatory patients are attended at 8 emergency rooms (ERs) and 36 urgent primary care services. After a 12-month pilot study in 3 ERs, health authorities collected blood cultures from children <36 months of age with high fever seen in the ER as standard practice. isolates were serotyped. RESULTS: Blood cultures of 18 (1.2%) of 1,503 outpatients 6 to 35 months of age with high fever in the pilot study yielded S. In the ensuing 24 months 236 children <36 months old were hospitalized with invasive pneumococcal disease (incidence, 33.9 cases/10(5) children), and 188 bacteremias were detected among ambulatory ER patients with high fever (incidence, 27.0 cases/10(5) children). Although serotypes were similar among hospitalized and ambulatory cases (except 18C, which was more common in the latter), case fatality was 9.5% in hospitalized (21 of 236) 0% in ambulatory cases (0 of 188) (P = <0.0001). High level resistance to penicillin (25.8% vs 10.1%) and cefotaxime (19.5% vs 6.2%) was observed more often among pneumococcal isolates from hospitalized than among ambulatory cases (P < 0.001). CONCLUSIONS: ER surveillance detected approximately one case of pneumococcal bacteremia among febrile ambulatory patients for each hospitalized invasive case. Because 71% of cases were caused by vaccine serotypes (and 87% by vaccine serogroups), 9- and 11-valent pneumococcal conjugate vaccines could prevent most invasive pediatric pneumococcal disease in Chile.

Evolution of an international external quality assurance model to support laboratory investigation of Streptococcus pneumoniae, developed for the SIREVA project in Latin America, from 1993 to 2005.

In 1993 the Pan American Health Organization initiated a laboratory-based surveillance system, called the SIREVA project, to learn about Streptococcus pneumoniae invasive disease in Latin American children. In 1994, National Laboratories in six countries were trained to perform serotyping and antibiotic susceptibility testing using broth microdilution to determine the MIC for specified antibiotics. An international External Quality Assurance (EQA) program was developed to monitor and support ongoing laboratory performance. The EQA program was coordinated by the National Centre for Streptococcus (NCS), Edmonton, Canada, and included external proficiency testing (EPT) and a validation process requiring regular submission of a sample of isolates from each laboratory to the NCS for verification of the serotype and MIC. In 1999, the EQA program was decentralized to use three of the original laboratories as regional quality control centers to address operational concerns and to accommodate the growth of the laboratory network to more than 20 countries including the Caribbean region. The overall EPT serotyping accuracies for phase I (1993 to 1998) and phase II (1999 to 2005) were 88.0 and 93.8%, respectively; the MIC correlations within +/-1 log(2) dilution of the expected result were 83.0 and 91.0% and the interpretive category agreements were 89.1 and 95.3%. Overall, the validation process serotyping accuracies for phases I and II were 81.9 and 88.1%, respectively, 80.4 and 90.5% for MIC agreement, and 85.8 and 94.3% for category agreement. These results indicate a high level of testing accuracy in participating National Laboratories and a sustained increase in EQA participation in Latin America and the Caribbean.

Analysis of molecular epidemiology of Chilean Salmonella enterica serotype enteritidis isolates by pulsed-field gel electrophoresis and bacteriophage typing.

Human Salmonella enterica serotype Enteritidis infections emerged in Chile in 1994. S. enterica serotype Enteritidis phage type 1 isolates predominated in the north, and phage type 4 isolates predominated in the central and southern regions. A study was planned to characterize this epidemic using the best discriminatory typing technique. Research involved 441 S. enterica serotype Enteritidis isolates, including clinical preepidemic samples (n = 74; 1975 to 1993) and epidemic (n = 199), food (n = 72), poultry (n = 57), and some Latin American (n = 39) isolates. The best method was selected based on a sample of preepidemic isolates, analyzing the discriminatory power (DP) obtained by phage typing and randomly amplified polymorphic DNA and pulsed-field gel electophoresis (PFGE) analysis. The highest DP was associated with BlnI PFGE-bacteriophage typing analysis (0.993). A total of 38 BlnI patterns (B patterns) were identified before the epidemic period, 19 since 1994, and only 4 in both periods. Two major clusters were identified by phylogenetic analysis, and the predominant B patterns clustered in the same branch. Combined analysis revealed that specific B pattern-phage type combinations (subtypes) disappeared before 1994, that different genotypes associated with S. enterica serotype Enteritidis phage type 4 had been observed since 1988, and that strain diversity increased before the expansion of S. enterica serotype Enteritidis in 1994. Predominant subtype B3-phage type 4 was associated with the central and southern regions, and subtype B38-phage type 1 was associated with the north (P < 0.0001). Food and poultry isolates matched the predominant S. enterica serotype Enteritidis subtypes, but isolates identified in neighboring countries (Peru and Bolivia) did not match S. enterica serotype Enteritidis subtypes identified in the north of Chile. The results of this work demonstrate that genetic diversity, replacement, and expansion of specific S. enterica serotype Enteritidis subtypes were associated with epidemic changes.

Resistencia a antibióticos no betalactámicos de aislamientos invasores de Streptococcus pneumoniae en niños latinoamericanos: SIREVA II, 2000-2005 / Resistance to non-beta-lactam antibiotics in the clinical isolates of Streptococcus pneumoniae of children in Latin America: SIREVA II, 2000-2005

OBJETIVO. Determinar la evolución de la resistencia a la eritromicina, el cloranfenicol, el trimetoprim-sulfametozaxol (SXT) y la vancomicina de aislamientos invasores de Streptococcus pneumoniae obtenidos de niños de 10 países de América Latina y del Caribe en seis años de vigilancia. MÉTODOS. Se analizaron 8 993 aislamientos de S. pneumoniae recuperados entre 2000 y 2005 de niños menores de 6 años con infecciones invasoras, procedentes de Argentina, Brasil, Chile, Colombia, Cuba, México, Paraguay, República Dominicana, Uruguay y Venezuela. La sensibilidad a los antibióticos se determinó mediante los métodos establecidos y estandarizados en el proyecto SIREVA. La resistencia a múltiples antibióticos se definió como la resistencia a tres o más familias de antibióticos, de los no betalactámicos analizados en este estudio o de los betalactámicos evaluados en un estudio previo en el que 37,8% de estos aislamientos presentaron sensibilidad disminuida a la penicilina. RESULTADOS. Se encontró algún grado de resistencia al SXT y la eritromicina (56,4% y 15,4% de los aislamientos estudiados, respectivamente) y 4,6% presentó alta resistencia al cloranfenicol. Todos los aislamientos fueron sensibles a la vancomicina. Se observó la mayor frecuencia de resistencia al SXT en los aislamientos de neumonía y a la eritromicina en los casos de sepsis (61,6% y 25,5%, respectivamente; P < 0,01). La mayor frecuencia de resistencia al SXT se observó en Brasil (71,9%) y a la eritromicina en México (38,2%) y Venezuela (32,9%). Los serotipos 14, 6B, 19F y 23F fueron los que más frecuentemente se asociaron con la resistencia a los antibióticos estudiados. CONCLUSIONES. Se observó una elevada y creciente frecuencia de aislamientos resistentes al SXT y la eritromicina, y una disminución en la proporción de aislamientos resistentes al cloranfenicol. Estas tendencias mostraron diferencias entre los países estudiados.

OBJECTIVE. To examine the development of resistance to erythromycin, chloramphenicol, trimethoprim-sulfamethoxazole (TMP-SMZ), and vancomycin of the invasive isolates of Streptococcus pneumoniae obtained from children in 10 Latin American/Caribbean countries during six years of surveillance. METHODS. Analysis of 8 993 isolates of S. pneumoniae recovered in 2000­2005 from children with invasive infections, who were less than 6 years of age, and from Argentina, Brazil, Chile, Colombia, Cuba, Dominican Republic, Mexico, Paraguay, Uruguay, or Venezuela. Antibiotic susceptibility was determined through the methods established and standardized by the SIREVA project. Multidrug resistance was defined as: resistance to three or more antibiotics of the same class; to the non-beta-lactams analyzed by this study; or, to the beta-lactams evaluated by a previous study, in which 37.8% of these isolates showed decreased susceptibility to penicillin. RESULTS. Some degree of resistance was found to TMP-SMZ and erythromycin (56.4% and 15.4% of the isolates studied, respectively), with 4.6% highly resistant to chloramphenicol. All isolates were susceptible to vancomycin. The highest prevalence of TMP-SMZ resistance was observed in the pneumonia isolates; and that of erythromycin, in cases of sepsis (61.6% and 25.5%, respectively; P < 0.01). The highest prevalence of TMP-SMZ resistance was found in Brazil (71.9%), and that of erythromycin, in Mexico (38.2%) and Venezuela (32.9%). The 14, 6B, 19F, and 23F serotypes were most often associated with resistance to the antibiotics in the study. CONCLUSIONS. High and increasing rates of isolates resistant to TMP-SMZ and erythromycin were observed, as well as a decreasing percentage of isolates resistant to chloramphenicol. These trends highlight differences among the countries studied

Salmonella enteritidis, un patógeno entérico ligado a la industria de los alimentos / Salmonella enteritidis, an enteric pathogen related to the industry of foods

Chile ha experimentado un cambio epidemiológico en la última década con la desaparición progresiva de la fiebre tifoidea, causada mayoritariamente por Salmonella Typhi y la emergencia epidémica de Salmonella Enteritidis, un agente de diarrea sin tratamiento antibiótico eficaz y ligado estrechamente a productos avícolas contaminados e inadecuadamente preparados. La fiebre tifoidea ha disminuido su importancia debido al desarrollo humano experimentado en Chile con un alto grado de cobertura de agua potable y de manejo de excretas que, en conjunto con un mayor nivel de educación, han limitado la contaminación del ambiente por este agente y la adquisición de él por huéspedes susceptibles. A pesar de este notable avance, un nuevo serotipo de Salmonella ha irrumpido en Chile, denominado Enteritidis, que ha logrado aprovechar el nuevo escenario obtenido con la industrialización avícola donde miles de aves convivenen pequeños espacios, facilitando la infección cruzada entre ellas. La contaminación intermitente de huevos, ya sea por vía transovárica o superficial, ha permitido la llegada de este agente en forma errática, pero persistente al ser humano. Este nuevo panorama obliga a que nuestro país adopte estrategias de prevención que involucran a productores, distribuidores y consumidores de productos avícolas

Evolutionary control of infectious disease: prospects for vectorborne and waterborne pathogens

Evolutionary theory may contribute to practical solutions for control of disease by identifying interventions that may cause pathogens to evolve to reduce virulence. Theory predicts, for example, that pathogens transmitted by water or arthropod vectors should evolve to relatively high levels of virulence because such pathogens can gain the evolutionary benefits of relatively high levels of host exploitation while paying little price from host illness. The entrance of Vibrio cholerae into South America in 1991 has generated a natural experiment that allows testing of this idea by determining whether geographic and temporal variations in toxigenicity correspond to variation in the potencial for waterborne transmission. Preliminary studies show such correspondences: toxigenicity is negatively associated with access to uncontaminated water in Brazil; and in Chile, where the potential for waterborne transmission is particularly low, toxigenicity of strains declined between 1991 and 1998. In theory vector-proofing of houses should be similarly associated with benignity of vectorborne pathogens, such as the agents of dengue, malaria, and Chagas'disease. These preliminary studies draw attention to the need for definitive prospective experiments to determine whether interventions such as provisioning of uncontaminated water and vector -proofing of houses cause evolutionary reductions in virulence.