Antibiotic-resistant Salmonella typhi from two outbreaks: few ribotypes and IS200 types harbor Inc HI1 plasmids.

To investigate factors that could be involved in the emergence of antibiotic resistant S. typhi, we characterized R plasmids and antibiotic resistant S. typhi strains from two outbreaks of typhoid in Peru and Chile. Differences in the Inc HI1 plasmids of Peruvian and Chilean strains were identified by conjugation and incompatibility studies and plasmid DNA characterization. Antibiotic-resistant S. typhi harboring Inc HI1 plasmids belonged to a reduced number of Pst1 and Cla1 ribotypes and IS200 types, in contrast to the high genetic diversity found among epidemic antibiotic-susceptible S. typhi. The low diversity of antibiotic-resistant S. typhi suggests that they may express properties that are related to both their ability to harbor Inc HI1 R plasmids and to disseminate.

Epidemic typhoid in Chile: analysis by molecular and conventional methods of Salmonella typhi strain diversity in epidemic (1977 and 1981) and nonepidemic (1990) years.

From 1977 to 1986, Chile experienced an important typhoid fever epidemic, despite statistics that indicated apparently improving levels of sanitation of drinking water and sewage disposal. The lack of antibiotic resistance among the Salmonella typhi strains isolated during this period, the mild clinical presentation of the disease, and the initially low level of efficacy of the S. typhi Ty21a vaccine in the population exposed to the epidemic suggested that this epidemic might have resulted from the dissemination of S. typhi strains with unique characteristics. To investigate this hypothesis, we used conventional methods (bacteriophage typing and biotyping) and molecular methods (restriction fragment length polymorphism analysis, ribotyping, IS200 typing, and PCR amplification of the fliC-d gene) to study a population of 149 S. typhi isolates during 1977, 1981, and 1990, the years that included periods with low (when the disease was endemic) and high (when the disease was epidemic) morbidities. Our results indicate that these S. typhi isolates in Chile represent a number of highly diverse variants of the clone of S. typhi with a worldwide distribution described by Selander et al. (R. K. Selander, P. Beltran, N.H. Smith, R. Helmuth, F.A. Rubin, D.J. Kopecko, K. Ferris, B.D. Tall, A. Cravioto, and J.M. Musser, Infect. Immun. 58:2262-2275, 1990). For example, we detected 26 PstI and 10 ClaI ribotypes among 47 and 16 S. typhi strains belonging to this clone, respectively. These results suggest that the Chilean epidemic was probably produced by multiple sources of infection because of deficient sanitary conditions. These findings illustrate the usefulness of molecular methods for characterizing the potential causes of the typhoid epidemics and the possible routes of transmission of S. typhi strains in typhoid epidemics.

[Bacterial isolation in infants hospitalized for acute diarrhea]. / Aislamiento bacteriano en lactantes hospitalizados por diarrea aguda.

Bacteria were investigated in stools of 156 children under two years of age admitted to the pediatric wards of a general hospital at the western metropolitan area of Santiago, Chile, because of acute diarrhea with only one stool sample. A known pathogenic agent was isolated from 115 cases (73.7%), this being a bacteria in 87/115 (75.6%). Most prevalent microorganisms were Enteropathogenic Escherichia coli (EPEC). (65.5%), specially serogroups 0111, 0119 and 055, Enterotoxigenic Escherichia coli (ETEC) (18.4%), Campylobacter yeyuni (13.8%), Salmonellae (9.2%) and Shigellae (6.9%). Invasive Escherichia coli (EIEC) and Aeromonas hydrophila were observed in only one case. Yersinia enterocolitica was not isolated. Age was under one year in 92% of patients and 83% were normally or slightly under nourished. Fecal leucocytes were abnormally increased (greater than 5 per high power field) in 41.4% of positive bacterial isolates, in 83% of children with Shigellae, in 50% of those with EPEC and Salmonellae and in 25% of the Campylobacter yeyuni group.

[Pathogenic agents in acute non-enterocolic diarrheal syndrome]. / Agentes patógenos en el síndrome diarreico agudo no enterocólico.

Along a one year period 112 infants admitted with non enterocolic acute diarrhea were studied for isolation of potentially ethiologic agents, namely enteropathogenic bacteria (Salmonella, Shigella, Campylobacter, classic enteropathogenic, enteroinvasive and enterotoxigenic Escherichia coli), Rotavirus (viral RNA electrophoresis) and enteroparasites (Telemann and PAFS). The most frequently identified pathogen was rotavirus (57.8%), followed by thermo labile toxin producing Escherichia coli (19.7%). The frequency of classic enteropathogenic Escherichia coli was 13.9%, that of thermo stable toxin producing Escherichia coli 5.7%, Shigella 4.1%, Campylobacter 3.3% and Salmonella 1.6%. Bacteriae were isolated from 40.2%, of patients, predominantly in summer. Enteroparasites were detected in 13.1% of the cases, Entamoeba histolytica being the most frequent. In 32.8% of the cases more than one pathogen was isolated.

Further characterization of Escherichia coli O153:H45, an ETEC serotype disseminated in Chile.

The newly described stable enterotoxin producing, enterotoxigenic Escherichia coli, serotype O153:H45, capable of expressing colonizing factor antigen I, is frequently isolated as a cause of diarrhea among Chilean children. Hybridization studies of five new strains confirmed previous results which indicated that the stable enterotoxin genes are contained in nonconjugative plasmids ranging in size from 81 to 87 kilobases. The strains expressed similar antibiotic resistance and metabolic properties but differed in their plasmid content.

The use of Moore swabs for isolation of Salmonella typhi from irrigation water in Santiago, Chile.

In Chile, a country with an exceedingly high incidence of typhoid, untreated sewage is applied directly to fields where salad vegetables are cultivated. Water used for irrigation was examined for the presence of Salmonella typhi, by making use of the sewer-swab technique. S typhi was isolated in 8 (11%) of 76 irrigation samples examined from nonindustrial, polluted water. This supports the hypothesis that crops grown with water contaminated with feces are important vehicles in the transmission of S typhi in this endemic area. Since sewage treatment plants will not be available in Santiago in the near future, emphasis is being placed on devising alternative methods of irrigation and on growing vegetables that are cooked before being eaten.