Population-based study of the incidence of Shigella diarrhea and causative serotypes in Santiago, Chile.

BACKGROUND: Shigella is an important cause of diarrheal disease in children in developing countries. The increasing prevalence of antibiotic-resistant strains has stimulated interest in the use of multivalent Shigella vaccines. Because Shigella vaccines under development are based on eliciting immunity to O antigens, monitoring the distribution of serotypes in defined target populations is critical. We initiated health center-based surveillance in a poor semirural community in Colina, Santiago (7489 children <60 months of age) to determine the age-specific incidence of Shigella disease and the responsible serotypes. FINDINGS: Surveillance was maintained at the 2 health centers during warm seasons (November 1 through April 30) for 4 successive years (1994 to 1998). Shigella was recovered from 54 of 243 cases of dysentery (22%) and from 215 of 3966 cases of nondysenteric diarrhea (5.4%) (P < 0.001). The peak mean annual incidence of shigellosis occurred among children 12 to 47 months of age (9.0 to 12.6 cases/10(3) children), although the incidence in infants (5.2/10(3)) and children 48 to 59 months of age (6.2/10(3)) was also substantial. During the 1995 through 1996 season, an age-matched healthy control was cultured for every child <60 months of age with diarrhea. Shigella isolation from cases (34 of 576, 5.9%) was >8-fold higher than controls (4 of 576, 0.7%) (P < 0.01). Four serotypes, Shigella sonnei (45%), Shigella flexneri 2b (19%), S. flexneri 2a (14%) and S. flexneri 6 (11%), accounted for 89% of all cases. INTERPRETATION: Shigella remains an important pediatric pathogen in Santiago. The serotype distribution from Colina, which closely resembles data from a population-based surveillance study in Santiago in the mid-1980s, demonstrates a remarkable degree of serotype stability in Santiago during a 15-year period.

Breast abscess associated with Helcococcus kunzii.

Helcococcus kunzii, a nonvirulent member of the human skin flora, has recently been implicated in causing infections in immunosuppressed patients. We report a case of breast abscess associated with H. kunzii in an immunocompetant patient and discuss the criteria used in its identification and our observations of susceptibility testing for this species.

Antimicrobial susceptibility of pathogenic Yersinia enterocolitica isolated in Canada from 1972 to 1990.

Yersinia enterocolitica has emerged as an enteropathogen associated with several types of human infections that often require antimicrobial therapy, but little is known about the antimicrobial susceptibilities of pathogenic strains isolated from humans in Canada. To determine the present patterns of antimicrobial susceptibility, to identify changes in these patterns that occurred during the past two decades, and to investigate the relationships between O serotypes and patterns of susceptibility, we tested a total of 1,105 pathogenic Y. enterocolitica strains isolated during 1972 to 1976, 1980, 1985, and 1990 for their susceptibilities to 22 antimicrobial agents. Susceptibility testing was performed by using a single breakpoint concentration in agar procedure. The results showed that all strains were susceptible to ciprofloxacin and piperacillin, and 98% or more of the strains from each period were susceptible to trimethoprim, sulfamethoxazole, cotrimoxazole, tetracycline, chloramphenicol, cefamandole, cefotaxime, aztreonam, and four aminoglycosides. In contrast, all strains were nonsusceptible to erythromycin, furazolidone, and clindamycin and 90% or more of the strains from each period were nonsusceptible to ampicillin, carbenicillin, ticarcillin, and cephalothin. Strains belonging to serotypes O:3, O:5,27, and O:8 had different patterns of susceptibility to ampicillin, carbenicillin, ticarcillin, and amoxicillin-clavulanic acid. No major difference in susceptibility was observed between any of the groups of human or animal strains included in the study, but nonsusceptibility to tetracycline increased from 0.4% in 1985 to 2% in 1990 in human strains isolated in those years. Our results indicate that between 1972 and 1990 there was no marked decrease in susceptibility to agents commonly used for therapy among pathogenic Y. enterocolitica strains isolated in Canada.

Genetic variability and molecular typing of Shigella sonnei strains isolated in Canada.

Restriction fragment length polymorphisms (RFLPs) of genomic DNAs from 49 clinical isolates of Shigella sonnei were analyzed by using a modified restriction endonuclease analysis procedure to investigate the genetic variability of this species. After cleavage with the restriction enzyme HaeIII or RsaI, DNA samples were electrophoresed in polyacrylamide gels and the RFLP patterns were visualized by silver staining. The results showed that among 20 strains associated with sporadic cases of infection in three Canadian provinces, 15 distinct RFLP patterns were revealed by HaeIII digestion and 12 distinct patterns were revealed by RsaI digestion. In contrast, the RFLP patterns of individual isolates within six groups of epidemiologically related isolates were identical to each other but distinct from those of unrelated isolates, and these patterns could be used to determine the genetic relationships between isolates associated with separate outbreaks of shigellosis. Our results indicate that the modified restriction endonuclease analysis technique represents a rapid, reproducible, and highly discriminatory method for the molecular typing of this species.

Evaluation of the L-pyrrolidonyl-beta-naphthylamide hydrolysis test for the differentiation of members of the families Enterobacteriaceae and Vibrionaceae.

A simple, rapid, and inexpensive spot test incorporating the substrate pyrrolidonyl naphthylamide was used to examine pyrrolidonyl peptidase activity among 800 bacterial strains belonging to the families Enterobacteriaceae and Vibrionaceae. The pyrrolidonyl naphthylamide test was found to be particularly useful in separating Citrobacter spp. (100% positive) from Salmonella spp. (0.4% positive) and Escherichia coli (0% positive). Furthermore, it would appear to offer a safer alternative to the traditional potassium cyanide test for differentiating citrobacters from salmonellae.

Rapid biochemical test to identify verocytotoxin-positive strains of Escherichia coli serotype O157.

Fluorogenic procedures were used with the substrate 4-methylumbelliferyl-beta-D-glucuronide (MUG) to identify Escherichia coli. Most strains produced beta-glucuronidase and, thus, were MUG positive. A 20-min procedure was developed to detect glucuronidase activity in 1,295 bacterial cultures, representing 23 genera, of strains that were isolated from clinical specimens. Very few organisms other than E. coli were MUG positive. Of 682 E. coli strains that were isolated, 630 (92.4%) were MUG positive. When an additional 188 E. coli serotype O157 isolates were examined, 155 E. coli O157:H7, 10 E. coli O157:H-, and 1 E. coli O157:H (rough) isolate were MUG negative. All 166 cultures were verocytotoxin positive. Of the remaining 22 E. coli O157 isolates, 2 isolates were O157:H-, 1 isolate was O157:H (rough), and 19 isolates were other H types (H6, H16, H19, H25, H42, and H45); these 22 isolates were MUG positive. All 22 cultures were verocytotoxin negative. The rapid MUG procedure can be used to predict verocytotoxin-positive isolates of E. coli O157; that is, there is a very good likelihood that MUG-negative E. coli O157 isolates are verocytotoxin positive.

A severe outbreak of Escherichia coli O157:H7--associated hemorrhagic colitis in a nursing home.

In September 1985, an outbreak of Escherichia coli O157:H7 enteritis affected 55 of 169 residents and 18 of 137 staff members at a nursing home. The outbreak was characterized by two phases: a primary wave whose source was probably a contaminated sandwich meal and a secondary wave compatible with person-to-person transmission of infection. Among the elderly residents, the incubation period was 4 to 9 days (mean, 5.7 +/- 1.2). Older age and previous gastrectomy increased the risk of acquiring the infection (P = 0.01 and 0.03, respectively). Antibiotic therapy during exposure was associated with acquiring a secondary infection (P = 0.001). Hemolytic uremic syndrome developed in 12 affected residents (22 percent), 11 of whom died. Overall, 19 (35 percent) of the affected residents died, 17 (31 percent) from causes attributable to their infection. Antibiotic therapy after the onset of symptoms was associated with a higher case fatality rate in the more severe cases, possibly because patients with more severe disease tended to be treated with antibiotics. There were no complications or deaths among the affected members of the staff. Evidence of infection by verotoxin-producing E. coli O157:H7 was detected in 30 of 70 cases on the basis of isolation of this organism or demonstration of free verotoxin in stools. All isolates belonged to the same phage type. The high morbidity and mortality associated with this condition emphasize the need for proper food hygiene, rapid identification of outbreaks of disease, and prompt institution of infection-control techniques among the institutionalized elderly.

Use of a single-tube medium, o-nitrophenyl-beta-D-galactopyranoside-phenylalanine-motility sulfate, for screening of pathogenic members of the family Enterobacteriaceae.

A single-tube, multiple-test medium for the screening of Enterobacteriaceae in enteric and other clinical specimens is described. This medium allows the detection of motility, beta-galactosidase and phenylalanine deaminase activities, and H(2)S and indole production.