Increasing antimicrobial resistance of Shigella isolates in Israel during the period 1984 to 1992.

Recent (1984 to 1992) trends in the antimicrobial resistance of Shigella isolates in Israel were studied by analyzing the results of 106,000 stool cultures, 3,511 of which yielded Shigella spp. Over the study period, resistance to trimethoprim-sulfamethoxazole (TMP-SMX) increased from 59 to 92% (P = 0.0038) and that to ampicillin increased from 13 to 86% (P < 0.0001). Resistances to nalidixic acid, chloramphenicol, and broad-spectrum cephalosporins remained low. Shigella sonnei, which currently accounts for 90% of Shigella infections, was more resistant than S. flexneri to TMP-SMX (81 versus 57%, P < 10(-6)), ampicillin (42 versus 32%, P < 10(-5)), and tetracycline (38 versus 28%, P < 10(-5)). S. boydii and S. dysenteriae were relatively rare. Seasonality in antimicrobial resistance was found, with summer isolates being less resistant to TMP-SMX, ampicillin, or both than isolates obtained over the rest of the year (P < 10(-5)). We conclude that the resistance of shigellae, especially S. sonnei, to TMP-SMX and ampicillin is increasing to approximately 90%. Resistance should be recorded locally, and empiric therapy for suspected shigellosis should be changed accordingly.

Recent trends in the epidemiology of Shigella species in Israel.

Trends in the epidemiology of infections due to Shigella species over a period of 6 years (1986-1991) in Israel were studied by analysis of the results of 51,300 stool cultures, of which 2,987 yielded Shigella species. In a university hospital, the relative prevalence of Shigella sonnei in patients with shigellosis increased over the years from 60% in 1986 to 91% in 1991 (r = 0.93; P = .007); concomitantly, the prevalence of Shigella flexneri decreased from 29% to only 8% (r = -0.80; P < .05). In the community, the increase in prevalence of S. sonnei was more moderate and occurred only from 1989 to 1991. Since 1990, S. sonnei has been isolated from more hospitalized patients than has S. flexneri, in contrast to their rates of isolation in the past. The increase in prevalence of S. sonnei was most prominent among children, in whom it caused 94% of shigella infections in 1991. Shigella boydii and Shigella dysenteriae remained relatively rare, causing approximately 5% and approximately 1%, respectively, of the cases of shigella infection. Concomitantly, the antimicrobial resistance of S. sonnei has become significantly greater, and it is currently 2.7 and 1.6 times higher than that of S. flexneri to trimethoprim-sulfamethoxazole and ampicillin, respectively. We conclude that the relative frequency of S. sonnei is increasing, especially in hospitalized patients, and hypothesize that this may be related to its increasing antimicrobial resistance. These trends have clinical implications.

Enterotoxigenic Escherichia coli (ETEC) isolated in the Tel-Aviv (Israel) area.

The prevalence of enterotoxigenic E coli (ETEC) as a pathogenic agent of diarrhoea in the Tel-Aviv (Israel) area was determined, and the isolated E. coli strains characterized. During three periods (summer 1977, summer 1978, and summer 1979), a total of 335 specimens were tested for the presence of E. coli producing LT and ST toxin. Most of the specimens were from sporadic ambulatory diarrhoea cases (children and adults) attending a number of health care clinics in Tel-Aviv. Two to five colonies were tested from each sample. ETEC was detected in 69 cases (20%): LT/ST strains were isolated from 9 cases (2.7%); LT from 7 cases (2.1%); and ST from 53 cases (15.2%). ETEC was isolated in all age groups. In 19 specimens, 2 or more of 4 colonies tested were enterotoxigenic and were identical according to biotype, antibiotic sensitivity, and serogroup. These findings suggest that enterotoxigenic strains predominated in the bacterial population of the stool specimen. Part of the isolated ETEC strains belonged to serotypes already known as enterotoxigenic in different geographic areas of the world. The most frequently encountered were serogroups O8 (9 cases) represented by at least three serotypes, among them O8:K40:H9, and serotype O6:K15:H16 (5 cases); a number of serotypes were represented only by two cases or by single cases. Among 16 LT-producing stains (LT/ST and LT-only), 13 belonged to 3 serogroups, while ST-only strains represented a large spectrum of serotypes, some of which are now known as enterotoxigenic. Several serotypes common in other geographical locations were not detected.