Antimicrobial Susceptibilities of Shigellae Isolated in Houston, Texas, in 1974

Abstract

One hundred seventy-three strains of shigellae (113 Shigella sonnei, 56 S. flexneri, and four others) isolated in Houston during 1974 were tested for susceptibility to commonly used and newer antimicrobial agents. Forty-five percent of S. sonnei strains were susceptible to ampicillin, whereas 93% of S. flexneri strains were susceptible to that agent. S. sonnei and S. flexneri strains were equally susceptible to tetracycline (35 and 33%, respectively). All 173 strains were uniformly susceptible to quinoline drugs (cinoxacin, oxolinic acid, and nalidixic acid) and to trimethoprim-sulfamethoxazole. This study supports recent suggestions that the initial therapy of bacillary dysentery no longer should be ampicillin or tetracycline. It remains for field testing to determine whether quinoline agents or trimethoprim-sulfamethoxazole will be the treatment of choice.Resistance of shigellae to a number of commonly used antimicrobial agents has prompted a search for new effective drugs in the treatment of shigellosis. Ampicillin (Am) has been considered the drug of choice for pediatric bacillary dysentery. Adults with shigellosis have generally been treated with either Am or tetracycline (Te). In light of recent reports of rapidly emerging multiple-resistant shigellae isolated in the United States, the use of Am and Te as primary drugs must be questioned (5, 11). Strains commonly isolated today reveal resistance to one or more of the following antimicrobial agents: Am, Te, streptomycin (Sm), chloramphenicol (C), and sulfonamides (3).The present study was designed to determine the in vitro antimicrobial susceptibility patterns of shigella strains recently isolated in Houston, Tex. We were interested in documenting the frequency of resistance to commonly used antimicrobial agents, but more importantly in determining the susceptibilities to newer antimicrobial agents, the quinoline drugs and trimethoprim-sulfamethoxazole.MATERIALS AND METHODS Bacterial strains. One hundred seventy-three isolates of shigellae were studied. The strains were obtained and identified by the Houston City Health Department during 1974. Each culture was a singlecolony primary isolate from a fecal specimen and/ or a pure culture sent to the Health Department for evaluation. Storage was less than 12 months at 4 C or at room temperature. All strains were representative isolates from numerous individuals in Houston, and multiple strains from common source outbreaks or individual households were excluded from study. Strains were streaked by us on MacConkey agar (Difco) for isolations before inclusion in the study. In total, 113 strains of Shigella sonnei, 56 strains of S. flexneri, 3 strains of S. dysenteriae, and 1 strain of S. boydii were evaluated for their antimicrobial susceptibility patterns. Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922) were obtained in lyophilized form from Bactrol Discs, set A, Difco Laboratories, Detroit, Mich., and were included as controls in the susceptibility testing.Antimicrobial agent susceptibility ...

Shigellaspecies from Addis Ababa: frequency of isolation andin vitrodrug sensitivity

“…This is in agreement with the findings from Thailand (Lexomboon et al 1972), United States (Byers et al 1976), Sweden (Frazen, Lidin-Janson & Nygren, 1972), England (Jarvis & Scrimgeour, 1970) and from Ethiopia (Gebre-Yohannes & Limenih, 1980). Evaluation of ampicillin and trimethoprimsulphamethoxazole in the treatment of shigellosis has demonstrated the greater effectiveness oftrimethoprim-sulphamethoxazole in producing bacteriological cure as well as better clinical response (Chang et al 1977;Nelson et al 1976;Rodriguez et al 1978).…”

“…The resistance patterns of our strains were generally different from those of other reports (Neu et al 1975;Byers et al 1976;Mitsuhashi, 1969;Chun & Seol, 1978). The most common resistance pattern was that of streptomycin/sulphadiazine Drug 8ensitivity of shigella 53 (23 %) followed by ampicillin/carbenicillin/chloramphenicol/streptomycin/ sulphadiazine/tetracycline resistance (11 %).…”

“…This frequency of ampicillin resistance is very similar to that reported by Gebre-Yohannes & Limenih (1980) on strains isolated at about the same period. From the trend of increasing frequency of resistance to ampicillin reported by various investigators (Byers et al 1976;Controni et al 1978;Davies et al 1970;Gordon et al 1975;Lexomboon et al 1972;Nelson et al 1976;Ross et al 1972;Urban, 1972), it is not unreasonable to consider our 21 % of ampicillin resistance a reflexion of the same trend. Twenty-one of the 22 ampicillin resistant strains were also resistant to two or more other drugs.…”

“…resistance to two or more drugs, was detected in (Neu et al 1975;Byers et al 1976;Controni et al 1978). The same trend was reported from Sweden in 1970 (Urban, 1972), from United Kingdom (Gillies, 1964) and from the Far East (Aoki, 1968).…”

“…Shigella strains are particularly noted for their multiple drug resistance. Such strains have been the cause of several outbreaks and epidemics in both developing and developed countries (Aoki et al 1969;Byers, Dupont & Goldschmidt, 1976;Chun & Seol, 1978; Davies, Farrant & Uttley, 1970;Farr & Dekle, 1967;Gangarosa et al 1972;Gebre-Yohannes & Limenih, 1980;Martin et al 1970;Mero, 1976;Olarte, Filloy & Galindo, 1976;Ross et al 1972;Salzman, Scher & Moss, 1967; Urban, 1972).…”