Spread of multiresistant Salmonella typhi
Lancet 336(8722): 1065-1066
1990
ISSN/ISBN: 0140-6736 PMID: 1977034 Document Number: 347655
Multiply-resistant strains of Salmonella typhi investigated at the Central Public Health Laboratory, Colindale, London, between 1978 and 1985 comprised only 0.5% of 2356 isolates. Between 1986 and 1989, 12 of 790 (1.5%) Salm. typhi isolates were resistant to chloramphenicol with minimum inhibitory concentrations (MICs) >64 mg/l. All 12 infections had been acquired in Pakistan or India. Between January and September 1990, 199 isolates from UK patients were studied. Of these patients, 73 had returned recently from Pakistan and 25 (34%) of their isolates were chloramphenicol resistant (MIC 250 mg/l), ampicillin resistant (MIC 125 mg/l), and trimethoprim resistant (MIC >125 mg/l). Eleven of 82 isolates (13%) from patients who had returned from other countries were chloramphenicol resistant and 9 were also resistant to trimethoprim and ampicillin. Another 2 isolates from patients with no history of foreign travel but with contact with people returned from Pakistan were resistant to all 3 drugs. Of the 73 patients returned from Pakistan and the 2 contacts, all 30 with multiply-resistant organisms were infected with a strain of phage type M1. Drug resistance was mediated by a single plasmid of Mr 120 x 106 and incompatibility group H1. Strains resistant only to ampicillin and trimethoprim were plasmid-free suggesting transposition of resistance to the chromosome.Advice that chloramphenicol remains the drug of first choice may no longer be appropriate in the UK when Pakistan is the likely source of infection. Ciprofloxacin is a possible alternative.A second letter (by M. Wallace and A.A. Yousif, ibid., 1065-1066) records that Salm. typhi infection is endemic in Bahrain and resistance to chloramphenicol has been noted in 13 patients since 1986, 9 of them in July-September 1990. All but 1 case were linked to recent arrivals from India. Twelve of the 13 patients were treated with parenteral cephalosporins, and of 7 patients given cefuroxime 2 were treatment failures. Of these, one responded only slowly to a combination of ceftazidime and gentamicin; the other responded rapidly after 24 h of ciprofloxacin, as did the thirteenth patient treated initially with ciprofloxacin. These correspondents note that combined resistance to chloramphenicol, co-trimoxazole and ampicillin occurs in most isolates of Shigella flexneri in the Persian Gulf area.K.C. Watson.