Antimicrobial drug resistance in non-typhoidal salmonellas from humans in England and Wales in 1999: Decrease in multiple resistance in Salmonella enterica serotypes Typhimurium, Virchow, and Hadar

In 1999 the incidence of multiple drug resistance (to four or more antimicr obials) in non-typhoidal salmonellas from humans in England and Wales fell in isolations of Salmonella enterica serotypes Typhimurium, Virchow, and Ha dar. This fall has been most noticeable in S. Typhimurium, where 59% of iso lates were multiresistant compared to 81% in 1996. The main reason for this has been a 75% decline in isolations of multiply-resistant S. Typhimurium definitive phage type (DT) 104 (MR DT104) since 1996. Nevertheless MR DT104 remains second to S. Enteritidis phage type 4 as the most common strain in cases of human salmonellosis in England and Wales. Multiple resistance has also remained high in S. Hadar, with 49% of isolates resistant to four dru gs or more compared to 56% in 1996. Isolates with decreased sensitivity to ciprofloxacin (minimal inhibitory concentration: 0.25-1.01 mg/L) have incre ased in incidence in S, Enteritidis, S. Virchow, and S. Hadar; in S. Hadar 70% of isolates were resistant to ciprofloxacin at this level. It is hoped that Codes of Practice introduced by some pharmaceutical companies, governm ents, professional organisations, and others to combat the unnecessary prop hylactic use of fluoroquinolones in animal husbandry will not result in a r eduction in the incidence of resistance to ciprofloxacin in salmonella orga nisms causing infections in humans.