Increase in Multiple Antibiotic Resistance in Nontyphoidal Salmonellas from Humans in England and Wales: A Comparison of Data for 1994 and 1996

The incidence of multiple drug resistance (to four or more antimicrobials) in salmonellas from humans in England and Wales in 1996 has been compared with corresponding data for 1994. For Salmonella enteritidis multiple resistance has remained rare, although a high proportion of isolates of phage type 6A have shown resistance to amp ici Hin. For S. typhimurium multiple resistance has continued to increase, with 81% of isolates now multiresistant. Of particular importance in S. typhimurium has been the continued epidemic of multiresistant DT 104 and the increasing occurrence of strains of this phage type with additional resistance to trimethoprim and/or ciprofloxacin. For S. virchow , a 10% increase in multiple resistance is mainly concentrated in two phage types common in returning travellers. For S. hadar , there has been a substantial increase in the incidence of multiple resistance with over 50% of isolates now multiresistant. Substantial increases in the incidence of resistance to ciprofloxacin in multiresistant S. typhimurium DT 104, S. virchow , and S. hadar since 1993, when the fluoroquinolone antibiotic enrofloxacin was licensed for veterinary use in the UK, are of particular concern.