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Antimicrobial Drug Resistance in Escherichia coli from Humans and Food Animals, United States, 1950–2002

Year: 2012

Type: article

Abstract: We conducted a retrospective study of Escherichia coli isolates recovered from human and food animal samples during 1950-2002 to assess historical changes in antimicrobial drug resistance.A total of 1,729 E. coli isolates (983 from humans, 323 from cattle, 138 from chickens, and 285 from pigs) were tested for susceptibility to 15 antimicrobial drugs.A signifi cant upward trend in resistance was observed for ampicillin (p<0.001),sulfonamide (p<0.001), and tetracycline (p<0.001).Animal strains showed increased resistance to 11/15 antimicrobial agents, including ampicillin (p<0.001),sulfonamide (p<0.01), and gentamicin (p<0.001).Multidrug resistance (≈3 antimicrobial drug classes) in E. coli increased from 7.2% during the 1950s to 63.6% during the 2000s.The most frequent co-resistant phenotype observed was to tetracycline and streptomycin (29.7%), followed by tetracycline and sulfonamide (29.0%).These data describe the evolution of resistance after introduction of new antimicrobial agents into clinical medicine and help explain the range of resistance in modern E. coli isolates.A ntimicrobial drugs have played an indispensable role in decreasing illness and death associated with infectious diseases in animals and humans.However, selective pressure exerted by antimicrobial drug use also has been the major driving force behind the emergence and spread of drug-resistance traits among pathogenic and commensal bacteria (1).In addition, resistance has developed after advent of every major class of antimicrobial drugs, varying in time from as short as 1 year (penicillin) to >10 years (vancomycin) (2,3).Escherichia coli is usually a commensal bacterium of humans and animals.Pathogenic variants cause intestinal and extraintestinal infections, including gastroenteritis, urinary tract infection, meningitis, peritonitis, and septicemia (4,5).Therapeutic options vary depending on the type of infection.For example, for urinary tract infections, trimethoprim/sulfamethoxazole and fl uoroquinolones are treatments of choice (6), whereas for Shiga toxinproducing E. coli infections, antimicrobial drug therapy is not recommended ( 7).E. coli is sometimes used as a sentinel for monitoring antimicrobial drug resistance in fecal bacteria because it is found more frequently in a wide range of hosts, acquires resistance easily (8), and is a reliable indicator of resistance in salmonellae (9).Surveillance data show that resistance in E. coli is consistently highest for antimicrobial agents that have been in use the longest time in human and veterinary medicine (10).The past 2 decades have witnessed major increases in emergence and spread of multidrug-resistant bacteria and increasing resistance to newer compounds, such as fl uoroquinolones and certain cephalosporins (3).For example, a study of the susceptibility of E. coli isolates recovered from hospitals during a 12-year period (1971)(1972)(1973)(1974)(1975)(1976)(1977)(1978)(1979)(1980)(1981)(1982) showed no major change in resistance to any of the antimicrobial drugs tested (11).In contrast, a retrospective analysis of E. coli from urine specimens collected from patients during 1997-2007 showed an increasing resistance trend for ciprofl oxacin, trimethoprim/sulfamethoxazole, and amoxicillin/clavulanic acid (12).Similarly a 30-year follow-up study on E. coli in Sweden showed Antimicrobial Drug Resistance in Escherichia coli from Humans and Food Animals, United States,

Source: Emerging infectious diseases

DOI: 10.3201/eid1805.111153