Related Experiment Videos
Emergence of highly trimethoprim-sulfamethoxazole-resistant Shigella in a native American population: an
P M Griffin1, R V Tauxe, S C Redd
1Enteric Diseases Branch, Center for Infectious Diseases, Atlanta, GA 30333.
Abstract:
Resistance to trimethoprim-sulfamethoxazole (TMP-SMX) emerged among Shigella isolates from the Navajo Reservation in the southwestern United States in 1985, years after this antimicrobial agent came into common use. In the study area, TMP-SMX resistance increased dramatically from 3 per cent in 1983 to 21 per cent in 1985. Resistance was polyclonal and occurred in both S. sonnei and S. flexneri. No single plasmid was common to all resistant strains. However, all 28 TMP-SMX resistant isolates examined were resistant to ampicillin and streptomycin and had minimum inhibitory concentrations to sulfamethoxazole of greater than or equal to 4,096 micrograms/ml and to trimethoprim of greater than or equal to 1,024 micrograms/ml. The authors found that 28 of 101 Navajo children with gastrointestinal symptoms who were not taking antimicrobials had TMP-SMX-resistant aerobic fecal flora. To determine risk factors for acquiring resistant strains, they compared 40 case-patients with TMP-SMX-resistant Shigella to 66 controls with TMP-SMX-sensitive Shigella. Case-patients were more likely than controls to have used antimicrobials recently (p = 0.004) and to be hospitalized for shigellosis (p = 0.05). These findings suggest that polyclonal highly TMP-SMX-resistant Shigella emerged by transfer of trimethoprim resistance genes from aerobic bowel flora to endemic Shigella strains, that use of antimicrobials can lead to symptomatic shigellosis and thus the persistence of trimethoprim-resistant Shigella, and that appropriate therapy of shigellosis on the reservation is now a major challenge.
Insights
Trimethoprim-sulfamethoxazole resistance in Shigella increased significantly on the Navajo Reservation. Antimicrobial use was linked to acquiring resistant strains, complicating shigellosis treatment.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Trimethoprim-sulfamethoxazole (TMP-SMX) is a common antimicrobial agent.
- Emergence of antimicrobial resistance is a significant public health concern.
Purpose of the Study:
- To investigate the emergence and risk factors for TMP-SMX-resistant Shigella on the Navajo Reservation.
- To understand the genetic basis and transmission of TMP-SMX resistance in Shigella.
Main Methods:
- Surveillance of Shigella isolates for TMP-SMX resistance from 1983 to 1985.
- Antimicrobial susceptibility testing and characterization of resistant isolates.
- Case-control study to identify risk factors for TMP-SMX-resistant Shigella infection.
Main Results:
- TMP-SMX resistance in Shigella increased from 3% in 1983 to 21% in 1985.
- Resistance was polyclonal, affecting both Shigella sonnei and Shigella flexneri.
- Recent antimicrobial use and hospitalization for shigellosis were associated with TMP-SMX-resistant Shigella.
Conclusions:
- Polyclonal, highly TMP-SMX-resistant Shigella likely emerged through gene transfer from fecal flora.
- Antimicrobial use may drive the selection and persistence of resistant Shigella strains.
- Effective treatment of shigellosis on the reservation is challenged by widespread TMP-SMX resistance.