domingo, 20 de agosto de 2017

Antimicrobial Drug–Resistant Shiga Toxin–Producing Escherichia coli Infections, Michigan, USA - Volume 23, Number 9—September 2017 - Emerging Infectious Disease journal - CDC

Antimicrobial Drug–Resistant Shiga Toxin–Producing Escherichia coli Infections, Michigan, USA - Volume 23, Number 9—September 2017 - Emerging Infectious Disease journal - CDC



Volume 23, Number 9—September 2017

Research Letter

Antimicrobial Drug–Resistant Shiga Toxin–Producing Escherichia coli Infections, Michigan, USA

Tables

Technical Appendices

Altmetric

    Article has an altmetric score of 15
Sanjana Mukherjee, Rebekah E. Mosci, Chase M. Anderson, Brian A. Snyder, James Collins, James T. Rudrik, and Shannon D. ManningComments to Author 
Author affiliations: Michigan State University, East Lansing, Michigan, USA (S. Mukherjee, R.E. Mosci, C.M. Anderson, B.A. Snyder, S.D. Manning)Michigan Department of Health and Human Services, Lansing (J. Collins, J.T. Rudrik)

Abstract

High frequencies of antimicrobial drug resistance were observed in O157 and non-O157 Shiga toxin–producing E. coli strains recovered from patients in Michigan during 2010–2014. Resistance was more common in non-O157 strains and independently associated with hospitalization, indicating that resistance could contribute to more severe disease outcomes.
Shiga toxin–producing Escherichia coli (STEC) contributes to 265,000 cases of foodborne illness annually in the United States (1). Most infections are caused by O157 strains; however, non-O157 STEC infections have increased (2). Antimicrobial drug resistance among STEC has been reported (35) but is probably underestimated. Given the importance of resistance in E. coli pathotypes, we sought to determine the prevalence of resistant STEC infections and assess the effects of resistance on disease.
We obtained 358 STEC isolates from the Michigan Department of Health and Human Services (MDHHS) Reference Laboratory (Lansing, MI, USA), collected during 2010–2014. Of these, 14 were outbreak associated. We examined 1 strain per outbreak using protocols approved by Michigan State University (MSU; Lansing, MI, USA; IRB #10-736SM) and MDHHS (842-PHALAB). Overall, 31 (8.8%) strains (23 non-O157, 8 O157) were resistant to antimicrobial drugs (Table). Resistance to ampicillin (7.4%) was most common, followed by trimethoprim/sulfamethoxazole (SXT) (4.0%) and ciprofloxacin (0.3%). Compared with national rates, resistance to ampicillin and SXT was higher, but not significantly different, for O157 isolates from Michigan (Technical Appendix[PDF - 454 KB - 4 pages] Figure 1) (6). One strain was resistant to all drugs, and all resistant strains had high MICs (ampicillin, >64 μg/mL; ciprofloxacin, >32 μg/mL; SXT, in 1:19 ratio, >32/608 μg/mL). Notably, resistance was twice as common for non-O157 (11.1%) than for O157 (5.5%) strains. O111 strains (n = 7) had significantly higher resistance frequencies (24.1%) than other non-O157 serogroups (p = 0.03). We found variation by year and season; resistance frequencies were highest in 2012 (Technical Appendix[PDF - 454 KB - 4 pages], Figure 2) and during winter/spring (Technical Appendix[PDF - 454 KB - 4 pages] Table 1), but neither trend was significant. We also observed a strong but nonsignificant association between resistance and hospitalization but no association for urban versus rural residence (7) or county after stratifying by prescription rates (8) in the univariate analyses.
We conducted a multivariate analysis using logistic regression, with hospitalization as the dependent variable; we included variables with significant (p<0.05) and strong (p<0.20) associations from the univariate analysis as independent variables. Forward selection indicated that hospitalized patients were more likely to have resistant infections (odds ratio [OR] 2.4, 95% CI 1.00–5.82) and less likely to have non-O157 infections (OR 0.4, 95% CI 0.21–0.61) (Technical Appendix[PDF - 454 KB - 4 pages] Table 2), suggesting that resistant infections or O157 infections may cause more severe clinical outcomes. Patients >18 years of age, women, and patients with bloody diarrhea were also more likely to be hospitalized.
Although we found no significant difference by stx profile, strains possessing stx1 only were more commonly resistant than strains with stx2 alone (p = 0.27 by Fisher exact test). All 23 (100%) resistant non-O157 STEC and 1 (12.5%) resistant O157 strain had stx1 only. Strains positive for eae were less likely to be resistant (n = 27; 8.4%) than eae-negative strains (n = 4; 23.5%); this nonsignificant difference (p = 0.07 by Fisher exact test) could be due to small sample sizes. All 8 resistant O157 strains and 18 (78.3%) of 23 resistant non-O157 strains had eae, demonstrating correlations between virulence genes and serogroups.
Overall, we detected a high frequency of resistance among non-O157 STEC (11.2%), similar to findings from Mexico (15%), although we evaluated fewer drugs (5). Resistance to ciprofloxacin was low despite its routine use for treating enteric infections, perhaps because resistance development in E. colirequires multiple mutations (9). Resistance frequencies in STEC were low relative to other E. coli pathotypes such as extraintestinal E. coli, which may be attributable to differences in the source of the infections (3).
The higher O157 resistance frequencies in Michigan than nationwide indicate that selection pressures vary by location and source. Although we observed no difference in resistance frequencies for counties with high versus low antimicrobial drug prescription rates (8), we have not investigated selection pressures from drug use in farm environments that may affect resistance emergence in Michigan. Approximately 12 × 106 kg of antimicrobial drugs are administered to food animals annually in the United States; roughly 61% of these are medically relevant. Higher resistance frequencies in winter/spring (12.2%) than summer/fall (7.5%) could be attributed to variation in prescription rates by season (10).
Because Michigan is not part of the Centers for Disease Control and Prevention Foodborne Diseases Active Surveillance Network and resistance in STEC has not been widely researched, data about the prevalence and impact of resistance are lacking. This study detected a high frequency of STEC resistance to antimicrobial drugs commonly used in human and veterinary medicine, particularly for non-O157 serotypes, which have increased in frequency (2). Monitoring resistance in STEC is essential because of the risk of transmitting resistant strains from food animals to humans and the high likelihood of horizontal transfer of resistance genes from STEC to other pathogens. Routine monitoring can uncover new treatment approaches and guide development of strategies for controlling emergence and spread of resistance in STEC and other E. coli pathotypes.
Miss Mukherjee is a PhD student in the Department of Microbiology and Molecular Genetics at MSU. She is studying antimicrobial drug resistance in STEC and nontyphoidal Salmonella. Her primary research interests are molecular epidemiology and medical microbiology.

Acknowledgments

We thank Ben Hutton and Jason Wholehan for help with specimen processing and isolation.
This work was supported by the National Institutes of Health Enterics Research Investigational Network Cooperative Research Center (U19AI090872 to S.D.M.) and the US Department of Agriculture National Institute of Food and Agriculture (2011-67005-30004 to S.D.M.). The Department of Microbiology and Molecular Genetics at MSU and the Ronald and Sharon Rogowski Fellowship provided student support to S.M.

References

  1. Scallan EHoekstra RMAngulo FJTauxe RVWiddowson MARoy SLet al. Foodborne illness acquired in the United States—major pathogens.Emerg Infect Dis2011;17:715DOIPubMed
  2. Tseng MSha QRudrik JTCollins JHenderson TFunk JAet al. Increasing incidence of non-O157 Shiga toxin-producing Escherichia coli (STEC) in Michigan and association with clinical illness. Epidemiol Infect2016;144:1394405DOIPubMed
  3. Schroeder CMMeng JZhao SDebRoy CTorcolini JZhao Cet al. Antimicrobial resistance of Escherichia coli O26, O103, O111, O128, and O145 from animals and humans. Emerg Infect Dis2002;8:140914DOIPubMed
  4. Mora ABlanco JEBlanco MAlonso MPDhabi GEcheita Aet al. Antimicrobial resistance of Shiga toxin (verotoxin)–producing Escherichia coliO157:H7 and non-O157 strains isolated from humans, cattle, sheep and food in Spain. Res Microbiol2005;156:793806DOIPubMed
  5. Amézquita-López BAQuiñones BSoto-Beltrán MLee BGYambao JCLugo-Melchor OYet al. Antimicrobial resistance profiles of Shiga toxin-producing Escherichia coli O157 and non-O157 recovered from domestic farm animals in rural communities in northwestern Mexico. Antimicrob Resist Infect Control2016;5:16DOIPubMed
  6. Centers for Disease Control and Prevention. NARMS now: human data 2016 [cited 2016 Oct 12]. http://wwwn.cdc.gov/narmsnow/
  7. Ingram DDFranco SJ2013 NCHS urban-rural classification scheme for counties. Vital Health Stat 22014;(166):173.PubMed
  8. Center for Healthcare Research and Transformation. Antibiotic prescribing and use. 2011 [cited 2016 Oct 12]. http://www.chrt.org/document/antibiotic-prescribing-and-use/
  9. Jacoby GAMechanisms of resistance to quinolones. Clin Infect Dis2005;41(Suppl 2):S1206DOIPubMed
  10. Suda KJHicks LARoberts RMHunkler RJTaylor THTrends and seasonal variation in outpatient antibiotic prescription rates in the United States, 2006 to 2010. Antimicrob Agents Chemother2014;58:27636DOIPubMed

Table

Technical Appendix

Cite This Article

DOI: 10.3201/eid2309.170523

No hay comentarios:

Publicar un comentario