Ana Carolina da C Campos1, Nathália L Andrade2, Natacha Couto3, Nico T Mutters4, Marjon de Vos5, Ana Cláudia de P Rosa2, Paulo V Damasco6, Jerome R Lo Ten Foe3, Alex W Friedrich3, Monika A Chlebowicz-Flissikowska3, John W A Rossen7. 1. Universidade do Estado do Rio de Janeiro, Faculdade de Ciências Médicas, Departamento de Microbiologia, Inmunologia e Parasitologia, Boulevard 28 de Setembro, 77 - Vila Isabel, RJ-20551-030, Rio de Janeiro, Brazil; University of Groningen, University Medical Center Groningen, Department of Medical Microbiology and Infection Prevention, Hanzeplein 1, 9713 GZ, Groningen, The Netherlands. 2. Universidade do Estado do Rio de Janeiro, Faculdade de Ciências Médicas, Departamento de Microbiologia, Inmunologia e Parasitologia, Boulevard 28 de Setembro, 77 - Vila Isabel, RJ-20551-030, Rio de Janeiro, Brazil. 3. University of Groningen, University Medical Center Groningen, Department of Medical Microbiology and Infection Prevention, Hanzeplein 1, 9713 GZ, Groningen, The Netherlands. 4. Heidelberg University Hospital, Center for Infectious Diseases, Medical Microbiology and Hygiene, Im Neuenheimer Feld 672, 69120, Heidelberg, Germany. 5. University of Groningen, Institute for Evolutionary Life Sciences, Linnaeusborg 5(th) floor, Nijenborgh 7, 9747 AG, Groningen, The Netherlands. 6. Universidade do Estado do Rio de Janeiro, Departamento de Doenças Infecciosas e Parasitárias, Boulevard 28 de Setembro, 77 - Vila Isabel, RJ-20551-030, Rio de Janeiro, Brazil; Universidade Federal do Estado do Rio de Janeiro, Departamento de Doenças Infecciosas e Parasitárias, R. Voluntários da Pátria, 107 - Botafogo, RJ- 22270-000, Rio de Janeiro, Brazil. 7. University of Groningen, University Medical Center Groningen, Department of Medical Microbiology and Infection Prevention, Hanzeplein 1, 9713 GZ, Groningen, The Netherlands. Electronic address: j.w.a.rossen@rug.nl.
Abstract
OBJECTIVES: Urinary tract infections (UTIs) caused by multidrug-resistant Escherichia coli have become a major medical concern. Old antibiotics such as fosfomycin have become an alternative therapeutic option due to their effectiveness and, as a result, fosfomycin is now used as a first-line drug for the treatment of UTIs in many countries. Despite low resistance rates, fosfomycin heteroresistance, defined as a phenomenon where subpopulations of bacteria are resistant to high antibiotic concentrations whereas most of the bacteria are susceptible, is an underestimated problem. METHODS: The frequency of heteroresistance in E. coli isolated from hospitalized patients in Brazil and its effect on susceptibility of E. coli in biofilms was studied and the isolates were molecularly characterized to reveal the mechanisms behind their fosfomycin heteroresistance using whole-genome sequencing. RESULTS: A higher frequency of fosfomycin heteroresistance compared with other studies was found. In biofilms, most heteroresistant isolates were less sensitive to fosfomycin than control isolates and showed overexpression of metabolic genes thereby increasing their survival rate. Molecular characterization showed that some resistant subpopulations derived from heteroresistant isolates had a defect in their fosfomycin uptake system caused by mutations in transporter and regulatory genes, whereas others overexpressed the murA gene. None to minor effects on bacterial fitness were observed. Oxidative stress protection, virulence and metabolic genes were differentially expressed in resistant subpopulations and heteroresistant isolates. CONCLUSION: Frequent detection of heteroresistance in UTIs may play a role in the failure of antibiotic treatments and should therefore be more carefully diagnosed.
OBJECTIVES: Urinary tract infections (UTIs) caused by multidrug-resistant Escherichia coli have become a major medical concern. Old antibiotics such as fosfomycin have become an alternative therapeutic option due to their effectiveness and, as a result, fosfomycin is now used as a first-line drug for the treatment of UTIs in many countries. Despite low resistance rates, fosfomycin heteroresistance, defined as a phenomenon where subpopulations of bacteria are resistant to high antibiotic concentrations whereas most of the bacteria are susceptible, is an underestimated problem. METHODS: The frequency of heteroresistance in E. coli isolated from hospitalized patients in Brazil and its effect on susceptibility of E. coli in biofilms was studied and the isolates were molecularly characterized to reveal the mechanisms behind their fosfomycin heteroresistance using whole-genome sequencing. RESULTS: A higher frequency of fosfomycin heteroresistance compared with other studies was found. In biofilms, most heteroresistant isolates were less sensitive to fosfomycin than control isolates and showed overexpression of metabolic genes thereby increasing their survival rate. Molecular characterization showed that some resistant subpopulations derived from heteroresistant isolates had a defect in their fosfomycin uptake system caused by mutations in transporter and regulatory genes, whereas others overexpressed the murA gene. None to minor effects on bacterial fitness were observed. Oxidative stress protection, virulence and metabolic genes were differentially expressed in resistant subpopulations and heteroresistant isolates. CONCLUSION: Frequent detection of heteroresistance in UTIs may play a role in the failure of antibiotic treatments and should therefore be more carefully diagnosed.