Molecular characterization of fluoroquinolone resistance in nontypeable Haemophilus influenzae clinical isolates.
Nontypeable Haemophilus influenzae (NTHi) is a common cause of respiratory infections in adults, who are frequently treated with fluoroquinolones. The aims of this study were to characterize the genotypes of fluoroquinolone-resistant NTHi isolates and their mechanisms of resistance. Among 7,267 H. influenzae isolates collected from adult patients from 2000 to 2013, 28 (0.39%) were ciprofloxacin resistant according to Clinical and Laboratory Standards Institute (CLSI) criteria. In addition, a nalidixic acid screening during 2010 to 2013 detected five (0.23%) isolates that were ciprofloxacin susceptible but nalidixic acid resistant. Sequencing of their quinolone resistance-determining regions and genotyping by pulse-field gel electrophoresis and multilocus sequence typing of the 25 ciprofloxacin-resistant isolates available and all 5 nalidixic acid-resistant isolates were performed. In the NTHi isolates studied, two mutations producing changes in two GyrA residues (Ser84, Asp88) and/or two ParC residues (Ser84, Glu88) were associated with increased fluoroquinolone MICs. Strains with one or two mutations (n = 15) had ciprofloxacin and levofloxacin MICs of 0.12 to 2 μg/ml, while those with three or more mutations (n = 15) had MICs of 4 to 16 μg/ml. Long persistence of fluoroquinolone-resistant strains was observed in three chronic obstructive pulmonary disease patients. High genetic diversity was observed among fluoroquinolone-resistant NTHi isolates. Although fluoroquinolones are commonly used to treat respiratory infections, the proportion of resistant NTHi isolates remains low. The nalidixic acid disk test is useful for detecting the first changes in GyrA or in GyrA plus ParC among fluoroquinolone-susceptible strains that are at a potential risk for the development of resistance under selective pressure by fluoroquinolone treatment.
Microbiology Department, Hospital Universitari Bellvitge, Universitat de Barcelona-IDIBELL, Barcelona, Spain CIBER de Enfermedades Respiratorias (CIBERes), Instituto de Salud Carlos III, Madrid, Spain.
Carmen
C
Puig
CIBER de Enfermedades Respiratorias (CIBERes), Instituto de Salud Carlos III, Madrid, Spain Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain.
José Manuel
JM
Tirado-Vélez
Microbiology Department, Hospital Universitari Bellvitge, Universitat de Barcelona-IDIBELL, Barcelona, Spain CIBER de Enfermedades Respiratorias (CIBERes), Instituto de Salud Carlos III, Madrid, Spain.
Laura
L
Calatayud
Microbiology Department, Hospital Universitari Bellvitge, Universitat de Barcelona-IDIBELL, Barcelona, Spain CIBER de Enfermedades Respiratorias (CIBERes), Instituto de Salud Carlos III, Madrid, Spain.
Fe
F
Tubau
CIBER de Enfermedades Respiratorias (CIBERes), Instituto de Salud Carlos III, Madrid, Spain Instituto de Agrobiotecnología-CSIC-Universidad Pública de Navarra-Gobierno de Navarra, Navarra, Spain.
Junkal
J
Garmendia
Microbiology Department, Hospital Universitari Bellvitge, Universitat de Barcelona-IDIBELL, Barcelona, Spain CIBER de Enfermedades Respiratorias (CIBERes), Instituto de Salud Carlos III, Madrid, Spain.
Carmen
C
Ardanuy
Microbiology Department, Hospital Universitari Bellvitge, Universitat de Barcelona-IDIBELL, Barcelona, Spain CIBER de Enfermedades Respiratorias (CIBERes), Instituto de Salud Carlos III, Madrid, Spain.
Sara
S
Marti
CIBER de Enfermedades Respiratorias (CIBERes), Instituto de Salud Carlos III, Madrid, Spain Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain Presidencia, Consejo Superior de Investigaciones Científicas, Madrid, Spain fina.linares@bellvitgehospital.cat agcampa@isciii.es.
Adela G
AG
de la Campa
Microbiology Department, Hospital Universitari Bellvitge, Universitat de Barcelona-IDIBELL, Barcelona, Spain CIBER de Enfermedades Respiratorias (CIBERes), Instituto de Salud Carlos III, Madrid, Spain fina.linares@bellvitgehospital.cat agcampa@isciii.es.
Josefina
J
Liñares
D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D015373:Bacterial Typing Techniques; D001483:Base Sequence; D002939:Ciprofloxacin / Q000627:therapeutic use; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005260:Female; D024841:Fluoroquinolones / Q000627:therapeutic use*; D014644:Genetic Variation; D006192:Haemophilus Infections / Q000188:drug therapy* / Q000382:microbiology; D006193:Haemophilus influenzae / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D064704:Levofloxacin / Q000627:therapeutic use; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D058885:Multilocus Sequence Typing; D009268:Nalidixic Acid / Q000627:therapeutic use; D029424:Pulmonary Disease, Chronic Obstructive / Q000382:microbiology; D012141:Respiratory Tract Infections / Q000188:drug therapy* / Q000382:microbiology; D017422:Sequence Analysis, DNA
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D024841:Fluoroquinolones; D009268:Nalidixic Acid; D002939:Ciprofloxacin; D064704:Levofloxacin; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase