TY - JOUR
T1 - In vitro development and analysis of escherichia coli and shigella boydii azithromycin-resistant mutants
AU - Gomes, Cláudia
AU - Pons, Maria J.
AU - Magallon-Tejada, Ariel
AU - Durand, David
AU - Lluque, Angela
AU - Mosquito, Susan
AU - Riveros, Maribel
AU - Mercado, Erik
AU - Prada, Ana
AU - Ochoa, Theresa J.
AU - Ruiz, Joaquim
PY - 2013/4/1
Y1 - 2013/4/1
N2 - The aim of this study was to develop and analyze in vitro azithromycin (AZM)-resistant mutants of Escherichia coli and Shigella boydii. Three clinical isolates of E. coli and one S. boydii isolated from feces samples collected from children under 5 years of age with diarrhea in Lima, Peru were inoculated onto Mueller-Hinton plates containing increasing serial dilutions of AZM ranging from their specific minimal inhibitory concentration (2 or 4 mg/l) to 64 mg/l. From these plates, 16 AZM-resistant mutants were selected to determine the stability of the resistance and the presence of cross resistance with other antibiotics. The role of Phe-Arg-β-Naphthylamide (PAβN)-inhibitible efflux pumps as well as the presence of mutations in the rplV, rplD, and rrlH (23S rRNA) genes and alterations in the outer membrane profiles were determined in these 16 mutants. The rate of mutation ranged from < 2.70×10-10 to 2.17×10-7 for E. coli and from < 9.58×10-10 to 1.05×10-8 for S. boydii. E. coli mutants showed an increase in the AZM-MIC up to sixfold with one strain achieving a MIC >256 mg/l. In contrast, S. boydii only presented increases of up to twofold in MIC levels. All the strains obtained, but one showed stable AZM resistance. In the presence of PAβN, the AZM MICs decreased to parental levels in Shigella mutants, while no MIC returned to parental levels among the E. coli mutants. No cross resistance to other classes of antibiotics was found. These results show the relevance of PAβN-inhibitible efflux pumps in the basal levels and development of AZM resistance. Further studies to characterize the remaining unidentified mechanisms of AZM resistance are needed.
AB - The aim of this study was to develop and analyze in vitro azithromycin (AZM)-resistant mutants of Escherichia coli and Shigella boydii. Three clinical isolates of E. coli and one S. boydii isolated from feces samples collected from children under 5 years of age with diarrhea in Lima, Peru were inoculated onto Mueller-Hinton plates containing increasing serial dilutions of AZM ranging from their specific minimal inhibitory concentration (2 or 4 mg/l) to 64 mg/l. From these plates, 16 AZM-resistant mutants were selected to determine the stability of the resistance and the presence of cross resistance with other antibiotics. The role of Phe-Arg-β-Naphthylamide (PAβN)-inhibitible efflux pumps as well as the presence of mutations in the rplV, rplD, and rrlH (23S rRNA) genes and alterations in the outer membrane profiles were determined in these 16 mutants. The rate of mutation ranged from < 2.70×10-10 to 2.17×10-7 for E. coli and from < 9.58×10-10 to 1.05×10-8 for S. boydii. E. coli mutants showed an increase in the AZM-MIC up to sixfold with one strain achieving a MIC >256 mg/l. In contrast, S. boydii only presented increases of up to twofold in MIC levels. All the strains obtained, but one showed stable AZM resistance. In the presence of PAβN, the AZM MICs decreased to parental levels in Shigella mutants, while no MIC returned to parental levels among the E. coli mutants. No cross resistance to other classes of antibiotics was found. These results show the relevance of PAβN-inhibitible efflux pumps in the basal levels and development of AZM resistance. Further studies to characterize the remaining unidentified mechanisms of AZM resistance are needed.
UR - http://www.scopus.com/inward/record.url?scp=84875611548&partnerID=8YFLogxK
U2 - 10.1089/mdr.2012.0036
DO - 10.1089/mdr.2012.0036
M3 - Artículo
C2 - 23176550
AN - SCOPUS:84875611548
SN - 1076-6294
VL - 19
SP - 88
EP - 93
JO - Microbial Drug Resistance
JF - Microbial Drug Resistance
IS - 2
ER -
