ABSTRACT
INTRODUCTION: Small colony variants of Staphylococcus aureus (SCVSA) are a sub-population with special features. METHODS: The phenotypic features and antibiotic susceptibility of four clinical isolates SCVSA were studied. RESULTS: Colonies grew in the usual culture media, except in Mueller Hinton. All isolates were resistant to ciprofloxacin and co-trimoxazole. DISCUSSION: As SCVSA are isolated with low frequency, it is necessary to determine the optimal methods for their identification and antibiotic susceptibility study.
Subject(s)
Drug Resistance, Multiple, Bacterial , Microbial Sensitivity Tests , Staphylococcal Infections/microbiology , Staphylococcus aureus/growth & development , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/therapeutic use , Bacteriological Techniques , Clone Cells/drug effects , Colony Count, Microbial , Culture Media , Cystic Fibrosis/complications , Cystic Fibrosis/microbiology , Hemin/pharmacology , Humans , Otitis/microbiology , Phenotype , Sputum/microbiology , Staphylococcal Infections/complications , Staphylococcal Infections/diagnosis , Staphylococcus aureus/drug effects , Staphylococcus aureus/isolation & purification , Thymidine/pharmacology , Vitamin K 3/pharmacologyABSTRACT
Introducción: La resistencia combinada a quinolonas y (..) (AU)
Background: Combined resistance to quinolones and (..) (AU)
Subject(s)
Plasmids/isolation & purification , Klebsiella oxytoca/pathogenicity , Klebsiella pneumoniae/pathogenicity , Drug Resistance, Microbial , Microbial Sensitivity Tests , Bacterial Typing Techniques/methodsABSTRACT
BACKGROUND: Combined resistance to quinolones and ß-lactams is common in Enterobacteriaceae. The appearance in enterobacteria coding for metallo-ß-lactamases and determinants of plasmid-mediated quinolone resistance are an emerging problem in our country. METHODS: The susceptibility was determined by E-test. The resistance genes were detected by PCR and the corresponding plasmids were characterised. RESULTS: This study describes 2 strains (1 Klebsiella oxytoca, 1 Klebsiella pneumoniae) carrying the genes qnrS2 and blaVIM-1 in a transferable plasmid of 70-Kb isolated in surveillance cultures at the University Hospital Virgen Macarena in Seville. CONCLUSION: This is the first combination of qnrS2 and bla(VIM-1) on the same non-typeable plasmid isolated in our centre.
Subject(s)
Bacterial Proteins/genetics , Drug Resistance, Bacterial/genetics , Klebsiella oxytoca/drug effects , Klebsiella oxytoca/genetics , Klebsiella pneumoniae/drug effects , Klebsiella pneumoniae/genetics , Plasmids/genetics , Humans , Spain , beta-Lactamases/geneticsABSTRACT
BACKGROUND: Extended-spectrum AmpC cephalosporinases (ESACs) have been reported in Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii. Here, we characterize a new AmpC variant presenting a broadened substrate activity towards fourth-generation cephalosporins, selected in vivo following cefepime treatment for Enterobacter aerogenes. METHODS: Two consecutive clonally related isolates of E. aerogenes were evaluated. Screening for ESAC production was performed using plates containing 200 mg/L cloxacillin. MICs were determined by microdilution (CLSI guidelines). bla(AmpC) genes were cloned into a pCR-Blunt II-TOPO vector and expressed in Escherichia coli. The ampC genes were cloned into vector pGEX-6P-1 for protein purification. RESULTS: Isolate Ea595 was resistant to two fourth-generation cephalosporins, cefepime and cefpirome; using plates containing cloxacillin, susceptibility to ceftazidime and cefepime was restored, suggesting overproduction of the ESAC ß-lactamase. Sequencing identified a new AmpC ß-lactamase variant presenting one amino acid substitution, Val291Gly, inside the H-10 helix. Recombinant plasmids harbouring this ESAC ß-lactamase conferred a broadened resistance profile to cefepime and cefpirome, with resistance levels increasing from 16- to 32-fold in E. coli. AmpC-Ea595 hydrolysed ceftazidime, cefepime and cefpirome at high levels, presenting a lower K(m) and enabling us to classify the enzyme as an ESAC. Homology modelling suggested that the size of the active site could have increased. CONCLUSIONS: We characterized an ESAC ß-lactamase selected in vivo and conferring a high level of resistance to fourth-generation cephalosporins in E. aerogenes. The broadened spectrum was caused by a new modification to the H-10 helix, which modified the active site.
