Characterization of order types of pointwise linearly ordered families of Baire class 1 functions

ABSTRACT During a survey conducted to evaluate the incidence of class B carbapenemase (metallo-β-lactamase [MBL])-producing Pseudomonas aeruginosa strains from hospitals in Majorca, Spain, five clinical isolates showed a positive Etest MBL screening test result. In one of them, strain PA-SL2, the presence of a new bla VIM derivative (bla VIM-13) was detected by PCR amplification with bla VIM-1-specific primers followed by sequencing. The bla VIM-13-producing isolate showed resistance to all β-lactams (except aztreonam), gentamicin, tobramycin, and ciprofloxacin. VIM-13 exhibited 93% and 88% amino acid sequence identities with VIM-1 and VIM-2, respectively. bla VIM-13 was cloned in parallel with bla VIM-1, and the resistance profile conferred was analyzed both in Escherichia coli and in P. aeruginosa backgrounds. Compared to VIM-1, VIM-13 conferred slightly higher levels of resistance to piperacillin and lower levels of resistance to ceftazidime and cefepime. VIM-13 and VIM-1 were purified in parallel as well, and their kinetic parameters were compared. The k cat/K m ratios for the antibiotics mentioned above were in good agreement with the MIC data. Furthermore, EDTA inhibited the activity of VIM-13 approximately 25 times less than it inhibited the activity of VIM-1. VIM-13 was harbored in a class 1 integron, along with a new variant (Ala108Thr) of the aminoglycoside-modifying enzyme encoding gene aacA4, which confers resistance to gentamicin and tobramycin. Finally, the VIM-13 integron was apparently located in the chromosome, since transformation and conjugation experiments consistently yielded negative results and the bla VIM-13 probe hybridized only with the genomic DNA.

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Molecular characterization of class 1 integrons in MDRPseudomonas aeruginosaisolated from clinical settings in Iran, Tehran

FEMS Immunology & Medical Microbiology ◽

10.1111/j.1574-695x.2009.00636.x ◽

2010 ◽

Vol 58 (3) ◽

pp. 421-425 ◽

Cited By ~ 19

Author(s):

Fereshteh Shahcheraghi ◽

Farzad Badmasti ◽

Mohammad M. Feizabadi

Keyword(s):

Molecular Characterization ◽

Clinical Settings ◽

Class 1 Integrons ◽

Class 1

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Incidence and Characterization of Integrons, Genetic Elements Mediating Multiple-Drug Resistance, in AvianEscherichia coli

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.43.12.2925 ◽

1999 ◽

Vol 43 (12) ◽

pp. 2925-2929 ◽

Cited By ~ 165

Author(s):

Lydia Bass ◽

Cynthia A. Liebert ◽

Margie D. Lee ◽

Anne O. Summers ◽

David G. White ◽

...

Keyword(s):

Antibiotic Resistance ◽

Resistance Gene ◽

Multiple Drug Resistance ◽

Marker Gene ◽

Clinical Isolates ◽

Multiple Antibiotic Resistance ◽

Class 1 Integron ◽

E Coli ◽

Class 1

ABSTRACT Antibiotic resistance among avian bacterial isolates is common and is of great concern to the poultry industry. Approximately 36% (n = 100) of avian, pathogenic Escherichia coli isolates obtained from diseased poultry exhibited multiple-antibiotic resistance to tetracycline, oxytetracycline, streptomycin, sulfonamides, and gentamicin. Clinical avian E. coli isolates were further screened for the presence of markers for class 1 integrons, the integron recombinase intI1 and the quaternary ammonium resistance gene qacEΔ1, in order to determine the contribution of integrons to the observed multiple-antibiotic resistance phenotypes. Sixty-three percent of the clinical isolates were positive for the class 1 integron markersintI1 and qacEΔ1. PCR analysis with the conserved class 1 integron primers yielded amplicons of approximately 1 kb from E. coli isolates positive for intI1 andqacEΔ1. These PCR amplicons contained the spectinomycin-streptomycin resistance gene aadA1. Further characterization of the identified integrons revealed that many were part of the transposon Tn21, a genetic element that encodes both antibiotic resistance and heavy-metal resistance to mercuric compounds. Fifty percent of the clinical isolates positive for the integron marker gene intI1 as well as for theqacEΔ1 and aadA1 cassettes also contained the mercury reductase gene merA. The correlation between the presence of the merA gene with that of the integrase and antibiotic resistance genes suggests that these integrons are located in Tn21. The presence of these elements among avianE. coli isolates of diverse genetic makeup as well as inSalmonella suggests the mobility of Tn21 among pathogens in humans as well as poultry.

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