Toyoji Okubo

Detection of a Variant Metallo-β-Lactamase, IMP-10, from Two Unrelated Strains of Pseudomonas aeruginosa and an Alcaligenes xylosoxidans Strain

ABSTRACT The gene blaIMP-10 of a variant metallo-β-lactamase, IMP-10, had a single base replacement of G by T at nucleotide 145, which led to an amino acid alteration of Val49 to Phe compared to the IMP-1 enzyme, indicating that IMP-10 was a point mutation derivative of IMP-1. Highly purified enzymes revealed that IMP-10 was different from IMP-1 in its extremely low hydrolyzing activities for penicillins, such as benzylpenicillin, ampicillin, and piperacillin.

Presence of Pseudomonas putida Strains Harboring Plasmids Bearing the Metallo-β-Lactamase Gene blaIMP in a Hospital in Japan

ABSTRACT To determine the persistence and spread of antibiotic-resistant strains in Gunma University Hospital, 83 Pseudomonas putida strains (each from a different patient) were isolated from January 1997 through December 2001. Of the 83 strains isolated, 27 were resistant to carbapenems. All 27 produced metallo-β-lactamase and were found to be PCR positive for the blaIMP gene. Most (22 strains) were primarily isolated from the wards (W7 [9 strains] and W4 [8 strains]). Another five blaIMP-positive P. putida strains from wards W7 and W4 were obtained by swabbing around the water pipes. A total of 32 blaIMP-positive P. putida strains were assessed by pulsed-field gel electrophoresis (PFGE) and testing of drug susceptibility to 10 chemotherapeutic agents. Both PFGE and MIC patterns revealed that there were long-term resident strains among inpatients and hospital environments. The blaIMP genes of 22 of 32 strains were all transferable to a recipient strain of Pseudomonas aeruginosa by conjugation or transformation and conferred resistance to carbapenems and cephems. The blaIMP plasmids were conjugally transmissible among P. aeruginosa strains and mediated resistance to amikacin as well as β-lactams. Ten of the 22 plasmids mediated additional resistance to gentamicin and tobramycin. Plasmids with identical DNA and drug resistance patterns were found in P. putida strains with identical PFGE patterns and with different PFGE patterns. We presumed that P. putida was one of the resident species in inpatients and especially in hospital environments, spreading drug resistance genes via plasmids among P. putida strains and supplying them to more pathogenically important species, such as P. aeruginosa.

Integration of the erythromycin (ero) resistance gene of a staphylococcal plasmid into S1ppen.ion phage

Abstract The nonconjugative plasmid rms8 encoding resistance to penicillin (PC, pen ), cadmium (Cd, cad ), arsenite (As, asi ), and mercury (Hg, mer ) was transduced with bacteriophage S1. A phage lysate capable of transducing the character of either (PC.Cd).As.Hg) or (PC.Cd) resistance at an extremely high frequency was obtained. Lysogenization always accompanied the transduction of either the (PC.Cd.As.Hg) or (PC.Cd) characters. These phages were named S1 ppen.ion1 (ion1 = cad) and S1 ppen.ion2 (ion2 = cad.asi.mer) . When one of the transductants containing the rms9 plasmid encoding erythromycin (EM, ero ) resistance was lysogenized with S1 ppen.ion2, the EM resistant character was transduced along with the S1 ppen.ion2, the EM resistant character was transduced along with the S1 ppen.ion2 phage at an extremely high frequency. All of these EM-resistant transductants showed (PC.Cd.As) resistance and produced active transducing phages, but had lost the Hg-resistant character. Accordingly, it is concluded that the phage possessing resistance to the (PC.Cd.As.EM) character arose by recombination between rms9 and S1 ppen.ion2 at the site of the mer loci in S1 ppen.ion2 , resulting in the loss of the resistance to the Hg character.