High affinity of interaction between superantigen and T cell receptor Vbeta molecules induces a high level and prolonged expansion of superantigen-reactive CD4+ T cells.

In mice implanted with an osmotic pump filled with the superantigen (SAG) staphylococcal enterotoxin A (SEA), the Vβ3(+)CD4(+) T cells exhibited a high level of expansion whereas the Vβ11(+)CD4(+) T cells exhibited a mild level of expansion. In contrast, in mice implanted with an osmotic pump filled with SE-like type P (SElP, 78.1% homologous with SEA), the Vβ11(+)CD4(+) T cells exhibited a high level of expansion while the Vβ3(+)CD4(+) T cells exhibited a low level of expansion, suggesting that the level of the SAG-induced response is determined by the affinities between the TCR Vβ molecules and SAG.

Molecular epidemiology of outbreaks and containment of drug-resistant Pseudomonas aeruginosa in a Tokyo hospital.

We witnessed outbreaks of multidrug-resistant (MDR) and drug-resistant Pseudomonas aeruginosa at a hospital in Tokyo, Japan, during the period September 2004 through May 2005. The first outbreak occurred in September and October 2004. Three isolates of MDR P.

Outbreaks of multidrug-resistant Pseudomonas aeruginosa in community hospitals in Japan.

We previously reported an outbreak in a neurosurgery ward of catheter-associated urinary tract infection with multidrug-resistant (MDR) Pseudomonas aeruginosa strain IMCJ2.S1, carrying the 6'-N-aminoglycoside acetyltransferase gene [aac(6')-Iae]. For further epidemiologic studies, 214 clinical isolates of MDR P.

Emergence of rifampicin resistance in methicillin-resistant Staphylococcus aureus in tuberculosis wards.

To assess whether the occurrence of rifampicin (RFP) resistance in methicillin-resistant Staphylococcus aureus (MRSA) is related to treatment of tuberculosis, we determined the RFP susceptibility of MRSA isolates obtained from tuberculosis patients and screened for mutation(s) in the rpoB gene of these isolates. The MICs of RFP for 84 MRSA isolates obtained from two hospitals in Japan were determined. DNA was sequenced in the region 1318-1602 nucleotides (nt) of the rpoB gene, which includes RFP resistance-determining clusters I (1384-1464 nt, 462-488 amino acids).

Cloning and characterization of a novel trimethoprim-resistant dihydrofolate reductase from a nosocomial isolate of Staphylococcus aureus CM.S2 (IMCJ1454).

A novel gene, dfrG, encoding a trimethoprim (TMP)-resistant dihydrofolate reductase (DHFR, designated S3DHFR) was cloned from a clinical isolate of methicillin-resistant Staphylococcus aureus. Escherichia coli expressing dfrG was highly resistant to TMP. Recombinant S3DHFR exhibited DHFR activity that was not inhibited by TMP.

[Antimicrobial activity of fosfomycin against beta-lactamase-producing methicillin-sensitive Staphylococcus aureus and methicillin-sensitive coagulase-negative staphylococci].

Antimicrobial activity of fosfomycin (FOM), cefazolin (CEZ), cefmetazole (CMZ), cefotiam (CTM) and piperacillin (PIPC) against clinical isolates of methicillin-sensitive Staphylococcus aureus (MSSA) (beta-lactamase-producing or non-producing) and methicillin-sensitive coagulase-negative Staphylococci (MSCNS) (beta-lactamase-producing or non-producing) were determined to make clear the differences in antimicrobial activity of FOM and beta-lactam antibiotics. The antimicrobial activity of PIPC against beta-lactamase-producing strains of MSSA was lower than that against non-producing ones, judging from the distribution patterns of susceptibility of the strains to PIPC. There were no differences in the antimicrobial activity of FOM, CEZ and CMZ for the producing and non-producing strains.

[Antibacterial activity of biapenem against recent clinical isolates].

Antibacterial activity of biapenem (BIPM) against clinical isolates of 8 species between 2000 and 2002 was compared with those of imipenem/cilastatin (IPM/CS), meropenem (MEPM), panipenem/betamipron (PAPM/BP) and ceftazidime (CAZ). The MICs of biapenem for Gram-positive bacteria were higher than those of IPM/CS and PAPM/BP, equal to those of MEPM and lower than those of CAZ. The MICs of BIPM for Gram-negative bacteria were higher than those of MEPM, equal to those of IPM/CS and PAPM/BP, and lower than those of CAZ.

[Relationship between arbekacin-susceptibility and aminoglycoside-resistant gene of methicillin-resistant Staphylococcus aureus (MRSA)].

The susceptibility to arbekacin (ABK) of methicillin-resistant Staphylococcus aureus (MRSA) was investigated to find out how it related to aac(6')/aph(2") gene. In 49 isolates of MRSA for which MIC of ABK ranged from 0.125 to 64 micrograms/ml, the MICs of ABK for 38 strains carrying aac(6')/aph(2") gene were widely distributed from 0.

[Inhibitory activity of NM394, the active form of prodrug prulifloxacin against type II topoisomerase from Pseudomonas aeruginosa].

The inhibitory activity of NM394, the active form of the prodrug prulifloxacin, against type II topoisomerase from Pseudomonas aeruginosa was compared with those of ciprofloxacin (CPFX), levofloxacin (LVFX) and gatifloxacin (GFLX). The 50% inhibitory concentrations (IC50S) of NM394 for supercoiling activity of DNA gyrase and the decatenation activity of topoisomerase IV were 1.21 and 21.

[Antibacterial activities of fosfomycin against several fresh clinical isolates--comparison of the test methods for antibacterial activity].

In vitro antibacterial activity of fosfomycin was evaluated by various methods. Strains of methicillin-sensitive Staphylococcus aureus, methicillin-sensitive coagulase-negative Staphylococci and Escherichia coli were much more susceptible when glucose-6-phosphate was added to the test medium, but strains of Serratia marcescens and Pseudomonas aeruginosa were not affected. Nutrient agar instead of Mueller-Hinton agar allowed to exhibiting the higher activity of fosfomycin against all the species tested.

[In vitro short-term bactericidal activity and accumulation of NM394, the active metabolite of prulifloxacin, for Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa: comparison with ciprofloxacin, levofloxacin, and gatifloxacin].

The in vitro short-term bactericidal activity and accumulation of NM394, the active metabolite of prulifloxacin, was compared with those of ciprofloxacin (CPFX), levofloxacin (LVFX) and gatifloxacin (GFLX), using Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Of the 4 fluoroquinolones examined, NM394 accumulated to the highest concentration in all three strains. The order of concentration of the fluoroquinolones accumurated in S.

[In vitro antibacterial activity of prulifloxacin, a new oral fluoroquinolone].

We compared antibacterial activity of NM394, which is the active metabolite of a prodrug of new fluoroquinolone prulifloxacin (PUFX), against clinical isolates of bacteria with those of ciprofloxacin (CPFX), levofloxacin (LVFX), gatifloxacin (GFLX), tosufloxacin (TFLX) and fleroxacin (FLRX). 1. NM394 showed a broad-spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria.

[Bactericidal activity of biapenem against various efflux system mutants of Pseudomonas aeruginosa].

The bactericidal activity of biapenem, a new carbapenem, against various efflux-mutants of Pseudomonas aeruginosa was compared with those of imipenem, panipenem, meropenem and ceftazidime. The bactericidal activity of biapenem against P. aeruginosa KG5001, a strain deficient in MexAB-OprM, MexCD-OprJ and MexXY-OprM, was very strong compared with those of imipenem and meropenem.

Airway hyper-responsiveness to neurokinin A and bradykinin following Mycoplasma pneumoniae infection associated with reduced epithelial neutral endopeptidase.

To determine whether mycoplasma infection produces airway hyper-responsiveness to tachykinins and bradykinin and, if so, to elucidate the role of neutral endopeptidase (NEP), isolated hamster tracheal segments were studied under isometric conditions in vitro. Nasal inoculation with Mycoplasma pneumoniae potentiated contractile responses to neurokinin A and bradykinin, causing a leftward shift of the dose-response curves to a lower concentration by 1 log unit for each agonist, whereas there was no response with acetylcholine. Pretreatment of tissues with the NEP inhibitor phosphoramidon augmented neurokinin A- and bradykinin-induced contractions in saline-treated control tissues, but did not further potentiate the responsiveness in M.