Yasuhiro Mine

Immunoactive peptides, FK-156 and FK-565. I. Enhancement of host resistance to microbial infection in mice.

The protective effect of an immunoactive peptide, D-lactoyl-L-alanyl-gamma-D-glutamyl-(L)-meso-diaminopimelyl-(L)-glycine (FK-156) and a related compound, heptanoyl-gamma-D-glutamyl-(L)-meso-diaminopimelyl-(D)-alanine (FK-565) was determined in mice with various kinds of microbial infections. FK-156 and FK-565 were given to mice either subcutaneously or orally before challenge. The drugs enhanced significantly the defense of mice against acute systemic infections induced by various extracellular and facultative intracellular organisms, and subcutaneous abscess by Staphylococcus aureus. The protective effect of these drugs against Escherichia coli infection differed considerably depending on the route of administration; FK-156 was only effective by the parenteral route; however, FK-565 was effective by both parenteral and oral routes. After subcutaneous dosing with FK-156, the enhancement of host defense of mice against E. coli infection was more rapid than against Listeria infection. The enhancing effects of FK-156 and FK-565 on host defense of mice against pseudomonal infection was more potent than other immunoactive drugs.

Characterization of BRO enzymes and beta-lactamase transfer of Moraxella (Branhamella) catarrhalis isolated in Japan.

Of the 68 strains of beta-lactamase-producing Moraxella (Branhamella) catarrhalis isolated in Japan that were studied, 62 (91%) produced the BRO-1-type beta-lactamase and 6 (9%) produced the BRO-2 type. There were no strains containing the BRO-3-type beta-lactamase. We compared the susceptibility of BRO-1- and BRO-2-producing strains to various oral beta-lactam antibiotics. We found that the BRO-1-producing strains were less susceptible than the BRO-2-producing strains. Although the BRO-1 and BRO-2 types showed a similar hydrolysis pattern, the specific activity of BRO-1 was 3-fold that of BRO-2. We examined the transfer of the BRO-1 and BRO-2 genes to non-beta-lactamase-producing M. catarrhalis No. 4020 and found that of the 13 donor strains producing BRO-1, 11 (85%) were able to transfer the gene for BRO-1 production by conjugation. Of the 6 donor strains producing BRO-2, 2 (33%) were able to transfer the gene for BRO-2 production by conjugation. For 3 of the 13 (23%) BRO-1-producing strains and 1 of the 6 (17%) BRO-2-producing strains, about 13 Mdalton of plasmids were detected. These plasmid-containing strains were used as donors, and in beta-lactamase-producing transconjugants the same size of plasmids was detected. However, when the total DNA is extracted from strains with the ability to transfer by conjugation, the transformation of the beta-lactamase-producing gene can occur regardless of the presence or absence of plasmids. Furthermore, even if purified plasmids are transformed, beta-lactamase-producing transformants are not obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Simulation of Human Plasma Levels of β-Lactams in Mice by Multiple Dosing and the Relationship between the Therapeutic Efficacy and Pharmacodynamic Parameters

A mathematical multiple dosing model was designed so that human plasma concentration-versus-time curves of beta-lactams are reproduced in mouse plasma. The pharmacokinetic parameters of FK037, a new injective cephalosporin, in volunteers and in the mice model were 6,966 and 6,894 ml, respectively, for Vc, 2.592 and 2.698/h for alpha, 0.2875 and 0.3027/h for beta, and 0.9079 and 1.0506 for K21. Therefore, real pharmacokinetics of humans were reproduced in mice by this method. The 8-hour therapeutic efficacy (the decrease of the viable counts in the lung) against pneumonia with Staphylococcus aureus and Pseudomonas aeruginosa in mice was well correlated with the time above MIC value, but not with AUC, Cmax or AUC above MIC. These results indicate that this model was valuable to evaluate the beta-lactam antibiotics for predicting their clinical efficacy and that the time above MIC is an important factor in selecting beta-lactam agents and determining dosage in pulmonary infection.

In vitro and in vivo Transferrable β‐Lactam Resistance Due to a New Plasmid‐Mediated Oxyiminocephalosporinase from a Clinical Isolate of Proteus mirabilis

A new plasmid‐mediated β‐lactamase (FPM‐1) with an isoelectric point of 7.2 and a molecular weight of 26,000 was found in a cefuroxime‐resistant clinical isolate of Proteus mirabilis strain 6003. FPM‐1 can be classified as a type I oxyiminocephalosporinase on the basis of its substrate specificity and inhibition pattern by clavulanic acid etc., and it conferred resistance on both the strain and transconjugants against most oxyme‐type cephalosporins as well as the older ones but not against cefamycins and a few exceptional oxyme‐type cephalosporins such as ceftizoxime, ceftazidime and cefixime. In a murine systemic infection model, only these FPM‐1‐stable drugs exhibited protective activity against the FPM‐1‐producing P. mirabilis 6003 similar to that against a nonproducing derivative strain. The FPM‐1‐mediated cefuroxime resistance in P. mirabilis 6003 was transferred to co‐infected Escherichia coli 7004 at frequencies between 3.8 × 10−3 and 4.0 × 10−2 in a murine ascending urinary tract infection model. In the same infection model due to the FPM‐1‐producing E. coli transconjugant, FPM‐1‐stable cefixime was significantly more effective than FPM‐1‐labile cefteram pivoxil, although both drugs had similar therapeutic effect against its FPM‐1‐nonproducing counterpart strain.

Nature of Monocyclic β-Lactam Antibiotic Nocardicin A to β-Lactamases

Nocardicin A is the antibiotic which was first found to possess a monocyclic β‐lactam ring. This antibiotic was inactivated by the cleavage of its β‐lactam ring. The direct spectrophotometric assay was applied to measure the rate of enzymatic hydrolysis of Nocardicin A. Nocardicin A was highly stable to both chromosomal and plasmid‐mediated β‐lactamases. Of the nine β‐lactam antibiotics including cefoxitin and cefuroxime, Nocardicin A was the most stable to the β‐lactamases tested excluding those from Klebsiella oxytoca and Proteus vulgaris. The latter broad‐spectrum β‐lactamases hydrolyzed Nocardicin A rather intensively. Extreme stability of Nocardicin A to β‐lactamases was suggested to be due to the combination of its low affinity to the enzymes and stabilization of its monocyclic β‐lactam ring. Nocardicin A was shown to have inducing ability toward β‐lactamases.

Antibacterial activity of cefixime against Streptococcus pneumoniae, Streptococcus pyogenes, and Haemophilus influenzae in the presence of Moraxella (Branhamella) catarrhalis

We measured the sizes of the inhibition zones of oral beta-lactam antibiotics for Streptococcus pneumoniae, Streptococcus pyogenes and Haemophilus influenzae in the presence of beta-lactamase-producing-Moraxella (Branhamella) catarrhalis by the agar double-layer method. The sizes of the zones of amoxicillin for S. pneumoniae alone were the largest, followed in a descending order by those of cefixime and cefaclor. In the presence of 10(7) CFU/ml of M.(B.) catarrhalis, however, significant reduction of the sizes of the zones was seen with amoxicillin and cefaclor; inhibition with cefixime was nearly unchanged. Similar results were observed in those for S. pyogenes. These variable findings were attributed to the difference in stability of these drugs to the beta-lactamase produced by M.(B.) catarrhalis. When the susceptibility of H. influenzae in the presence of 10(8) CFU/ml of M.(B.) catarrhalis to cefixime, cefoteram, cefpodoxime, cefotiam and cefuroxime was examined, the sizes of the inhibition zones of all the drugs were reduced by the presence of 10(8) CFU/ml of M.(B.) catarrhalis, but those of cefixime were the largest of all the drugs tested. Our agar double-layer method is simple and useful for evaluating the influence of beta-lactamase-producing organism, as M.(B.) catarrhalis, on the disk susceptibility of other pathogens to antibiotics.