Yoshiko Yokota

Novel plasmid-mediated beta-lactamase from Escherichia coli that inactivates oxyimino-cephalosporins.

A highly cephem-resistant Escherichia coli strain, FP1546, isolated from the fecal flora of laboratory dogs previously administered beta-lactam antibiotics was found to produce a beta-lactamase, FEC-1, of 48-kilodalton size and pI 8.2. FEC-1 hydrolyzed cefuroxime, cefotaxime, cefmenoxime, and ceftriaxone, as well as the enzymatically less-stable antibiotics cephaloridine, cefotiam, and cefpiramide. Of the oxyimino-cephalosporins, ceftizoxime was fairly stable to FEC-1. FEC-1 differed notably from chromosomal E. coli cephalosporinase, especially in its broad-spectrum substrate profile and its high inhibition by clavulanic acid, sulbactam, and imipenem. A conjugation study revealed that FEC-1 was encoded by a 74-megadalton plasmid, pFCX1. This may be the first instance of a plasmid-mediated oxyimino-cephalosporinase from E. coli.

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.

Low Prevalence of Helicobacter pylori Infection in Patients with Hamartomatous Fundic Polyps

Helicobacter pylori infection of the gastricmucosal surface was investigated in patients withhamartomatous fundic polyps or hyperplastic polyps andin patients without endoscopic evidence of disease(healthy subjects). Presence of H. pylori infection wasdetermined by culture, histologic examination, and theendoscopic phenol red test. Adherence of H. pylori wasevaluated with scanning electron microscopic examination of antral biopsy specimens. Bothprevalence of H. pylori infection (P < 0.001) and H.pylori adherence (P < 0.05) were less in patientswith hamartomatous fundic polyps than in healthy subjects and patients with hyperplastic polyps.However, the percentages of plasma cells in gastricmucosa that contained IgA and of gastric epithelialcells that expressed Lewis b did not differsignificantly among the three groups. These findings suggestthat defense mechanisms against the attachment of H.pylori other than IgA or Lewis b antigen are present inpatients with hamartomarous fundic polyps.

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)

Activity of cefixime against Helicobacter pylori and affinities for the penicillin-binding proteins.

Cefixime induced the formation of rounded cells from the spiral bacillary form of Helicobacter pylori at the MIC or less. Three main penicillin-binding proteins, called A, B and C, were separated from H. pylori. Cefixime had the strongest affinity to penicillin-binding protein B. The binding of cefixime to this protein may induce the formation of rounded H. pylori cells. Images

In Vitro and In Vivo Evaluation of Ceftezole, a New Cephalosporin Derivative

Ceftezole, a new cephalosporin derivative, was compared with cefazolin, cephaloridine, and cephalothin. Data obtained indicate that it is a broad-spectrum antibiotic, with almost identical antimicrobial activity against pathogenic organisms isolated from patients. The therapeutic effect of ceftezole on experimental infections in mice was similar to that of cefazolin and was superior to that of cephalothin. The binding of ceftezole to serum proteins was somewhat less than that of cefazolin. The concentrations of ceftezole in the sera of test animals and human volunteers were determined after intramuscular injection of 20 mg/kg and after a single dose of 500 mg, respectively. The concentration of ceftezole in the serum of volunteers peaked at 24.9 μg/ml 15 min after injection and remained effective (about 2.6 μg/ml) at 4 h. The half-life in serum under the same conditions was 56 min, i.e., about one-half that of cefazolin. The 24-h urinary recovery rate was 87.5%. Most of the administered ceftezole was excreted unchanged mainly through the urinary tract. The biliary excretion rate in SD strain rats after intramuscular injection of 20 mg/kg was about 4.4%. As compared with commercially available cephalosporins, ceftezole was second only to cefazolin in biliary excretion rate. Various tissue levels of ceftezole in animals were higher than cephalothin but, with the exception of renal levels in the early stage after administration, were lower than cefazolin.

Interaction of Beta-Lactam Antibiotics with the Penicillin-Binding Proteins of Penicillin-Resistant Streptococcus pneumoniae

The binding of five structurally diverse beta-lactam antibiotics to penicillin-binding proteins (PBPs) of two clinical isolates of Streptococcus pneumoniae resistant to penicillin G was compared with that of a susceptible strain. A common feature of the PBP patterns of the resistant strains was the absence of PBP 1a detected in the susceptible strain. For each beta-lactam antibiotic tested, there appeared to be significant decreases in the affinity for BPB 1b, 2a and 2b of the resistant strains. We attempted to evaluate a quantitative correlation between the antibacterial activity of the drugs for three strains and their affinity for the various PBPs. A close correlation was found between the minimum inhibitory concentrations and the affinity for PBP 2a, but not for any of the other PBPs.

Laboratory Evaluation of FR10024, a New Cephalosporin Derivative

FR10024 is a broad-spectrum antibiotic. The in vitro antibacterial activity of FR10024 against clinical isolates of Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis is greater than that of any of the cephalosporins developed to date. Indole-positive Proteus, Enterobacter, and Citrobacter are resistant to FR10024, as is true for the other cephalosporins. However, more than half of the strains of Enterobacter and Citrobacter tested were susceptible to FR10024 at an inoculum of 106 cells/ml. A single subcutaneous injection of FR10024 to mice with peritoneal infections due to S. aureus and several species of gram-negative bacilli gave a protective effect inferior to that of cefazolin but appeared to be superior to that of cephalothin. When given in two divided doses, however, the protective effect of FR10024 was enhanced and almost equaled that of cefazolin. The serum levels and rates of urinary recovery of FR10024 varied in different animal species. The mean peak serum level of FR10024 in humans after a single intramuscular injection of 500 mg was two times higher than that of cephalothin. The serum half-life after intramuscular injections of 250 and 500 mg was slightly shorter than that of cephalothin. After receiving 250 mg of FR10024 intramuscularly the urinary recovery rate was 87.7% in healthy volunteers. The biliary excretion rate of FR10024 was particularly high. The 24-h excretion of FR10024 in rats was 63.3%, this being six to seven times higher than that for cefazolin, which has the highest biliary excretion of the other known cephalosporins. When FR10024 was injected intramuscularly (20 mg/kg), it was found that the hepatic levels of FR10024 in rats were the highest of all the cephalosporins, including cefazolin, but the levels of FR10024 in other tissues were not as high as those of cefazolin.

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.

Characteristics of Biliary Excretion of Cefazolin and Other Cephalosporins with Reference to the Relationship between Serum Levels and Administration Conditions

The biliary excretion of cefazolin was compared with that of cephalothin and cephaloridine in rats and man. In rats, the biliary levels were dose-related with cefazolin and cephalothin but not with cephaloridine. Biliary levels were higher than serum levels after injection of 10--80 mg/kg of cefazolin and cephalothin, whereas serum levels of cephaloridine after injection were higher than biliary levels. The highest biliary levels of cefazolin were obtained by intravenous injection, followed by intramuscular injection and drip infusion. In man, a crossover study was made to compare biliary levels of cefazolin with those of cephaloridine and cephalothin. After a single 1-gram intravenous injection, the peak levels of cefazolin ranged from 0.85 to 21 mug/ml and those of cephaloridine varied from 0.55 to 3.9 mug/ml. After a 3-gram intravenous injection, the peak biliary levels of cefazolin ranged from 35.5 to 270 mug/ml and those of cephalothin from 0.3 to 64 mug/ml. The chemotherapeutic biliary levels of cefazolin able to inhibit susceptible organisms were obtained by 3-gram intravenous injections.