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The objective of this study was to determine the antimicrobial susceptibility of anaerobic bacteria from the intestinal microflora of healthy children who had not been treated with antimicrobial agents since birth or at 1, 3, 6, 12, 18 and 24 months of age, as well as from children of the same ages treated with the most commonly used antimicrobial agents in Nicaragua. A total of 947 Bacteroides and 745 Clostridium strains were isolated from 67 healthy and 94 antimicrobial-treated children. The minimal inhibitory concentrations of ampicillin, cefoxitin, imipenem, clindamycin, metronidazole and chloramphenicol were determined by the agar dilution method. Detection of ss-lactamase was made by the nitrocefin assay. No bacterial strains resistant to imipenem, clindamycin, metronidazole or chloramphenicol were found. The susceptibility of Bacteroides species to ampicillin and cefoxitin isolated from antimicrobial-treated children decreased progressively as the children reached 24 months of age, from 88% to 78% and from 94% to 81%, respectively. All the Bacteroides strains isolated from the healthy children were 100% susceptible to cefoxitin when they were <=12 months and 92% susceptible after this age; the susceptibility of Bacteroides strains to ampicillin in these children was from 91% at 1 month to 86% at 24 months of age. All Clostridium strains were susceptible to ampicillin and cefoxitin. The ss-lactamase production was seen only in Bacteroides species. These data indicate that a rational use of antimicrobial agents is needed to avoid the development of resistance in anaerobic bacteria.

Aim of the present study was to evaluate the effect of cefamandole, cefuroxime and cefoxitin on the level of gastrointestinal (GI) colonization by Candida albicans in humans. Twenty-eight adult patients received one of these three cephalosporins for 10 days, as treatment of infection, and were studied prospectively. Quantitative stool cultures for yeasts were performed immediately before, at the end, and 1 week after discontinuation of treatment. All three antibiotics caused an increase of the yeast concentration in the fecal flora. The increase caused by cefoxitin was the highest (2.5 log10 CFU/g of stool). Our results suggest that the cephalosporins tested cause minor increases of the colonization of the GI tract by C. albicans.

Fifteen isolates of Klebsiella pneumoniae producing extended-spectrum beta-lactamases (ESBLs) isolated during a nosocomial outbreak were studied. The strains belonged to the same clonal type, as shown by pulsed-field gel electrophoretic analysis of chromosomal DNA. All the isolates were resistant to extended-spectrum cephalosporins, aztreonam, gentamicin, and fluoroquinolones and were susceptible to carbapenems, tobramycin, netilmicin, and amikacin. None of the isolates expressed the OmpK36 porin. Eight isolates, for which the MICs of cefoxitin were > or = 64 micrograms/ml, showed a diminished level or no expression of a 35-kDa porin. The MICs of meropenem, cefotaxime, and cefpirome were three to eight times higher for porin-deficient isolates than for isolates expressing the 35-kDa porin, but the MICs of imipenem increased two times for porin-deficient isolates compared to those for isolates expressing the porin. This MIC increase reverted to a level similar to that for the parental strain when porin-deficient isolates were transformed with the gene coding for the K. pneumoniae porin OmpK36. It is concluded that the high level of resistance to cefoxitin and the increase in the MICs of meropenem, cefotaxime, and cefpirome for the ESBL-producing K. pneumoniae isolates studied are associated with porin deficiency.

Clinafloxacin was more active than ciprofloxacin against 4,213 aerobic and facultative anaerobic bacterial isolates from 10 medical centers, as tested by broth microdilution and disk diffusion methods. The percentage of 201 anaerobes susceptible to clinafloxacin by broth microdilution was comparable to cefoxitin. Our data support the proposed disk diffusion interpretive criteria for aerobic bacteria with 5-microg clinafloxacin disks.

The in vitro activity of BAY 12-8039 against 360 anaerobic clinical isolates was determined by the agar dilution method and compared to that of five other antimicrobial agents. BAY 12-8039 and imipenem were the most active agents tested. The following MIC90 values were determined for BAY 12-8039: Peptostreptococcus spp. (50 isolates), 1 mg/l; Propionibacterium acnes (30 isolates). 0.25 mg/l; Clostridium perfringens (30 isolates), 0.5 mg/l; Clostridium difficile (50 isolates), 2 mg/l; Bacteroides fragilis (50 isolates), 1 mg/l; non-fragilis Bacteroides, Porphyromonas, and Prevotella spp. (100 isolates), 2 mg/l; and Fusobacterium spp. (50 isolates), 0.25 mg/l. The results of the present study show that BAY 12-8039 may be useful in the treatment and prophylaxis of anaerobic infections.

The agar dilution MIC method was used to test the activity of cefminox, a beta-lactamase-stable cephamycin, compared with those of cefoxitin, cefotetan, moxalactam, ceftizoxime, cefotiam, cefamandole, cefoperazone, clindamycin, and metronidazole against 357 anaerobes. Overall, cefminox was the most active beta-lactam, with an MIC at which 50% of isolates are inhibited (MIC50) of 1.0 microg/ml and an MIC90 of 16.0 microg/ml. Other beta-lactams were less active, with respective MIC50s and MIC90s of 2.0 and 64.0 microg/ml for cefoxitin, 2.0 and 128.0 microg/ml for cefotetan, 2.0 and 64.0 microg/ml for moxalactam, 4.0 and > 128.0 microg/ml for ceftizoxime, 16.0 and > 128.0 microg/ml for cefotiam, 8.0 and >128.0 microg/ml for cefamandole, and 4.0 and 128.0 microg/ml for cefoperazone. The clindamycin MIC50 and MIC90 were 0.5 and 8.0 microg/ml, respectively, and the metronidazole MIC50 and MIC90 were 1.0 and 4.0 microg/ml, respectively. Cefminox was especially active against Bacteroides fragilis (MIC90, 2.0 microg/ml), Bacteroides thetaiotaomicron (MIC90, 4.0 microg/ml), fusobacteria (MIC90, 1.0 microg/ml), peptostreptococci (MIC90, 2.0 microg/ml), and clostridia, including Clostridium difficile (MIC90, 2.0 microg/ml). Time-kill studies performed with six representative anaerobic species revealed that at the MIC all compounds except ceftizoxime were bactericidal (99.9% killing) against all strains after 48 h. At 24 h, only cefminox and cefoxitin at 4x the MIC and cefoperazone at 8x the MIC were bactericidal against all strains. After 12 h, at the MIC all compounds except moxalactam, ceftizoxime, cefotiam, cefamandole, clindamycin, and metronidazole gave 90% killing of all strains. After 3 h, cefminox at 2 x the MIC produced the most rapid effect, with 90% killing of all strains.

The interaction of type-I beta-lactamases from Enterobacter cloacae with diverse beta-lactam compounds was examined. The ability of penicillin and cefoxitin to induce beta-lactamase production in this strain was assessed. The effect of beta-lactamase inhibitors was measured on beta-lactamase extracts and on intact cells. E. cloacae 78 strain is a stably derepressed mutant showing limited susceptibility to a number of antibiotics except imipenem. Imipenem would therefore be the appropriate choice for therapy of infections caused by stably derepressed mutants of Enterobacter sp. producing type-I beta-lactamases.

The objective of this study was to assess the prophylactic efficacy of cefoxitin, ceftizoxime, and metronidazole-gentamicin in colorectal surgery. A double-blind, randomized prospective clinical trial design was used in a Canadian tertiary care teaching hospital. Patients were randomized to one of three treatment groups and received three doses of a study drug (30 min preoperative and 2 postoperative doses at 12 and 24 h). Cefoxitin and ceftizoxime were given as 1000-mg doses. Metronidazole-gentamicin was given as 500 mg of metronidazole plus 120 mg of gentamicin in a minibag. High-risk patients (bowel ischemia, diabetic, current steroid use, etc.) received 10 postoperative doses. Patients with infections, prior antibiotics, or study drug allergies were excluded. Over 30 months, 153 patients were enrolled. Thirty-one patients were excluded for protocol violations. Of the 122 evaluable patients (38 ceftizoxime, 45 metronidazole-gentamicin, 39 cefoxitin), there was no difference across groups regarding sex, age, weight, preoperative Apache II score, and prior history of bowel surgery. Groups were equivalent regarding surgeon, nursing unit, high-risk status (six ceftizoxime, seven metronidazole-gentamicin, seven cefoxitin), bowel preparation, and procedure (including blood loss, drains, organ injury, intraoperative complications). Clinically significant infection requiring systemic antibiotics (7-day hospital and 30-day follow-up) was identified in 0% of ceftizoxime, 15% of metronidazole-gentamicin, and 26% of cefoxitin receiving patients (p = 0.005). Mean ASEPSIS scores for each group were 2.3 (range 0-15) for ceftizoxime, 9.2 (range 0-45) for metronidazole-gentamicin, and 10.4 (range 0-75) for cefoxitin (p = 0.01). Ceftizoxime patients tended to have a shorter total hospital stay (12.2 days versus 19.7 days for cefoxitin versus 13.9 days for metronidazole-gentamicin; p = 0.04), although the procedure to discharge interval was not significantly different (p = 0.09). There was no difference in clinical outcome according to risk status. Anaerobic bacteria were observed more commonly in the ceftizoxime and cefoxitin groups, whereas enteric Gram-negative aerobes were observed most often in the metronidazole-gentamicin group. The study regimens were generally well tolerated. Drug costs were equivalent between ceftizoxime and cefoxitin and lowest with the metronidazole-gentamicin regimen. Ceftizoxime appears to be more effective for the prevention of infection in colorectal surgery than either cefoxitin or metronidazole-gentamicin in the dosage regimens studied.

The effectiveness of cycloserine-cefoxitin-fructose agar (CCFA) and taurocholate-CCFA (TCCFA) in isolating Clostridium difficile from swabs of the rectum or stools from 184 hospitalized patients who were monitored weekly and when they had diarrhea was compared. The number of surveillance time points ranged from two to eight per patient over a period of 4 to 34 days per patient, totalling 621 comparisons of the media. C. difficile was isolated more frequently by TCCFA than CCFA at seven of eight surveillance points, a significant trend (O'Brien test, p = 0.002). This difference reached statistical significance at the second surveillance time point when the prevalence of C. difficile was sufficiently high. At the second surveillance point, C. difficle was isolated only by TCCFA in 7 of 184 comparisons of the media, only by CCFA in none of the comparisons, and by both media in 19 comparisons (p = 0.016). C. difficle was first isolated at an earlier surveillance time point on TCCFA in 11 of 36 patients and on CCFA first only once (p = 0.005). Use of TCCFA media increased the rapidity and sensitivity of culture for C. difficle when doing patient surveillance but did not increase sensitivity when diagnosing patients with diarrhea.

An Escherichia coli strain resistant to a broad spectrum of beta-lactams, including cephamycins, was isolated from a patient suffering from urinary tract infection. A resistance plasmid (pMVP-7) was transferred from the clinical isolate to an Escherichia coli recipient. Both strains produce a cefoxitin-hydrolyzing beta-lactamase focusing at pI 6.7. The phenotype was similar to that of a Klebsiella pneumoniae strain producing cephamycinase FOX-1, so primers were selected from the FOX-1 sequence to amplify the bla gene of the transconjugant. The PCR product obtained was sequenced. The percentage of identity of the deduced amino acid sequence with sequences of other AmpC-type beta-lactamases was 96.9% with FOX-1, 74.9% with CMY-1, and 67.7% with MOX-1. This new plasmid-mediated enzyme is most closely related to FOX-1 (11 amino acid exchanges). We therefore propose the designation FOX-2.

A cosmid library from Mycobacterium tuberculosis H37Ra was introduced into Mycobacterium smegmatis, and eight recombinant clones with increased resistance to cefoxitin were identified. Isoelectric focusing detected an M. tuberculosis-derived beta-lactamase in one of these recombinant clones. A sequence analysis identified it as a class A beta-lactamase whose expression correlated with the increased resistance phenotype.

A plasmidic beta-lactamase which hydrolyzed cephamycins was first detected and reported in 1989. At that time its description was restricted to phenotypic characteristics. We analyzed nucleotide sequence of its gene and explored it genetic relationship with other bla genes. The deduced amino acid sequence of the blaCMY-1 product was compared with those of other known plasmidic cephamycinases and of chromosomal AmpC beta-lactamases. The results indicate that the relationship of CMY-1 is closest to MOX-1 among the plasmidic cephamycinases and to AmpC of Pseudomonas aeruginosa among the chromosomal cephalosporinases. We conclude that the plasmidic cephamycinases described up to now may be classified into three families, as follows: CMY-1, MOX-1, and FOX-1 with AmpC of P. aeruginosa; CMY-2, BIL-1 and LAT-1 with AmpC of Citrobacter freundii; and MIR-1 with AmpC of Enterobacter cloacae. Plasmidic cephamycinases are now recognized as clinically relevant class C beta-lactamases.

Cefoxitin resistance in Klebsiella pneumoniae from Escherichia coli strains isolated in Greek hospitals was found to be due to the acquisition of similar plasmids coding for group 1 beta-lactamases. The plasmids were not self-transferable but were mobilized by conjugative plasmids. These elements have also been spread to Enterobacter aerogenes. The most common enzyme was a Citrobacter freundii-derived cephalosporinase (LAT-2) which differed from LAT-1 by three amino acids.

Routine determination of antimicrobial susceptibility of anaerobic clinical isolates is difficult. The E-test is a practical alternative technique that we evaluated while testing clinical isolates in a multicenter study. The susceptibility to 9 antibiotics (penicillin, amoxycillin/clavulanate, ticarcillin/clavulanate, piperacillin/tazobactam, imipenem, cefoxitin, metronidazole, clindamycin, chloramphenicol) of 351 strains belonging to 63 different species was determined by the NCCLS reference agar dilution procedure using Wilkins-Chalgren agar medium with 5% sheep blood and was compared to the E-test performed on the same medium and using manufacturer's recommendations. The MIC values obtained with the E-test were generally one dilution lower than those obtained with the reference technique, 87.1% of the results being within two dilutions. In terms of susceptibility categories, 95.1% agreement was observed with 3.8% minor errors and only 0.5% major and 0.6% very major errors. With some Fusobacterium spp. and Clostridium spp. strains, the E-test was difficult to read or not interpretable because of the presence of growth within the inhibition zone of all beta-lactam antibiotics, representing a trailing phenomenon. We conclude that, if some interpretation difficulties are taken into account, the E-test is a convenient and reliable technique that can be applied in all clinical laboratories. It could be used for the individual testing of important anaerobes in certain clinical situations but cannot yet be considered as a reference technique. Its utility is emphasised by the increased resistance rate against clindamycin and the appearance of a few strains in the B. fragilis group with a reduced susceptibility against metronidazole.

Four Klebsiella pneumoniae isolates (LB1, LB2, LB3, and LB4) with increased antimicrobial resistance were obtained from the same patient. The four isolates were indistinguishable in biotype, plasmid content, lipopolysaccharide, and DNA analysis by pulse-field gel electrophoresis. Isolate LB1 made TEM-1 and SHV-1 beta-lactamases. Isolates LB2, LB3, and LB4 produced SHV-5 in addition to TEM-1 and SHV-1. MICs of cefoxitin, ceftazidime, and cefotaxime against LB1 were 4, 1, and 0.06 micrograms/ml, respectively. MICs of ceftazidime against K. pneumoniae LB2, LB3, and LB4 were > 256 micrograms/ml, and those of cefotaxime were 2, 4, and 64 micrograms/ml, respectively. MICs of cefoxitin against K. pneumoniae LB2 and LB3 were 4 micrograms/ml, but that against K. pneumoniae LB4 was 128 micrgrams/ml. K. pneumoniae LB4 could transfer resistance to ceftazidime and cefotaxime, but not that to cefoxitin, to Escherichia coli. Isolate LB4 and cefoxitin-resistant laboratory mutants lacked an outer membrane protein of about 35 kDa whose molecular mass, mode of isolation, resistance to proteases, and reaction with a porin-specific antiserum suggested that it was a porin. MICs of cefoxitin and cefotaxime reverted to 4 and 2 micrograms/ml, respectively, when isolate LB4 was transformed with a gene coding for the K. pneumoniae porin OmpK36. We conclude that the increased resistance to cefoxitin and expanded-spectrum cephalosporins of isolate LB4 was due to loss of a porin channel for antibiotic uptake.

The phenotype of Klebsiella pneumoniae HEL-1 indicates a plasmidic cephamycinase gene (blaCMY-2). Its sequence shows one open reading frame coding for a protein of 381 amino acids. CMY-2 is classified as class C beta-lactamase that is closely related to the plasmidic enzymes BIL-1 and LAT-1 and the chromosomal AmpC of Citrobacter freundii. The blaCMY-2 gene possibly was translocated onto a plasmid of C. freundii which spread to K. pneumoniae.

Eighty isolates of Actinobacillus actinomycetemcomitans from 30 Brazilian periodontitis patients were examined to determine the distribution of biotypes and in vitro antimicrobial susceptibility. Seventy-seven percent of the isolates belonged to biotype X. All A. actinomycetemcomitans isolates were susceptible to cefoxitin, imipenem and tetracycline.

The bactericidal effect of free versus liposomal cefoxitin was evaluated in the major reticuloendothelial organs in a porcine model of intra-abdominal sepsis. Yorkshire Landrace pigs were inoculated with 3.2 x 10(10) (n = 5) or 1.4 x 10(11) (n = 7) cfu of Escherichia coli mixed in sterile feces/animal. Two treatment groups inoculated with 1.4 x 10(11) cfu were established: free cefoxitin (n = 9) and liposomal cefoxitin (n = 9). All animals were maintained under anesthesia and euthanized after 24 h. The number of E. coli recovered in the liver, lungs, and spleen was significantly affected by inoculum size (p < .05). The liver had significantly higher numbers of bacteria (p < .05) compared with the other organs, regardless of the inoculum size. The liver and the lung of the liposomal cefoxitin-treated group showed significantly lower numbers of E. coli (5.0 x 10(4) and 6.3 x 10(2), respectively) compared with the untreated (liver, 6.3 x 10(7); lung, 2.0 x 10(6)) and free cefoxitin (liver, 5.0 x 10(6); lung, 7.9 x 10(4))-treated groups (p < .05). At 2 h following the injection of free and liposomal cefoxitin, the decrease of E. coli in peritoneal fluid compared with the nontreated septic group was significant (p < .05). No growth was observed from blood cultures taken 24 h after sepsis induction. All control experiments yielded negative cultures. The results of these experiments demonstrated that liposomal cefoxitin exerts an enhanced bactericidal effect in liver and lungs during Gram-negative sepsis.

Lytic action of cefminox (CMNX) against slowly growing Escherichia coli (E. coli) K-12 JE1011 was compared with that of the related cephamycin cefmetazole (CMZ) or ampicillin (ABPC). The growth rate in doubling time was 30 min. at 37 degrees C. Minimal concentrations of CMNX, CMZ and ABPC showing clear lysis were 0.39, 3.13 and 12.5 micrograms/ml, respectively, under these conditions. When E. coli was cultured at 12 degrees C, the doubling time was 720 and 816 min. which were 24 and 27.2 fold as slow as those at 37 degrees C, respectively. In 12 degrees C culture, the minimal concentrations showing clear lysis were 0.78 (2 fold at 37 degrees C), 25 (8 fold) and 100 micrograms/ml and higher (8 fold or more) with CMNX, CMZ and ABPC, respectively. Therefore, it appeared that the lytic activity of CMNX was not significantly affected by bacterial growth rate and was demonstrated effectively against slowly growing bacteria at a low concentration. We determined release activity of cell wall peptidoglycan fragments by 5 beta-lactam antibiotics in addition to the above-mentioned 3 antibiotics. The results showed that the release activity was not proportional to the MIC and that of CMNX was the strongest among those antibiotics. The rapid and strong bactericidal action of CMNX against bacteria at the early stationary phase was suggested to result from the characteristic lytic action against slowly growing bacteria.

A study was done to determine susceptibilities of Haemophilus influenzae that were obtained in our laboratory in 1994 to new quinolones (NQ) and other drugs. The results were as follows; 1. Among the 300 isolates, the detection frequency of NQ-resistant strains was 8.7% (26 strains), including isolates from chronic lower respiratory tract infections (22 strains) and those from middle meatus of nose (2 strains), etc. NQ-resistant strains were not isolated from children. 2. The cross resistance was studied for different NQs against NQ-resistant strains. Clavulanic acid/amoxicillin, cefteram, cefpodoxime, cefditoren, cefodizime (CDZM) and cefpirome showed strong antimicrobial activities against NQ-resistant strains. MIC90 of CEPs against all isolated strains including NQ-resistant strains and beta-lactamase producers was low. And the MIC90 of CDZM was < or = 0.025 microgram/ml, which was the lowest among all the antibiotics tested. 3. We found 47 strains (15.7%) of beta-lactamase producers among the 300 isolates, the frequency of beta-lactamase producing strains was high among strains obtained from children.

Suckling and adult mice were infected intragastrically with different doses of viable Listeria monocytogenes. The 50% lethal dose for the intragastric infection was 10(3.7) CFU for suckling mice, while adult mice were highly resistant and the 50% lethal dose was more than 10(9.3) CFU. When adult mice were infected intragastrically with 5 x 10(8) CFU of L. monocytogenes, no mice died. However, 35% of adult mice died when they were treated with cyclosporin A 1 day before infection. Although mice did not die when treated with an L. monocytogenes-resistant broad-spectrum cephalosporin, sodium cefbuperazone, before and during infection, the number of L. monocytogenes bacteria increased in the feces. The sodium cefbuperazone treatment of mice resulted in superinfection, i.e., a marked decrease of Escherichia coli and an increase of Enterococcus spp. in the intestines. Furthermore, host resistance against the intragastric infection markedly decreased when the mice were treated with both drugs. The growth of L. monocytogenes was augmented in the spleens, mesenteric lymph nodes, Peyer's patches, and feces, and the mortality of the mice was 65%. These results suggest that both cellular immunity and the intestinal bacterial flora are required for host resistance against oral L. monocytogenes infection.

Over 2800 clinical strains of the Bacteroides fragilis group were collected during a 5-year period from ten geographically separate sites and tested for their susceptibility to various antimicrobial agents using a broth microdilution method. Among the cephalosporins, ceftizoxime was the most active (13% resistance) and importantly exhibited relatively equal activity against both B. fragilis species and non-B. fragilis species. Cefotaxime exhibited similar activity with an overall resistance rate of 18%. Both ceftriaxone and cefoperazone were appreciably less active cephalosporins especially against non-B. fragilis species. With regard to cephamycins, cefoxitin (MIC90, 32 micrograms/ml) was more active than cefotetan (MIC90, > or = 256 micrograms/ml) and cefmetazole (MIC90, 64 micrograms/ml). Non-B. fragilis species were highly resistant to cefotetan and cefmetazole. Imipenem was highly active against all strains with the exception of four strains of B. fragilis. Ampicillin-sulbactam, amoxicillin-clavulanate, piperacillin-tazobactam, and cefoperazone-sulbactam were all highly active with resistance rates < 2%. No resistance was detected to metronidazole, whereas 14% of isolates were resistant to clindamycin. When compared with other studies, these findings underscore the wide variability in susceptibility patterns reported nationwide and the need to continue monitoring these patterns to aid in choosing the most active compounds for therapy.

Plasma concentration of cefminox and serum bactericidal activity against four ATCC strains (Escherichia coli 25992, Klebsiella pneumoniae 13833, Serratia marcescens 8100 and Bacteroides fragilis 25285), were determined over a 24 h period after administration of cefminox 1 and 2 g to six healthy volunteers in a randomized, cross-over, single blind study. The increase observed in the area under the bactericidal curve (AUBC) with the 2 g dose was at least 3.5 times that seen with the 1 g dose for all four test strains and was larger than predicted by the corresponding increase (1.84 times) in the area under the serum concentration versus time curve (AUC); a correlation (r = 0.88, P = 0.0001) between the cefminox concentration and the serum bactericidal titres was, however, observed with all four strains tested. The MBC6h showed a better association with the serum bactericidal titre (P < 0.01) than did the MIC or MBC.

Against main clinical isolates at our center in 1990 to 1992, the minimum inhibitory concentrations (MICs) of cefminox (CMNX) and some other comparable cephems were determined. The results are summarized as follows. 1. As to the strains resistant to cephems including CMNX, annual increases were observed for Streptococcus pneumoniae among Gram-positive bacteria and Proteus vulgaris among Gram-negative bacteria. Moreover, cephem-resistant strains of Escherichia coli were constantly isolated, and there were signs indicating that cephem-resistant strains would increase among strains of Klebsiella pneumoniae. 2. The annual increases in cephem-resistant strains of S. pneumoniae and P. vulgaris may respectively reflect the recent increases in the incidence of benzylpenicillin (PCG)-insensitive strains of S. pneumoniae (PISP) and multi-drug resistant strains including oxime type cephems and new quinolones introduced into clinical use in the latter half of the 1980s. 3. Concerning antimicrobial activities of CMNX against recent clinical isolates, the same problems as described above will remain. However, these tendencies have been observed only with regard to MIC90. No remarkable changes have been noted for MIC50 or MIC80 at this time.

We reported a case of abscess in which Serratia marcescens was isolated as the causative organism. We measured the postantibiotic effect (PAE) of dibekacin (DKB) and gentamicin (GM) against S. marcescens and studied the relationship between the clinical effect and the PAE. The minimal inhibitory concentration (MIC) of DKB against S. marcescens was 6.25 micrograms/mL and the serum concentration 30 min after infusion of 100 mg DKB was 5.99 micrograms/mL. The abscess was cured by the administration of DKB every 12 h. The PAE in vivo was 2.5, 2.9 and 3.3 h when DKB was administered at 50 mg/kg, 100 mg/kg and 200 mg/kg, respectively. This PAE is one of the reasons that infection can be effectively treated with intermittent administration, even if the serum concentration is below the MIC.

The purpose of this study was to assess the effect of different MIC statistics on the in-vitro evaluation of cefoxitin, cefotetan, ceftizoxime, cefotaxime, desacetylcefotaxime, and cefotaxime:desacetylcefotaxime (1:1 ratio) against clinical isolates of Bacteroides fragilis from the Medical University of South Carolina. MICs were determined by the agar dilution method following NCCLS guidelines. Statistical analyses included arithmetic and geometric means, median, mode, MIC50, MIC90, and range. Differences between antimicrobial agents were determined using parametric and nonparametric methods. Consistent with previous in-vitro studies on anaerobes with these agents, a wide range in the MICs was observed. The arithmetic mean MIC was lowest for cefotetan, but the geometric mean MIC was lowest for ceftizoxime. Using the MIC90, cefotetan was at least a two-fold dilution more active than the other agents. After natural logarithmic transformation of the MIC data, analysis of variance with the Scheffé post-hoc test demonstrated that the MICs of ceftizoxime were significantly lower than those of cefoxitin (P < 0.001), cefotetan (P < 0.05), cefotaxime (P < 0.05), and desacetylcefotaxime (P < 0.001). Median and mode MICs were lowest for ceftizoxime and cefotaxime:desacetylcefotaxime. Using published breakpoints, cumulative percent susceptibility was similar for all agents studied. In this analysis of the antimicrobial susceptibility of B. fragilis in our institution, the in-vitro activity of the cephalosporins and cephamycins tested appeared to be very similar when all statistical data were evaluated. Since apparent in-vitro activity may be influenced by the statistic evaluated, we suggest that all MIC data be reported to allow for a more complete analysis of microbiological potency.

Combined antibacterial effects of imipenem (IPM)+arbekacin (ABK) and cefminox (CMNX)+ABK against methicillin-resistant Staphylococcus aureus (MRSA) were examined and the obtained results are summarized below. 1. Either combination, IPM+ABK or CMNX+ABK, showed a strong antibacterial effect against MRSA when blood concentration of ABK were sustained at MIC as could be expected in clinical situations. While at sub MICs of ABK the antibacterial effect of these combination was slightly less than those of the previously reported combinations of ABK and other antibiotics. 2. Antibacterial effects of the combinations against MRSA were strongly dependent on the concentration of ABK and less dependent on the concentration of IPM or CMNX. As were observed in the previously tested combinations of ABK with other antibiotics, the antibacterial effect of the combination appeared to be highly dependent on the antibacterial activity and the concentration of ABK. 3. As IPM has potent antibacterial activities against Gram-negative bacteria (GNB) including Pseudomonas aeruginosa while CMNX has potent antibacterial activities against GNB except P. aeruginosa, it is likely that the combinations of IPM+ABK or CMNX+ABK are useful for treatment of infections with MRSA together with GNB.

MICs and turbidimetric experiments revealed a negligible inoculum effect with two Escherichia coli strains exposed to cefminox and cefoxitin, whereas a marked inoculum effect was revealed after exposure to cefotaxime, ceftizoxime, and imipenem. The activities of the cephamycins were associated with spheroplast formation and bacteriolysis at concentrations close to the MIC, whereas the other agents induced the formation of filaments or, in the case of imipenem, rounded cells.

When evaluating antimicrobial agents, in vitro microbiologic activity and pharmacokinetics are important factors, but these data are usually not assessed simultaneously. The purpose of the study was to compare cefoxitin, cefotetan, ceftizoxime, cefotaxime (CT), desacetylcefotaxime (DACT), and CT/DACT (1:1 ratio) by integrating their microbiologic activity against clinical isolates of Bacteroides fragilis with their pharmacokinetic properties. Minimal inhibitory concentrations (MIC) were determined by the agar dilution method. Steady-state serum concentration--time profiles were simulated for 2-gm doses in a 70-kg patient using ADAPT software and pharmacokinetic data from published studies. Serum protein binding (%) of each agent was also obtained from published studies and used to calculate the unbound serum concentration--time profiles. As estimates of pharmacodynamic activity, time below the MIC (T less than MIC) and percentage of the dosing interval below the MIC (% INT less than MIC) were calculated for individual isolates using total and unbound serum concentrations. Data analysis included MIC50, MIC90, range, breakpoint susceptibility, and analysis of variance for T less than MIC and % INT less than MIC (Scheffé post-hoc test, P less than 0.05). The MIC90 of cefotetan was at least a twofold dilution lower than the other agents. However, using unbound (pharmacologically active) serum concentrations, T less than MIC and % INT less than MIC for ceftizoxime (at a simulated eight-hour dosing interval) were significantly smaller than with the other antibiotic regimens. Integration of in vitro and pharmacokinetic data may provide additional information to assist in the evaluation of antimicrobials. For B fragilis from our institution, the pharmacodynamic profile of unbound ceftizoxime is superior to the other antianaerobic cephalosporins/cephamycins tested.

Citrobacter diversus ULA-27, a clinical isolate showing a broad resistance pattern towards both penicillins and cephalosporins, produces chromosome encoded beta-lactamases. However, the strain remains susceptible to some cephamycins, imipenem, ceftazidime and tetracyclines. Crude bacterial extracts analyzed by isoelectric focusing on polyacrylamide gels, revealed the presence of two main isoforms and some "satellite" bands focusing in the pH range 5.7-7.2. The isoform showing the pIs 6.8 and 6.2 were characterized as class "A" beta-lactamases (according to Ambler's classification) based on the rate of interaction of beta-iodopenicillanate and the amino acid sequence around the active site serine. The substrate specificity of the Citrobacter diversus beta-lactamases explains the resistance phenomenon of this bacterium to penicillins and cephalosporins.

The results of in vitro and in vivo studies of cefmetazole, a second-generation cephamycin, were reviewed. Cefmetazole's spectrum of activity includes clinical coverage of many Enterobacteriaceae, staphylococci, streptococci, Haemophilus species, pathogenic Neisseria organisms, Moraxella (Branhamella) catarrhalis and anaerobic bacteria. Cefmetazole is generally two to eight times more potent than cefoxitin against organisms within their spectra and is most active against staphylococci (minimal inhibitory concentration90 = 2.0 micrograms/mL). Methicillin-resistant Staphylococcus aureus strains are more susceptible to cefmetazole, alone or in combination with fosfomycin, than to any other cephamycins, and cefmetazole is remarkably resistant to the beta-lactamases produced by aerobic and anaerobic bacteria. The incidence of adverse drug reactions is low (8.8% in the United States, 2.2% in Japan), and the drug has been demonstrated to have cost-containment potential.

Cefminox (CMNX), one of newly developed cephamycin antibiotics, was administered to 7 cases of diffuse peritonitis associated with infantile acute appendicitis to determine its concentrations in the blood, the appendiceal tissue and the purulent ascites and simultaneously to investigate its clinical efficacy. CMNX was intravenously injected at a dose of 20 mg/kg (at a maximum amount of 1.0 g/body) before operation and intravenously by bolus injection or by drip infusion twice daily after operation for 3 to 11 days in a total dose of 2.36 to 14.06 g. Fourteen strains of bacteria were isolated from the purulent ascites: Escherichia coli was isolated from 6 cases but superinfections in 5 cases. MICs of CMNX against these isolated organisms were at or lower than 3.13 micrograms/ml for 12 out of 14 strains. CMNX penetrated into the appendiceal tissue and the purulent ascites very well. The concentrations in the pus reached higher than those in the tissue in about 1 hour after administration and were found to reach as high as 9.63 micrograms/ml in 5 hours after administration. Its clinical efficacies were excellent in 4 cases, good in 2 cases and poor in 1 case. No subjective or objective adverse reactions were observed nor any abnormalities were found in laboratory examinations.

The in vitro activity of certain beta-lactam agents against aerobic and anaerobic bacteria is influenced by the method and medium used for susceptibility testing. The in vitro activity of ceftizoxime and cefoxitin against Bacteroides fragilis group strains varies when either the broth microdilution or agar dilution method is used. In general, minimal inhibitory concentration values from broth microdilution are two- to fourfold lower than those from agar dilution. Broth microdilution test results with ceftizoxime have recently been shown to correlate more closely with clinical outcome in patients than those from agar dilution testing. Broth microdilution has become the recommended method of the National Committee for Clinical Laboratory Standards for testing ceftizoxime. Using broth microdilution testing, the in vitro activity of ceftizoxime has been shown to be as good as or better than that of cefoxitin, cefotetan, and cefotaxime against anaerobes, including the B fragilis group. Ceftizoxime also had good activity against B fragilis group strains resistant to cefoxitin or cefotetan. Time-kill kinetic studies have shown that the bactericidal activity of ceftizoxime is equal to or greater than that of cefoxitin or cefotetan against both cefoxitin-susceptible or cefoxitin-resistant strains of the B fragilis group.

Cefminox is a new cephamycin antibiotic possessing a D-amino acid moiety derived from D-cysteine at the C-7B side chain. Cefminox is active against a wide range of bacteria, especially Gram-negative and anaerobic bacteria. Cefminox shows excellent in vivo efficacy (ED50) which is higher than would be expected from its in vitro activity (MIC). Moreover, cefminox possesses more potent activity in suppression of bacterial regrowth than other cephems. These phenomena are surmised to be caused by strong bactericidal activity which is attributed to a dual action mechanism.

Initially, cefotetan interacts with beta-lactamases to form a classical Michaelis complex characterized by a term Ki (the inhibition constant). In a second phase, this complex develops with time to form a new entity devoid of enzymic activity. This new entity may have the structure of an acyl enzyme with variable stability. In the case of TEM-1 and TEM-2 beta-lactamases, the process is progressively and totally reversible. The same phenomena were observed in varying degrees for Pitton's type 2 (PIT-2) penicillinase, OXA-1 and CARB-1. The Klebsiella oxytoca and Proteus vulgaris beta-lactamases are also inactivated by this same process. However, four other cephalosporinases appear to be unaffected by this mechanism.

Although moxalactam is not, technically speaking, a cephalosporin it is chemically and microbiologically so closely related to those compounds that it can be viewed as a member of the cephalosporin family. Moxalactam has a spectrum of activity that includes both gram positive and gram negative bacteria. Its gram positive activity is less than earlier cephalosporins, but its activity against the Enterobacteriaceae is similar to that of the aminoglycoside family of antibiotics in most comparative studies. Although moxalactam is considerably less active against gram positive bacteria than cefotaxime, another third generation cephalosporin, its higher and more prolonged serum levels probably offset this disadvantage. Compared to cefoperazone, the stability of moxalactam to many types of beta lactamases produced by gram negative bacteria may be advantageous in the therapy of infections caused by hospital-acquired pathogens. Clinical studies suggest that moxalactam can be used for empiric therapy of suspected gram negative infections when Pseudomonas and other non-fermentative bacteria, such as Acinetobacter, are not suspected. Impressive improvements in the survival of patients with gram negative enteric bacillary meningitis have been reported. Although moxalactam, cefotaxime, and cefoperazone have activity against Pseudomonas aeruginosa, none of these antibiotics should be used alone as therapy for suspected or proven severe systemic infections caused by this pathogen. Cost is a major problem with all of the new cephalosporin-like antibiotics. While this high cost may be partially balanced by the use of a single agent compared to an antibiotic combination for therapy in some situations, these antibiotics are not cost effective for prophylactic use. Superinfection with fungi, such as Candida, and Streptococcus faecalis have occurred, and toxicities, such as bleeding due to vitamin K deficiency and disulfuram-like reactions, have also been reported. Reports of resistance to moxalactam and the other third generation cephalosporins are of major concern and indicate the need to closely monitor antibiotic susceptibility patterns of hospital acquired organisms if these antibiotics are to be used for empiric therapy of suspected gram negative non-pseudomonas sepsis.

The activities of cefotaxime, moxalactam, MK 0787 (N-formimidoyl thienamycin), ampicillin, oxacillin, vancomycin, and clindamycin were compared against gram-positive cocci. MK 0787 was the most active and moxalactam was the least active of these drugs, except against methicillin-resistant Staphylococcus aureus, where vancomycin was most active, and penicillin-resistant pneumococci, where cefotaxime was more active.

Cefbuperazone was given intravenously in a dose of 1 g at induction of anaesthesia, followed by a subsequent dose of 1 g 12 h after the first dose, to 10 patients undergoing colorectal surgery. A series of serum and faecal specimens were taken for analysis of cefbuperazone concentrations. Tissue samples from the gut wall were taken at surgery. The maximum serum concentrations (mean value 98.6 +/- 9.1 mg/l) during surgery were reached 30 min after cefbuperazone administration. The cefbuperazone concentration in the tissue samples varied between 7.3 and 40.5 mg/kg and the concentration in the faecal samples between 0 and 27.0 mg/kg. Faecal samples were also collected during the investigation period for cultivation of aerobic and anaerobic bacteria. The aerobic bacteria--streptococci, enterococci and enterobacteria--were suppressed significantly during the prophylaxis period. Among the anaerobic bacteria, cocci, bifidobacteria, eubacteria, lactobacilli, clostridia, fusobacteria and bacteroides decreased markedly during the same period. After four weeks the microflora was normalized in all patients. No postoperative infections occurred.

Moxalactam (LY127935) is a 1-oxa-beta-lactam which was active in vitro against the majority of 128 strains of gram-negative enteric bacilli isolated from meningitis in neonates. Pharmacokinetics and bacteriological efficacy of LY127935 were studied in a lapin meningitis model. The average penetration of this investigational oxa-cephalosporin into cerebrospinal fluid of infected rabbits was 23% compared with 25% for netilmicin and 11% for ampicillin. The cerebrospinal fluid concentrations of LY127935 produced median bactericidal titers of 1:64 to 1:128 against five coliform organisms (two Escherichia coli K1 strains, Klebsiella pneumoniae, Salmonella saint-paul, and Citrobacter diversus) used in these experiments compared with median titers of 1:2 to 1:8 for netilmicin and 1:2 to 1:4 for ampicillin. LY127935 was statistically significantly more effective than netilmicin or ampicillin in reducing cerebrospinal fluid bacterial colony counts and in sterilizing cerebrospinal fluid of experimentally infected rabbits. These results suggest that LY127935 has theoretical advantages over netilmicin and ampicillin for therapy of gram-negative bacillary meningitis.

Three new beta-lactams were evaluated against 94 anaerobic strains representing 15 species using a Wilkins-Chalgren broth microdilution method. The penems, Sch 29482 and Sch 34343, were most active with all minimum inhibitory concentrations (MICs) at less than or equal to 4.0 micrograms/ml and MIC90s of less than or equal to 0.25 micrograms/ml. BMY 28142 had a more limited antianaerobic activity against Bacteroides fragilis with a MIC50 and MIC90 of 32 and 128 micrograms/ml, respectively. Cefbuperazone (T-1982) had low B. fragilis MICs (MIC90, 8.0 micrograms/ml), but potentially resistant range MIC90 results for the other species in the B. fragilis group and Clostridium species.

The filamentous forms of a serum resistant Escherichia coli strain developed under in vitro exposure to subminimal inhibitory concentration of the compound LY 127935 showed a higher resistance against host defence than the nontreated control bacteria. Significantly diminished LD50 values and a longer lasting persistence in the peritoneal cavity of the mouse were found after intraperitoneal infection. In order to exclude the suggestion that the enhanced virulence was only due to the separation of filaments into normal virulent bacilli, the course of experimental infection with normal virulent germs was investigated under treatment with subtherapeutic doses of the antibiotic. When animals treated with repeated doses of 10-15 microgram/kg of LY 127935 were intraperitoneally infected a significantly smaller elimination rate of bacteria was observed in the peritoneal cavity than in animals injected with saline.

Fundamental and clinical studies were carried out to objectively evaluate the effectiveness and safety of cefmetazole (CMZ) in the treatment of S. aureus infections of the skin, and the following results were obtained. 1. Blisters are induced with cantharis ointment to determine transfer of CMZ and cefazolin (CEZ) into the sclerosity and skin. The sensitivity of clinically isolated S. aureus was measured to these drugs. 2. In case of CMZ, antibacterial activity, exudate and tissue transfer were favorable, and the sclerosity and skin concentration of the drug was such that it covered the major portion of MIC distribution of the clinically isolated S. aureus. 3. In the crossover test following one shot intravenous injection of CMZ and CEZ at the doses of 1 g, drug concentrations in the serosity and skin were higher after CMZ as compared with those after CEZ. 4. Clinical effect of this drug in the treatment of S. aureus infections of the skin in 10 cases was such that it was markedly effective in 4 cases, moderately effective in 4 and slightly effective in 2 cases. Bacteriological, effect of CMZ was eradication of the bacteria in 9 cases and change of bacterial flora in 1 case. In addition, the clinical effect of the drug in 2 cases in which cephalexin had been ineffective was that it was markedly effective in 1 and slightly effective in the other. 5. Side effect was not observed in any of the treated cases. From the above, it was concluded that CMZ is highly useful drug in the treatment of S. aureus infections of the skin.