Synergistic action of cefodizime with other antimicrobial agents on clinically isolated microorganisms. II. Synergistic action with sisomicin]

Cefodizime (CDZM) possesses a broad antimicrobial spectrum and a relatively long half life in the blood. In addition, it shows excellent therapeutic efficacies in the treatment of infections in leukopenic animal models, hence it is expected that CDZM may have good efficacies against various infections in immunocompromised hosts. In the meantime, sisomicin (SISO) not only has strong antibacterial activities against Gram-negative rods (GNR), but has relatively low nephrotoxicity and ototoxicity. Thus, we examined antibacterial effectiveness of the combination of CDZM and SISO against clinical isolates in vitro. 1. Antibacterial effects of CDZM+SISO combination were examined using SISO susceptible strains of Escherichia coli, Citrobacter freundii, Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens, Proteus vulgaris, Morganella morganii and Pseudomonas aeruginosa. Observations that the combination of the 2 drugs showed FIC indices between less than 0.5-less than 1.0 against most of these strains at SISO concentrations of 1 MIC or sub MIC levels strongly suggested the presence of a synergistic action between the 2 drugs against SISO susceptible strains of GNR. 2. Of the strains tested, 10% of C. freundii, 6.7% of E. cloacae, 63.3% of S. marcescens, 23.3% of P. vulgaris and 18.0% of P. aeruginosa were found to be resistant to SISO, and little synergistic effect of the 2 drugs was observed against these strains. 3. As the synergistic effect of the 2 drugs against GNR was observed against SISO susceptible strains including those which were resistant to CDZM, but not against those strains which were resistant to SISO, it seems reasonable to conclude that the appearance of the synergistic effect between the 2 drugs depends on the activity of SISO.     

Susceptibilities of clinical bacterial isolates to antimicrobial agents. A study mainly focused on imipenem. Reported by the Research Group for Testing Imipenem Susceptibility on Clinical Isolates

This study was conducted to investigate susceptibilities of clinical bacterial isolates to imipenem (IPM) and other antibacterial agents at 64 hospital laboratories throughout Japan from September to December of 1988. In this study, identification and susceptibility testing were carried out at each laboratory and the tests were performed according to the disk dilution method recommended by NCCLS in which susceptibilities are classified into "S", "MS", "I" and "R". IPM showed markedly high in vitro activities against Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus agalactiae, Enterococcus faecalis, Haemophilus influenzae, Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter aerogenes, Enterobacter cloacae, Serratia marcescens, Salmonella spp., Citrobacter freundii, Proteus mirabilis, Proteus vulgaris, Morganella morganii, Providencia rettgeri, Providencia stuartii, Acinetobacter calcoaceticus, Moraxella (Branhamella) catarrhalis, Alcaligenes spp., Peptococcus spp./Peptostreptococcus spp., Bacteroides fragilis and Bacteroides spp. IPM also had strong activities against Achromobacter xylosoxidans and Pseudomonas aeruginosa, but less active against Flavobacterium spp., E. faecium, coagulase-negative staphylococci (CNS), Staphylococcus aureus and Pseudomonas cepacia. In a study in which activities of IPM against bacteria isolated from different clinical sources were compared, differences in susceptibilities were observed among S. aureus, CNS, A. calcoaceticus and P. aeruginosa, but such differences were not apparent among S. pneumoniae, E. faecalis, H. influenzae, E. coli, K. pneumoniae, E. cloacae, C. freundii, S. marcescens or P. mirabilis.     

Metronidazole-quinolone combination: antibacterial activity in vitro

Combination of metronidazole and oxolinic or pipemidic acid were tested in vitro against some of the bacteria most commonly responsible for genito-urinary infections (E. coli, K. pneumoniae, Enterob. cloacae, Serratia marcescens, Pr. mirabilis, Pr. morganii, Str. faecalis and 3 strains of Ps. aeruginosa). The metronidazole-oxolinic acid combination was found to be additive or synergistic against E. coli, K. pneumoniae, Enterob. cloacae and Serratia marcescens. The results show that subinhibitory concentrations of oxolinic acid may reveal an activity of metronidazole against aerobic and facultative anaerobic bacteria, under aerobic conditions.     

Antibacterial activity of aztreonam: a synthetic monobactam. A comparative study with thirteen other antibiotics

The in vitro activity of aztreoman (SQ 26, 776), a new monocyclic beta-lactam antimicrobial agent, was determined against 1720 bacteria, all clinical isolates, and compared with that of thirteen beta-lactam and aminoglycoside antibiotics. Aztreonam inhibited 90% of Citrobacter diversus, Citrobacter freundii, Enterobacter agglomerans, E. coli, Klebsiella pneumoniae, Proteus mirabilis, Proteus morganii, Proteus rettgeri, Proteus vulgaris and Salmonella sp. by less than or equal to 0.4 micrograms ml-1. This activity was superior to moxalactam, piperacillin, cefamandole, cefoperazone, cefoxitin, cefsulodin, ceftazidime and aminoglycoside antibiotics. Aztreonam was as active as moxalactam against Enterobacter aerogenes, Enterobacter cloacae and Shigella species. Pseudomonas aeruginosa strains resistant to moxalactam, piperacillin, cefamandole, cefoperazone, cefotaxime, cefoxitin, cefsulodin and ceftazidime were inhibited by aztreonam 50% by 6.3 micrograms ml-1 and 90% by 16 micrograms ml-1. Aztreonam was as active as ceftazidime against Serratia marcescens, all strains were inhibited by 3.1 micrograms ml-1 and 90% by 1.6 micrograms ml-1. There was no major difference between MBC and MIC values of aztreonam and the effect of inoculum size upon MIC values was observed at 10(7) CFU.     

Yearly changes in antibacterial activities of cefozopran against various clinical isolates between 1996 and 2001--II. Gram-negative bacteria

The in vitro antibacterial activities of cefozopran (CZOP), an agent of cephems, against various clinical isolates obtained between 1996 and 2001 were yearly evaluated and compared with those of other cephems, oxacephems and carbapenems. A total of 3,245 strains in 32 species of Gram-negative bacteria were isolated from the clinical materials annually collected from January to December, and consisted of Moraxella subgenus Branhamella catarrhalis, Escherichia coli, Citrobacter freundii, Citrobacter koseri, Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter aerogenes, Enterobacter cloacae, Serratia marcescens, Proteus mirabillis, Proteus vulgaris, Morganella morganii, Providencia spp. (P. alcalifaciens, P. rettgeri, P. stuartii), Pseudomonas aeruginosa, Pseudomonas putida, Burkholderia cepacia, Stenotrophomonas maltophilia, Haemophilus influenzae, Acinetobactor baumannii, Acinetobactor lwoffii, Bacteroides fragilis group (B. fragilis, B. vulgatus, B. distasonis, B. ovatus, B. thetaiotaomicron), and Prevotella spp. (P. melaninogenica, P. intermedia, P. bivia, P. oralis, P. denticola). CZOP possessed stable antibacterial activities against M. (B.) catarrhalis, E. coli, C. freundii, C. koseri, K. pneumoniae, K. oxytoca, E. aerogenes, E. cloacae, S. marcescens, P. mirabilis, P. vulgaris, M. morganii, Providencia spp., P. aeruginosa, and A. lwoffii throughout 6 years. The MIC90 of CZOP against those strains were consistent with those obtained from the studies performed until the new drug application approval. On the other hand, the MIC90 of CZOP against H. influenzae yearly obviously increased with approximately 64-time difference during the study period. The MIC90 of cefpirome, cefepime, and flomoxef against H. influenzae also yearly tended to rise. The present results demonstrated that CZOP had maintained the antibacterial activity against almost Gram-negative strains tested. However, the decrease in antibacterial activities of CZOP against B. cepacia, and H. influenzae was suggested.     

Susceptibilities of clinical bacterial isolates to antimicrobial agents, 1989. A study mainly focused on imipenem. The Research Group for Testing Imipenem Susceptibilities of Clinical Isolates]

We investigated susceptibilities of clinical bacterial isolates to imipenem (IPM) and other antimicrobial agents at hospital laboratories throughout Japan from September to December of 1989. The susceptibility testing was carried out according to the 1-dilution or 3-dilution disc technique in which susceptibilities are classified into 4 grades: (+++), (++), (+) and (-). IPM showed markedly high in vitro activities against Streptococcus pneumoniae, Neisseria gonorrhoeae, Moraxella catarrhalis, Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Citrobacter freundii, Acinetobacter calcoaceticus, Bacteroides fragilis and had rather strong activities against Enterococcus faecalis, Haemophilus influenzae, Serratia marcescens, Proteus mirabilis, Morganella morganii, Pseudomonas aeruginosa and Achromobacter xylosoxidans, but was less active to Staphylococcus aureus, coagulase-negative staphylococci and Xanthomonas maltophilia. IPM has been found to have activities superior to those of other antibiotics tested against E. faecalis, E. cloacae, C. freundii, S. marcescens, P. aeruginosa and B. fragilis. No antibiotics tested showed good activities against MRSA except minocycline.     

Susceptibilities of clinical bacterial isolates to antimicrobial agents. A study mainly focused on imipenem. Research Group for Testing Imipenem Susceptibility on Clinical Isolates

We investigated susceptibilities of clinical bacterial isolates to imipenem (IPM) and other antimicrobial agents at 459 hospital laboratories throughout Japan from September to December of 1988. In this study, identification and susceptibility testing were performed at each hospital laboratory and the tests were carried out according to the 1-dilution or 3-dilution disc technique in which susceptibilities are classified into 4 grades: , ++, + and -. IPM had significantly high activity against Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus agalactiae, Neisseria gonorrhoeae, Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter aerogenes, Enterobacter cloacae, Salmonella spp., Citrobacter freundii, Proteus mirabilis, Providencia rettgeri, Acinetobacter calcoaceticus, Moraxella catarrhalis, Alcaligenes spp., Peptococcus spp./Peptostreptococcus spp., Bacteroides fragilis and Bacteroides spp. and should slightly lower activities on coagulase-negative staphylococci (CNS), Enterococcus faecalis, Haemophilus influenzae, Serratia marcescens, Proteus vulgaris, Providencia stuartii and Pseudomonas aeruginosa than on the above mentioned bacteria. In a comparative study on activities of IPM against bacteria from different clinical sources, no remarkable differences were found due to different sources among S. pneumoniae, E. faecalis, H. influenzae, E. coli, K. pneumoniae, E. cloacae, C. freundii, P. mirabilis or A. calcoaceticus, whereas slight differences were found among Staphylococcus aureus, CNS, S. marcescens and P. aeruginosa.     

Antimicrobial activity of sulbactam/cefoperazone. Comparison with other new cephems

Antimicrobial activities of sulbactam/cefoperazone (SBT/CPZ) against 50 fresh clinical isolates of Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Citrobacter freundii, Enterobacter spp., Serratia marcescens, Proteus mirabilis, Proteus vulgaris and Pseudomonas aeruginosa were compared to those of CPZ, Cefotiam (CTM), Cefotaxime (CTX) and Latamoxef (LMOX). Minimal inhibitory concentrations (MIC's) of SBT and CPZ mixed in a ratio of 1:1 were determined by the dilution method using Mueller-Hinton agar and expressed by absolute concentrations of CPZ. Antimicrobial activities of SBT/CPZ against principally penicillinase (PCase) producing bacteria, i.e., S. aureus, E. coli, K. pneumoniae, P. mirabilis, were superior to those of CPZ alone. The presence of SBT in concentrations around 0.39 approximately 1.56 micrograms/ml clearly enhanced CPZ's antimicrobial activities against these PCase producing strains. The synergistic antimicrobial effects of SBT in combination with CPZ were less pronounced against principally cephalosporinase (CEPase) producing bacteria, i.e., C. freundii, Enterobacter spp., S. marcescens, P. vulgaris, and P. aeruginosa, and exerted with SBT at concentrations around 3.13 approximately 12.5 micrograms/ml. Comparative antimicrobial activities indicated by MIC80's of tested agents showed that SBT/CPZ had more stable activities against bacteria ranging from Gram-positive to Gram-negative bacteria than CTM, CTX and LMOX. MIC's of SBT/CPZ were higher than 25 micrograms/ml against 8% of S. aureus, 18% of C. freundii, 10% of Enterobacter spp., 26% of S. marcescens, 2% of P. vulgaris, and 18% of P. aeruginosa. These resistant strains against which the addition of SBT showed no synergism, may possess other mechanism of resistance than beta-lactamase production. It is concluded that the presence of CPZ resistant strains is an actual current problem and not an imaginary future problem, and that the number of resistant strains against other new cephems which have different chemical structure from CPZ is increasing. When these present bacteriological environments are considered, the appearance of SBT/CPZ in the clinical practice is timely and meaningful.     

Antimicrobial activity of dactimicin in vitro compared with that of dibekacin, netilmicin, sisomicin and micronomicin

Antimicrobial activity of dactimicin, a pseudo-disaccharide aminoglycoside antibiotic, was compared with those of dibekacin, netilmicin, sisomicin and micronomicin using clinical isolates of four Gram-positive and sixteen Gram-negative bacteria. Dactimicin was more active than the reference amino-glycosides against Serratia marcescens, especially gentamicin-resistant Serratia sp., Proteus vulgaris, P. rettgeri and Klebsiella oxytoca, but less active against Pseudomonas aeruginosa and P. mirabilis. Dactimicin was equally active as the references excepting netilmicin against Gram-positive bacteria and some Gram-negative bacteria including Escherichia coli, K. pneumoniae, Morganella morganii, Haemophilus influenzae, Citrobacter freundii, Enterobacter aerogens, E. cloacae, Acinetobacter calcoaceticus and Campylobacter jejunii. Dactimicin was active against resistant strains possessing various aminoglycoside-modifying enzymes including AAC(3)-1, by which dactimicin was acetylated.     

Sensitivity distribution of bacteria newly isolated from urinary tract infections to micronomicin

The antibacterial activity of micronomicin (MCR) was studied comparatively with that of AMK, GM, CMZ and CFX against 346 strains of E. coli, K. pneumoniae, S. marcescens, P. mirabilis, P. rettgeri, P. vulgaris, M. morganii, E. cloacae, P. aeruginosa, S. aureus and S. epidermidis isolated from patients with urinary tract infections on a nation-wide scale from January to July, 1981. MCR was as high as GM in antibacterial activity against all of strains tested, especially very potent against E. coli and P. mirabilis. On the other hand, AMK showed a tendency to be a little lower in antibacterial activity than MCR and GM, CMZ and CFX were weaker in antibacterial activity against the strains tested in this study than MCR, AMK and GM.     

Antibacterial activities of monobactams against fresh clinical isolates

Antibacterial activities of monobactam antibiotics (carumonam (CRMN) and aztreonam (AZT] against Gram-negative bacilli isolated from inpatients in the latter half of 1987 were investigated using penicillin (PC: piperacillin (PIPC], cephems (CEPs: ceftazidime (CAZ), cefotaxime (CTX), latamoxef (LMOX), cefsulodin (CFS], carbapenem (imipenem (IPM] and pyridonecarboxylic acids (norfloxacin (NFLX) and ofloxacin (OFLX] as reference antibiotics. A total of 400 strains of 13 species, i.e. Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Proteus mirabilis, Proteus vulgaris, Morganella morganii, Providencia rettgeri, Citrobacter freundii, Enterobacter cloacae, Enterobacter aerogenes, Serratia marcescens, Pseudomonas aeruginosa and Haemophilus influenzae, were used as test strains. 1. CRMN and AZT, both monobactam antibiotics, were roughly comparable in their activities and no resistant strain to these antibiotics were found among isolates of E. coli, Klebsiella spp., Proteus spp., M. morganii, P. rettgeri or H. influenzae and few resistant strains were observed among isolates of S. marcescens. On the other hand, isolates of C. freundii, Enterobacter spp. and P. aeruginosa included rather numerous strains resistant to the monobactam antibiotics. Among these cases, whereas R strains, i.e. resistant strains showing MICs greater than or equal to 50 micrograms/ml, accounted for a large proportion of strains resistant to PC and CEPs, I strains, i.e. intermediately resistant strains showing MICs between 12.5 and 25 micrograms/ml, accounted for a large proportion of strains resistant to the monobactam antibiotics. 2. Strains resistant to PIPC, a PC, were detected with high and more or less uniform frequencies over the entire spectrum of the isolates examined. 3. Antibacterial activities of CEPs varied against different bacterial species. While strains resistant to CTX, CAZ and LMOX were commonly detected with high frequencies among isolates of C. freundii, Enterobacter spp. and S. marcescens, large percentages of LMOX-resistant strains of C. freundii and Enterobacter spp. were of the I type. CTX-resistant strains were also found among isolates of P. vulgaris and M. morganii. Proportions of CEP-resistant strains of P. aeruginosa were 28% for CFS and 12% for CAZ. 4. No or few strains among the isolates of 13 species investigated were resistant to IPM, a carbapenem antibiotic, which showed the most stable antibacterial activity, but it was less active than monobactam antibiotics and CEPs against Klebsiella spp., P. mirabilis and H. influenzae.(ABSTRACT TRUNCATED AT 400 WORDS)     

Antibacterial activities of sisomicin against fresh clinical isolates]

To investigate antibacterial activities of sisomicin (SISO), MICs of SISO as well as other aminoglycosides (AGs) were determined against many clinical isolates which were obtained in 1991. Results are summarized below: 1. No SISO-resistant strains were observed among isolates of Escherichia coli, Citrobacter diversus, Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter aerogenes, Proteus mirabilis and Morganella morganii. 2. In comparison with the results of our previous study against isolates obtained in 1986, the rate of methicillin-resistant Staphylococcus aureus (MRSA) was higher, and SISO-resistant strains were observed at a high rate among the MRSA. Also, SISO-resistant strains of Serratia marcescens increased. However, the rate of SISO-resistant strains of Pseudomonas aeruginosa decreased, and among Citrobacter freundii, Enterobacter cloacae and Proteus vulgaris, SISO-resistant strains did not increase over the years. 3. MICs of SISO against Providencia rettgeri and Providencia stuartii were high, suggesting that antibacterial activities of SISO was weak against genus Providencia. 4. For comparison, according to MICs of ofloxacin and imipenem, new quinolone-resistant strains were observed at a high rate among various organisms, and carbapenem-resistant strains were observed at a high rate among S. marcescens and P. aeruginosa. 5. SISO is still one of the useful AGs in the 1990's since it maintains its strong antibacterial activities against most clinical isolates obtained in recent years and its potential as a combination drug with beta-lactams is being reported.     

Yearly changes in antibacterial activities of cefozopran against various clinical isolates between 1996 and 2000--II. Gram-negative bacteria

The in vitro antibacterial activities of cefozopran (CZOP), an agent of cephems, against various clinical isolates obtained between 1996 and 2000 were yearly evaluated and compared with those of other cephems, oxacephems, and carbapenems. Thirty-two species 2,697 strains of Gram-negative bacteria were isolated from the clinical materials annually collected from January to December, and consisted of Moraxella subgenus Branhamella catarrhalis (n = 125), Escherichia coli (n = 250), Citrobacter freundii (n = 153), Citrobacter koseri (n = 97), Klebsiella pneumoniae (n = 150), Klebsiella oxytoca (n = 100), Enterobacter aerogenes (n = 50), Enterobacter cloacae (n = 125), Serratia marcescens (n = 153), Proteus mirabillis (n = 103), Proteus vulgaris (n = 77), Morganella morganii (n = 141), Providencia spp. (P. alcalifaciens, P. rettgeri, P. stuartii; n = 154), Pseudomonas aeruginosa (n = 211), Pseudomonas putida (n = 49), Burkholderia cepacia (n = 102), Stenotrophomonas maltophilia (n = 101), Haemophilus influenzae (n = 210), Acinetobactor baumannii (n = 63), Acinetobactor Iwoffii (n = 30), Bacteroides fragilis group (B. fragilis, B. vulgatus, B. distasonis, B. ovatus, B. thetaiotaomicron; n = 129), and Prevotella spp. (P. melaninogenica, P. intermedia, P. bivia, P. oralis, P. denticola; n = 124). CZOP possessed stable antibacterial activities against M. (B.) catarrhalis, E. coli, C. freundii, C. koseri, K. pneumoniae, K. oxytoca, E. aerogenes, E. cloacae, S. marcescens, P. mirabilis, P. vulgaris, M. morganii, Providencia spp., P. aeruginosa, and A. lowffii throughout 5 years. The MIC90 of CZOP against those strains were consistent with those obtained from the studies performed until the new drug application approval. On the other hand, the MIC90 of CZOP against H. influenzae yearly obviously increased with approximately 65-time difference during study period. The MIC90 of cefpirome, cefepime, and flomoxef against H. influenzae also yearly tended to rise. The present results demonstrated that CZOP had maintained the antibacterial activity against almost Gram-negative strains tested. However, the decrease in the antibacterial activity of CZOP against H. influenzae was suggested.     

Susceptibilities of clinical isolates to antibacterial agents. Focusing mainly on ofloxacin (first report). Reported by the Research Group for Testing Ofloxacin Susceptibility of Clinical Isolates

Susceptibility tests were carried out on a variety of clinically isolated pathogens using the susceptibility disc method at 197 hospitals in Japan between May, 1985 through March, 1986. These tests were organized by the Research Group for Testing Ofloxacin Susceptibility on Clinical Isolates, and the results were statistically analyzed. This paper describes a comparison of susceptibilities of clinical isolates including Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Streptococcus pneumoniae, Neisseria gonorrhoeae, Escherichia coli, Enterobacter aerogenes, Enterobacter cloacae, Citrobacter freundii, Klebsiella pneumoniae subsp. pneumoniae, Proteus mirabilis, Morganella morganii, Serratia marcescens, Haemophilus influenzae, Pseudomonas aeruginosa, Acinetobacter calcoaceticus, Acinetobacter sp. and Campylobacter jejuni to ofloxacin (OFLX) and conventional antibacterial drugs. The results obtained were summarized as follows. 1. OFLX showed strong antibacterial activity against S. aureus, S. epidermidis, N. gonorrhoeae, E. coli, E. aerogenes, E. cloacae, C. freundii, K. pneumoniae subsp. pneumoniae, P. mirabilis, M. morganii, H. influenzae, A. calcoaceticus, Acinetobacter sp. and C. jejuni and only a few strains were resistant to OFLX. Moreover, OFLX has superior antibacterial activity against many species compared not only to norfloxacin but also to most of the conventional antibacterial drugs. 2. When studied by sampled materials such as sputum, urine, abscesses and otorrhea, OFLX occasionally showed different actions against the same species from different sources. Almost species from the urinary isolates were less sensitive than those from the sputum.     

Antimicrobial activity of imipenem against 1386 clinical isolates

1386 isolates from clinical specimens were tested against imipenem by disc agar diffusion. The bacteria used in this study consisted of Escherichia coli, Enterobacter aerogenes, E. agglomerans, E. cloacae, Klebsiella pneumoniae, K. oxytoca, K. ozanae, Proteus mirabilis, P. vulgaris, Providencia stuartii, P. rettgeri, Acinetobacter calcoaceticus, Citrobacter diversus, C. freundii, Morganella morganii, Serratia liquefaciens, S. marcescens, Hafnia alvei, Aeromonas hydrophila, Pseudomonas aeruginosa, P. cepacia, P. maltophila, P. fluorescens, Staphylococcus aureus, S. epidermidis, S. saprophyticus, pneumococcus, Lancefield group A, B and D streptococci, viridans streptococci, diphtheroids and Bacillus species. In vitro activity of imipenem was compared with the following antibiotics: ampicillin, amikacin, carbenicillin, cefoperazone, cefoxitin, cephalothin, chloramphenicol, clindamycin, colistin, erythromycin, gentamicin, methicillin, penicillin, tetracycline, tobramycin, trimethoprim-sulfamethoxazole and vancomycin. Of the 819 strains of Enterobacteriaceae tested, 99.5% were susceptible to imipenem. Ninety-seven percent strains of P. aeruginosa were also susceptible to imipenem. All the 161 isolates of S. aureus and 116 of the 117 isolates of enterococci exhibited in vitro susceptibility to this antibiotic. All gram positive bacteria tested were inhibited by imipenem except 28% isolates of S. epidermidis and 5% isolates of S. agalactiae.     

Combined antibacterial activity of aztreonam and clindamycin against clinically isolated strains

It has been reported in some studies that the combination of aztreonam (AZT) and clindamycin (CLDM) have high clinical effectiveness in the treatment of intractable infections. We, therefore, studied combined in vitro antibacterial activity of these 2 compounds using many freshly isolated strains. 1. AZT and CLDM in combination had synergistic effects on Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, and Haemophilus influenzae, which are sensitive or quasi-sensitive to CLDM, in the presence of CLDM at MIC or sub-MIC. 2. For Escherichia coli, Klebsiella pneumoniae, Citrobacter freundii, Enterobacter cloacae, Serratia marcescens, and Pseudomonas aeruginosa, which are not sensitive to CLDM, the 2 drugs in combination showed synergistic effects on some species and additive or slightly additive effects on most species in the presence of CLDM at those concentrations which are usually maintained in blood. 3. The 2 drugs showed no antagonism.     

In vitro antibacterial activity of various cephems against clinical isolates from complicated urinary tract infections

In vitro antibacterial activity of several cephems (CEZ as the first generation (group A); CTM and CMZ as the second generation (group B); CMX, CPZ, LMOX, CTX and CZX as the third generation (group C)) against 8 species, each of 54 strains, of Gram-negative clinical isolates from complicated urinary tract infection was compared by determination of the MICs. The following results were obtained: The most sensitive drugs against each species in MIC80; CTX (MIC80 0.20 microgram/ml) against E. coli, CMX (1.56 microgram/ml) against K. pneumoniae, LMOX (0.39 microgram/ml) against P. mirabilis, LMOX (0.78 microgram/ml) against Indole (+) Proteus, CMX and CPZ (50 micrograms/ml) against E. cloacae, CMX and LMOX (50 micrograms/ml) against C. freundii, CMX (3.13 micrograms/ml) against S. marcescens and CPZ (25 micrograms/ml) against P. aeruginosa The most sensitive drugs against each species in MICS100; CMX (MIC100 3.13 micrograms/ml) against E. coli, CMX (6.25 micrograms/ml) against K. pneumoniae, CTX (0.78 microgram/ml) against P. mirabilis, LMOX (1.56 microgram/ml) against Indole (+) Proteus, CPZ (100 micrograms/ml) against E. cloacae, CMX (100 micrograms/ml) against C. freundii, CMX (12.5 microgram/ml) against S. marcescens and CPZ (50 micrograms/ml) against P. aeruginosa. In each species, the group C were most sensitive followed by those of the group B. Many isolates were highly resistant to the group A (especially in C. freundii, S. marcescens and P. aeruginosa).     

Combination antibacterial effects between aztreonam and eight other antibiotics

In vitro interactions between aztreonam (AZT) and 8 other antibiotics were studied using the agar dilution checkerboard technique against 88 clinical isolates of Escherichia coli, Proteus vulgaris, Serratia marcescens and Pseudomonas aeruginosa. Combinations of AZT with 8 other antibiotics were generally additive or indifferent. Synergism was occasionally seen against S. marcescens or P. aeruginosa with AZT plus isepamicin (ISP). Antagonism was observed only between AZT and latamoxef against P. vulgaris. In a phase-contrast microscopic study, synergistic effects between AZT and aspoxicillin or ISP were confirmed against E. coli 177 and P. aeruginosa 15846. AZT in combination with ISP demonstrated a synergy against experimental urinary tract infection in mice caused by P. aeruginosa 15846. We believe that combinations of several antibiotics with AZT should be considered for initial therapy of infections because synergism and additive action were observed and antagonism was rarely found in our study.     

Susceptibility of Pseudomonas aeruginosa to a photodynamic effect of the arginine hematoporphyrin derivative

The photodynamic effect of the arginine hematoporphyrin derivative (HpD-Arg(2)) on the growth of selected Pseudomonas aeruginosa clinical isolates is described as compared to the effect of hematoporphyrin derivative (HpD). Growth inhibition of HpD-Arg(2) of three Gram-positive strains (Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus) and five laboratory strains of Gram-negative bacteria (Escherichia coli, Proteus vulgaris, P. aeruginosa, Klebsiella pneumoniae and Enterobacter cloacae) was observed as well. Serratia marcescens strain was resistant to light-activated HpD-Arg(2) or HpD. The antimicrobial activity of light-activated HpD-Arg(2) against P. aeruginosa may offer an additional option in the anti-pseudomonal therapy of wounds.     

The antibacterial activity of fluoroquinolones against gram-negative bacteria isolated from Gifu Prefecture (2005)

We investigated the susceptibility to 6 fluoroquinolones against 433 strains of Gram-negative bacteria isolated from 6 medical facilities in Gifu prefecture between January and September in 2005, determined by the agar dilution methods in according with the Japan Society of Chemotherapy. We also investigated the correlation between the degree of resistance to fluoroquinolones and the amino acid substitutions in the quinolone resistance-determining region (QRDR). The tested clinical isolates were as follows, Salmonella spp.; 17 strains, Escherichia coli; 112 strains Citrobacter freundii; 35 strains, Enterobacter cloacae; 31 strains, Klebsiella pneumoniae; 73 strains, Proteus spp.; 18 strains, Providencia spp.; 3 strains, Morganella morganii; 14 strains, Serratia marcescens; 27 strains and Pseudomonas aeruginosa; 103 strains. The number of the strains resistant to ciprofloxacin (CPFX) (MIC > or = 6.25 microg/mL) was twenty (E. coli; 14 strains, E. cloacae; I strain, Proteus spp.; 2 strains and P. aeruginosa; 3 strains). Among these strains, 12 strain (E. coli; 11 strains and E. cloacae; 1 strain) were highly resistant to CPFX (MIC > or =25 microg/mL). The E. coli strains highly resistant to CPFX had the multiple amino acid mutations in QRDR of ParC an GyrA. However in other strains, there was no strains possessing multiple mutations in both ParC and GyrA.