Antimicrobial activity, beta-lactamase stability and beta-lactamase inhibition of cefotetan and other 7-alpha-methoxy beta-lactam antimicrobials

An in vitro evaluation of HRE 664, a novel penem antibiotic

HRE 664 is a novel parenteral penem with a broad antimicrobial spectrum. In this study, HRE 664 inhibited 90% of Enterobacteriaceae at less than or equal to 2.0 micrograms/ml, Haemophilus influenzae and Neisseria gonorrhoeae at less than or equal to 0.5 microgram/ml, oxacillin-susceptible staphylococci at less than or equal to 0.13 microgram/ml, oxacillin-resistant staphylococci at less than or equal to 8.0 micrograms/ml, enterococci at less than or equal to 8.0 micrograms/ml, and streptococci at less than or equal to 0.13 microgram/ml. All strains of Pseudomonas aeruginosa were resistant (MICs were greater than 32 micrograms/ml). HRE 664 exhibited a minimal inoculum effect and good bactericidal activity with all organisms tested except an oxacillin-resistant Staphylococcus aureus. With the latter, there was a marked inoculum effect and no on-scale bactericidal endpoints. No measurable hydrolysis of HRE 664 occurred with any of the five Gram-negative bacterial beta-lactamases tested. When stored at -20 degrees C, HRE 664 showed no significant loss of activity for up to 6 wk, but detectable deterioration occurred thereafter. At -60 degrees C, no loss in HRE 664 potency was observed for up to 12 wk. Proposed HRE 664 MIC quality control parameters are: 0.03-0.13 microgram/ml for S. aureus ATCC 29213, 0.25-1.0 micrograms/ml for Escherichia coli 25922, and 2.0-8.0 micrograms/ml for Enterococcus faecalis ATCC 29212.

Cefotetan: a review of the microbiologic properties and antimicrobial spectrum

Cefotetan (formerly ICI 156834 and YM09330) is a 7-methoxy cephalosporin possessing some advantageous antimicrobial spectrum, safety, and pharmacokinetic characteristics compared with other so-called second-generation cephalosporins. The published literature was reviewed and the cefotetan quantitative susceptibility testing data from nearly 31,000 isolates was tabulated. Against 15,769 enteric bacilli, cefotetan was observed to have a potency and spectrum more closely resembling a third-generation cephalosporin and markedly superior to cefoxitin. The mean of all MIC 90s reported for the Enterobacteriaceae ranged from 0.06 to 13 micrograms/ml except for citrobacter species, E. cloacae, Enterobacter species, and C. freundii. The mean MIC 50 for all 22 recorded species was in the susceptible range. Cefotetan was very effective against B. catarrhalis, H. influenzae, and pathogenic Neisseria species. However, cefotetan and cefoxitin were not active against Pseudomonas species, Acinetobacter species, and some rarely isolated species. Cefotetan was moderately active against the staphylococci (mean MIC 50, 7.6 to 26 micrograms/ml) and streptococci (mean MIC 50, 0.9 to 6.6 micrograms/ml). The coagulase-negative staphylococcus species generally had higher cefotetan and cefoxitin minimum inhibitory concentrations compared with the S. aureus isolates. Oxacillin-resistant staphylococci were resistant to cefotetan. The enterococci, JK group diphtheroids, Corynebacterium species, and L. monocytogenes isolates were resistant. A review of 4,751 strict anaerobes showed cefotetan to have a very comparable activity and spectrum to cefoxitin. The 1,291 B. fragilis strains had a mean MIC 50 and MIC 90 of 5.4 and 23 micrograms/ml, respectively. These values were slightly superior to cefoxitin when tested in parallel. More elevated minimum inhibitory concentrations were observed for other B. fragilis group species for cefoxitin and cefotetan. The mean cefotetan MIC 90 for all other anaerobic bacteria except the Eubacterium species and Lactobacillus species predict favorable clinical efficacy. The beta-lactamase stability of cefotetan is very similar to that of other 7-methoxy cephalosporins. Cefotetan also inhibits Type Ia cephalosporinases with high enzyme affinity and is an inducer of these beta-lactamases, although cefotetan is not rapidly hydrolyzed. Synergy between cefotetan and numerous other antibiotics has been reported, but antagonism has also been occasionally observed.

Criteria for in vitro susceptibility testing of cefotetan. Correlations with clinical and bacteriologic responses

Standardized in vitro susceptibility testing criteria and quality-control guidelines for cefotetan have been well documented in the scientific literature. Cefotetan and cefoxitin differ in their in vitro spectrums of activity and cannot be used interchangeably for in vitro tests. In vitro susceptibility information failed to correlate with clinical or bacteriologic responses of treated patients when 314 anaerobic bacteria from 145 patients were evaluated. All cefotetan-resistant anaerobic bacteria were eradicated by cefotetan therapy, and 93 percent of patients with resistant strains were clinically curved. Most members of the Bacteroides distasonis-ovatus-thetaiotaomicron group of pathogens were resistant in vitro, but only one strain persisted after cefotetan therapy for a 96.6 percent cure rate. There was better correlation when 2,336 aerobic bacteria from 1,630 infected body sites were considered. Microorganisms susceptible or moderately susceptible by in vitro tests were equally responsive to therapy (95 percent of patients clinically cured and 94 percent of isolates eradicated). However, strains that were resistant by in vitro test criteria were less likely to respond clinically. Development of resistance during therapy or superinfections (1.7 percent) were not found to be clinically important problems with cefotetan chemotherapy.

Use of new beta-lactam antibiotics for surgical infections

The availability of beta-lactam antibiotics with extended spectra of activity against organisms commonly seen in surgical infections suggests that aminoglycoside-based therapy is no longer needed for most such community-acquired infections. The primary problems with specific beta-lactams are lack of activity against Bacteroides species and variable activity against Pseudomonas aeruginosa and enterococci. The pharmacokinetic properties of the newer beta-lactams vary considerably. This variation suggests specific settings in which these properties may be taken advantage of to improve clinical outcome.

Cross susceptibility and absence of cross resistance to cefotetan and cefoxitin

Tests with 2,713 bacterial isolates (members of the family Enterobacteriaceae and gram-positive cocci) from 14 laboratories compared cefoxitin MICs with cefotetan MICs. Strains that were susceptible to cefoxitin could be assumed to be susceptible to cefotetan. Over half of the cefoxitin-resistant isolates of the Enterobacteriaceae were susceptible to cefotetan.

In vitro susceptibility of the Bacteroides fragilis group in community hospitals

The antimicrobial susceptibility of clinical isolates of the Bacteroides fragilis group was determined at six community hospitals (one large, greater than 600 beds; and five smaller, 96-325 beds). Imipenem was the most active beta-lactam with 100% of isolates being sensitive at 4 micrograms/ml. The percentage of isolates inhibited at 16 micrograms/ml (and 32 micrograms/ml) for the 7-alpha-methoxy antibiotics was: cefoxitin 66 (90); moxalactam 73 (85); cefotetan 68 (72); cefmetazole 40 (61). Metronidazole, chloramphenicol, and clindamycin were active against 100%, 100%, and 89% at breakpoints of 8 micrograms/ml, 8 micrograms/ml, and 4 micrograms/ml, respectively. The activity of several beta-lactams in our report differed slightly from that reported from university teaching hospitals. There were differences at many of the breakpoints for activity of some of the beta-lactam antibiotics for isolates from the large community hospital as compared with the combined isolates from the smaller community hospitals. Interestingly, the pattern was one of more resistance at the smaller community hospitals.

Evaluation of the in vitro activity of BMY-28142, a new broad-spectrum cephalosporin

The in vitro activity of BMY-28142, a new cephalosporin, was tested by a broth microdilution system and compared with those of cefotaxime, ceftazidime, cefoperazone, moxalactam, and HR 810 against 747 bacterial isolates, one-third of which were resistant to one or more third-generation cephalosporins. BMY-28142 was the most active drug tested against 326 Enterobacteriaceae with an MIC for 90% of the organisms tested (MIC90) of 1.0 micrograms/ml. Against these Enterobacteriaceae the relative activities were: BMY-28142 greater than HR 810 greater than moxalactam and ceftazidime greater than cefotaxime greater than cefoperazone. For cefotaxime- and cefoperazone-resistant strains, the MIC90 of BMY-28142 was 4.0 micrograms/ml (compared with 0.13 micrograms/ml for susceptible strains). BMY-28142, with an MIC90 of 8.0 micrograms/ml for Pseudomonas aeruginosa, was about half as active as ceftazidime. The relative activities against P. aeruginosa were: ceftazidime greater than BMY-28142 greater than HR 810 greater than cefoperazone greater than moxalactam and cefotaxime. The MIC90 of BMY-28142 against staphylococci was 2.0 micrograms/ml, which was fourfold less active than HR 810, slightly less active than cefotaxime and cefoperazone, and fourfold more active than ceftazidime and moxalactam. BMY-28142 was very active against beta-lactamase-positive and -negative Haemophilus influenzae (MIC90, 0.06 micrograms/ml), Neisseria gonorrhoeae (MIC90, 0.015 micrograms/ml),aand nonenterococcal streptococci. Its activity against Streptococcus faecalis was poor (MIC90, 64 micrograms/ml). BMY-28142 was stable against the several beta-lactamases tested but exhibited little beta-lactamase inhibitory effect.

In vitro evaluation of HR810, a new wide-spectrum aminothiazolyl alpha-methoxyimino cephalosporin

HR810 (Hoechst-Roussel Pharmaceuticals Inc., Somerville, N.J.) is a new, cyclical-pyridinium cephalosporin that appeared superior to numerous comparison drugs against 658 strains of aerobic and facultative anaerobic bacteria. Seventeen Enterobacteriaceae spp. were tested by broth microdilution methods, and the 50% MICs (MIC50S) and 90% MICs (MIC90s) were 0.03 to 0.12 and 0.03 to 2.0 micrograms/ml, respectively. Only one strain had an MIC greater than 8.0 micrograms/ml (99.6% is considered susceptible). HR810 inhibited 98% of Pseudomonas aeruginosa isolates at less than or equal to 16 micrograms/ml, and the MIC90 for Acinetobacter spp. was 4.0 micrograms/ml. It was also very active against Pseudomonas spp. and Staphylococcus aureus (MIC90, 0.5 micrograms/ml) but marginally active against methicillin-resistant staphylococcal strains (MIC90, 16 micrograms/ml) and enterococcus (MIC90, 32 micrograms/ml). Non-enterococcal streptococci had MIC50s ranging from 0.008 micrograms/ml for Streptococcus pyogenes to 0.12 micrograms/ml for pneumococci. All MICs of HR810 against Haemophilus and Neisseria spp. were less than or equal to 0.03 micrograms/ml (MIC50, 0.002 to 0.008 micrograms/ml). HR810 poorly inhibited beta-lactamases and was very stable against 11 tested beta-lactamases of plasmid (TEM, OXA, SHV-1, and PSE) and chromosomal (K1, K14, P99) types.

In vitro evaluation of U63196-E (AC-1370): antimicrobial activity, beta-lactamase stability, and beta-lactamase inhibition

Upjohn compound U63196 -E (formerly AC-1370) is a new semisynthetic cephalosporin with a broad spectrum of antimicrobial activity that includes Pseudomonas aeruginosa (minimum inhibitory concentration, 8.0 micrograms/ml), nearly all members of the Enterobacteriaceae, and most gram-positive cocci except enterococci and staphylococci resistant to to methicillin. The compound was stable to most commonly isolated beta-lactamases, especially TEM-1, TEM-2, and P-99; the highest rates of hydrolysis of U63196 -E were by PSE enzymes (23.4-92.5% of the relative hydrolysis rate of cephaloridine). Compared to eight other beta-lactams, U63196 -E was a poor inhibitor of beta-lactamases.

Temocillin: in vitro activity against 734 selected clinical isolates, including beta-lactamase-producing strains

The in vitro activity of temocillin against 734 clinical isolates was tested by broth microdilution. Good activity was demonstrated against Enterobacteriaceae and both beta-lactamase-positive and -negative strains of Haemophilus influenzae and Neisseria gonorrhoeae. There was little to no activity against gram-positive cocci and nonfermenting gram-negative bacilli. Bactericidal activity and effect of inoculum size on temocillin activity were comparable to that of ticarcillin. Temocillin was stable to commonly encountered beta-lactamases and significantly inhibited Richmond-Sykes type 1 enzymes of Enterobacter cloacae.