Antimicrobial activities of BMY-28142, cefbuperazone, and cefpiramide compared with those of other cephalosporins

Discovery of Quaternized Pyridine-Thiazole-Pleuromutilin Derivatives with Broad-Spectrum Antibacterial and Potent Anti-MRSA Activity

The quaternization of compounds has emerged as a promising molecular design strategy for the development of antibiotics. Herein, we report the design, synthesis, antibacterial activities, and structure-activity relationships of a series of novel pleuromutilin derivatives containing a quaternary amine C-14 side chain. Most of these derivatives exhibited broad-spectrum antibacterial activity against the tested bacteria. 10b was the most effective antibacterial agent that displayed excellent antibacterial activity against five clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates, remarkable antimycoplasma activity, rapid bactericidal effects, and a strong ability to damage bacterial biofilms. Further mechanistic studies indicated that 10b destroyed bacterial cell membranes to exert its antibacterial effects. Moreover, 10b exhibited high survival protection and potent in vivo antibacterial efficacy (ED₅₀ = 4.94 mg/kg) in a mouse model of systemic MRSA infection. These findings suggest that 10b is a promising candidate for the treatment of multi-drug-resistant infectious diseases, especially MRSA infections.

The Chemical Relationship Among Beta-Lactam Antibiotics and Potential Impacts on Reactivity and Decomposition

Beta-lactam antibiotics remain one of the most commonly prescribed drug classes, but they are limited by their propensity to cause hypersensitivity reactions (e.g., from allergy to anaphylaxis) as well as by the emergence of bacteria with a myriad of resistance mechanisms such as β-lactamases. While development efforts continue to focus on overcoming resistance, there are ongoing concerns regarding cross-contamination of β-lactams during manufacturing and compounding of these drugs. Additionally, there is a need to reduce levels of drugs such as β-lactam antibiotics in waste-water to mitigate the risk of environmental exposure. To help address future development of effective remediation chemistries and processes, it is desired to better understand the structural relationship among the most common β-lactams. This study includes the creation of a class-wide structural ordering of the entire β-lactam series, including both United States Food and Drug Association (US-FDA)-approved drugs and experimental therapies. The result is a structural relational map: the "Lactamome," which positions each substance according to architecture and chemical end-group. We utilized a novel method to compare the structural relationships of β-lactam antibiotics among the radial cladogram and describe the positioning with respect to efficacy, resistance to hydrolysis, reported hypersensitivity, and Woodward height. The resulting classification scheme may help with the development of broad-spectrum treatments that reduce the risk of occupational exposure and negative environmental impacts, assist practitioners with avoiding adverse patient reactions, and help direct future drug research.

Cefepime. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Cefepime is a 'fourth' generation cephalosporin that has a broader spectrum of antibacterial activity than the third generation cephalosporins and is more active in vitro against Gram-positive aerobic bacteria. The fact that cefepime is stable to hydrolysis by many of the common plasmid- and chromosomally-mediated beta-lactamases, and that it is a poor inducer of type I beta-lactamases, indicates that cefepime may be useful for treatment of infections resistant to earlier cephalosporins. In comparative trials, cefepime 1 to 2 g, usually administered intravenously twice daily, was as effective as ceftazidime 1 to 2 g, usually administered 3 times daily, for treatment of bacteraemia and infections of the lower respiratory tract, urinary tract, pelvis and skin and skin structures. Furthermore, cefepime was as effective as ceftazidime and piperacillin or mezlocillin in combination with gentamicin when administered as empirical treatment for fever in patients with neutropenia. A limited number of trials have found cefepime to be as effective as cefotaxime for the treatment of gynaecological and lower respiratory tract infections. Similarly, cefepime 2 g twice daily intravenously (alone or in combination with metronidazole) was as effective as gentamicin in combination with mezlocillin or clindamycin, respectively, for the treatment of intra-abdominal infection. Cefepime has a linear pharmacokinetic profile, an elimination half-life of approximately 2 hours and is primarily excreted by renal mechanisms as unchanged drug. Cefepime has a tolerability profile similar to that of other parenteral cephalosporins; adverse events are primarily gastrointestinal in nature. A total of 1.4 and 2.9% of patients receiving cefepime < or = 2 g/day and > 2 g/day, respectively, required treatment withdrawal as a result of any adverse event. Thus, cefepime has the advantage of an improved spectrum of antibacterial activity, and is less susceptible to hydrolysis by some beta-lactamases, compared with third generation cephalosporins. Despite these advantages, cefepime has not been found to be more effective than ceftazidime and cefotaxime in clinical trials, although most trials selected patients with organisms sensitive in vitro to both comparator agents. Further trials, particularly in areas of widespread bacterial resistance, are required to confirm the positioning of cefepime for treatment of serious infection, and in particular to further explore whether its potential advantages result in clinical benefits.

Cefepime clinical pharmacokinetics

Cefepime is a new parenteral cephalosporin with antimicrobial activity similar to third-generation cephalosporins. It acts against the Enterobacteriaceae family, and Pseudomonas aeruginosa, but maintains Gram-positive activity similar to that of first- or second-generation cephalosporins. Cefepime has in vitro activity against many bacterial isolates resistant to ceftazidime and cefotaxime, is stable against chromosomally mediated beta-lactamases, demonstrates lower affinity for these enzymes and shows a high resistance to enzymatic hydrolysis. Clinical uses thus far include treatment of lower respiratory tract, intra-abdominal and urinary tract infections, skin and soft tissue infections and for prophylaxis in biliary tract and prostate surgery. Pharmacokinetic studies indicate that cefepime exhibits linear pharmacokinetic behaviour. Pharmacokinetic variables are not significantly different between single- and multiple-dose administration, indicating a lack of drug accumulation in patients with normal renal function. Cefepime is not highly bound to plasma proteins, with binding values of approximately 16 to 19%. The drug is widely distributed in various biological tissues and fluids. The primary route of elimination is from the kidneys, with over 80% of the drug recovered in the urine as unchanged drug in patients with normal renal function. Total drug clearance and renal clearance are similar to creatinine clearance, and glomerular filtration is thought to be the primary mechanism of renal excretion. The elimination half-life is approximately 2 to 2.5 h in patients. Cefepime is removed by haemodialysis (over 3h) and peritoneal dialysis (over 72h) to an appreciable extent, with 40 to 68% and 26% of the drug removed, respectively. Overall, cefepime is well tolerated by patients and no significant drug interactions have been reported to date.

Pharmacokinetics of cefepime after single and multiple intravenous administrations in healthy subjects

The pharmacokinetics of cefepime in 31 young, healthy volunteers were assessed after the administration of single and multiple 250-, 500-, 1,000-, or 2,000-mg intravenous doses. Each subject received a single dose of cefepime via a 30-min intravenous infusion on day 1 of the study. Starting from day 2, subjects received multiple doses of cefepime every 8 h for 9 days, and on the morning of day 11, they received the last dose. Serial blood and urine samples were collected after administration of the first dose and on days 1, 6, and 11. Cefepime concentrations in plasma and urine were assayed by using reverse-phase high-performance liquid chromatography with UV detection. Data were evaluated by noncompartmental methods to determine pharmacokinetic parameters. The mean half-life of cefepime was approximately 2 h and did not vary with the dose or duration of dosing. The regression analyses of peak levels (Cmax) in plasma at the end of the 30-min intravenous infusion and the area under the plasma concentration-versus-time curve (AUCo-infinity) showed a dose-proportional response. The steady-state volume of distribution (Vss) was approximately 18 liters and was independent of the administered dose. The multiple-dose pharmacokinetic data are suggestive of a lack of accumulation or change in clearance of cefepime on repeated dosing. Cefepime was excreted primarily unchanged in urine. The recovery of intact cefepime in urine was invariant with respect to the dose and accounted for over 80% of the dose. The values for renal clearance ranged from 99 to 132 ml/min and were suggestive of glomerular filtration as the primary excretion mechanism. It is concluded that cefepime linear pharmacokinetics in healthy subjects.

Modulation of the intestinal flora of mice by parenteral treatment with broad-spectrum cephalosporins

A study was performed to determine the effect of parenteral treatment with four broad-spectrum cephalosporins (cefoperazone, ceftriaxone, ceftazidime, and cefepime) on the number of aerobic gram-negative rods and on the outgrowth of Candida albicans and a multiresistant strain of Citrobacter freundii in the feces of mice. The estimated fractions of a parenteral dose that were excreted into the gastrointestinal tract were 0.37 for cefoperazone, 0.11 for ceftriaxone, 0.03 for ceftazidime, and 0.002 for cefepime. All four cephalosporins significantly decreased the number of aerobic gram-negative rods in the feces, and virtually all gram-negative rods were eliminated at high doses of cefoperazone, ceftazidime, and ceftriaxone. Furthermore, at high doses these three compounds led to a significant increase of the outgrowth of resistant Citrobacter freundii. The outgrowth of Candida albicans was increased at high doses of cefoperazone and ceftriaxone, whereas ceftazidime and cefepime did not have this effect. The most profound changes in the gastrointestinal ecology were observed during treatment with high doses of cefoperazone. The results suggest that the colonization resistance of the gastrointestinal tract can be substantially decreased by parenteral treatment with cefoperazone and, to a lesser extent, with ceftriaxone and ceftazidime.

Comparative activity of cefepime, alone and in combination, against clinical isolates of Pseudomonas aeruginosa and Pseudomonas cepacia from cystic fibrosis patients

The comparative in vitro activity and synergy of cefepime were evaluated with clinical isolates of Pseudomonas aeruginosa and Pseudomonas cepacia from cystic fibrosis patients. The activity of cefepime, both alone and in combination, was comparable to those of other antibiotics. The clinical efficacy of cefepime in cystic fibrosis patients merits investigation.

In vitro activity and stability against novel beta-lactamases of investigational beta-lactams (cefepime, cefpirome, flomoxef, SCE2787 and piperacillin plus tazobactam) in comparison with established compounds (cefotaxime, latamoxef and piperacillin)

The therapeutic perspectives of flomoxef, SCE 2787, cefpirome, cefepime, latamoxef, cefotaxime and of piperacillin plus tazobactam were comparatively evaluated by their in vitro activity against 1119 clinical isolates of 83 bacterial species. Escherichia coli, Klebsiella spp. Enterobacter sakazakii, Proteus spp. and Shigella spp. were about equally susceptible to the cephalosporins (MIC90: 0.06 to 0.5 mg/l), while the MIC90 for piperacillin plus tazobactam was between 2 and 16 mg/l. Enterobacter cloacae, Enterobacter aerogenes and Serratia spp. were most susceptible to SCE 2787, cefpirome and cefepime (MIC90: 0.06 to 2 mg/l) followed by latamoxef, cefotaxime, flomoxef and piperacillin plus tazobactam. For Citrobacter spp., Providencia spp. and Yersinia enterocolitica MIC90 were between 0.06 and 0.5 mg/l. Flomoxef was between 2 to 4 log2 less active against these species but more active than piperacillin plus tazobactam (MIC90: 2 and 8 mg/l). Morganella morganii and Hafnia alvei were most susceptible to cefepime, cefpirome and latamoxef (MIC90: 0.13 to 0.5 mg/l) while cefotaxime (MIC90: 8 mg/l) and piperacillin plus tazobactam (MIC90: 8 and greater than 64 mg/l) were the least active compounds. SCE 2787, cefepime and cefpirome were the most potent beta-lactams against the majority of the 13 species of non-fermentative bacilli (NFB) investigated (MIC90: 0.5 to 16 mg/l). The oxacephems were the least active compounds against NFB. Cefepime was the most active of the compounds included against Pseudomonas aeruginosa (MIC90: 16 mg/l). Haemophilus spp., Neisseria gonorrhoeae and Bordetella pertussis were most susceptible to cefotaxime (MIC90: 0.03 to 0.06 mg/l). Latamoxef had the lowest activity of all compounds against gram-positive cocci. Flomoxef was the most active compound against penicillinase producing Staphylococcus aureus and about equally active as the other betalactams against methicillin susceptible staphylococci of other staphylococcal species.(ABSTRACT TRUNCATED AT 250 WORDS)

Open trial of cefepime (BMY 28142) for infections in hospitalized patients

The safety and efficacy of cefepime, a new broad-spectrum, semisynthetic parenteral cephem antibiotic, were evaluated in an open trial at a single hospital. Seventy patients were treated with cefepime: 44 had lower respiratory tract infections, 4 had urinary tract infections, and 22 had skin or soft tissue infections. Of 65 clinically evaluable patients, 64 (98%) had satisfactory responses. No mortality or superinfections occurred. Of 57 respiratory and urinary tract pathogens, 54 (95%) were eradicated and 3 (5%) persisted after therapy. Five bacteremias (two with Streptococcus pneumoniae and one each with Staphylococcus aureus, Proteus mirabilis, and a coagulase-negative staphylococcus) were eradicated. MICs ranged from 1 to 8 micrograms/ml for 13 S. aureus and 9 Pseudomonas aeruginosa isolates and were less than or equal to 0.125 micrograms/ml for 10 streptococcal isolates. Adverse effects occurred in two patients: transient diarrhea and Clostridium difficile toxin in the stool in one patient and loose bowel movements and increased transaminases in the other patient. Cefepime appeared to be well tolerated in humans and was effective against a wide range of isolates, including S. aureus and P. aeruginosa.

Comparative in vitro activity of cefepime (BMY 28142) against multiresistant nosocomial isolates of Pseudomonas aeruginosa

The in vitro activity of a new parenteral cephalosporin cefepime (BMY 28142) was compared with that of ceftazidime, cefotaxime, piperacillin, imipenem, gentamicin, amikacin and ciprofloxacin against 173 recent multiresistant Pseudomonas aeruginosa isolates of nosocomial origin using an agar dilution technique with an inoculum of 10(4) CFU per spot. The activity of cefepime was comparable to that of ceftazidime, superior to that of cefotaxime, piperacillin, gentamicin and amikacin, but inferior to that of imipenem and ciprofloxacin. Cross-resistance of Pseudomonas aeruginosa to ceftazidime and cefepime occurred in nearly 50% of the cefepime resistant strains and 61.5% of the ceftazidime resistant strains respectively.

High hepatic excretion in humans of cefpiramide, a new cephalosporin

After intravenous administration of 1 g of cefpiramide, the biliary elimination of the drug was studied by using high-performance liquid chromatography. In five healthy volunteers, a mean peak concentration of 339 +/- 107 (standard error of the mean) micrograms/ml was measured in aspirated duodenal fluid during h 2 after administration, and 1.2% of the dose given was recovered over a 4-h period. A maximal concentration of 1,161 +/- 392 micrograms/ml was reached during h 2 in T-tube bile from 10 recently cholecystectomized patients, with a 24-h biliary recovery of 23.1%; urinary recovery over the same period averaged 49.4%. In 10 patients undergoing cholecystectomy, the concentrations in serum, choledochal bile, gallbladder bile, and gallbladder wall 1 h after cefpiramide administration were 157 +/- 21, 1,726 +/- 501, and 84 +/- 33 micrograms/ml and 23 +/- 4 micrograms/g, respectively. These figures represent the highest biliary concentrations attained so far with a beta-lactam antibiotic and are therefore a good prerequisite for treatment of biliary tract infections with cefpiramide.

Cefmenoxime. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Cefmenoxime is an aminothiazolyl cephalosporin administered intravenously or intramuscularly. Like other 'third-generation' cephalosporins it is active in vitro against most common Gram-positive and Gram-negative pathogens, is a potent inhibitor of Enterobacteriaceae (including beta-lactamase-producing strains), and is resistant to hydrolysis by beta-lactamases. Cefmenoxime has a high rate of clinical efficacy in many types of infection and is at least equal in clinical and bacteriological efficacy to several other cephalosporins in urinary tract infections, respiratory tract infections, postoperative infections and gonorrhoea. Cefmenoxime, like latamoxef, cefoperazone and cefamandole, has an N-methyltetrazole side chain at the 3-position of the cephalosporin nucleus and thus possesses the potential for producing hypoprothrombinaemic bleeding and disulfiram-like reactions. However, these reactions have been reported very rarely and the antibacterial is generally well tolerated. It is likely that cefmenoxime will most closely resemble cefotaxime and ceftizoxime in therapeutic profile and usefulness.

In vitro activity of carumonam (RO 17-2301), BMY-28142, aztreonam, and ceftazidime against 7,620 consecutive clinical bacterial isolates

For 45-60 days four geographically separate clinical laboratories tested routine clinical bacterial isolates for susceptibility to carumonam, aztreonam, BMY-28142, and ceftazidime by the broth microdilution method. All four drugs were highly active against Enterobacteriaceae, inhibiting greater than 96% of the 4887 strains tested at less than or equal to 8.0 microgram/ml. The minimal inhibitory concentration at which 50% of the isolates were inhibited for each drug was less than or equal to 0.125 micrograms/ml. Ceftazidime was the most active against nonenteric gram-negative bacilli (86% inhibited at less than or equal to 8.0 micrograms/ml), followed by BMY 28142 (82%), carumonam (75%), and aztreonam (68%). The two monobactams exhibited no activity against gram-positive cocci at the concentrations tested, whereas BMY-28142 had excellent activity against nonenterococcal streptococci and good activity against staphylococci.

Tentative disk diffusion susceptibility interpretive criteria for BMY-28142, a new cephalosporin

A total of 750 bacterial isolates, including 37 different species, were tested for susceptibility to BMY-28142 by standardized broth microdilution and disk diffusion tests. The zone diameter interpretive criteria tentatively suggested for the 30-micrograms BMY-28142 disk are as follows: susceptible = greater than or equal to 18 mm (MIC less than or equal to 8.0 micrograms/ml), resistant = less than or equal to 14 mm (MIC greater than or equal to 32 micrograms/ml), and indeterminate = 15 to 17 mm.

In vitro activity of cefpiramide (SM-1652) against gram-negative bacilli

The susceptibilities of 317 gram-negative bacilli to cefpiramide, cefotaxime, and piperacillin were determined by standardized microdilution and disk diffusion tests. Cefpiramide and piperacillin were more consistently active against nonfermenters than against Enterobacteriaceae, whereas cefotaxime was more active against Enterobacteriaceae. Inhibitory zone diameters of approximately 75-micrograms cefpiramide disks correlated well with minimal inhibitory concentrations (r = 0.85); breakpoints for defining susceptibility and resistance were recommended.

Efficacy of BMY-28142 in experimental bacteremia and meningitis caused by Escherichia coli and group B streptococci

We evaluated the activity of BMY-28142 against a K1 E. coli strain and a type III group B streptococcal strain in vitro and in vivo and compared the results with those of cefotaxime and penicillin G, respectively. In vitro, the MICs and MBCs of BMY-28142 were close to those of cefotaxime (less than or equal to 2-fold difference) for E. coli and fourfold less than those of penicillin G for group B streptococci. In vivo studies with an experimental bacteremia and meningitis model in newborn rats revealed that the mean penetration of BMY-28142 into the cerebrospinal fluid was 15% that of concomitant levels in serum and that significantly greater bactericidal titers were achieved in blood and cerebrospinal fluid for both test organisms with BMY-28142 than with cefotaxime and penicillin G. However, the overall efficacy of BMY-28142 was similar to that of cefotaxime for the E. coli infection and that of penicillin G for the group B streptococcal infection. This was shown by similar rates of bacterial clearance from blood and cerebrospinal fluid and similar mortality rates. These findings indicate that the activity of BMY-28142 is bactericidal in vitro and in vivo against E. coli and group B streptococci, suggesting that this agent may be a suitable alternative for the therapy of E. coli and group B streptococcal bacteremia and meningitis.

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.

Ceftizoxime. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Ceftizoxime is a 'third generation' cephalosporin administered intravenously or intramuscularly. Like other third generation cephalosporins it has a wide spectrum of in vitro activity against Gram-positive and Gram-negative bacteria, is particularly active against Enterobacteriaceae (including beta-lactamase-positive strains), and is resistant to hydrolysis by beta-lactamases. However, the third generation cephalosporins are less active than earlier cephalosporins against staphylococci and so could not be considered the drugs of choice. Like many currently available third generation cephalosporins, ceftizoxime has limited activity against Pseudomonas aeruginosa, and thus cannot be recommended as sole treatment of known or suspected non-urinary tract pseudomonal infections. Similarly, although favourable clinical results have been obtained in patients treated with ceftizoxime for infections caused by mixed aerobic/anaerobic organisms (such as intra-abdominal, and obstetric and gynaecological infections), the relatively low in vitro activity of ceftizoxime (in common with most other third generation cephalosporins) against Bacteroides fragilis and enterococci may restrict its usage in situations where these organisms are the suspected or proven pathogens. Ceftizoxime appears to be similar in efficacy to several other cephalosporins in lower respiratory tract infections in elderly and/or debilitated patients, and in chronic and/or complicated urinary tract infections, 2 clinical situations in which third generation cephalosporins may have a major role. Ceftizoxime is also effective clinically and bacteriologically in skin, soft tissue, bone and joint infections, septicaemia/bacteraemia, meningitis and neonatal infections. However, a few large, well designed clinical comparisons of efficacy with aminoglycosides are needed before ceftizoxime can be recommended as an alternative in patients in whom potential aminoglycoside toxicity is a concern. Single intramuscular doses of ceftizoxime appear similar in efficacy to aqueous procaine penicillin G in gonorrhoeae due to nonpenicillinase-producing Neisseria gonorrhoea, and ceftizoxime is also highly effective against penicillinase-producing strains. Although only a few infections have been treated to date, ceftizoxime may be useful in the treatment of gonorrhoea in places where penicillinase-producing strains are common. Thus, ceftizoxime appears to be an effective addition to the growing number of third generation cephalosporins. However, further studies are needed to confirm its relative efficacy compared with other new cephalosporins, in particular cefotaxime.(ABSTRACT TRUNCATED AT 400 WORDS)

In vitro activity of cefbuperazone, a new cephamycin, against anaerobic bacteria

The 90% MIC of cefbuperazone (BMY 25182) was 32 micrograms/ml for Bacteroides fragilis and Bacteroides spp., 128 micrograms/ml for Fusobacterium and Clostridium spp., 64 micrograms/ml for Eubacterium and Peptococcus spp., 8 micrograms/ml for Actinomyces spp., and 32 micrograms/ml for Peptostreptococcus spp. The level of activity of cefbuperazone was higher against B. fragilis and lower against anaerobic cocci than those of related cephalosporins, i.e., cefoxitin, cefoperazone, cefotaxime, ceftizoxime, and cefmenoxime. However, the activity of cefbuperazone was comparable to that of moxalactam against all groups tested. Size of inoculum and type of media used did not alter the MICs of cefbuperazone for B. fragilis. Cefbuperazone showed synergistic activity when combined with cefoxitin against resistant strains of B. fragilis.

In vitro activity of BMY-28142 in comparison with those of other beta-lactam antimicrobial agents

The in vitro susceptibility of 406 clinical isolates to BMY-28142, a new semisynthetic cephem, was evaluated and compared with cefpimizole, HR 810, ceftazidime, cefotaxime, moxalactam, and cefoperazone in a broth microdilution assay. On a weight basis, the activity of BMY-28142 against Escherichia coli, Proteus species, and Klebsiella-Enterobacter-Serratia was superior to the other cephems. Against gentamicin-susceptible and -resistant Pseudomonas aeruginosa, BMY-28142 was more active than the other cephems, except ceftazidime and HR 810. A total of 74% of gram-negative and 56% of gram-positive isolates resistant to third-generation cephalosporins were susceptible to less than or equal to 8 micrograms of BMY-28142 per ml. Finally, for 83% of tested isolates, the bactericidal concentration of BMY-28142 was within one dilution of the inhibitory concentration.

Respiratory superinfections after the use of third-generation cephem antibiotics

This paper is a report on our studies on superinfections in respiratory tract infections treated during the years 1981-1984. The isolated strains of Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus faecalis, Streptococcus faecium and glucose non-fermentative gram-negative rods such as Pseudomonas aeruginosa were resistant to third-generation cephem antibiotics. These organisms proved to be widely distributed in hospitals and were frequently isolated from the sputum, excised lung and cardiac blood. The colonization of the sputum by bacteria in respiratory tract infections before, during and after treatment with third-generation cephem antibiotics revealed a tendency for these organisms to appear after treatment. Among the gram-positive cocci, S. faecium was most resistant to these antibiotics, followed by S. faecalis, S. epidermidis and S. aureus in that order. The incidence of resistant isolates in 1984 exceeded that in 1983, suggesting an annual increase in resistant bacteria.