IN VITRO AND IN VIVO LABORATORY EVALUATION OF CEPHALOGLYCIN AND CEPHALORIDINE

Aztreonam, cefoperazone, and gentamicin in the treatment of experimental Enterobacter aerogenes endocarditis in rabbits

The effectiveness of aztreonam, cefoperazone, and gentamicin alone and in combination was evaluated in Enterobacter aerogenes endocarditis in rabbits. The minimal inhibitory concentration/minimal bactericidal concentration ratios for E. aerogenes were as follows: aztreonam, 0.4/0.4 microgram/ml; cefoperazone, 0.8/0.8 microgram/ml; and gentamicin, 3.1/3.1 micrograms/ml. With an inoculum of 10(9) organisms per ml, aztreonam and cefoperazone were equivalent in reducing titers of E. aerogenes in broth, and both drugs demonstrated an increased rate of reduction when gentamicin was added; gentamicin alone was least effective. E. aerogenes endocarditis in rabbits was treated intramuscularly with aztreonam (60 mg/kg) every 6 h, with cefoperazone (60 mg/kg) every 6 h, with gentamicin (1.7 mg/kg) every 8 h, and with aztreonam plus gentamicin or cefoperazone plus gentamicin for 5 and 10 days, respectively. All of the therapeutic regimens were effective in reducing vegetation titers as compared with untreated controls. Aztreonam plus gentamicin was more effective than either aztreonam or gentamicin alone. Cefoperazone plus gentamicin was more effective than cefoperazone alone but was not more effective than gentamicin alone. Neither aztreonam and cefoperazone nor aztreonam and gentamicin differed significantly, but gentamicin was significantly more effective than cefoperazone. Aztreonam plus gentamicin did not differ significantly in effectiveness from cefoperazone plus gentamicin. Aztreonam gave a peak level of about 135 micrograms/ml and a half-life of 0.7 h. Cefoperazone gave a peak level of about 155 micrograms/ml and a half-life of 1.1 h. Gentamicin gave a peak level of 7.4 micrograms/ml and a half-life of 1.3 h.

Cefoperazone treatment of experimental endocarditis

Cefoperazone (10 mg/kg) and cephalothin (20 mg/kg) administered intramuscularly every 6 h were both effective in reducing the number of Staphylococcus aureus cells in vegetations in rabbits with endocarditis. Cefoperazone produced higher peak concentrations and greater bactericidal activity in serum than did cephalothin. Cefoperazone (40 mg/kg) administered every 6 h was significantly more effective than cefamandole (40 mg/kg) administered every 6 h in reducing the number of Enterobacter aerogenes cells in vegetations. Although cefamandole produced higher peak concentrations in serum, the serum bactericidal activity was greater with cefoperazone. The half-lives in serum were 0.64 h for cefoperazone and 0.46 h for cephalothin and cefamandole.

Comparison of ceforanide, cefazolin, methicillin, and nafcillin in Staphylococcus aureus endocarditis therapy in rabbits

Ceforanide (30 mg/kg) administered every 12 h, cefazolin (20 mg/kg) administered every 8 h and methicillin or nafcillin (40 mg/kg) administered every 6 h were equally effective in reducing the number of Staphylococcus aureus in vegetations in rabbits with endocarditis. These treatments were more effective than methicillin or nafcillin administered every 12 h. Ceforanide produced higher peak concentrations and greater bactericidal activity in serum than the other drugs and had the longest half-life (5.8 h, compared with 0.4 to 0.8 h for the other agents.

Effectiveness of nafcillin, methicillin, and cephalothin in experimental Staphylococcus aureus endocarditis

Nafcillin, methicillin, and cephalothin (40 mg/kg every 6 h) were all effective in reducing the number of Staphylococcus aureus in vegetations in rabbits with endocarditis. Nafcillin and methicillin reduced the number of S. aureus at a significantly faster rate than did cephalothin. Nafcillin and methicillin also reduced titers of the S. aureus more rapidly than did cephalothin in vitro, both in broth and in rabbit serum.

Treatment of experimental Staphylococcus aureus abscesses: comparison of cefazolin, cephalothin, cefoxitin, and cefamandole

Cefazolin (CZ), cephalothin (CF), cefoxitin (CX), and cefamandole (CM) were evaluated in therapy of Staphylococcus aureus infection produced in perforated table tennis balls placed intraperitoneally in rabbits. Four weeks after placement of two balls in each rabbit, a beta-lactamase producing strain of S. aureus was injected into one of the balls. Twenty-four hours later therapy was initiated with 40 mg of CZ or 80 mg of CF, CX, or CM per kg intramuscularly every 6 h. After 24 h of treatment, the mean log(10) colony-forming units per ml were 7.1 for CZ, 6.7 for CF, 6.5 for CX, and 7.2 for CM. After 72 h the mean log(10) colony-forming units per ml were 5.0 for CZ, 4.1 for CF, 3.6 for CX, and 5.6 for CM. After 8 days, the titers were 1.6/ml for CZ, 1.0 for CF, 1.9 for CX, and 3.6 for CM. CZ serum levels were about double CF and CX levels and about two-thirds of CM levels. In sterile ball fluid CZ and CM levels were more than double CF or CX concentrations. Concentrations of all four antibiotics were lower in infected balls.

Treatment of experimental Staphylococcus aureus endocarditis: comparison of cephalothin, cefazolin, and methicillin

The effectiveness of cefazolin in Staphylococcus aureus endocarditis has been questioned because of in vitro inactivation by staphylococcal beta-lactamase. Cefazolin, although inactivated in vitro by S. aureus beta-lactamase, was as effective as cephalothin in the treatment of left-sided S. aureus endocarditis in rabbits. Cefazolin (20 mg/kg every 6 or 8 h), cephalothin (40 mg/kg every 6 h), and methicillin (40 mg/kg every 6 h), administered intramuscularly, were compared in the treatment of left-sided endocarditis caused in rabbits by a highly penicillin-resistant strain of S. aureus. The three antibiotics were all effective in reducing titers in vegetations. However, at the dose used, methicillin reduced the titers more rapidly than cephalothin or cefazolin. Cefazolin concentrations in serum were about double those achieved with cephalothin or methicillin. However, cefazolin was only half as active as methicillin and one-eighth as active as cephalothin in vitro in a serum assay. The half life in serum of cefazolin, cephalothin, and methicillin were each about 30 min. Serum bactericidal activities of the three antibiotics were very similar.

In vitro evaluation of BL-S640, a new oral cephalosporin antibiotic

BL-S640, a new oral cephalosporin analogue, was evaluated in vitro against 102 gram-negative and 80 gram-positive bacteria. The antimicrobial spectrum was similar to that of previous cephalosporin analogues. Good antimicrobial activity against strains of Escherichia coli, Klebsiella, staphylococci, and streptococci was demonstrated. Relatively poor activity and/or resistance was noted among most strains of Proteus, Providencia, Pseudomonas, and Serratia. In comparative studies BL-S640 had better activity against strains of Hemophilus influenzae, Staphylococcus aureus, and Enterobacteriaceae than many cephalosporin analogues. Variation of susceptibility results was dependent upon the type of media and inoculum size. Cross-resistance between BL-S640 cephalexin, cephalothin, and cefazolin was demonstrated. Among strains of Klebsiella the more rapid selection of resistance ot other cephalosporins was in contrast to BL-S640. Experience in vitro with BL-S640 has documented its antimicrobial activity,and further studies of pharmacokinetics and therapeutic efficacy are indicated.

Compound 64716, a new synthetic antibacterial agent

Compound 64716, 1-ethyl-4 (1H)-oxo-[1,3]dioxolo[4,5-g]cinnoline-3-carboxylic acid, is a new synthetic antibacterial agent. The antibacterial spectrum of this compound includes gram-negative bacteria that are most frequently isolated from urinary tract infections. Minimal inhibitory concentration values of 64716 for isolates of Escherichia coli and Proteus sp. ranged from 2 to 4 and 2 to 8 mug/ml, respectively, and the compound was bactericidal at concentrations close to the minimal inhibitory concentration values. In vivo, doses required for successful therapy of experimental mouse infections were comparable to those for nalidixic acid. After oral administration of 40 mg/kg, peak concentrations of this compound in mouse blood reached 19.2 mug/ml. Within 30 min after doses of 20 mg/kg, bacteriologically active drug concentrations of 64716, nalidixic acid, and oxolinic acid in mouse urine were >1,000, 170, and <1.5 mug/ml, respectively. Resistant bacteria were not selected when bacteria were exposed to 500 mug/ml of 64716. Compound 64716 was less bound by human serum proteins than was nalidixic acid. Equivalent antibacterial activity along with superior pharmacological properties of 64716 when compared with nalidixic acid lead to the conclusion that this new compound is a promising antibacterial agent.

New synthetic antibacterial compound, 1-(2-hydroxyethyl)-3-nitro-4-pyrazole carboxamide

A series of 3-nitropyrazole compounds represent a new class of synthetic antibacterial agents. One member of this series, 1-(2-hydroxyethyl)-3-nitro-4-pyrazolecarboxamide, exhibited an antibacterial spectrum similar to that of nitrofurantoin. The inhibitory concentrations of this nitropyrazole were lower than those required for nitrofurantoin. Single oral doses of 20 mg/kg resulted in peak nitropyrazole concentrations of 5.8 and >1,000 mug/ml in mouse blood and urine, respectively. In dogs, 87% of a 10 mg/kg oral dose was recovered in urine during a 24-h period with a peak serum concentration of 13.6 mug/ml. This nitropyrazole was highly effective against experimental bacterial infections in mice. The low acute toxicity in mice, rats, or dogs and significant antibacterial activity lead to the conclusion that further evaluation of this compound is warranted.

Clinical and in vitro evaluation of cefazolin, a new cephalosporin antibiotic

Cefazolin sodium, a cephalosporin for parenteral use, was evaluated in vitro and in 26 patients. Cefazolin had activity equivalent to cephalothin against Streptococcus pneumoniae, Staphylococcus aureus, group A streptococci, and Proteus mirabilis. Cefazolin was four- to eightfold more active against Escherichia coli and slightly more active against Klebsiella pneumoniae, whereas cephalothin was slightly more active against indole-positive Proteus species. After a 500-mg dose of cefazolin intramuscularly, peak concentrations in the serum were high enough to inhibit all strains of S. pneumoniae, S. aureus, group A streptococci, E. coli, K. pneumoniae, and P. mirabilis, as well as 60% of strains of Proteus species other than P. mirabilis. All of 26 patients (18 with pneumonia, 6 with urinary tract infection, and 2 with skin infections) responded clinically and bacteriologically to cefazolin therapy. There were no major side effects of therapy, and no patient complained of pain at the site of intramuscular injection. Cefazolin is an effective cephalosporin which can be used intramuscularly for therapy of serious bacterial infections. Its major advantages over other cephalosporins are higher, more sustained concentrations in the blood and apparent lack of pain on intramuscular injection.

Biological properties of three 3-heterocyclic-thiomethyl cephalosporin antibiotics

Three new cephalosporin antibiotics, prepared by substitution of heterocyclic groups on 7-aminocephalosporanic acid, possess certain desirable chemical or biological properties. All three compounds are active in vitro against a variety of gram-positive and gram-negative bacteria. Minimal inhibitory concentrations (MIC) of these bactericidal antibiotics were not significantly affected by changes in pH or NaCl content of nutrient broth, or by the use of different inoculum sizes. However, agar-dilution MIC values were generally two- to fourfold lower than the MIC values in comparable broth-dilution tests. Stability to cephalosporinase by two of the compounds extended their antibacterial spectra over cephalothin and cephaloridine to include strains of Enterobacter sp. and indole-positive Proteus sp. Binding to serum proteins of the new cephalosporins was intermediate between cephalothin and cephaloridine. Excellent concentrations of the antibiotics were attained in mouse blood, after subcutaneous administration of 20 mg per kg. In vitro biological characteristics of the antibiotics were verified by successful therapy of experimental mouse infections. Regression lines were calculated to show the correlation of agar-dilution MIC values with zones of inhibition by the disc testing procedure. Because each of the three new cephalosporins has certain advantageous properties over cephalothin and cephaloridine, additional toxicological and pharmacological data should be obtained for all three compounds.

Clinical and in vitro evaluation of cephapirin, a new cephalosporin antibiotic

Cephapirin sodium, a cephalosporin for parenteral use, was evaluated in vitro and in 27 patients. Cephapirin had activity equivalent to cephalothin against 25 strains each of Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Staphylococcus aureus; 10 strains each of Diplococcus pneumoniae, Pseudomonas species, and Enterobacter species; and 8 strains of Proteus species other than P. mirabilis. All strains of S. aureus and D. pneumoniae and most strains of E. coli, K. pneumoniae, and Proteus species were inhibited by concentrations of cephapirin achieved in the serum. Of 27 patients (20 with pneumonia, 2 with S. aureus empyema, and 5 with miscellaneous infections), 25 responded to cephapirin therapy. The only major toxicity thought to be drug-related occurred in a patient who developed reversible bone marrow depression with leukopenia, neutropenia, and anemia. Although cephapirin was painful on intramuscular injection, phlebitis and pain were absent in patients treated intravenously. In a controlled comparison of intravenously administered cephalothin and cephapirin in four additional patients, the latter caused much less pain than the former and caused no phlebitis.

Cephaloglycin and its biologically active metabolite desacetylcephaloglycin

Chromatographic studies and microbiological assays show that, after oral administration, cephaloglycin is partially converted in man to a biologically active metabolite desacetylcephaloglycin. The antibacterial activity of this metabolite compared to that of cephaloglycin is equivalent against gram-positive organisms but is lower against gram-negative bacilli. Successful therapy of urinary tract infections with cephaloglycin must be mainly attributed to the antibacterial activity of this metabolite. At the present time, it is not possible to assess what influence low amounts of unaltered cephaloglycin have on the outcome of therapy.

Semisynthetic coumermycins: structure-activity relationships

The relative antimicrobial activity of a large series of semisynthetic coumermycins has been determined. Most of the derivatives, which were 3-substituted-4-hydroxy-8-methyl-7-[3-O-(5-methyl-2-pyrrolylcarbonyl) noviosyloxy] coumarins, had an in vitro antibacterial spectrum similar to that of the parent compound, coumermycin A(1), but were generally less potent in minimal inhibitory concentration (MIC) tests. Derivatives with an alkylcarboxamido, arylcarboxamido, or arylsulfonamido group in the 3 position had considerably greater in vitro activity than those possessing an amino-, aryl-, or alkyureido substituent. Efficacy in Staphylcoccous aureus Smith infections of mice was greater for those compounds with branched-chain alkylcarboxamido, unsubstituted, mono- or disubstituted aryl- and heteroaryl-carboxamido groups than for derivatives having an n-alkylcarboxamido, aralkyl-carboxamido, arylsulfonamido, or trisubstituted arylcarboxamido substituent. Significant in vitro activity against Klebsiella pneumoniae and other gram-negative species was restricted to those compounds having a 3-(3-n-alkyl-4-hydroxy-phenyl-carboxamido) group. Only the n-hexyl homologue demonstrated in vivo activity in a K. pneumoniae infection. Many derivatives were two- to threefold more active than coumermycin A(1) in orally treated mouse infections, despite the fact that their MIC values were considerably higher. This result was undoubtedly a reflection of the markedly greater oral absorbability possessed by many of the derivatives. Although peak oral mouse blood levels of some compounds were > 25 times higher than those of coumermycin A(1), their toxicity for the host was no greater. In addition, the semisynthetic coumermycins caused much less local irritation than coumermycin A(1) when administered parenterally.

Assay of the antibiotic activity of serum

One of the drawbacks of the "tube dilution" method for the assay of antibiotics in human serum has been illustrated by utilizing serum-sensitive and serum-resistant strains of Escherichia coli. In the case of serum-sensitive strains, it was found that fresh serum alone may account for the same degree of inhibition and thus yield minimal inhibitory concentrations identical to those obtained with serum combined with antibiotics, that is, "simulated" serum assay specimens. This fallacy of the method is discussed with regard to those instances in which laboratories were merely to utilize the patient's own coliform organism as the test organism, or with respect to the assay of, for example, polymyxins, in which inadvertently a R(ough) and therefore, serum-sensitive strain of E. coli were to be used as the indicator organism. It is recommended that serum-resistant laboratory strains of Staphylococcus aureus or E. coli of known antibiotic susceptibility be employed as the test organisms proper in order to circumvent the inherent bactericidal activity of serum.

In vitro antimicrobial activity and human pharmacology of cephalexin, a new orally absorbed cephalosporin C antibiotic

Concentrations of cephalexin (an orally absorbed derivative of cephalosporin C) in serum and urine were determined in normal volunteers and patients. The in vitro antibacterial activity was also studied. All strains of group A beta-hemolytic streptococci and Diplococcus pneumoniae were inhibited by 3.1 mug/ml. Of the Staphylococcus aureus strains, 88% were inhibited by 6.3 mug/ml, and 12.5 mug/ml was inhibitory for all S. aureus, 80% of Escherichia coli, 72% of Klebsiella-Aerobacter, and 56% of Proteus mirabilis strains. About 90 to 96% of E. coli, Klebsiella Aerobacter, and P. mirabilis strains were inhibited by 25 mug of cephalexin per ml. Pseudomonas and indole-positive Proteus strains proved to be quite resistant to cephalexin. Cephalexin was well absorbed after oral administration. A peak serum concentration of cephalexin of at least 5 mug/ml was achieved in each volunteer with 250 and 500-mg doses. A mean peak serum concentration of 7.7 mug/ml was achieved with 250-mg doses; 12.3mug/ml was achieved with 500-mg doses of antibiotic. Food did not interfere with absorption. Probenecid enhanced both the peak serum concentration and the duration of antibiotic activity in the serum. Over 90% of the administered dose was excreted in the urine within 6 hr. The mean peak serum concentration of cephalexin after an oral dose of 500 mg was adequate to inhibit all group A streptococci, D. pneumoniae, and S. aureus, 85% of E. coli, and about 40 to 75% of Klebsiella-Aerobacter and P. mirabilis strains. Levels of cephalexin in urine were adequate to inhibit over 90% of E. coli, and P. mirabilis and 80 to 96% of Klebsiella-Aerobacter strains.

Cephalexin and cephaloglycin activity in vitro and absorption and urinary excretion of single oral doses in normal young adults

A large number of recently isolated bacterial pathogens were tested for susceptibility to cephalexin and cephaloglycin by the replica inoculating method. Strains of group A hemolytic streptococci, viridans (alpha and gamma) streptococci, pneumococci, gonococci, meningococci, and penicillin G-sensitive Staphylococcus aureus were all moderately to highly susceptible to both of these cephalosporin analogues, nearly all of the strains being two to eight (median four) times more susceptible to cephaloglycin than to cephalexin. The penicillin G-resistant, penicillinase-producing strains of S. aureus varied in their susceptibility; many were moderately resistant to both analogues, particularly to cephalexin. Strains of enterococci, Haemophilus influenzae, and most of the common gram-negative bacilli were moderately to highly resistant. Reducing the size of the inoculum had variable effects on inhibition by these drugs, depending on the species or strain. The activity of cephalexin was very little affected by pH of the medium within the clinical range or by incubation at 37 C in broth for up to 24 hr. In contrast, cephaloglycin in broth deteriorated rapidly at 37 C, and its activity was markedly reduced in alkaline medium. Both cephalexin and cephaloglycin were rapidly absorbed and excreted into the urine after single oral doses of 500 mg. Much higher levels were achieved and sustained with the former. Absorption of both analogues was delayed when taken with food, and the levels in the serum were significantly higher and better sustained when probenecid was also given. Very high concentrations of cephalexin were excreted into the urine during the first 4 hr, and the levels were still high in the 4- to 8-hr collection. The concentrations of cephaloglycin in the urine at these times were much lower. An average of 80 to 93% of the dose of cephalexin and 25 to 30% of the cephaloglycin were accounted for as active drug in the urine collected in 8 hr. Both analogues were well tolerated.

Susceptibility of salmonellae to cephalosporins and to nine other antimicrobial agents

Three cephalosporin-related antibiotics and nine other antimicrobial agents were studied for in vitro effectiveness against 54 recently isolated strains of Salmonella. Minimal inhibitory concentrations determined by the plate dilution method demonstrated the following percentages of resistance: ampicillin, 6%; tetracycline, 13%; streptomycin, 52%; sulfadiazine, 94%; cephaloglycin, 96%; and lincomycin, 100%. No strains were resistant to cephalothin, cephaloridine, chloramphenicol, colistimethate, kanamycin, and polymyxin B. The commonest serotype studied, S. typhimurium, showed the greatest antibiotic resistance, with 21% resistant to ampicillin, 36% resistant to tetracycline, and 71% resistant to streptomycin. Cephalothin and cephaloridine were highly effective in vitro but inhibitory concentrations of 20 to 40 mug of cephaloglycin per ml were required for the majority of Salmonella strains.

In vitro antimicrobial activity and human pharmacology of cephaloglycin

Serum and urine concentrations of cephaloglycin (an orally absorbed derivative of cephalosporin C) were determined in normal volunteers and in patients. The in vitro activity of cephaloglycin was also studied. All strains of group A streptococci (Streptococcus pyogenes) and Diplococcus pneumoniae were inhibited by 0.4 mug of cephaloglycin per ml. Eighty per cent of the Staphylococcus aureus strains and about 50% of the Escherichia coli and Proteus mirabilis strains were inhibited by 1.6 mug of cephaloglycin per ml. Klebsiella-Aerobacter species were more resistant to cephaloglycin and 12.5 mug per ml was required to inhibit 70% of these strains. When single doses of 250, 500, or 1,000 mg of cephaloglycin were administered to fasting volunteers, a peak serum concentration of at least 0.5 mug per ml was achieved. A full breakfast did not interfere with absorption of cephaloglycin. Probenecid enhanced both the peak serum concentration and the duration of antibiotic activity in the serum. Serum concentrations of cephaloglycin were even higher in patients who were receiving repeated doses. The peak serum concentrations of cephaloglycin in all volunteers and patients were adequate to inhibit all strains of group A streptococci and D. pneumoniae. Many of the peak serum concentrations were adequate to inhibit some strains of S. aureus, E. coli, and P. mirabilis. Urine levels of cephaloglycin were high enough in all volunteers and patients to inhibit more than 90% of the E. coli and P. mirabilis strains and over 70% of the strains of Klebsiella-Aerobacter.

Cephalexin, a new orally absorbed cephalosporin antibiotic

A new antibiotic, structurally related to cephaloglycin, has been assigned the generic name cephalexin, 7-(D-alpha-amino-alpha-phenylacetamido)-3-methyl-3-cephem-5-carboxylic acid. In vitro antimicrobial activity of cephalexin does not equal that of cephaloglycin. However, excellent oral absorption and lack of serum binding of cephalexin compensates significantly for the lower in vitro activity. Exceptional efficacy against experimental bacterial infections in mice was obtained with cephalexin therapy as compared with cephaloglycin, tetracycline, and chloramphenicol. The data suggest that cephalexin merits clinical trial.