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PubMed1986

In vitro susceptibilities of four species of coagulase-negative staphylococci.

The in vitro susceptibilities of 260 strains of coagulase-negative staphylococci to penicillin G, oxacillin, nafcillin, methicillin, cephalothin, and seven non-beta-lactam antimicrobial agents were determined and compared with the susceptibilities of 54 strains of Staphylococcus aureus with known patterns of susceptibility. Penicillin G susceptibility for S. aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus hominis was readily determined by using beta-lactamase tests with induced cells and with a standardized microdilution test. MIC criteria for susceptibility used for S. aureus were applicable to the coagulase-negative species. Percentages of organisms susceptible were as follows: S. epidermidis, 7%; S. haemolyticus, 5%; and S. hominis, 47%. Oxacillin susceptibility for these four species was readily determined by using a modification of the microdilution test. MIC criteria for susceptibility used for S. aureus were applicable to S. haemolyticus and S. hominis, but alternate criteria were necessary for S. epidermidis. Percentages of organisms susceptible were as follows: S. epidermidis, 29%; S. haemolyticus, 36%; and S. hominis, 97%. Staphylococcus saprophyticus differed from the other staphylococcal species; all strains were beta-lactamase negative and were penicillin susceptible but had higher penicillin G MICs than did susceptible strains of the other species. There was total cross resistance among the penicillinase-resistant penicillins and cephalothin for the coagulase-negative staphylococci as well as for S. aureus; oxacillin MICs were more reliable than MICs of the other drugs or a standardized disk diffusion test for distinguishing resistant from susceptible strains. Vancomycin, rifampin, and ciprofloxacin were consistently active against all staphylococci. Erythromycin, clindamycin, gentamicin, and trimethoprim-sulfamethoxazole were more active against oxacillin-susceptible staphylococci than against oxacillin-resistant staphylococci.

Anti-Bacterial Agents↗
PubMed1976

Influence of cephalosporin antibiotics on blood coagulation and platelet function.

Administration of cephalothin to normal volunteers in maximal doses of 300 mg/kg per day resulted in a combined defect of platelet function and blood coagulation. No such abnormalities were evident after infusion of cefazolin or cephapirin at a maximal dosage of 200 mg/kg per day. The observed thrombocytopathy was similar to but less severe than that induced by carbenicillin or ticarcillin and was not reflected by a prolonged bleeding time test or impaired prothrombin consumption. Moreover, it was not a consistent finding in those persons receiving cephalothin. A separate defect involving blood coagulation appeared to result from delayed fibrinogen-fibrin polymerization and was evidenced by extended values of the activated partial thromboplastin and thrombin time tests. It remains uncertain whether the abnormalities described may constitute clinically important hemostatic disorders in patients with normal renal function receiving large doses of cephalosporin antibiotics.

Blood Coagulation↗
PubMed1968

Synergistic antibacterial activity of ampicillin-cloxacillin mixtures against Proteus morganii.

Synergistic antibacterial effects of mixtures of ampicillin and cloxacillin and induced penicillinases were investigated in 48 strains of Proteus. The serial tube dilution method was used to determine the minimal inhibitory concentration of ampicillin, cloxacillin, and 2:1 and 1:1 mixtures of ampicillin and cloxacillin. Production of penicillinases was determined by the cellulose acetate membrane method, with ampicillin, cloxacillin, mixtures of ampicillin and cloxacillin, penicillin G, and cephalothin as inducing agents and as substrates for penicillinase. Synergism occurred against P. morganii, but against no other species. The 1:1 ampicillin-cloxacillin combination was synergistic against 13 of 17 P. morganii strains; the 2:1 combination was synergistic against only 9 strains. Penicillinases, demonstrated in all species except P. mirabilis, hydrolyzed penicillin G and cephalothin. Although only P. vulgaris hydrolyzed ampicillin, no species of Proteus hydrolyzed cloxacillin or the ampicillin-cloxacillin mixtures. Penicillinases were, however, induced by ampicillin, cloxacillin, and the mixtures. There was no relationship between production of penicillinase and synergism with mixtures of ampicillin and cloxacillin.

Ampicillin↗
PubMed1968

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.

Ampicillin↗
PubMed1969

In vitro action of carbenicillin against bacteria isolated from clinical material.

More than 500 bacteria isolated from patient material were tested against carbenicillin (disodium alpha-carboxybenzylpenicillin) by diffusion and dilution modalities. The same bacteria, which included Pseudomonas aeruginosa, Escherichia coli, Klebsiella-Aerobacter-Enterobacter group, various species of Proteus, Staphylococcus aureus and epiddermidis, enterococci, pneumococci, Streptococcus pyogenes, etc., were examined for susceptibility to other antibiotics commonly used with special emphasis on ampicillin and cephalothin. The responses of pyocine-typed P. aeruginosa were the most remarkable. The majority of these bacteria displayed susceptibility to carbenicillin by both the dilution and the diffusion techniques. The concentrations of this antibiotic used in the laboratory were of the same order of magnitude as that of the other drugs. The laboratory behavior of the other bacteria, toward this new semisynthetic penicillin derivative approximated their response to ampicillin and cephalothin.

Ampicillin↗
PubMed1970

Regression curve analysis of cephalosporin activity.

Regression lines were calculated for cephalothin, cephalexin, and cephaloridine by relating zone diameters of inhibition to minimal inhibitory concentrations (MIC) obtained in Mueller-Hinton agar and in Trypticase Soy Agar. A regression line was calculated for cephaloglycin by obtaining MIC values in Trypticase Soy Agar at pH 6.6. Regression lines calculated from MIC values in Mueller-Hinton agar were practically superimposable on those based on MIC values in Trypticase Soy Agar. Organisms susceptible by disc testing to cephalothin were usually susceptible to cephalexin and cephaloridine.

Agar↗
PubMed1980

Aberrant forms of Escherichia coli in blood cultures: in vitro reproduction of an in vivo observation.

Aberrant filamentous forms of Escherichia coli were observed on direct Gram stain of blood cultures from a patient being treated with the beta-lactam antibiotic cephalexin. After the institution of an alternative antibiotic regimen which included a different cell wall-active agent, E. coli of normal morphology was detected in blood cultures for an additional 48 h. Filamentous forms of E. coli could be reproduced reliably in vitro by incubating the organism in Mueller-Hinton broth containing various concentrations of cephalexin. Both supra- and subinhibitory concentrations of cephalexin resulted in filament formation after 4 h of incubation, whereas 24 h of incubation yielded intact filaments at only a narrow range of subinhibitory concentrations of cephalexin. In vitro comparison of the ability of cephalexin, cephalothin, ampicillin, and gentamicin to cause filamentous forms of E. coli showed that cephalexin and cephalothin produced pure filament formation after 4 h of incubation at subinhibitory concentrations of as low as one-fourth the minimum inhibitory concentration of the antibiotic. Ampicillin was not associated with pure filament formation at concentrations below the minimum inhibitory concentration, and gentamicin produced no filaments at any concentration. The effect of preincubation of E. coli with subinhibitory concentrations of cephalexin on subsequent minimum inhibitory concentrations of ampicillin was examined in an effort to develop an explanation for the persistent sepsis exhibited by the patient. No diminution of the activity of ampicillin by preincubation with cephalexin could be demonstrated. Other possible clinical implications of filamentous forms of gram-negative bacilli are discussed.

Ampicillin↗
PubMed1983

Successful use of broth microdilution in susceptibility tests for methicillin-resistant (heteroresistant) staphylococci.

We studied the broth microdilution antimicrobial susceptibility testing procedure to see whether it could be made reliable for determining resistance of staphylococci to methicillin, oxacillin, nafcillin, and cephalothin. With 45 selected strains of Staphylococcus aureus and 12 selected strains of Staphylococcus epidermidis we found that the addition of 2% NaCl to cation-supplemented Mueller-Hinton broth permitted us to discriminate reliably between resistant and susceptible organisms. A screening test in which resistant staphylococci grew on agar containing 4% NaCl and methicillin (10 micrograms/ml), oxacillin (6 micrograms/ml), or nafcillin (6 micrograms/ml) incubated at 35 degrees C for 24 h (additional 24 h if no growth) was also reliable. In vitro cephalothin resistance occurred in heteroresistant S. aureus but usually did not occur in heteroresistant S. epidermidis.

Cephalothin↗
PubMed1984

Reevaluation of the ability of the standardized disk diffusion test to detect methicillin-resistant strains of Staphylococcus aureus.

To reevaluate the ability of the disk diffusion method to detect methicillin-resistant Staphylococcus aureus, 73 such isolates from 13 cities were tested for antimicrobial susceptibility with the standardized disk diffusion test. Duplicate plates were incubated at 30 and 35 degrees C and read after 18, 24, and 48 h. After incubation at 35 degrees C for 24 h, 97% of isolates appeared resistant to methicillin, and 99% appeared resistant to oxacillin. A significantly smaller proportion of isolates appeared resistant to cephalothin (P less than 0.001) and cefamandole (P less than 0.001). Isolates from some cities had no zones of inhibition around methicillin and oxacillin disks, whereas those from other cities had measurable zones of inhibition, with light growth inside the zones. Patterns of growth around cephalothin and cefamandole disks also varied among isolates from different cities. Incubation at 30 degrees C for 24 h did not result in better detection of methicillin or oxacillin resistance. All study isolates appeared resistant to methicillin and oxacillin after 48 h of incubation at 35 degrees C. The results suggest that methicillin-resistant S. aureus strains from many areas will be detected if standardized disk diffusion tests are incubated at 35 degrees C for 24 h.

Bacteriophage Typing↗
PubMed1973

The relative susceptibility of four cephalosporins to a beta-lactamase from Bacillus cereus.

The effects of purified beta-lactamase from Bacillus cereus on the activity of four cephalosporins are described. Drug inactivation was measured spectrophotometrically and confirmed by microbiological assay and by microbiological techniques involving determinations of minimum inhibitory concentrations and growth curves of Staphylococcus aureus NCTC 6571 (Oxford) in broth containing drug +/- enzyme. Cephaloridine was the most sensitive of the four cephalosporins, followed by cephalothin and the sodium salt of 7-cyanacetamidocephalosporanic acid, with cephalexin considerably resistant to inactivation. The possible use of this beta-lactamase in the sterility testing of cephaloridine and cephalothin is examined.

Bacillus cereus↗
PubMed1978

Proteolytic proenzymes in the pancreas in the course of experimental bile-induced pancreatitis in the guinea pig.

The levels of the proenzymes trypsinogen and chymotrypsinogen were studied in guinea pigs with pancreatitis induced by injection of sodium taurocholate containing the antibiotic cephalothin. This treatment inhibited the enzyme activities and prolonged the activation times of the proenzymes. Both trypsinogen and chymotrypsinogen content decreased after induction of pancreatitis, but there were no significant changes in the proenzyme contents in relation to injection-to-excision times. Sodium taurocholate and cephalothin were cleared from the pancreas in 2 h. Administration of chlorophyll-a together with the inducer caused a slight increase in proenzyme levels.

Animals↗
PubMed1977

In vitro sensitivity of anaerobic bacteria to fosfomycin.

The minimum inhibitory concentrations were determined in 98 strains of anaerobic bacteria that came from clinical samples against fosfomycin, penicillin, cephalothin, tetracycline, chloramphenicol, clindamycin and lincomycin. The results obtained indicate that fosfomycin is usually inactive against Bacteroides sp. and is active up to 32 mug/ml or less against 85% of Peptococcus and 95% of Peptostreptococcus, being consequently comparatively less active than the rest of the antibiotics that were tested against Bacteroides, sp., while against Peptococcus and Peptostreptococcus it is less active than penicillin, cephalothin, clindamycin and lincomycin, and somewhat more active than chloramphenicol and tetracycline.

Anti-Bacterial Agents↗
PubMed1981

Comparative in vitro activity of 8 cephalosporins on 109 strains of Neisseria gonorrhoeae and 60 strains of Neisseria meningitidis.

The in vitro activity of 8 cephalosporins - cephalothin, cefamandole, cefoxitin, cefuroxime, cefotaxime, cefoperazone, moxalactam and ceftriaxone (Rocephin) was studied on 109 strains of Neisseria gonorrhoeae and 60 strains of Neisseria meningitidis, isolated from pathological material. Determination of the MICs of these antibiotics by an agar dilution method shows that on N. gonorrhoeae ceftriaxone (geometric mean of the MICs: 0.0008 microgram/ml) is the most active, followed by cefotaxime (0.001 microgram/ml); cefoperazone (0.008 microgram/ml) and moxalactam (0.01 microgram/ml) are one-tenth as active; then come cefuroxime (0.05 microgram/ml), cefamandole (0.10 microgram/ml) and finally cephalothin (0.26 microgram/ml) and cefoxitin (0.26 microgram/ml). The least susceptibility to penicillin and, to a greater degree, the production of beta-lactamase (8 strains) affect the level of susceptibility to these cephalosporins, but the MICs always remain relatively low.

Cefamandole↗
PubMed1983

Susceptibility of 324 nonfermentative gram-negative rods to 6 cephalosporins and azthreonam.

Susceptibility of 324 isolates of nonfermentative gram-negative bacteria to cephalothin, cefamandole, cefoxitin, ceftazidime, cefsulodin, and azthreonam was determined by agar dilution and disc diffusion techniques. With the exception of Moraxella species, first- and second-generation cephalosporins were minimally active against nonfermenters tested. Cefsulodin and azthreonam were mainly active against Pseudomonas aeruginosa. In contrast, ceftazidime and ceftriaxone exhibited wider activity spectra. Cefsulodin and ceftazidime were the most active against P. aeruginosa, followed by azthreonam and ceftriaxone. Ceftazidime was the only drug with significant activity against Pseudomonas maltophilia and Pseudomonas fluorescens/Pseudomonas putida, and was also the most active against Pseudomonas cepacia. Acinetobacter calcoaceticus and Alcaligenes strains were most sensitive to ceftazidime, followed by ceftriaxone and azthreonam. Ceftriaxone was the most active against moraxellas, followed by cefamandole/cefoxitin, ceftazidime, cephalothin, cefsulodin, and azthreonam. Ceftazidime was the most active against uncommonly isolated nonfermenters. Results observed in this study reflect a potential use for ceftazidime in therapy of infections caused by most gram-negative nonfermenters; therapy with cefsulodin and azthreonam in nonfermenter infections should be restricted to those caused by P. aeruginosa, and that with ceftriaxone reserved for non-P. aeruginosa infections.

Acinetobacter↗
PubMed1982

Correlation of the results of antibiotic synergy and susceptibility testing in vitro with results in experimental mouse infections.

Recent clinical isolates (approximately 150 strains) of the family Enterobacteriaceae were examined by agar diffusion, microdilution, and the Autobac automated system for their responses to beta-lactam antibiotics singly and in combination with amdinocillin (formerly called mecillinam). The ratio of ampicillin, carbenicillin, and cephalothin to amdinocillin was maintained at a 10:1 ratio in most of the evaluations. The same isolates were studied in mice challenged with 100 to 1000 LD50s and treated with graded doses of the antibiotics singly and in combination. Efficacy in vivo was based on the concentration of antibiotic in milligrams per kilograms (mg/kg) required to protect 50% of the animals (PD50). After a single administration of the antibiotics, plasma levels were determined in the critical time period (30 min to 4 hr) during which the acute, overwhelming systemic infections could be controlled by appropriate therapy. Regression curves comparing in vivo and in vitro results were used to establish cut-off points for categorizing bacterial susceptibility in each of the laboratory tests for the single agents and combinations. A high degree of synergism between amdinocillin and the beta-lactam agents was demonstrated in animals (54 to 78% of the strains examined) and to a lesser extent by laboratory methodologies. There was an excellent correlation of in vivo and in vitro responses to ampicillin, carbenicillin, and cephalothin alone and in combination with amdinocillin for those species for which the single antibiotics are generally indicated. The correlations validated the chosen cut-off points. The correlation of in vivo and in vitro responses to the single or combined antibiotics was generally poorer for those species not usually responsive to the single antibiotics. The greatest difficulty in predicting proper in vivo responses, based on the results of in vitro tests, was observed with amdinocillin.

Ampicillin↗
PubMed1985

Effect of high-dose ampicillin and cloxacillin on bleeding time and bleeding in open-heart surgery.

To determine if platelet dysfunction caused by high doses of penicillin compounds is of practical importance in patients with additional haemostatic defects perioperatively, a study was made of patients undergoing open-heart surgery. They were randomly assigned to prophylactic treatment with ampicillin 8 g plus cloxacillin 4 g daily for three days, or with cephalothin 8 g daily for three days. Fifty patients in each group were evaluated. The median bleeding time preoperatively and on days 1 and 4 postoperatively did not differ between the groups. The bleeding time was prolonged beyond the normal range in eight patients of the ampicillin/cloxacillin group and in three of the cephalothin group (p less than 0.05). Prolonged bleeding time was not associated with lower platelet count or greater blood loss. The total blood loss and the amounts of transfused blood, platelets and cryoprecipitate were all greater in the ampicillin/cloxacillin group, but the difference was not statistically significant. Combined use of ampicillin and cloxacillin in open-heart surgery is associated with increased bleeding, but the increase is without practical importance.

Adolescent↗
PubMed2002

Antimicrobial susceptibility of coagulase-negative staphylococci isolated from bovine mastitis in Argentina.

A total of 123 isolates of coagulase-negative staphylococci isolated from bovine clinical and subclinical mastitis in Argentina from March 1998 to March 2000 was investigated for in vitro susceptibility to several antimicrobial agents. Minimum inhibitory concentrations that inhibit 90% of the isolates tested (reported in micrograms per milliliter) were: 4.40, 0.38, 4.00, 0.75, 0.75, 3.60, and 2.00 for penicillin, oxacillin, cephalothin, gentamicin, erythromycin, clindamycin, and ampicillin-sulbactam, respectively. Resistance was detected in 34 (27.6%), 4 (3.2%), 7 (5.7%), and 6 (4.8%) isolates for penicillin, oxacillin, erythromycin, and pirlimycin, respectively. No resistance was detected for gentamicin, cephalothin, or ampicillin-sulbactam. Results indicated that coagulase-negative staphylococci isolates in Argentina exhibited the highest degree of resistance to penicillin of all antimicrobial agents tested.

Ampicillin↗
PubMed1975

Comparative inhibitory activity of BL-S640 and two other cephalosporins.

In vitro antibacterial activity of BL-S640 was compared to that of cephalothin and cephalexin against Gram-negative and Gram-positive bacteria isolated from clinical specimens. BL-S640 demonstrated the best activity on nearly all microbial species studied, except for Haemophilus influenzae and Diplococcus pneumoniae against which cephalothin was slightly more active.

Cephalexin↗