In vitro combination effects of cefotetan with four aminoglycosides, piperacillin and mezlocillin on gram-positive and gram-negative nosocomial bacteria

The in vitro efficacy of cefotetan in combination with gentamicin, tobramycin, amikacin, netilmicin against Staphylococcus aureus, Staphylococcus epidermidis and Enterobacter cloacae and with piperacillin and mezlocillin against Escherichia coli, Klebsiella pneumoniae, Serratia marcescens and Enterobacter cloacae was compared by use of the checkerboard agar dilution technique. On average, 60% of the gram-negative and 46% of the gram-positive strains were inhibited by additive, but only 22% of the gram-negative and 2% of the gram-positive bacteria were inhibited by synergistic cefotetan-aminoglycoside combinations. Netilmicin combinations were least active. On gram-negative bacteria, 63% of the cefotetan-penicillin combinations were additive and 11% synergistic. No antagonism occurred with any of the combinations.

In vitro and in vivo action of mezlocillin and azlocillin combined with sisomicin

Combined action in vitro and in vivo of ureidopenicillins (azlocillin and mezlocillin) with sisomicin has been studied with employment of strains of Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. In vitro effects of these combinations were most spectacular with Pseudomonas aeruginosa; azlocillin and sisomicin were potently synergistic. Other tested microorganisms reacted also but less markedly. Evaluation of therapeutic efficacy of ureidopenicillins combined with sisomicin was performed on 90 rabbits, infected intravenously with heavy inocula. Synergistic action has been confirmed in vivo during treatment of infections evoked by Escherichia coli and Pseudomonas aeruginosa. Therapy of these infections may be successful with doses of azlocillin or mezlocillin combined with sisomicin diminished by half, as compared with treatment of these infections with above antibiotics applied singly. Further decrease of sisomicin dosage in combined therapy of P. aeruginosa infections with ureidopenicillin is possible.

Interference of new penicillins and cephalosporins with urine glucose monitoring tests

The possibility that three new penicillins (mezlocillin, pipericillin, and azlocillin) and two new cephalosporins (ceftazidime and cefoperazone) might give false positive urine glucose testing results was studied. High and low concentrations of antibiotics were dissolved in urine and tested with Clinitest (Ames Division, Miles Laboratories, Elkhart, Indiana) and Tes-Tape (Eli Lilly and Company, Indianapolis, Indiana) at four different concentrations of glucose. None of the antibiotics interfered with the accuracy of Tes-Tape readings. All antibiotics interfered with Clinitest readings; the greatest interference was noted at high concentrations of antibiotics and low concentrations of glucose, and with the two cephalosporins. A summary of all reported cephalosporin interactions with Clinitest urine glucose testing is included.

A comparison of the effects of mezlocillin and carbenicillin on haemostasis in volunteers

Mezlocillin and carbenicillin were administered intravenously to healthy male volunteers, for six days each, in a double-blind crossover study. Tests to detect abnormalities in haemostasis were performed before, during and after administration. Platelet aggregation studies indicated that both antibiotics interfered with platelet aggregation and secretion resulting in prolonged bleeding times. The effect was dose related and rapidly reversible after discontinuation of the antibiotics. It always occurred earlier and was more profound with carbenicillin than with mezlocillin (P = 0.008). Bleeding times greater than 15 min were observed in 17% of volunteers who received 18 g/day of mezlocillin and 83% of volunteers who received 18 g/day of carbenicillin (P less than 0.05). There were no abnormalities in the coagulation cascade. The risk of acquiring an antibiotic-induced clinical bleeding disorder is lower with mezlocillin than with carbenicillin.

The in-vitro activity of mezlocillin against community hospital isolates in comparison to other penicillins and cephalosporins

The in-vitro activity of mezlocillin was evaluated against 1795 fresh clinical isolates at a 320-bed community hospital and compared with that of ticarcillin, piperacillin, cefoxitin, cefamandole, moxalactam, cefotaxime and cefoperazone. Only 25 isolates (1.4%) were highly resistant to mezlocillin (greater than 128 mg/l). The MIC 90 values were less than or equal to 32 mg/l for all species studied, including Klebsiella, but excluding Acinetobacter and Pseudomonas where the MIC 90 values were 64 mg/l. The anti-pseudomonal activity of mezlocillin was equivalent to that of ticarcillin but less than that of piperacillin, particularly at low MIC values. Against most members of the Enterobacteriaceae mezlocillin was more active than cefoxitin or cefamandole but was less active than moxalactam, cefotaxime or cefoperazone. Its activity against enterococci exceeded that of all other agents tested, inhibiting 82% of strains at an MIC value less than or equal to 1 mg/l. Because of its exceptionally broad spectrum, mezlocillin promises to be of value for the treatment of infections due to a wide variety of micro-organisms, and particularly for mixed infections due to Gram-negative bacilli and enterococci.

Phagocytosis of filaments of Escherichia coli produced with mezlocillin

The phagocytosis of filaments of Escherichia coli produced with mezlocillin differs from the phagocytosis of normal bacilli in that pseudopods are employed for bacilli, but the entire body of the polymorphonuclear cell (PMN) participates in the engulfment of a filament. A single PMN was observed phagocytizing one or more filaments 20-50 micron long. The mass of a filament is about ten times larger than the mass of a bacillus. When equal bacterial mass, one filament or 10 bacilli, is exposed to PMNs comparable bacterial killing results after 2-3 h of incubation.

The effects of mezlocillin, ticarcillin and placebo on blood coagulation and bleeding time in normal volunteers

Bleeding time, coagulation tests and platelet aggregation response to adenosine diphosphate (ADP), epinephrine, arachidonic acid, ristocetin and collagen were determined in 18 normal male volunteers in a randomized, double-blind, placebo-controlled parallel study. Six subjects each received either placebo or 4.0 g of either mezlocillin or ticarcillin every 6 h for 7 days. In the placebo-treated or mezlocillin-treated groups no changes in plasma coagulation tests or bleeding time were observed. Randomly scattered decreases in platelet aggregation responses to ADP, epinephrine or arachidonic acid were noted in some subjects in both the placebo and mezlocillin groups. In contrast to these observations, in the ticarcillin treated group the bleeding time was abnormally prolonged to more than 18 min in three of six volunteers. In two of these subjects, bleeding time was prolonged after only seven ticarcillin doses (28.0 g) and in the third subject after a total of 21 doses (84.0 g). A significant decrease in platelet aggregation (P less than 0.005) induced by ADP was found in these volunteers. Although platelet aggregation response to arachidonic acid and epinephrine also appeared to be reduced in this group, correlation between increased bleeding time and abnormal platelet function was not possible because of the small number of subjects. No changes in other coagulation function were observed. The results suggest that the risk of bleeding disorder is very high with therapeutic doses of ticarcillin but not with comparable doses of mezlocillin.

In-vitro and in-vivo comparison of mezlocillin and cefoxitin

The efficacy, toxicity, microbiology and pharmacology of cefoxitin and mezlocillin were compared in a clinical and laboratory study. In 81 patients treated with cefoxitin and 83 treated with mezlocillin, clinical and bacteriological cures were achieved in 79.2% and 85.5% respectively. Both antibiotics were effective in the treatment of septicaemia, pulmonary infections, urinary tract infections, intra-abdominal and pelvic infections and skin and soft-tissue infections. Both were also effective in the treatment of anaerobic infections. No major haematological, hepatic, or renal toxicity was encountered in patients treated with either drug.

Effects of mezlocillin on the pharmacokinetics of oxacillin and dicloxacillin

The pharmacokinetics of oxacillin and dicloxacillin, with and without the coadministration of mezlocillin, were studied in 16 patients with normal or severely impaired renal function. After a single administration to patients in terminal renal failure a decrease in total oxacillin clearance from 279 to 159 ml/min/1.73 m2 and total dicloxacillin clearance from 249 to 43 ml/min/1.73 m2 was observed. After coadministration of mezlocillin total oxacillin clearance fell by 38% in all patients irrespective of their renal function. This was caused by a reduction in renal and non-renal elimination rather than by a change in the volume of distribution. With the exception of a minor reduction in renal excretion, the pharmacokinetics of dicloxacillin showed no significant changes. In terminal renal failure the oxacillin dose needs to be reduced by half only when combined with mezlocillin. For dicloxacillin, however, the same dosage adjustment is required irrespective of whether administration is single or combined.

Comparative in vitro activity of ticarcillin, piperacillin, azlocillin and mezlocillin

The in vitro activity of ticarcillin, piperacillin, azlocillin and mezlocillin was determined against 403 clinical isolates. At MIC50, piperacillin was 2 to 8 times more active than the other three compounds against Pseudomonas, Escherichia coli, Proteus, Citrobacter, Acinetobacter and Salmonella species. Against Klebsiella, Enterobacter, Haemophilus, Bacteroides spp. and non-beta-lactamase producing Staphylococcus aureus the activity of piperacillin was similar to one or more of the most effective agents. However, azlocillin and mezlocillin were more active than piperacillin against enterococci. Ticarcillin was the least active in vitro. Despite these significant differences at MIC50 amongst the four compounds, they became much less discernible at MIC90, obviously due to beta-lactamase producing strains under study. The spectrum of activity of piperacillin encompasses those of azlocillin and mezlociLlin together except for Gram-positive organisms.