Use of ceftazidime in the therapy of serious infections, including those due to multiresistant organisms

Evaluation of ciprofloxacin's activity against recent clinical isolates

The in vitro antibacterial activity of ciprofloxacin, a new quinoline carboxylic acid, was tested against 1671 recently clinically isolated bacterial strains, by measuring the minimum inhibitory concentrations (MIC). Comparisons were made with other quinolones: nalidixic acid, norfloxacin, and other drugs: piperacillin, cefoxitin, cefotetan, ceftazidime, tobramycin, rifampin, tetracycline, chloramphenicol. Ciprofloxacin was very active against the tested species and was the most active drug against all the bacterial strains, with a geometric mean, a MIC50 and MIC90 of 0.27, 0.12 and 2 micrograms/ml, respectively.

Impact of LY146032 on Streptococcus (Enterococcus) faecalis translocation in mice

The susceptibility of Swiss White mice to colonization with Streptococcus (Enterococcus) faecalis was greatly increased when the animals were given 5 mg of streptomycin sulfate per ml in their drinking water. One week after initiation of streptomycin treatment, the mice were challenged orogastrically with graded doses of streptomycin-resistant S. faecalis. The number of S. faecalis cells required to implant the intestinal tract of 50% of untreated mice was 2.9 X 10(9), but was only 4.8 X 10(3) for streptomycin-treated animals. When both groups of mice were challenged orogastrically with 4.6 X 10(6) viable S. faecalis cells, the cecum and small intestine of 100% of the streptomycin-treated animals, but only 10% of the untreated animals, were colonized with the organism. Similarly, translocation of S. faecalis to extraintestinal sites occurred in a majority of streptomycin-treated mice, but in only a small number of untreated mice. Subcutaneous administration of the experimental antibiotic LY146032 (Eli Lilly & Co., Indianapolis, Ind.) to streptomycin-treated mice concomitant with orogastric challenge with 5.5 X 10(5) viable S. faecalis cells resulted in a significant decrease in the incidence of intestinal colonization by the organism, a significant reduction in S. faecalis populations, and the absence of the organism in the liver, spleen, and heart. However, once intestinal colonization had occurred and extraintestinal infections were established, LY146032 did not significantly reduce S. faecalis populations or ameliorate the infections. We conclude that LY146032 effectively prevents translocation of S. faecalis from the intestinal tract of mice but does not resolve established extraintestinal infections.

In vitro activity of ceftazidime, cefotaxime and gentamicin against 11,521 clinical isolates of bacteria

The in vitro activity of ceftazidime has been compared with those of another third-generation cephalosporin, cefotaxime, and the aminocyclitol aminoglycoside, gentamicin. A total of 11,521 clinical isolates of aerobic bacteria were employed, and an agar diffusion method was used for sensitivity testing. The MIC-values were calculated from regression lines. The mean inhibition zones for ceftazidime against Gram-positive organisms were significantly less than those against Gram-negative isolates (23 mm vs. 33 mm, p less than 0.0001). Cefotaxime inhibited 74.0%, gentamicin 66.3% and ceftazidime 20.4% of the Gram-positive isolates at a concentration of less than or equal to 2 mg/ml. Ceftazidime and cefotaxime were equally active against fermentative Gram-negative rods, inhibiting 92.7% of each of these isolates at 2 mg/l. Against Ps. aeruginosa, ceftazidime (MIC90 2.2 mg/l) was found to be almost as active as gentamicin (MIC90 1.2 mg/l), and far more active than cefotaxime (MIC90 434 mg/l). Gentamicin was the most active agent against Acinetobacter sp. (MIC90 6.0 mg/l), followed by ceftazidime (MIC90 18 mg/l) and cefotaxime (MIC90 83 mg/l).

Ceftazidime and amikacin alone and in combination against Pseudomonas aeruginosa and Enterobacteriaceae

The efficacy of ceftazidime alone and combined with amikacin was studied in a rabbit model simulating closed-space infections at locally neutropenic sites. Six strains of Pseudomonas aeruginosa, and six Enterobacteriaceae (two strains each of Klebsiella pneumoniae and Serratia marcescens and one strain each of Escherichia coli and Citrobacter freundii) in pooled rabbit serum were each inoculated into separate subcutaneous semipermeable chambers. Intramuscular antibiotic therapy was begun 4 hr later with ceftazidime (50 mg/kg) alone and combined with amikacin (15 mg/kg) for Enterobacteriaceae or ceftazidime (100 mg/kg) alone and combined with amikacin (15 mg/kg) for pseudomonads every 6 hr for 16 doses. Amikacin alone was ineffective for all 12 strains. Ceftazidime alone was successful (greater than or equal to 5.5 log10 colony forming units (CFU)/ml decrease from drug-free control) in eliminating five of six Enterobacteriaceae but was not successful against any of the pseudomonads. Ceftazidime plus amikacin was successful against the same five of six Enterobacteriaceae and five of six pseudomonads. The best in vitro tests for the prediction of in vivo outcome were high inoculum (greater than or equal to 7 log10 CFU/ml) susceptibility, checkerboard synergism testing, and conventional inoculum time-kill rates at concentrations of antimicrobials simulating extravascular levels obtained in vivo.

Double-blind, prospective, multicenter trial comparing ceftazidime with moxalactam in the treatment of serious gram-negative infections

Ceftazidime is a new antimicrobial agent possessing excellent in vitro activity against most members of the family Enterobacteriaceae and against Pseudomonas aeruginosa. We conducted a double-blind, prospective, multicenter trial to compare ceftazidime with moxalactam in the treatment of serious gram-negative infections. The overall favorable response rates for the two regimens were similar (93 of 106 [88%] and 84 of 97 [86%], respectively). Among these, the response rates of the 56 gram-negative bacteremias and the 23 P. aeruginosa infections were comparable. Both groups had similar incidences of subsequent infections with P. aeruginosa, enterococci, and yeasts. A total of 13% of the patients in the moxalactam group developed a prolonged prothrombin time (P less than 0.01), and three patients demonstrated clinical bleeding. These results suggest that although the overall efficacy of both regimens was similar, treatment with moxalactam resulted in a higher incidence of prolongation of prothrombin time with an attendant risk of bleeding. In nonneutropenic patients, ceftazidime as a single agent is safe and effective in gram-negative bacillary infections.

Randomized evaluation of ceftazidime or ticarcillin and tobramycin for the treatment of osteomyelitis caused by gram-negative bacilli

Ceftazidime, a new cephalosporin with enhanced activity against aerobic gram-negative bacilli, was compared with tobramycin and ticarcillin in a randomized clinical trial. Efficacy and safety were evaluated in 18 patients (17 males, 1 female) with gram-negative osteomyelitis. All organisms were susceptible to the treatment antibiotics(s). There were nine patients treated with tobramycin and ticarcillin for 27 to 62 days (mean, 42 days), and nine patients were treated with 4 g of ceftazidime per day for 26 to 63 days (mean, 45 days). All nine patients receiving tobramycin and ticarcillin had the osteomyelitis arrested after the initial treatment. Follow-up was for 2 to 38 months (mean, 22 months). Of nine patients receiving ceftazidime three were initial treatment failures. Follow-up was for 13 to 31 months (mean, 21 months). A patient receiving ceftazidime had a transient rise in serum glutamic oxalacetic transaminase and serum glutamic pyruvic transaminase. There were three treatment failures in the ceftazidime group; no failures occurred in the group receiving the combination of ticarcillin and tobramycin. A larger series would be required to detect a significant difference between the two treatment groups.

Serum bactericidal activity of ceftazidime increased by netilmicin

Cephalosporins are often used in combination with aminoglycoside antibiotics in the treatment of gram-negative infections. Although ceftazidime possesses activity against gram-negative bacteria, especially against Pseudomonas, combined use with aminoglycosides is useful. In this study, 12 healthy volunteers (6 men, 6 women; mean age 21.5 yr) received a single dose of ceftazidime 1 g iv and one week later ceftazidime 1 g iv with netilmicin 100 mg iv. Both antibiotics were infused over five minutes. Concentrations of ceftazidime were determined by high performance liquid chromatography. Serum bactericidal activity (SBA) was evaluated against seven microorganisms isolated from clinical specimens. The mean peak serum level of ceftazidime was 113.4 micrograms/ml. At eight hours, we observed a concentration of 2.6 micrograms/ml. The total clearance was 126 ml/min, while the renal clearance was 100 ml/min. Ceftazidime exhibited a half-life of 1.9 hours. Up to ten hours, the SBA of ceftazidime against Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, and Salmonella typhi was greater than 1:8 in more than 90 percent of samples. At one hour, ceftazidime exhibited a SBA of 1:4 for Staphylococcus aureus, and 1:16 for Pseudomonas aeruginosa. With the addition of netilmicin, median SBA against Staph. aureus and P. aeruginosa were 1:32 and 1:64, respectively, at one hour. Netilmicin enhanced the SBA of ceftazidime. The combination was not effective against Streptococcus faecalis.

Use of ceftazidime in the treatment of nosocomial lower respiratory infections

Patients with hospital-acquired lower respiratory infections pose both diagnostic and therapeutic challenges. Such infections are commonly seen in critically ill patients. When nosocomial pneumonia is suspected, treatment is generally initiated with broad-spectrum antibiotics before culture results become available. The usual therapeutic regimen includes an aminoglycoside with or without a beta-lactam agent. In a clinical efficacy study of a single agent, ceftazidime, in the treatment of 20 adults with hospital-acquired lower respiratory infection, 18 patients showed clinical improvement with ceftazidime therapy and pathogens were eradicated in 11. Therapeutic failures occurred in two patients who received empiric therapy prior to the isolation of pathogens resistant to ceftazidime. The median minimal inhibitory concentration of ceftazidime for the isolated pathogens was 0.78 micrograms/ml. Of the 15 patients infected with Pseudomonas aeruginosa, 14 showed a favorable clinical response. Therapy-limiting side effects occurred in two patients and bacillary resistance developed in one patient. The efficacy and safety of ceftazidime in the treatment of hospital-acquired pneumonias were comparable to results previously demonstrated for amikacin, cefotaxime, and imipenem in studies conducted at our institution. In studies reported in the literature, 44 of 51 patients (86 percent) with nosocomial pneumonia who were treated with ceftazidime had a favorable clinical response to therapy. The patients included in these studies were neither neutropenic nor commonly bacteremic, and none had cystic fibrosis. Ceftazidime appears to be a useful agent in the treatment of selected patients with nosocomial pneumonias, including those due to P. aeruginosa.

Ciprofloxacin therapy of infections caused by Pseudomonas aeruginosa and other resistant bacteria

Ciprofloxacin was administered orally to 48 patients with 24 Pseudomonas aeruginosa infections and 13 other infections caused by cephalothin-resistant gram-negative bacilli. The types of infections treated included those of skin or skin structure, bone, urinary tract, and respiratory tract. In 83% of P. aeruginosa infections, a favorable clinical outcome occurred, compared with 85% for all infections. Failure to achieve a cure correlated with the emergence of resistant P. aeruginosa and Acinetobacter calcoaceticus strains in four instances and superinfection with Candida (two cases) and Streptococcus (two cases) species. Therapy was discontinued in three patients because of the development of nausea. Ciprofloxacin appears to be safe and effective in the therapy of infections caused by resistant gram-negative bacilli.

Comparison of ceftazidime with cefamandole for therapy of community-acquired pneumonia

Ceftazidime and cefamandole were compared in the treatment of pneumonia. The median MIC of ceftazidime for all Streptococcus pneumoniae (n = 17) and Haemophilus influenzae (n = 10) isolates was 0.125 microgram/ml. All other isolates were inhibited by less than 0.5 microgram of ceftazidime per ml, with the exception of a group B streptococcus (MIC = 4 micrograms/ml). Satisfactory clinical responses were observed in 91% (20 of 22) of cefamandole-treated patients and 85% (17 of 20) of ceftazidime-treated patients.

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

Ceftazidime is a new 'third generation' cephalosporin administered intravenously or intramuscularly. Similarly to other third generation cephalosporins it has a broad spectrum of in vitro activity against Gram-positive and Gram-negative aerobic bacteria, is particularly active against Enterobacteriaceae (including beta-lactamase-positive strains) and is resistant to hydrolysis by most beta-lactamases. Importantly, in vitro ceftazidime is presently the most active cephalosporin available against Pseudomonas aeruginosa, but it is less active against Staphylococcus aureus than first and second generation cephalosporins. Only larger comparative trials are likely to discern any statistically significant differences in clinical efficacy which may exist between ceftazidime and other antibiotics, but ceftazidime appears to be similar in efficacy to 'standard' comparative drugs in lower respiratory tract infections and complicated and/or chronic urinary tract infections among debilitated or hospitalised patients. Thus, in patients having Gram-negative infections at these sites and in whom the potential toxicity of the aminoglycosides is a concern, ceftazidime may be a valuable alternative in that it apparently lacks serious side effects and does not require routine drug plasma concentration monitoring. In fibrocystic patients having acute respiratory tract infections, ceftazidime is highly effective at both reducing symptoms of infection and temporarily reducing the sputum counts of Pseudomonas species. However, in these patients resistance to ceftazidime may develop, as seen with other beta-lactam antibiotics. In the treatment of fever of unknown origin or documented infections in immunocompromised adults and children, ceftazidime appears to be similar in efficacy to various 2- or 3-drug combinations. Nevertheless, the coadministration of an antibiotic having greater efficacy against Gram-positive bacteria should be considered in immunocompromised patients. Results from a small number of comparative trials suggest that ceftazidime may be as effective as the aminoglycosides in intra-abdominal, obstetric and gynaecological, and skin and soft tissue infections. However, further clinical experience, particularly a few well designed comparative studies, is needed to clarify the comparative efficacy in these conditions as well as in septicaemia/bacteraemia, meningitis, and bone and joint infections.

Ceftazidime versus tobramycin/ticarcillin in treating hospital acquired pneumonia and bacteremia

Thirty-five patients in a neurosurgical intensive care unit who had nosocomial pneumonia and bacteremia were randomly assigned to receive either ceftazidime (Cef) or the combination of ticarcillin and pharmacokinetically adjusted doses of tobramycin (T/T). Fifteen of 17 patients (88%) who received Cef were cured or improved compared to 15 of 18 (83%) who received T/T. The original pathogen was eradicated from the respiratory secretion in 10 of 15 patients receiving Cef compared to only 6 of 18 patients receiving T/T (p = 0.12). All patients in both treatment groups who had positive blood cultures cleared the organism from the bloodstream. No cases of drug toxicity, including renal toxicity, were seen in either group. Cef used as a single agent in nosocomial pneumonias and bacteremias performed at least as well as T/T.