Activity of moxalactam and cefotaxime alone and in combination with ampicillin or penicillin against group B streptococci

Determination of the effect of antimicrobics in combination against Listeria monocytogenes

The in vitro activity of selected penicillins, extended spectrum cephalosporins, vancomycin, gentamicin, erythromycin, tetracycline, rifampin, and trimethoprim and sulfamethoxazole (alone and in combination) was determined by microtiter technique for 20 isolates of Listeria monocytogenes. The activity of selected combinations of antimicrobics was determined by the microtiter checkboard technique. Trimethoprim-sulfamethoxazole (1:20 ratio) was the most active agent in inhibitory tests and also showed bactericidal activity. The combinations of gentamicin with either ampicillin or vancomycin and that of erythromycin with tetracycline showed bactericidal effect in synergy studies. Combining ampicillin with an extended spectrum cephalosporin showed no antagonism, whereas, combining rifampin with trimethoprim or with trimethoprim/sulfamethoxazole led only to indifference or antagonism. These observations may have importance in selection of therapy in animal models or in selected clinical situations.

Cephalosporins in gram-positive infections

Infections caused by Gram-positive bacteria are an important and common cause of morbidity and mortality. Staphylococci and streptococci are the most frequent infecting organisms in skin and soft tissue infections, pneumonia, bone and joint infections, and endocarditis. Anaerobic Gram-positive bacteria such as Clostridia spp. cause infections that can rapidly produce tissue necrosis and death. The cephalosporins are indicated for the treatment of infections caused by Gram-positive bacteria in certain circumstances. These include selected patients with endocarditis, osteomyelitis, septic arthritis and cellulitis. They are also used as alternatives to the penicillins in penicillin-allergic patients and for 'mixed' infections caused by Gram-positive and Gram-negative organisms. This article discusses the indications for the cephalosporin group of antibiotics in patients suffering from infections caused by Gram-positive bacteria.

Emerging role of cephalosporins in bacterial meningitis

Since 1974, ampicillin and chloramphenicol have been standard therapeutic agents for initial treatment of bacterial meningitis occurring after the newborn period. Emerging problems necessitate a reappraisal and a search for alternatives to those drugs. The problems include the following: (1) Some strains of pneumococci (between 3 and 16 percent) are relatively resistant, with minimal inhibitory concentrations between 0.1 and 1.0 microgram/ml) to penicillin G and ampicillin. Such strains are not eradicated from the cerebrospinal fluid by the usual dosages of penicillin G or ampicillin. (2) Some strains of Hemophilus influenzae type B are resistant to ampicillin and chloramphenicol by virtue of beta-lactamase and acetyltransferase production. Such strains are currently rare in the United States, but it has been predicted that they might account for as many as one quarter of the isolates within a few years. (In Barcelona, Spain, their prevalence is 18 percent.) (3) Patients with meningitis often receive phenobarbital or phenytoin. Those drugs, and others metabolized by the liver, can significantly affect the pharmacology of chloramphenicol and result in either subtherapeutic or toxic concentrations of chloramphenicol in some patients. (4) For a variety of reasons, neither ampicillin plus gentamicin nor ampicillin plus chloramphenicol is an ideal combination for infants between one and four months of age when etiologic agents include coliform bacilli and group B streptococci, as well as Hemophilus, pneumococci, and meningococci. First-generation cephalosporins were unsuitable for the treatment of meningitis because of their low concentrations in the cerebrospinal fluid in relation to the bactericidal concentrations required for the common pathogens. Several of the newer cephalosporins achieve therapeutic concentrations in the cerebrospinal fluid and, in the case of three cephalosporin derivatives (cefuroxime, cefotaxime, and moxalactam), large, controlled clinical trials have demonstrated activity comparable to that of standard therapy. Limited experience suggests that several other cephalosporins (e.g., ceftizoxime, ceftazidime) will be shown to be effective when more experience is gained. Furthermore, the use of these drugs, with the exception of moxalactam, which has insufficient activity against gram-positive cocci, obviates the four problems just cited.

Reverse inoculum effect in bactericidal activity and other variables affecting killing of group B streptococci by penicillin

Variables of the effect of penicillin G on the numbers of viable group B streptococci in broth cultures were studied. One-fourth of the MIC was the lowest concentration that reduced the viable count compared with antibiotic-free controls. The rate of killing increased with the concentration of penicillin up to 4 X MIC, but no further. During the first 2 or 3 h, the bactericidal activity was more rapid than later on. The MIC and supraoptimal concentrations of penicillin killed an inoculum of 10(6) organisms more rapidly than an inoculum of 10(4) organisms. The MIC was not inoculum dependent. The reverse inoculum effect was revealed by the killing curves but not by the MBC. There were reproducible differences among strains as to the rate of killing by penicillin; these did not correlate with the rate of multiplication, which also varied among strains. Among the 11 strains tested, there were no tolerant ones.

Susceptibility to six antibiotics of group B streptococci isolated from cerebrospinal fluid

64 clinical isolates of group B streptococci from cerebrospinal fluids of neonates were tested for susceptibility to 6 antibiotics. The strains were obtained in The Netherlands during 7 years. The usefulness of the generally recommended initial therapy, a combination of ampicillin and gentamicin, is supported.

Clinical experience with cefotaxime for the therapy of bacteremias due to gram-positive organisms

Fifty-five patients with gram-positive bacteremias were treated with cefotaxime after enrollment in comparative and non-comparative study protocols. Forty-nine of these 55 patients were evaluable and followed for their response to therapy and adverse effects. Most patients were white males 50 years of age or older (69%); 45% had two or more serious underlying diseases. Pneumonias caused 59% of these bacteremias, which were etiologically due to Streptococcus pneumoniae (22 episodes), Staphylococcus aureus (15), coagulase-negative staphylococci (3) and other streptococci (12). Overall, 90% of bacteremias were cured with cefotaxime therapy. Among five treatment failures were included three deaths, one due to cefotaxime-associated pseudomembranous colitis, one caused by a bacteremic superinfection due to Pseudomonas aeruginosa and one due to a progressive pneumonia despite therapy. Adverse effects of therapy were infrequent and noteworthy for only one patient with questionable nephrotoxicity and a lack of cefotaxime-associated coagulopathy.

Cefotaxime. A review of its antibacterial activity, pharmacological properties and therapeutic use

SYNOPSIS

Cefotaxime is a new 'third generation' semisynthetic cephalosporin administered intravenously or intramuscularly. It has a broad spectrum of activity against Gram-positive and Gram-negative aerobic and anaerobic bacteria, and is generally more active against Gram-negative bacteria than the 'first' and 'second generation' cephalosporins. Although cefotaxime has some activity against Pseudomonas aeruginosa, on the basis of present evidence it cannot be recommended as sole antibiotic therapy for pseudomonal infections. However, cefotaxime has been effective in treating infections due to other 'difficult' organisms, such as multidrug-resistant Enterobacteriaceae. Like other cephalosporins, cefotaxime is effective in treating patients with complicated urinary tract and lower respiratory tract infections, particularly pneumonia caused by Gram-negative bacilli. High response rates have also been achieved in patients with Gram-negative bacteraemia. Although favourable clinical results have been obtained in patients with infections caused by mixed aerobic/anaerobic organisms (such as peritonitis or soft tissue infections), the relatively low in vitro activity of cefotaxime against Bacteroides fragilis may restrict its usage in situations where this organism is the suspected or proven pathogen. In preliminary studies, males and females treated with a single intramuscular dose of cefotaxime for uncomplicated gonorrhoea caused by penicillinase-producing strains of Neisseria gonorrhoeae responded very favourably. Encouraging results have also been reported in open studies in children including neonates, treated with cefotaxime for meningitis and various other serious infections. In some situations, cefotaxime has been given in combination with another antibiotic such as an aminoglycoside, but the merits of such a combination have not been clearly established. Whether cefotaxime alone is appropriate therapy for conditions previously treated with aminoglycosides (other than pseudomonal infections) also needs additional clarification, but if established as equally effective in such conditions cefotaxime offers potentially important clinical and practical advantages in its apparent lack of serious adverse effects and freedom from the need to undertake drug plasma concentration monitoring.

Ceftriaxone (Ro 13-9904) therapy of serious infection

Ceftriaxone (Ro 13-9904), a newly developed cephalosporin with a long half-life, was evaluated for efficacy and safety in 19 patients with serious infections. Underlying illnesses were present in 16 patients. Ceftriaxone was given intravenously every 12 h. Infections treated included gram-negative bacillary pneumonias (two cases), staphylococcal and streptococcal soft tissue-skeletal infections (six cases), spontaneous peritonitis (two cases), and complicated urinary tract infections (nine cases). Bacteremia was present in three patients. Microbiological and clinical cures were achieved in all but one case, although three patients with urinary infection had recurrences 6 weeks posttherapy. The only failure occurred in a patient with pneumonia who had a Pseudomonas aeruginosa isolated from sputum with an initial minimal inhibitory concentration of 4 micrograms/ml, but after 9 days of therapy, a repeat isolate had a minimal inhibitory concentration of 32 micrograms/ml. The minimal inhibitory concentrations for the other isolates ranged from less than or equal to 0.6 to 8.0 micrograms/ml. The mean peak plasma level of ceftriaxone was 99.9 micrograms/ml. The only side effects noted were drug fever in one patient, phlebitis in two patients, and thrombocytosis in four patients.