The treatment of enteric fever with mecillinam

Antibiotic resistance and plasmid profiling of Vibrio spp. in tropical waters of Peninsular Malaysia

Vibrio species isolated from four different sampling stations in the west coast of Peninsular Malaysia were screened for their antimicrobial resistance and plasmid profiles. A total of 138 isolates belonging to 15 different species were identified. Vibrio campbellii, V. parahaemolyticus, V. harveyi, and V. tubiashii were found to predominance species at all stations. High incidence of erythromycin, ampicillin, and mecillinam resistance was observed among the Vibrio isolates. In contrast, resistance against aztreonam, cefepime, streptomycin, sulfamethoxazole, and sulfonamides was low. All the Vibrio isolates in this study were found to be susceptible to imipenem, norfloxacin, ofloxacin, chloramphenicol, trimethoprim/sulfamethoxazole, and oxytetracycline. Ninety-five percent of the Vibrio isolates were resistant to one or more different classes of antibiotic, and 20 different resistance antibiograms were identified. Thirty-two distinct plasmid profiles with molecular weight ranging from 2.2 to 24.8 kb were detected among the resistance isolates. This study showed that multidrug-resistant Vibrio spp. were common in the aquatic environments of west coast of Peninsular Malaysia.

(p)ppGpp and drug resistance

In recent years, emerging and reemerging pathogens resistant to nearly all available antibiotics are on the rise. This limits the availability of effective antibiotics to treat infections, thus it is imperative to develop new drugs. The accumulation of alarmones guanosine tetraphosphate and guanosine pentaphosphate, collectively known as (p)ppGpp, is a global response of bacteria to environmental stress. (p)ppGpp has been documented to be involved in the resistance to beta-lactam and peptide antibiotics. Proposed mechanisms of action include occupation of drug targets, regulation of the expression of virulence determinants, and modification of protein activities. (p)ppGpp analogs might counteract these actions. Several such entities are being tested as new antibiotics. Further insights into the mechanisms of (p)ppGpp-mediated drug resistance might facilitate the discovery and development of novel antibiotics.

Amdinocillin: a novel penicillin. Antibacterial activity, pharmacology and clinical use

Amdinocillin is a novel penicillin whose antibacterial activity is derived from its ability to bind specifically and avidly to Penicillin Binding Protein-2 (PBP 2). Other beta-lactams bind almost exclusively to PBPs 1 and 3. This unique feature has prompted many investigators to predict that amdinocillin would aggressively synergize with other antimicrobials, particularly other beta-lactams. Certain features of these predictions have been realized. Amdinocillin is active alone against many gram-negative organisms. Pseudomonas and non-fermenting gram-negative bacteria, however, are usually resistant. Amdinocillin, in combination with many beta-lactams, exhibits marked synergy against many enterobacteriaceae. No such synergy can be demonstrated for gram-positive organisms or pseudomonas species. Amdinocillin is not beta-lactamase stable. Organisms which produce high levels of plasma-mediated beta-lactamase are resistant to the drug. Amdinocillin is widely distributed to most tissues of the body. It is removed by renal tubular secretion which results in prodigious levels of the drug in the urine. Co-administration of probenecid results in markedly elevated plasma levels of amdinocillin and delays its excretion. Amdinocillin has a plasma half-life of about one hour in patients with grossly normal renal function. Its half-life increases to 3 to 6 hours in anephric patients. The spectrum of adverse reactions observed with amdinocillin is similar to that of other penicillins. Amdinocillin, as a single agent, is effective in the treatment of urinary tract infections caused by susceptible strains of E. coli and klebsiella and enterobacter species. When amdinocillin is used in concert with other antimicrobials, synergy can frequently be demonstrated but it is essentially limited to gram-negative aerobic organisms. At present, insufficient data are available to precisely profile the utility of amdinocillin, either alone or in combination, in the treatment of systemic infections.

Review of clinical experience with amdinocillin monotherapy and comparative studies

Activity against gram-negative bacilli and frequent synergism with other beta-lactam antibiotics were demonstrated by amdinocillin in urinary tract infections, urosepsis, and in a variety of other infections. In a prospective study, 299 patients were assigned at random to receive amdinocillin or another antibiotic considered standard treatment for the infection. The majority of infections were of the urinary tract, and 58 of 59 patients treated with amdinocillin responded clinically, with cures in 49. Of the 52 patients treated with tobramycin or other comparative agents, 49 responded, and 42 were cured. Escherichia coli and other Enterobacteriaceae were the usual pathogens. Immediately after treatment, 90 percent of urine samples were negative in both treatment groups. At four to six weeks follow-up, relapse or reinfection rates were about 20 percent in either group. Miscellaneous infections were treated with either amdinocillin or a comparative agent. Eleven of 15 infections responded favorably to amdinocillin, and seven were cured. Adverse effects were usually mild and characteristic of the penicillins.

Treatment of Salmonella carriers with pivmecillinam alone or in combination with pivampicillin: experience with three patients

3 patients with salmonella infections who continued to excrete salmonella in fecal samples for more than 6 months were treated with pivmecillinam alone or in combination with pivampicillin. Mecillinam alone cured 1 of the carriers, but was without success in the 2 others. One of these patients was cured after treatment with pivmecillinam and pivampicillin. In the last patient salmonella excretion ceased after treatment with pivmecillinam, pivampicillin and probenecid. The choice of treatment was based upon in vitro demonstration of synergism between mecillinam and ampicillin. In the last patient the final treatment was chosen after studies of the bactericidal effect of the patient's serum during various regimes.

Pivmecillinam in the treatment of childhood pyelonephritis

In a prospective study, twenty children with a mean age of 4 years were treated with pivmecillinam, 25 mg to 40 mg per kilogram body-weight and day, for acute pyelonephritis. Urine cultures yielded growth of E. coli in sixteen instances, Klebsiella spp. in two, S. saprophyticus in one and a mixed Gram-positive flora in one patient. All children fulfilled the diagnostic criteria for upper urinary tract infection. In all cases where Gram-negative pathogens were responsible, the infections were eradicated. One reinfection was registered in a child with a concomitantly discovered congenital urological malformation. Pivmecillinam also cured one patient infected with S. saprophyticus but was ineffective in the case of mixed Gram-positive flora. It is concluded that pivmecillinam is a valuable new drug for the management of pyelonephritis in children, as most of these infections are caused by Gram-negative organisms.

The combination of pivmecillinam and pivampicillin compared to co-trimoxazole in the treatment of enteric fever

Typhoid fever is an infectious disease with multisystem involvement and is commonly seen in the tropics. Twelve patients with acute typhoid fever were successfully treated with a fixed dose combination of pivmecillinam and pivampicillin. The treatment results were compared to those obtained from the treatment of ten other patients with co-trimoxazole, which is the routine treatment of our Department. The two forms of treatment appeared to be equally effective, suggesting that the combination mecillinam/ampicillin may represent a valuable alternative to the antityphoidal drugs currently available. Eleven patients were infected with strains resistant in vitro to either ampicillin, chloramphenicol, or both. All clinical isolates were sensitive to co-trimoxazole and to the combination of mecillinam and ampicillin. MIC values for the combination ranged from 0.16 to 2.5 mg/l. No side-effects were recorded.

Mecillinam and ampicillin separately or combined in gram-negative septicemia

Of 20 patients with gram-negative septicemia treated with mecillinam alone or in combination with ampicillin, successful therapeutic results were obtained in 16. In 11 patients treated with ampicillin alone, three failures responded successfully to a combination of mecillinam and ampicillin. Mecillinam MIC values of isolated Enterobacteriaceae were 0.05-0.4 micrograms/ml. In patients receiving 5 mg/kg mecillinam intravenously every six hours, the mean 0.5 hour concentration was 11.0 micrograms/ml and in those given 10 mg/kg 23.3 migcrograms/ml. No serious side effects were recorded. One patient on mecillinam developed an exanthema, as did three patients on combined therapy.

Preliminary experience with parenteral mecillinam

Case reports are reviewed of 26 patients, mainly with severe Gram-negative infections, treatment with parenteral mecillinam. Twenty-three patients received other antibiotics in addition to mecillinam. In 19 patients, potentially synergistic antimicrobial therapy was given. Overall, a beneficial clinical effect was recorded in 17 (68%) of the 25 patients assessed. A better response was observed in those patients who had not received other antibiotics before treatment with mecillinam was instituted. It is concluded that parenteral mecillinam may have an important role in the treatment of severe Gram-negative infections.

Mecillinam in urinary tract infections and in septicaemia

The clinical and bacteriological efficacy as well as the tolerance of mecillinam, a new beta-lactam antibiotic, administered parenterally in a dose of 40 mg/kg body weight, was investigated in 21 hospitalized patients with urinary tract infections or septicaemia. Success, defined as eradication of infecting organisms two to five days after treatment, was found in eight of 16 patients with urinary tract infections. Persistence of the original pathogen after treatment was seen in four patients, all with complicated urinary tract infection. Reinfection was seen in two patients, while the results were unevaluable in two cases. The five patients with septicaemia were all cured of their infection, this result being attributed solely to mecillinam in two cases, while a combined action of mecillinam and another antibiotic produced a cure in the other three cases. Escherichia coli resistant to mecillinam were isolated from two patients with persistence of bacteriuria following mecillinam treatment. Impairment of renal function may have been a contributory factor to the poor treatment response in patients with complicated urinary tract infection. Inasmuch as no important side-effects were recorded and mecillinam appears safe in patients with impaired renal and liver function, a higher dose may be indicated in these more complicated cases.