Sodium Clavulanate Potentiation of Cephalosporin Activity Against Clinical Isolates of Cephalothin-Resistant
            <i>Klebsiella pneumoniae</i>

Strains of bacteria resistant to beta-lactam antibiotics have been increasing in number and are becoming troublesome in clinical medicine. The in vitro antibacterial activity of amoxicillin combined with clavulanic acid was determined on selected ampicillin-resistant clinical isolates. Synergistic effects were produced by amoxicillin with clavulanic acid against ampicillin-resistant strains of Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Proteus vulgaris, and Bacteroides fragilis. Inhibition of the beta-lactamases produced by the ampicillin-resistant strains was confirmed, especially against the penicillinases mediated by the R factor and the cephalosporinases produced by P. vulgaris and B. fragilis. The inhibitory effect of clavulanic acid against betalactamases was irreversible because of the high affinity of clavulanic acid to the enzymes.Bacterial strains resistant to beta-lactam antibiotics have been increasing in number. The resistance of these bacteria is due mainly to the production of beta-lactamase (1), and newer semisynthetic beta-lactam antibiotics, i.e., cefuroxime (8) and cefoxitin (12), resistant to betalactamase have been developed. Clavulanic acid (CVA) (2, 10) and CP-45899 (4) were found to be beta-lactamase inhibitors, although they have poor antibacterial activity. Combination of these products with other beta-lactam antibiotics possessing high antibacterial activity but less stability to beta-lactamase will be a new approach to chemotherapy against resistant strains capable of producing beta-lactamase. This paper deals with the combined antibacterial activity of amoxicillin (AMC) with CVA against ampicillin (APC)-resistant strains ofbacteria. MATERIALS AND METHODSTest strains. Stock strains of clinical isolated, maintained in the Reference Laboratory of Bacterial Resistance, Gunma University, were used in this study.Conjugation methods. R factors were conjugally transfered to Escherichia coli strains by a method previously described (5). E. coli ML1410 Nalr (resistant to nalidixic acid) and E. coli x1037 Rifr (resistant to rifampin) were used as the recipients for the conjugal transfer of R plasmid.Antibiotics. CVA, APC, AMC, and cloxacillin were provided by Beecham Yakuhin Co. Ltd., Tokyo, Japan. Cefoxitin was provided by Daiichi Pharmaceutical Co., Ltd., Tokyo, Japan. Other antibiotics, penicillin G and cephalothin, were commercially available.was used for the determination of antibacterial activity. Peptone water was used for liquid culture and consisted of 1% peptone and 0.5% NaCl. GAM (Nissui, Tokyo, Japan) broth and agar were used for the anaerobic bacteria. Antibiotic medium 3 (Difco) was used for the study of bactericidal activity.

“…Therefore, the combined antibacterial activity ofbeta-lactam antibiotics other than AMC with CVA may be found against APCresistant strains, as reported by earlier studies (6,9).…”

Section: Resultsmentioning

confidence: 54%

Combined antibacterial activity of amoxicillin with clavulanic acid against ampicillin-resistant strains

Matsuura¹,

Nakazawa²,

Hashimoto³

et al. 1980

“…are generally susceptible to cephalothin and most cephalosporins but are moderately resistant to penicillins by virtue of synthesis of a chromosomal penicillinase (14,20,21,27). Some Klebsiella isolates are resistant to high levels of penicillins by production of plasmid-mediated TEM-like penicillinases; these strains also have reduced susceptibility to the older cephalosporins (7,19,24). Recently, the emergence of resistance to broad-sprectrum cephalosporins has been reported in strains of Klebsiella oxytoca (6, 15) and Klebsiella pneumoniae (22).…”

mentioning

confidence: 99%

Novel plasmid-mediated beta-lactamase in clinical isolates of Klebsiella pneumoniae more resistant to ceftazidime than to other broad-spectrum cephalosporins

Petit

Sirot

Chanal

et al. 1988

Multiresistant Klebsiella pneumoniae strains isolated from three patients in the same intensive care unit were more resistant to ceftazidime than to cefotaxime and aztreonam but remained susceptible to moxalactam and imipenem. Resistance to I-lactams, kanamycin, streptomycin, sulfonamides, and tetracyclines was transferable to Escherichia coli by conjugation and was lost en bloc after treatment with ethidium bromide. Agarose gel electrophoresis of wild types and transconjugants indicated that these resistances were mediated by a 150-kilobase plasmid, pCFF14. The strains constitutively produced a ,-lactamase with isoelectric point close to 5.6 and which had a higher Vmax for ceftazidime and cephalothin than for cefotaxime. The substrate profile and isoelectric point of this enzyme thus differ from those of other known plasmid-mediated (-lactamases, including the broad-spectrum enzyme CTX-1. Hybridization studies support the derivation of the novel enzyme from a TEM-type ,I-lactamase.Klebsiella spp. are generally susceptible to cephalothin and most cephalosporins but are moderately resistant to penicillins by virtue of synthesis of a chromosomal penicillinase (14,20,21,27). Some Klebsiella isolates are resistant to high levels of penicillins by production of plasmid-mediated TEM-like penicillinases; these strains also have reduced susceptibility to the older cephalosporins (7,19,24). Recently, the emergence of resistance to broad-sprectrum cephalosporins has been reported in strains of Klebsiella oxytoca (6, 15) and Klebsiella pneumoniae (22). Transferable resistance to cefotaxime was demonstrated in the latter species (10). We previously described an outbreak of infections caused by K. pneumoniae resistant to all P-lactams except moxalactam and imipenem by production of the novel plasmid-mediated P-lactamase, . In this paper, we describe another novel plasmid-mediated P-lactamase, which is markedly active against ceftazidime and which was isolated in K. pneumoniae (25). MATERIALS AND METHODSBacterial strains. Three multiply resistant strains of K. pneumoniae, CF504, CF514, and CF524, were isolated from patients hospitalized in the same intensive care unit at St.-Jacques Hospital, Clermont-Ferrand, France. The biotypes of the strains determined by the API 50CH system were the same for CF504 and CF514. K. pneumoniae CF104 (CTX-1 producing) was included in this study for comparison. A rifampin-resistant mutant of Escherichia coli K-12, C600, was used in transfer experiments (1).Antibiotics Transfer of resistance characters and curing. Conjugation experiments were done at 37°C for 40 min, as previously described (16). Plasmids were transferred to mutants of E. coli K-12 strain C600 resistant to rifampin. Transconjugants CF604, CF614, and CF624 were selected on Mueller-Hinton agar containing rifampin (300 ,ug/ml) plus ceftazidime (4 ,ug/ml), kanamycin (20 ,ug/ml), tetracycline (2 pug/ml), or sulfonamide (200 p.g/ml). The frequency of transfer was expressed relative to the number of donor cells. Curing of antibiotic re...

“…Although it has little inherent antibacterial activity, it protects the labile penicillins and cephalosporins from destruction by bacterial , 8-lactamase (4,6,8,9,13). In vitro studies have demonstrated that clavulanic acid possesses a very wide spectrum of inhibition (3), which results in marked enhancement of,-lactam antibiotics against many 8-lactamase-producing organisms (3,9,13) found to have infecting strains with amoxicillin MICs above 10 ug/ml were considered for enrollment in the study.…”

mentioning

confidence: 99%

Amoxicillin-clavulanic acid in treatment of urinary tract infection due to gram-negative bacteria resistant to penicillin

Martinelli¹,

Lopes²,

Oliveira³

et al. 1981

Twenty-one adult patients with urinary tract infections caused by penicillinresistant bacteria completed treatment with amoxicillin alone or amoxicillin plus clavulanic acid in a randomized double-blind clinical trial. Of the 13 patients treated with amoxicilhin plus clavulanic acid, the absence of bacteriuria within 7 days of therapy was observed in 85%, as compared with only 25% of the 8 patients receiving amoxicillin only. There were no significant side effects nor any clinical, biochemical, or hematological abnormalities related to either treatment. It was concluded that the combination of clavulanic acid and amoxicillin could be useful in the treatment of uncomplicated urinary tract infection caused by penicillinresistant bacteria.Clavulanic acid, a natural product of Streptomyces clavuligerus, is a potent, irreversible inhibitor of a wide variety of 8-lactamase enzymes (5, 7). Although it has little inherent antibacterial activity, it protects the labile penicillins and cephalosporins from destruction by bacterial ,8-lactamase (4, 6, 8, 9, 13). In vitro studies have demonstrated that clavulanic acid possesses a very wide spectrum of inhibition (3), which results in marked enhancement of,-lactam antibiotics against many 8-lactamase-producing organisms (3, 9, 13), including staphylococci and enterobacteria.Urinary tract infections caused by ,8-lactamase-producing species are common and often require treatment with antibiotics which are potentially toxic. Since clavulanic acid protects the ,8-lactam-sensitive antibiotics from enzymatic destruction, it should serve as a useful adjunct to therapy with those agents. Therefore, the purpose of this initial clinical trial was to determine the efficacy and safety of amoxicilhin plus clavulanic acid in the treatment of uncomplicated urinary tract infection caused by penicillin-resistant organisms. MATERIALS AND METHODSTwenty-one patients presenting with uncomplicated urinary tract infections caused by bacteria resistant to both ampicillin and amoxicillin were considered suitable for this trial. Urinary tract infection was defined as the presence of at least 105 bacteria per ml in patients complaining of dysuria, urgency, frequency, and back pain, or by two consecutive urine cultures containing 105 or more bacteria per ml of the same species in asymptomatic patients. There was no attempt to differentiate between upper and lower urinary tract infection for the purpose of this trial. All bacterial isolates were identified by standard procedures (2) and tested for susceptibility with a 10-,.g ampicillin disk by the Bauer-Kirby method (1). If the isolate was found to be resistant to ampicillin, a tube dilution minimum inhibitory concentration (MIC) to amoxicilhin was determined. All patients who were found to have infecting strains with amoxicillin MICs above 10 ug/ml were considered for enrollment in the study. In addition, a further MIC of amoxicilhin was obtained in the presence of 10 ug of clavulanic acid per ml. This concentration of clavulanic acid has been shown to...