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Potential mechanisms for failure to eradicate group A streptococci from the pharynx.

OBJECTIVE: To investigate the relative efficacy of orally administered cefadroxil and penicillin V in the treatment of group A streptococcal (GABHS) pharyngitis and the mechanism(s) responsible for failure of antimicrobial therapy to eradicate GABHS from the pharynx. STUDY DESIGN: A prospective, randomized clinical trial was conducted in four pediatric offices in which 462 patients with acute pharyngitis and positive culture for GABHS were randomly assigned to receive cefadroxil (n = 232) or penicillin V (n = 230). RESULTS: Bacteriologic treatment success rates for patients in cefadroxil and penicillin groups were 94% and 86%, respectively. However, among patients classified clinically as likely to have bona fide GABHS pharyngitis, there was no difference in bacteriologic treatment success rates in cefadroxil and penicillin groups (95% and 94%, respectively). Among patients classified clinically as likely to be streptococcal carriers, bacteriologic treatment success rates in cefadroxil and penicillin groups were 92% and 73%, respectively. The presence of beta-lactamase and/or bacteriocin-producing pharyngeal flora had no consistent effect on bacteriologic eradication rates among patients in either penicillin or cefadroxil treatment groups or among patients classified as having either GABHS pharyngitis or streptococcal carriage. CONCLUSIONS: Neither beta-lactamase nor bacteriocin produced by normal pharyngeal flora are related to bacteriologic treatment failures in GABHS pharyngitis. Cefadroxil seems to be more effective than penicillin V in eradicating GABHS from patients classified as more likely to be streptococcal carriers. However, among patients we classified as more likely to have bona fide GABHS pharyngitis, the effectiveness of cefadroxil and penicillin V seems to be comparable.

Acute Disease↗

Differential recognition of beta -lactam antibiotics by intestinal and renal peptide transporters, PEPT 1 and PEPT 2.

This study was initiated to determine if there are differences in the recognition of beta -lactam antibiotics as substrates between intestinal and renal peptide transporters, PEPT 1 and PEPT 2. Reverse transcription-coupled polymerase chain reaction and/or Northern blot analysis have established that the human intestinal cell line Caco-2 expresses PEPT 1 but not PEPT 2, whereas the rat proximal tubule cell line SKPT expresses PEPT 2 but not PEPT 1. Detailed kinetic analysis has provided unequivocal evidence for participation of PEPT 2 in SKPT cells in the transport of the dipeptide glycylsarcosine and the aminocephalosporin cephalexin. The substrate recognition pattern of PEPT 1 and PEPT 2 was studied with cefadroxil (a cephalosporin) and cyclacillin (a penicillin) as model substrates for the peptide transporters constitutively expressed in Caco-2 cells (PEPT 1) and SKPT cells (PEPT 2). Cyclacillin was 9-fold more potent than cefadroxil in competing with glycylsacosine for uptake via PEPT 1. In contrast, cefadroxil was 13-fold more potent than cyclacillin in competing with the dipeptide for uptake via PEPT 2. The substrate recognition pattern of PEPT 1 and PEPT 2 was also investigated using cloned human peptide transporters functionally expressed in HeLa cells. Expression of PEPT 1 or PEPT 2 in HeLa cells was found to induce H(+)-coupled cephalexin uptake in these cells. As was the case with Caco-2 cells and SKPT cells, the uptake of glycylsarcosine induced in HeLa cells by PEPT 1 cDNA and PEPT 2 cDNA was inhibitable by cyclacillin and cefadroxil. Again, the PEPT 1 cDNA-induced dipeptide uptake was inhibited more potently by cyclacillin than by cefadroxil, and the PEPT 2 cDNA-induced dipeptide uptake was inhibited more potently by cefadroxil than by cyclacillin. It is concluded that there are marked differences between the intestinal and renal peptide transporters in the recognition of beta -lactam antibiotics as substrates.

Animals↗

Randomized comparative trial and cost analysis of 3-day antimicrobial regimens for treatment of acute cystitis in women.

OBJECTIVE: To determine the efficacy, safety, and costs associated with four different 3-day regimens for the treatment of acute uncomplicated cystitis in women. DESIGN: A prospective randomized trial with a cost analysis. STUDY POPULATION: Women with acute cystitis attending a student health center. INTERVENTIONS: Treatment with 3-day oral regimens of trimethoprim-sulfamethoxazole, 160 mg/800 mg twice daily, macrocrystalline nitrofurantoin, 100 mg four times daily, cefadroxil, 500 mg twice daily, or amoxicillin, 500 mg three times daily. RESULTS: Six weeks after treatment, 32 (82%) of 39 women treated with trimethoprim-sulfamethoxazole were cured compared with 22 (61%) of 36 treated with nitrofurantoin (P = .04 vs trimethoprim-sulfamethoxazole), 21 (66%) of 32 treated with cefadroxil (P = .11 vs trimethoprim-sulfamethoxazole), and 28 (67%) of 42 treated with amoxicillin (P = .11 vs trimethoprim-sulfamethoxazole). Persistence of significant bacteriuria was less common with trimethoprim-sulfamethoxazole (3%) and cefadroxil (0%) compared with nitrofurantoin (16%; P = .05 vs trimethoprim-sulfamethoxazole) and amoxicillin (14%; P = .11 vs trimethoprim-sulfamethoxazole). Persistence of bacteriuria was associated with amoxicillin-resistant strains in the amoxicillin group but nitrofurantoin-susceptible strains in the nitrofurantoin group. Trimethoprim-sulfamethoxazole was more successful in eradicating Escherichia coli from rectal cultures soon after therapy and from urethral and vaginal cultures at all follow-up visits compared with the other treatment regimens. Adverse effects were reported by 16 (35%) of 46 patients receiving trimethoprim-sulfamethoxazole, 18 (43%) of 42 receiving nitrofurantoin, 12 (30%) of 40 receiving cefadroxil, and 13 (25%) of 52 receiving amoxicillin. The mean costs per patient were less with trimethoprim-sulfamethoxazole ($114) and amoxicillin ($131) compared with nitrofurantoin ($155) and cefadroxil ($155). CONCLUSIONS: A 3-day regimen of trimethoprim-sulfamethoxazole is more effective and less expensive than 3-day regimens of nitrofurantoin, cefadroxil, or amoxicillin for treatment of uncomplicated cystitis in women. The increased efficacy of trimethoprim-sulfamethoxazole is likely related to its antimicrobial effects against E coli in the rectum, urethra, and vagina.

Acute Disease↗

Functional expression of transporter for beta-lactam antibiotics and dipeptides in Xenopus laevis oocytes injected with messenger RNA from human, rat and rabbit small intestines.

A heterologous gene expression system, Xenopus laevis oocytes, was used to prove the intestinal absorption of various beta-lactam antibiotics mediated by an H(+)-dipeptide cotransport system in rat, rabbit and human small intestines. The microinjection of mRNA (messenger RNA) from rat intestine into Xenopus laevis oocytes led to significantly higher uptakes of p.o. active cephalosporins including zwitter-ionic derivatives (cephalexin, cephradine and cefadroxil) and dianionic derivatives (cefixime and ceftibuten) in comparison with oocytes injected with water, whereas the uptake of cefazolin, a parenterally administered derivative, was negligible in both mRNA- and water-injected oocytes. The uptake of cefadroxil was reduced significantly in the presence of dipeptide and various beta-lactam antibiotics, but not in the presence of an amino acid. After sucrose density gradient centrifugation of mRNA, the highest expression of transport activities of both cefadroxil and ceftibuten was observed in the same mRNA fraction with a size of 2.20 to 3.75 kilobases. mRNA-injected oocytes showed a marked pH-dependency in the uptakes of cefadroxil and ceftibuten, whereas water-injected oocytes exhibited only modes uptakes. The most stimulated uptakes of cefadroxil and ceftibuten were observed at an external pH of 5.5 and 5.0, respectively. Furthermore, injection of mRNA isolated from either rat rabbit or human small intestine into oocytes produced significantly higher uptake of cefadroxil and ceftibuten compared with those by oocytes injected with water. Thus, intestinal absorption of p.o. active beta-lactam antibiotics was confirmed to be mediated by an H+ gradient-dependent transport system across the brush-border membrane of rats, rabbits and humans. The carrier-protein for this process is likely a dipeptide transport system.

Animals↗

Expression cloning of a cDNA from rabbit small intestine related to proton-coupled transport of peptides, beta-lactam antibiotics and ACE-inhibitors.

Injection of poly(A)+ RNA from rabbit small intestine into Xenopus laevis oocytes resulted in expression of pH dependent transport of the aminocephalosporin cefadroxil. A cDNA library constructed from a 2.2 to 5 kb fraction was screened for expression of cefadroxil transport after injection of the corresponding cRNA synthetized in vitro from different pools of clones. The single clone identified stimulated uptake of cefadroxil into oocytes about 50-fold at pH 6.5. Kinetic analysis of expressed transport activity revealed a saturable transport system shared by amino beta-lactam antibiotics, dipeptides and selected angiotensin converting enzyme inhibitors. Evidence for rheogenic cefadroxil/H(+)-cotransport was obtained by a) The demonstration that cefadroxil influx increased the inward current in oocytes clamped at a holding potential of -60 mV in sodium-free medium and b) A decrease of intracellular pH in oocytes caused by cefadroxil uptake. Current-voltage relationships in the presence of glycylsarcosine or cefadroxil showed that transport activity is dependent on the membrane potential. Sequencing of the cDNA revealed its identity with the recently cloned peptide transporter from rabbit small intestine designated PepT1.

Angiotensin-Converting Enzyme Inhibitors↗

Cross-reactivity between a penicillin and a cephalosporin with the same side chain.

BACKGROUND: The cross-reactivity between penicillins and cephalosporins can be influenced by different factors, which are not all well known. The chemical structure of the side chain may contribute to the cross-reactivity. OBJECTIVE: The study was carried out in allergic subjects who are selectively responsive to amoxicillin to determine allergenic cross-reactivity with a cephalosporin containing a side chain identical to that of amoxicillin, cefadroxil, and one containing a different side chain, cefamandole. METHODS: Allergic subjects with a selective response to amoxicillin were chosen according to the following criteria: history of an immediate allergic reaction to amoxicillin, negative skin test responses to benzylpenicilloyl and minor determinant mixture of benzylpenicillin, negative RAST response to benzylpenicilloyl, and good tolerance to benzylpenicillin and phenoxymethyl penicillin challenges. In addition, subjects had to have a positive skin test response to amoxicillin and/or positive RAST response to amoxicilloyl or, if these test results were negative, a positive challenge test response to amoxicillin. In vivo cross-reactivity to cefadroxil was assessed by giving oral cefadroxil at increasing doses from 5 to 500 mg. In vitro cross-reactivity was determined by RAST inhibition studies with amoxicilloyl RAST disks and the following monomeric conjugates in the fluid phase: amoxicillin-butylamine, cefadroxil-butylamine, and the side chain para-hydroxy-phenylglycine. Tolerance to cefamandole was determined by giving 100 mg and then 500 mg parenterally. RESULTS: Twenty-one patients with a selective response to amoxicillin were included in the study. Eight subjects (38%) had a positive response to cefadroxil, and none reacted to cefamandole. In vitro RAST inhibition studies indicated that cefadroxil-butylamine monomers cross-reacted with amoxicillin butylamine and the side chain contributed relevantly to the inhibition. CONCLUSIONS: These results indicate that the percentage of cross-reactivity between penicillins and cephalosporins with an identical side chain is high and that this critical part of the molecule seems to be an important contributor to these results. The value is higher than previously reported data from similar studies of non-side-chain-related cephalosporins.

Adolescent↗

Target size analysis of the peptide/H(+)-symporter in kidney brush-border membranes.

The apparent functional molecular mass of the kidney peptide/H(+)-symporter was determined by radiation inactivation in brush-border membrane vesicles (BBMV) of rat kidney cortex. Purified BBMV were irradiated at low temperatures with high energy electrons generated by a 10-MeV linear accelerator at doses from 0 to 30 megarads. Uptake studies were performed with [3H]cefadroxil, a beta-lactam antibiotic which serves as a substrate for the kidney peptide/H(+)-symporter. Inhibition of influx of [3H]cefadroxil into BBMV was used to determine the functional molecular mass of the transporter. Additionally, direct photoaffinity labeling of the transport- and/or binding proteins for [3H]cefadroxil in control and irradiated BBMV was performed to determine the molecular mass of the putative transporter by SDS-polyacrylamide gel electrophoresis. Initial rates of pH-gradient dependent uptake of [3H]cefadroxil decreased progressively as a function of radiation dose. The apparent radiation inactivation size (RIS) of the transport function was found to be 414 +/- 16 kDa. Direct photoaffinity labeling yielded labeled membrane proteins with apparent molecular masses of 130 kDa and 105 kDa, respectively. The proteins displayed different labeling characteristics with respect to incubation time, specificity and the response to irradiation. It appears that only a 105 kDa protein is directly involved in transport function since (a) only it showed a specific pH gradient dependent labeling pattern and (b) the covalent incorporation of [3H]cefadroxil into this protein decreased parallel to the loss of transport function in irradiated BBMV. The peptide/H(+)-symporter in kidney brush-border membranes therefore appears to have a monomer mass of 105 kDa and may function in an oligomeric arrangement.

Affinity Labels↗

An audit of first generation cephalosporin usage.

Cefadroxil is a semi-synthetic first generation oral cephalosporin with advantages of almost 100% excretion in the urine within six hours and low cost. It was freely available in the formulary and we undertook an audit of its usage, the indications cited, underlying clinical conditions and relevant microbiology in 106 cases. Following the audit, cefadroxil was restricted, available only on the advice of a microbiologist. Subsequently, another survey was carried out to document the reasons for requesting cefadroxil by clinical staff and the alternatives suggested in each case. The first survey revealed that in 91% cases, cefadroxil had been used inappropriately. The second suggested that the reasons for requesting it were based upon misunderstanding by clinicians as to its value. The only useful indication identified was the treatment of susceptible bacteruria in pregnancy. A suitable oral alternative could be identified for all other cases where an antibiotic was indicated. We believe that first generation cephalosporins such as cefadroxil have little role in hospital practice and should therefore be restricted.

Bacterial Infections↗

[Effect of cephalosporins on lymphocyte proliferation and immunoglobulin E production].

We studied the effects of three cephalosporins (cefadroxil, cefaclor, cephalexin) on an in vitro model of human mononuclear cell proliferation in response to polyclonal mitogens. Cefadroxil, and to a lesser extent cefaclor and cephalexin, induced a decrease of proliferative responses to phytohaemagglutinin and concanavalin A. This decrease was not due to a direct effect on lymphocytes, but depended on the presence of adherent monocytes in the cultures. Cephalosporins stimulated the release of prostaglandins E2 by monocytes, generating a suppressive activity. Cefadroxil and cephalexin were in vivo given to Brown-Norway rats sensitized to DNP-OVA to induce a primary and secondary IgE specific response. The administration of cefadroxil provoked a clear decrease of the secondary IgE response. As the IgE production closely depends on T suppressor cells, we hypothesize that cefadroxil could interfere with that production by stimulating a suppressor cell activity linked to an increased PGE2-release.

Animals↗

Transport characteristics of differently charged cephalosporin antibiotics in oocytes expressing the cloned intestinal peptide transporter PepT1 and in human intestinal Caco-2 cells.

To investigate whether multiple peptide transporters mediate absorption of beta-lactams carrying different charges at physiological pH, we used the human intestinal cell line Caco-2 and Xenopus laevis oocytes expressing the cloned rabbit intestinal peptide transporter PepT1. Characteristics of transport of the anionic cefixime and the zwitterionic cefadroxil were assessed by 1) flux studies using radiolabeled compounds, by 2) measuring changes in pHin in cells and oocytes as a consequence of substrate-mediated proton influx and 3) by applying the two-electrode voltage clamp technique to assess the electrophysiological phenomena associated with beta-lactam transport in oocytes expressing PepT1. Both beta-lactams were rapidly taken up into Caco-2 cells and oocytes expressing PepT1 by a pH-dependent and saturable transport pathway. Mutual inhibition suggested that acidic and zwitterionic compounds may share a common transporter. Cefixime and cefadroxil caused a significant decline in intracellular pH as a consequence of proton coupled substrate influx. Uptake of cefixime and cefadroxil via PepT1 expressed in oocytes was electrogenic indicating that transport of both beta-lactams is associated with movement of net positive charge. The more acidic pH required for rheogenic cefixime uptake in both cell systems, when compared to cefadroxil uptake in both cell systems, when compared to cefadroxil uptake, and the concomitant faster intracellular acidification indicates that cefixime most likely is taken up only in its nonionized form with an additional proton being cotransported. This is supported by the observation that cefixime uptake at different pH correlated significantly with the percentage of the nonionized species being present. From our studies we conclude that a single peptide transport system can mediate electrogenic uptake of the neutral form of beta-lactam antibiotics into intestinal epithelial cells.

Animals↗