Double-blind Trial to Compare Ampicillin,Cephalexin, Co-trimoxazole,and Trimethoprim in Treatment of Urinary Infection

In order to test their value in urinary infection a double-blind trial was carried out using ampicillin, cephalexin, trimethoprim-sulphamethoxazole (co-trimoxazole), and trimethoprim. Eighty-three courses of treatment were given to hospital patients, 149 to pregnant women, and 107 to patients with dysuria and frequency seen in domiciliary practice. Thus infections of varying severity in defined groups of patients caused by organisms with different antibiotic sensitivities were treated.Analysis of the overall results (339 courses) was compared with those from the individual groups and considerable variation in response was found. In domiciliary infections and bacteriuria in pregnancy trimethoprim alone proved to be at least as effective as the other three compounds and caused fewer than half the number of side effects. In the hospital patients co-trimoxazole was superior to trimethoprim.The overall results for ampicillin and cephalexin were similar although cephalexin proved to be inferior in treating symptomatic domiciliary infections.     

Electron microscopic study of the combined action of ampicillin and cephalexin on E. coli]

The data of electron microscopy study of morphological variation of E. coli, strain 423 in the logarithmic phase after exposure to ampicillin (2 gamma/ml) and cephalexin (4 gamma/ml) are presented. Pronounced ultrastructural changes not only in the cell wall but also in the cytoplasm were found. After exposure to ampicillin alone changes of the same type were observed. However, after exposure to the combination of the 2 antibiotics these changes were more pronounced and observed in the predominating part of the cells. Examination of ultrathin slices of the strain treated with cephalexin revealed no ultrastructural changes. The morphological changes in the cells of E. coli, strain 423 after its treatment with ampicillin and cephalexin combination were due mainly to ampicillin effect, while cephalexin increased the level of the changes.     

Comparison of Cephalexin, Penicillin V, and Ampicillin in Streptococcal Infections in Monkeys

Intravenous inoculation of a group A hemolytic streptococcus caused lethal infections in all of 11 untreated monkeys. Daily intragastric administration of either 25 or 50 mg per kg per day, given in two equal morning and afternoon doses, yielded similar results in monkeys treated with cephalexin, penicillin V, and ampicillin; all eight monkeys in each therapy group survived. At dose levels of 12.5 mg per kg per day, six of eight, four of eight, and one of eight receiving cephalexin, penicillin V, and ampicillin, respectively, died. The differences observed at the lower dose level between cephalexin and ampicillin could be attributed, in part, to differences in the minimal inhibitory concentrations (MIC) of cephalexin (MIC = 0.24 mug/ml) and ampicillin (MIC = 0.01 mug/ml). The differences in results between penicillin V, which had the same MIC as ampicillin, could perhaps be attributed, in part, to shorter duration of antibacterial activity and higher protein binding of penicillin V. These studies support previous observations that cephalexin at 25 to 50 mg/kg doses is effective in severe streptococcal sepsis in monkeys.     

In vitro transformation of ampicillin to cephalexin by free and immobilized cells ofStreptomyces sp.

In vitro transformation of ampicillin to cephalexin was studied using calcium alginate-immobilized and freeStreptomyces sp. strain DRS-1 packed in glass columns. Tris-HCl buffer containing ampicillin was continuously circulated through the columns for four cycles, each cycle (with fresh ampicillin) being continued for 5 h. The pattern of product formation was identical in both cases,i.e. in each cycle, after reaching a certain concentration, its formation did not increase. Product formation was always higher with immobilized cells. Conversion of ampicillin to cephalexin by the strain was affected by cell and substrate concentration.     

Search for Microorganisms Producing Cephalosporin Acylase and Enzymatic Synthesis of Cephalosporins

Microorganisms were tested for production of cephalosporin acylase. Some bacteria showed strong acylase activity for all of cephalexin, cephaloridine, cephalotin, penicillin G and ampicillin. Some showed a rather specific activity for cephalexin. Pseudomonas melanogenum KY 3987 showed specific activity only for cephalexin and ampicillin which contain a side chain of d-phenylglycine. Most of these acylase-producing bacteria had the ability to synthesize cephalexin and other cephalosporins from 7-aminocephem compounds and organic acid esters. Among them, Ktuyvera citrophila KY 7844 was one of the most promising organisms for enzymatic synthesis of cephalosporins. This organism had the ability to catalyze N-acylation of 7-aminocephem compound not only with α-amino acid ester, but also with such acid esters as 1-(1 H)-tetrazolylacetate methylester which has no α-amino group.     

Characterization ofStreptomyces sp. Strain DRS-1 and its ampicillin transformation product

Incubation of ampicillin with whole cells ofStreptomyces sp. DRS-1 resulted in accumulation of four compounds different from ampicillin. One of them was isolated, purified and partially characterized. On the basis of spectroscopic characteristics,R _F value and antibacterial activity the compound was identified as cephalexin. It could also be obtained from ampicillin by using crude protein extract of the strain.     

Antibiotics and the Oral Streptococci of Man

The effects of 3 antibiotics, phenoxymethylpenicillin, cephalexin and clindamycin on the normal oral streptococcal flora in the region of the gingival crevice were investigated because these organisms are able to cause subacute bacterial endocarditis. Secretion of these antibiotics into the oral cavity was also examined. Penicillin and clindamycin exerted marked effects on the normal oral streptococci, whereas cephalexin did not cause any obvious change in the total flora. Following penicillin therapy, streptococci resistant to 1.5 μg/ml penicillin were observed and these organisms could be detected at least 8 weeks after the last dose of the antibiotic. They probably arose by selection from the mixed flora. Following cephalexin therapy, a much lower proportion of streptococci resistant to 15 μg/ml was found. The proportion of resistant strains fluctuated appreciably, however, probably due to their transient nature. Streptococci resistant to 1 μg/ml clindamycin were not observed in 10 out of 11 treated subjects.
Penicillin and clindamycin could be detected in the pooled saliva and gingival fluid after administering single doses of 500 mg and 300 mg, respectively. The peak levels were obtained between half and 1 h. The concentration of penicillin dropped rapidly within 3 h but clindamycin could be detected at significant levels for at least 6 h. No cephalexin could be detected in the pooled saliva or gingival fluid after a 500 mg dose. The implications of these findings in the prevention of subacute bacterial endocarditis are discussed.     

Comparative double-blind study of cephalexin and co-trimoxazole in urinary tract infections.

Treatment with cephalexin 1 g twiec daily and cotrimoxazole 2 tablets twice daily was compared in a double-blind, randomised study of 100 women with urinary tract infections. CO-trimoxazole gave a significantly higher cure rate compared with cephalexin two and six weeks after the one-week course of treatment. The higher failure rate with cephalexin was not related to the age of the patient, presentation, pyelographic appearances, or type of organism in the initial infection. Among the failures all but one of the organisms were sensitive to cephalexin. With the dosage regimen and duration of treatment used in this study cotrimoxazole appears to be superior to cephalexin in the management of acute urinary infections.     

Purification and characterization of inducible cephalexin synthesizing enzyme in Gluconobacter oxydans

Cephalexin synthesizing enzyme (CSE) of Gluconobacter oxydans ATCC 9324 was purified up to about 940-fold at a yield of 12%. CSE biosynthesis in G. oxydans was found inducible in the presence of D-phenylglycine but not its substrate phenylglycine methyl ester. The purified enzyme was shown homogeneous on SDS-PAGE and exhibited a specific activity of 440 U per mg protein. The apparent molecular mass of the native enzyme was estimated to be 70 kDa over a Superdex 200 gel filtration column and 68 kDa on SDS-PAGE, indicating that the native enzyme is a monomer. Its isoelectric focusing point is 7.1, indicating a neutral character. The enzyme had maximal activity around pH 6.0 to 6.5, and this activity was thermally stable up to 40 degrees C. Synthesis of cephalexin from D-phenylglycine methyl ester and 7-amino-3-deacetoxycephalosporanic acid (7-ADCA) by the purified CSE was demonstrated. Its L-enantiomer was not accepted by CSE. Apart from cephalexin, ampicillin was also synthesized by the purified CSE from its acyl precursors and 6-aminopenicillanic acid (6-APA). Substrate specificity studies indicated that the enzyme required a free alpha amino group and an activated carboxyl group as a methyl ester of D-form phenylglycine. Interestingly, the purified enzyme did not catalyze hydrolysis of its products, e.g., cephalexin, cephradine, and ampicillin, in contrast to enzymes from other strains of Pseudomonadaceae.     

In vitro studies on bacterial colonization. The effects of beta-lactam antibiotics on the growth of Escherichia coli and Pseudomonas aeruginosa in mixed culture.

Many cases of Pseudomonas aeruginosa infection are considered to be secondary superinfections, resulting from bacterial colonization. Such cases of superinfection with P. aeruginosa developing after administration of cephalosporin or penicillin are offering serious clinical problems. To make a fundamental analysis of the development of such superinfections, attempts were made to compare the growth patterns of Escherichia coli and P. aeruginosa in pure and mixed cultures and to determine the effects of cephalothin, cefazolin, cephalexin, and ampicillin on the growth patterns. In mixed cultures, the growth of P. aeruginosa was markedly inhibited by E. coli. The higher the concentration of each of the cephalosporins and ampicillin added to the mixed culture, the smaller the population of E. coli sensitive to these agents. When the population of E. coli became smaller than that of P. aeruginosa, which is resistant to these agents, the latter was restored to the same population level as that in pure cultures. Experimental bacterial colonization, by which the predominant population of E. coli was replaced by that of P. aeruginosa in mixed culture, was brought about more efficiently with the cephalosporins than with ampicillin. This might be accounted for by the difference in minimal inhibitory concentration for P. aeruginosa between ampicillin and the other three agents.     

Ampicillin Dosage and Use of Prednisolone in Treatment of Pneumonia: Co-operative Controlled Trial

A controlled trial was carried out to investigate whether the rate of recovery from pneumonia treated with ampicillin is dose related. Sixty-three patients received 1 g ampicillin daily and 63 received 2 g ampicillin daily for seven or 14 days depending on the rate of response. Twenty patients in each of these groups received, in addition, 20 mg prednisolone daily for seven days. The treatment groups were comparable and the results of treatment were similar in the four groups. The only difference which was of statistical significance was that a larger proportion of patients receiving 1 g ampicillin daily became afebrile within one week. All the ampicillin rashes occurred in the patients receiving 2 g ampicillin daily with and without prednisolone. Ampicillin 1 g daily appears to be adequate dosage in the treatment of pneumonia, and the rate of recovery has not been shown to be accelerated by using 2 g. No deleterious effects were noted with additional prednisolone therapy and this appeared to increase the rate at which the patients became afebrile, although the figures were not statistically significant.     

Chloramphenicol Combined with Ampicillin in Treatment of Typhoid

Fifty out of 100 patients with typhoid fever, matched for age, stage of illness, and degree of fever, were treated with chloramphenicol and the other 50 were treated with chloramphenicol combined with ampicillin. The febrile period was shortened by up to 29% in patients treated with the combined drugs compared with those given only chloramphenicol. Moreover, no patient on combined therapy had a febrile relapse, whereas two relapses occurred among patients treated with chloramphenicol only. We conclude that chloramphenicol and ampicillin together are better than chloramphenicol alone in the treatment of typhoid fever.     

Expandase-like activity mediated cell-free conversion of ampicillin to cephalexin by Streptomyces sp. DRS I

Cell-free extracts of Streptomyces sp. DRS I converted ampicillin to cephalexin, presumably due to the activity of the enzyme, expandase. The extract was fractionated and characterized by colorimetric and chromatographic measurements coupled with disc-agar diffusion bioassay against an ampicillin-resistant, cephalexin-sensitive E. coli strain. Though expandase could not be identified, the presence of a hitherto unreported expandase in Streptomyces sp. DRS I is suggested.     

Site-saturation mutagenesis and three-dimensional modelling of ROB-1 define a substrate binding role of Ser130 in class A beta-lactamases.

Site-saturation mutagenesis was performed on the class A ROB-1 beta-lactamase at conserved Ser130, which is centrally located in the antibiotic binding site where it can participate in both protein-protein and protein-substrate hydrogen bonding. Mutation Thr130 gave a beta-lactamase hydrolysing penicillins and cephalosporins but which showed a 3-fold lower affinity (Km) for ampicillin and cephalexin, and a 30-fold lower hydrolytic (Vmax) activity for ampicillin. In contrast, the hydrolytic activity for cephalexin was similar to the wild-type for the Thr130 mutation. Mutation Gly130 gave a beta-lactamase hydrolysing only penicillins with an affinity and hydrolysis activity for these compounds approximately 15-fold lower than the wild-type, but no detectable activity against cephalosporins. Mutation Ala130 produced an enzyme capable of hydrolysing penicillins only at a low rate. Modelling the ROB-1 active site was done from the refined 2 A X-ray structure of the homologous Bacillus licheniformis beta-lactamase. Ampicillin and cephalexin were docked into the active site and were energy minimized with the CVFF empirical force field. Dockings were stable only when Ser70 was made anionic and Glu166 was made neutral. Interaction energies and distances were calculated for fully hydrated pre-acylation complexes with the Ser, Thr, Gly and Ala130 enzymes. The catalytic data from all mutations and the computed interactions from modelling confirmed that the Ser130 has a structural as well as a functional role in binding and hydrolysis of penicillins. This highly conserved residue also plays a substrate specificity role by hydrogen binding the carboxylic acid group of cephalosporins more tightly than penicillins.     

Resistance of Escherichia coli to penicillins. V. Physiological comparison of two isogenic strains, one with chromosomally and one with episomally mediated ampicillin resistance

Two essentially isogenic strains of Escherichia coli K-12 were compared: D31 had chromosomally and D1-R1 episomally mediated resistance to ampicillin. The two strains had the same ability to form colonies on ampicillin plates, but in other tests they were quite different. In serial dilution tests as well as in exponentially growing cultures, D1-R1 was far more resistant to ampicillin than was D31. The inoculum effect with D1-R1 was large and with D31 was rather small. On plates, D31 was more resistant to penicillin G than was D1-R1. The penicillinase activity of buffer suspended cells against dl-ampicillin was 15 times higher for D1-R1 than for D31, but the two strains showed about the same rate of hydrolysis of penicillin G. With dl-ampicillin as substrate, for D1-R1 the apparent K(m) was 1.7 x 10(-4)m, whereas D31 gave a slightly sigmoid curve with a half-saturation concentration of about 5 x 10(-3)m. No induction of penicillinase activity was found. When the growth rate was varied by a factor of four, the amount of penicillinase per cell mass was constant in both D1-R1 and D31, whereas in two wild-type strains the amounts of penicillinase increased with increasing growth rates. With exponentially growing D1-R1, ampicillin disappearance started within 3 min, but at low ampicillin concentrations the rate was less than 10% of the rate of hydrolysis by buffer-suspended cells. Before D31 started hydrolysis, there was a lag period that lasted at least one generation and depended on the concentration of ampicillin. After this lag period, the rate of hydrolysis was 10 times higher than that observed with buffer-suspended cells. These differences between growing and nongrowing cells indicate that both the chromosomally and the episomally mediated penicillinases are controlled by some products present in growing cells.     

Effects of low concentrations of ampicillin in feed on the intestinal Escherichia coli of chicks

Ampicillin in low concentrations (1.7 and 5 g t^-1) was incorporated in the feed given to 1-d-old chicks for 2 weeks. This was sufficient to select, in the intestinal contents, resistant Escherichia coli strains for which the minimum inhibitory concentration of ampicillin was > 100 μg ml^-1. Different clones of E. coli were identified by their biotype, pattern of resistance to antibacterial agents and plasmid profile (designated P-P types). The experiment was repeated twice and the average proportion of ampicillin-resistant P-P types among 72 isolates of E. coli from chicks given feed containing 0, 1.7 and 5 g ampicillin t^-1 were 10%, 31% and 46% respectively.     

The effect of chemical preparations on the biological properties of the intestinal lactobacilli in experimental animals

The oral administration of the therapeutic doses of tetracycline, pefloxacin, ampicillin, cephalexin, rifampicin, sisomicin to Wistar rats for 5 days was accompanied by a decrease in the total number of lactobacilli in feces and by changes of the species spectre of these microorganisms. In those rats species, never found in intact animals, could be revealed rather frequently. All antimicrobial preparations administered in this investigation induced a decrease in the proportion of antibiotic-sensitive cultures and led to the selection of strains having multiresistance and increased antagonistic activity with respect to Pseudomonas indicator strain. The possible relationship between the markers antibiotic resistance and antagonistic activity in lactobacilli is discussed.     

Treatment of subclinical mastitis in Damascus goats during lactation

This study was carried out to determine the efficacy of three treatment protocols for subclinical mastitis during lactation in Damascus goats. For this purpose intramammarian ampicillin dicloxacillin, intramuscular amoxycillin clavulonic acid and the combination of intramammarian ampicillin dicloxacillin and intramuscular amoxycillin clavulonic acid were used in goats with subclinical mastitis during lactation.The microbiological treatment rates in the intramammarian ampicillin dicloxacillin, intramuscular amoxycillin clavulonic acid and the combination of intramammarian ampicillin dicloxacillin and intramuscular amoxycillin clavulonic acid groups in the 7th and 21st days after the treatment were 62.5% and 92.5%, 62.5% and 70%, 87.5% and 87.5%, respectively. The intramammarian and intramuscular combination group was found to have a statistically higher treatment rate than other two groups on the 7th day. On the 21st day intramammarian and combination groups were found to have statistically better treatment rates than that of intramuscular group.It was concluded that the goat subclinical mastitis could be successfully treated during lactation. While the intramammarian ampicillin dicloxacillin treatment had the best treatment rates, the combination of intramuscular amoxycillin clavulonic acid was also successful. Intramuscular amoxycillin clavulonic acid as the sole treatment was not as effective as intramammarian therapy.     

Alteration of the catalytic efficiency of penicillin amidase from Escherichia coli

Ampicillin and cephalexin are beta-lactam antibiotics that are synthesized by the condensation of D-(-)-alpha-aminophenylacetic acid with 6-aminopenicillanic acid or 7-aminodeacetoxycephalosporanic acid, respectively. The rates at which the penicillin amidase of Escherichia coli catalyzes these reactions are too low to be of practical use. The objective of this study was to determine whether it is possible to alter the substrate specificity of penicillin amidase and select enzymes that efficiently hydrolyze substrates with alpha-aminophenylacetyl moieties at low pH, at which the alpha-amino group is nearly completely protonated. In this study, D-(-)-alpha-aminophenylacetyl-(L)-leucine (APAL) was used as a substrate analog of ampicillin and cephalexin. The gene for the penicillin amidase of E. coli ATCC 11105 was cloned and transferred to a leucine auxotroph of E. coli; numerous amidase mutants were selected by their ability to cleave APAL and provide leucine for growth in low-pH medium. The plasmid encoding one of the mutant amidases (pA135) was used to transform naive cells, and transformants that expressed the mutant amidase were shown to grow more rapidly in medium at pH 6.5 containing 0.1 mM APAL as the sole leucine source than did cells with the wild-type amidase. The mutant amidase was purified, and the second-order rate constant (kcat/Km) for APAL hydrolysis at pH 6.5 was found to be 10-fold greater than the rate observed with the wild-type enzyme. The difference between the rates of APAL hydrolysis by the mutant and wild-type amidases increased as the pH of the reactions decreased.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cα-Methyl phenylglycine-based semi-synthetic ampicillin and cephalexin analogues

Summary Reaction of the N-carboxyanhydride from C^α-methyld-phenylglycine with either 6-aminopenicillanic acid or 7-amino-3-desacetoxy-cephalosporanic acid furnishes the corresponding ampicillin and cephalexin analogues. Neither the biological activity nor the chemical stability of these new semi-synthetic antibiotics are superior to those of their unmethylated counterparts.