Amoxycillin and Ampicillin

In vitro antibacterial activities of ampicillin and amoxycillin were compared against pigmented and non-pigmented strains of Serratia marcescens. Ampicillin appeared more effective than amoxycillin; three-fourths of all strains consistently exhibited an ampicillin minimum inhibitory concentration (MIC) of at least one tube less than that recorded for amoxycillin. Complete cross resistance was not observed as has previously been inferred. Further, greater bactericidal activity was demonstrated with ampicillin; minimum bactericidal concentrations (MBC) were either the same as or one tube greater than the MIC. MBCs for amoxycillin, however, were significantly higher; often four to five times greater than the MIC. Ampicillin exhibited greater bactericidal activity as inferred from differences observed in the biological lesions induced, as recorded through observations by scanning electron microscopy (SEM). Spheroplasts were the predominant morphological alteration induced by ampicillin. In contrast, only filament formation, which demonstrated a degree of reversibility, was induced by amoxycillin.     

Amoxycillin: A new Semi-synthetic Penicillin

Amoxycillin (α-amino-p-hydroxybenzylpenicillin) is a new semi-synthetic penicillin with a broad spectrum of antibacterial activity similar to that of ampicillin. Penicillin-sensitive strains of staphylococci, streptococci, and pneumococci were sensitive to concentrations of 0·1 μg or less of amoxycillin/ml. Strains of Haemophilus influenzae were inhibited by a level of 0·5 μg/ml, and most strains of Escherichia coli, Proteus mirabilis, Shigella sonnei, Salmonella species, and Streptococcus faecalis were sensitive to a concentration of 5 μg or less of amoxycillin/ml. Penicillinase-producing strains of Staphylococcus aureus and strains of Pseudomonas aeruginosa, indole-positive Proteus, Klebsiella, and Enterobacter were insensitive to amoxycillin. The new penicillin was bactericidal in activity, as with other penicillins, and its antibacterial activity was not reduced in the presence of serum. After oral administration to volunteer subjects amoxycillin produced serum concentrations twice as high as those obtained with similar doses of ampicillin, and the penicillin was recovered unchanged in high concentrations in the urine. The absorption of amoxycillin was not greatly influenced by food, and administration of probenecid resulted in increased and more prolonged concentrations of amoxycillin in serum.     

Amoxycillin and co-trimoxazole in presumed viral respiratory infections of childhood: placebo-controlled trial.

A double-blind randomized controlled trial of amoxycillin, co-trimoxazole, and placebo was conducted on 197 children presenting with presumed viral respiratory infections. Routine throat swabs were taken to exclude streptococcal diseases. The three disease categories studied--nasopharyngitis, pharyngotonsillitis, and bronchitis (including laryngotracheobronchitis)--showed a generally similar pattern of resolution irrespective of treatment. Nevertheless, seven out of 66 children receiving placebo were withdrawn from the trial with unremitting symptoms or complications thought to require antimicrobial treatment. Only two of 56 children receiving amoxycillin and none of 75 receiving co-trimoxazole were withdrawn. Three other children receiving amoxycillin and three receiving placebo were seen during the trial but further treatment was not thought to be necessary. Thus the return consultation rate in children receiving placebo therapy was 15% compared with 4% for those receiving antimicrobial treatment. Antimicrobial treatment was associated with less nasal discharge on the eighth day of treatment. Placebo treatment allowed an earlier return to normal activity. There was a high incidence of possible side effects on all regimens including placebo. It is concluded that the benefits of antimicrobial treatment in presumed viral respiratory infections are marginal, and they should not be routinely prescribed for these conditions.     

Typhoid outbreak in Kingston,Ont: experience with high-dose oral ampicillin.

Twenty-four children contracted typhoid fever at a summer camp near Kingston, Ont. Six were treated with chloramphenicol alone and 15 with high doses of ampicillin (300 mg/kg-d) by mouth. Ampicillin in this dosage was well tolerated except in three children in whom severe urticarial rashes developed and two who had significant diarrhea. However, high-dose oral ampicillin therapy had no advantage over that with lower doses or over chloramphenicol as judged by the rate of defervescence after the start of treatment, the rate of clinical relapse and the frequency of excretion of Salmonella typhi during convalescence.     

Talampicillin: a new derivative of ampicillin.

Talampicillin is a thiazolide carboxylic ester of ampicillin and is hydrolysed in the intestinal mucosa to release free ampicillin. The mean peak serum concentration of ampicillin occurred one hour after a dose of talampicillin and was about twice that attained by an equivalent dose of ampicillin. The presence of food in the stomach reduced and delayed the peak blood levels but did not affect the total amount of antibiotic absorbed or the urinary recovery. Talampicillin had less effect on the faecal flora in volunteers than ampicillin, and no overgrowth with Candida spp or Staphylococcus aureus was seen. Thirty-eight out of 47 urinary infections were eradicated by a seven-day course of talampicillin.     

Transformation of Coxiella burnetii to ampicillin resistance.

A 5.8-kb chromosomal fragment isolated from Coxiella burnetii initiates plasmid replication in Escherichia coli and was characterized as an autonomous replication sequence, ars (M. Suhan, S.-Y. Chen, H.A. Thompson, T.A. Hoover, A. Hill, and J.C. Williams, J. Bacteriol. 176:5233-5243, 1994). In the present study, an ars replicon was used to transform C. burnetii to ampicillin resistance. Plasmid pSKO(+)1000 contained the C. burnetii ars sequence cloned into a ColE1-type replicon encoding beta-lactamase. pSKO(+)1000 was introduced into C. burnetii by electroporation. Ampicillin-resistant cells were selected, and survivors were examined for the transformed genotype by Southern hybridization. Transformants stably maintained the pSKO(+)1000 bla DNA sequence in the chromosome as a result of homologous recombination. The recombination event resulted in the duplication of the 5.8-kb ars sequence in the C. burnetii chromosome. The bla gene was also located in an episome. However, an ampicillin resistance plasmid lacking the C. burnetii ars sequence did not stably transform C. burnetii. A biological assay analyzing beta-lactamase activity of C. burnetii transformants during acid activation in vitro provided evidence for expression of the bla (beta-lactamase) gene.