Minimum Inhibitory Concentration Of Ampicillin Research Articles

Comparison of Escherichia coli from Bacteriuric Patients with Those from Feces of Healthy Schoolchildren

The properties of 709 strains of Escherichia coli isolated from feces of healthy schoolchildren were compared with those of 115 strains from the urine of girls with asymptomatic bacteriuria (ABU) detected in a screening program. These fecal strains were also compared with 45 strains that caused asymptomatic reinfections and 10 that caused symptomatic reinfections in the same group of girls. Typing of O antigen was done by direct bacterial agglutination, and K typing was done with a serum agar technique. Hemolytic capacity was assessed in solid medium. Sensitivity to the bactericidal effect of normal serum and minimal inhibitory concentrations of ampicillin were also determined. The strains isolated from girls who had reinfections of ABU were found to be a random sample of the fecal flora, but the strains from children with symptomatic reinfection were not. Strains from index patients with ABU differed from the other groups in a way that was indicative of adaptive changes in the structure of cell envelopes.

Expression of R-plasmid functions during anaerobic growth of an Escherichia coli K-12 host

The normal habitat of enteric bacteria is largely anaerobic. Expression of the three characteristic properties of R-plasmids, drug resistance, vegetative replication, and fertility, was therefore studied in Escherichia coli K-12 during anaerobiosis. Replication and drug resistance functions were not altered in the 45 R-plasmids studies, whereas the expression of fertility varied considerably among different R-plasmids during anaerobiosis. The R-plasmids could be divided into three groups, one showing a strong, the second a moderate, and the third little or no reduction of fertility by anaerobiosis. Plasmid-determined sensitivity to F-, N-, and I-specific phage, respectively, was well, although not absolutely, correlated with each of three groups mentioned. Anaerobiosis-aerobiosis appears to change the fertility of type F R-plasmids by influencing the degree of repression of their fertility functions such as the formation of sex pili. Although the minimum inhibitory concentrations of ampicillin, chloramphenicol, streptomycin, and tetracycline were unaltered by anaerobiosis, sulfonamide was found to be four- to eightfold less active under this condition in both resistant and sensitive strains. A surprisingly high frequency and uniformity of minimal inhibitory concentrations was observed for R-plasmid-mediated resistance to streptomycin and chloramphenicol.

Clavulanic acid: a beta-lactamase-inhiting beta-lactam from Streptomyces clavuligerus.

A novel beta-lactamase inhibitor has been isolated from Streptomyces clavuligerus ATCC 27064 and given the name clavulanic acid. Conditions for the cultivation of the organism and detection and isolation of clavulanic acid are described. This compound resembles the nucleus of a penicillin but differs in having no acylamino side chain, having oxygen instead of sulfur, and containing a beta-hydroxyethylidine substituent in the oxazolidine ring. Clavulanic acid is a potent inhibitor of many beta-lactamases, including those found in Escherichia coli (plasmid mediated), Klebsiella aerogenes, Proteus mirabilis, and Staphylococcus aureus, the inhibition being of a progressive type. The cephalosporinase type of beta-lactamase found in Pseudomonas aeruginosa and Enterobacter cloacae P99 and the chromosomally mediated beta-lactamase of E. coli are less well inhibited. The minimum inhibitory concentrations of ampicillin and cephaloridine against beta-lactamase-producing, penicillin-resistant strains of S. aureus, K. aerogenes, P. mirabilis, and E. coli have been shown to be considerably reduced by the addition of low concentrations of clavulanic acid.

Antibiotics and the Aberdeen typhoid outbreak in 1964

This paper gives an abbreviated account of part of a research programme which followed the Aberdeen typhoid outbreak in 1964. Chloramphenicol, the main antibiotic used in treatment, was shown to have a minimum inhibitory concentration (MIC) of between 5 and 2-5 mug./ml. for the S. typhi phage type 34 of the outbreak. The MIC for methacycline was between 5 and 2-5 and 2 mug./ml. Whereas the deep and shallow broth techniques used gave similar results with these antibiotics, the MIC for ampicillin, and also cephaloridine, was less in the deep than in the shallow broths. Serum assays in patients given ampicillin or cephaloridine yielded abnormally high concentrations of both antiboitics when S. typhi phage type 34 was the test organism whereas, with other test organisms, the concentrations were within expectation. These abnormally high values fell within expected values when the sera under investigation had first been heated to 56 degrees C. for 30 min. before assay against the S. typhi of the outbreak. The findings with ampicillin suggested that dosages given were satisfactory. With cephaloridine the concentrations found in patients' sera seemed to show that twice daily doses of 0-5 g. fell short of adequacy.

養殖ハマチの類結節症に対するアンピシリンの水産薬としての応用 Ｉ 類結節症菌に対する?Eｉｎ ｖｉｔｒｏ?Fでの抗菌力，耐性獲得および耐性消失

Studies are being made to apply ampicillin for pseudotuberculosis of cultured yellowtails. In vitro sensitivity and development of drug-resistance characteristics of Pasteurella piscicida were examined. Chloramphenicol was used for comparison. The minimum inhibitory concentration of ampicillin to P. piscicida was 0.04 to 0.08 mcg/ml and the MIC of chloramphenicol was 0.63 mcg/ml. Antibacterial activity of ampicillin was 8 to 16 times greater than the activity of chloramphenicol. After 10 serial passages in vitro under the presence of drug, MIC values to ampicillin and to chloramphenicol were 4 to 8 times greater than the initial values. Reversion of acquired drug-resistance features to ampicillin also was studied. After 5 serial passages in vitro in BHI agar under the absence of the drug, the acquired drug-resistance characteristics of P. piscicida disappeared, i.e., MIC changing from 0.32 mcg/ml to 0.04-0.08 cmg/ml. Results of the study suggest that ampicillin is an useful antibacterial drug for pseudotuberculosis of cultured yellowtails.

Mechanisms of ampicillin resistance in Haemophilus influenzae type B.

The genetic mechanisms associated with ampicillin resistance in strains of Haemophilus influenzae type b were investigated. In experiments concerned with transfer of total deoxyribonucleic acid in vitro, expression of resistance by wild-type strains occurred at a frequency of about 10%. The minimum inhibitory concentration of ampicillin for the transformed strains was similar to that of the resistant donor strains, and resistance in transformants was associated with acquisition of the ability to produce beta-lactamase. Exposure to 39 mug of acridine per ml for 18 h cured resistance at a frequency of 80%, and there was spontaneous loss of resistance after repeated subculture of some strains. Analysis by cesium chloride-ethidium bromide density gradient centrifugation demonstrated the presence of extrachromosomal deoxyribonucleic acid in the resistant strains, providing further evidence that the resistance factor is plasmid mediated.

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. MBC's 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.

Antimicrobial Susceptibility of Haemophilus influenzae

Selected clinical isolates of Haemophilus influenzae were tested for their susceptibility to seven antibiotics by a microtiter broth dilution and an agar diffusion method. Eleven of 40 strains tested were resistant to ampicillin, the drug of choice, by both methods. All the strains tested were susceptible to chloramphenicol, and all but one were susceptible to tetracycline. Of the other four antibiotics tested, the ranges of minimal inhibitory concentrations (MICs) were: 0.5 to 4 mug of gentamicin per ml, 0.5 to 4 mug of erythromycin per ml, and 2 to 16 mug of clindamycin per ml. MICs of ampicillin for both the susceptible and resistant strains were markedly affected by inoculum concentration. The ampicillin MICs of the resistant strains were also affected by the time of incubation.

Susceptibility of pathogenic actinomycetes to antimicrobial compounds.

Current interest in antimicrobial susceptibility testing of anaerobic pathogens and recent recognition that actinomycetes other than Actinomyces israelii may cause actinomycosis in man prompted this in vitro survey of 74 strains of actinomycetes, representing seven species. Minimum inhibitory concentrations (MICs) for 24 antimicrobials were determined by inhibition of gross colonial enlargement in semisolid antibiotic agar after incubation at 37 C for 48 h under anaerobic conditions. Erythromycin and rifampin were the most active drugs in vitro (MICs of 0.008 to 0.25 mug/ml), although a small number of non-israelii strains were conspicuously more resistant to the latter (MICs >0.5 mug/ml). Penicillin G, cephaloridine, minocycline, and clindamycin were also very active in vitro (MICs of 0.03 to 1.0 mug/ml); for a few non-israelii strains the MICs of clindamycin were 2.0 to 8.0 mug/ml. MICs of cephalothin, ampicillin, lincomycin, tetracycline, doxycycline, and chloramphenicol were well within a therapeutic range for all strains of A. israelii and most other species, although the MIC of lincomycin against a few non-israelii strains and of tetracycline and doxycycline against the majority of these strains was 2.0 to 8.0 mug/ml. Oxacillin, dicloxacillin, and cephalexin were less active in vitro, particularly against strains other than A. israelii. Most non-israelii species were not suppressed by 125 mug of metronidazole per ml, which concentration inhibited all strains of A. israelii; otherwise, there were no antimicrobial susceptibility differences among the species tested. Aminoglycoside activity was negligible.

Ampicillin resistance in Escherichia coli by phage infection.

BACTERIAL genes may become incorporated in the genome of phages and, as a consequence, are transmitted from one bacterium to another during lysogenization. Antibiotic resistance genes can be incorporated2,3 and a naturally-occurring example—the phage concerned possessing genes for resistance to ampicillin—is described here. The phage lyso-genized a non-pathogenic strain of Escherichia coli (strain H) obtained from the faeces of a healthy human being who had never been treated with ampicillin. The minimum inhibitory concentration of ampicillin for this strain is 250 µg/ml.; it produced β-lactamase4.

Combined effects of ampicillin and methiciillin on cell wall morphology of a methicillin-resistant Staphylococcus.

Some semi-synthetic penicillins and cephalosporins are resistant to hydrolysis by beta-latamases. Hence, penicillin-resistant staphylococci exhibiting beta-lactamase activity become susceptible to these beta-lactam antibiotics. Methicillin (2, 6-dimethoxyphenyl penicillin) in combination with ampicillin (D(-)-alpha-aminobenzyl penicillin) showed either a synergistic (14 strains) or an additive (3 strains) effect (never antagonistic), against 17 methicillin-resistant staphylococcal strains. One of these strains did not produce beta-lactamase. This strain No. 667 grew well in broth containing either 50 mcg/ml of methicillin or half the minimum inhibitory concentration of ampicillin which indicated that inhibition of cell wall synthesis was not apparent. However, ampicillin in combination with methicillin, using half of the above concentrations, exhibited synergism* against the strain 667. In the presence of sub-lethal doses of either ampicillin or methicillin, Escherichia coli became thread-like, while spheroplasts of E. coli were formed under similar conditions when these 2 beta-lactam antibiotics were combined. Since methicillin has no inhibitory action on strain 667, it can be concluded that the inhibition of growth by the combined penicillin might be due to a change in mechanism or site of action (or change of pathways). This is more suggestive as (a) the staphylococcal strain 667 did not produce any beta-lactamase and (b) spheroplasts of E. coli were formed only when the 2 penicillins were combined.

Synergistic antibacterial activity of ampicillin-cloxacillin mixtures against Proteus morganii.

Synergistic antibacterial effects of mixtures of ampicillin and cloxacillin and induced penicillinases were investigated in 48 strains of Proteus. The serial tube dilution method was used to determine the minimal inhibitory concentration of ampicillin, cloxacillin, and 2:1 and 1:1 mixtures of ampicillin and cloxacillin. Production of penicillinases was determined by the cellulose acetate membrane method, with ampicillin, cloxacillin, mixtures of ampicillin and cloxacillin, penicillin G, and cephalothin as inducing agents and as substrates for penicillinase. Synergism occurred against P. morganii, but against no other species. The 1:1 ampicillin-cloxacillin combination was synergistic against 13 of 17 P. morganii strains; the 2:1 combination was synergistic against only 9 strains. Penicillinases, demonstrated in all species except P. mirabilis, hydrolyzed penicillin G and cephalothin. Although only P. vulgaris hydrolyzed ampicillin, no species of Proteus hydrolyzed cloxacillin or the ampicillin-cloxacillin mixtures. Penicillinases were, however, induced by ampicillin, cloxacillin, and the mixtures. There was no relationship between production of penicillinase and synergism with mixtures of ampicillin and cloxacillin.

Synergistic Antibacterial Activity of Ampicillin-Cloxacillin Mixtures Against Proteus morganii

Synergistic antibacterial effects of mixtures of ampicillin and cloxacillin and induced penicillinases were investigated in 48 strains of Proteus. The serial tube dilution method was used to determine the minimal inhibitory concentration of ampicillin, cloxacillin, and 2:1 and 1:1 mixtures of ampicillin and cloxacillin. Production of penicillinases was determined by the cellulose acetate membrane method, with ampicillin, cloxacillin, mixtures of ampicillin and cloxacillin, penicillin G, and cephalothin as inducing agents and as substrates for penicillinase. Synergism occurred against P. morganii, but against no other species. The 1:1 ampicillin-cloxacillin combination was synergistic against 13 of 17 P. morganii strains; the 2:1 combination was synergistic against only 9 strains. Penicillinases, demonstrated in all species except P. mirabilis, hydrolyzed penicillin G and cephalothin. Although only P. vulgaris hydrolyzed ampicillin, no species of Proteus hydrolyzed cloxacillin or the ampicillin-cloxacillin mixtures. Penicillinases were, however, induced by ampicillin, cloxacillin, and the mixtures. There was no relationship between production of penicillinase and synergism with mixtures of ampicillin and cloxacillin.

Susceptibility of Bordetella pertussis to ampicillin

Plate dilution susceptibility studies of 24 strains of Bordetella pertussis and twostrains of B. parapertussis demonstrate low minimal inhibitory concentrations of ampicillin. These data and the results of treatment of one patient indicate that further clinical experience with ampicillin therapy of pertussis would be worthwhile.