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J S Pitton

Publications and source records attributed to J S Pitton.

At least 19 recordsLinked to original sources
PubMed1991

[Evaluation of an automated system in bacteriology. Application to bacteriological susceptibility tests].

Susceptibility tests have been compared between a new automated system and the reference method by agar diffusion. The COBAS-Micro apparatus for bacterial susceptibility tests is intended for rapid determinations with, normally, an incubation time of 5 h at 37 degrees C. Its is compatible with strains requiring greater than 18 h incubation. With this technique a large range of antibacterial substances (greater than 60) can be studied, in groups of fifteen. With the help of a computerized soft-ware, one growth-index:EPR (End Point Ratio) is calculated, in comparison with a standard, for each antibacterial agent tested and expressed in three categories: SIR. The findings are optimized according to the limits prescribed by the NCCLS. The reference method, by agar-diffusion, is as described by the Comité de l'Antibiogramme de la Société Française de Microbiologie (CA-SFM). A total of 1,048 strains were tested by the two techniques: 518 Gram negative rods, 530 Gram positive cocci, with four common antibiotics. The percentages of agreement between the two groups were: 96% full agreement and minor discrepancy, 4% major and very major discrepancy. This automated system seems to be perfectly suitable for susceptibility testing in a routine laboratory, especially with strains isolated from ambulatory patients.

Anti-Bacterial Agents↗
PubMed1989

[Cervical infection caused by Chlamydia trachomatis at a family planning center: prevalence, analysis of risk factors, prediction model].

Chlamydia trachomatis (CT) was detected by culture in 111/600 patients aged 15 to 55; overall prevalence 18.5%, 17% among asymptomatic (52/306) and 20% (59/294) among symptomatic patients. The difference is not significant. Contraceptive practices have no significant influence upon CT prevalence, except for the obvious protective effect of barrier methods. From the history, the clinical and paraclinical findings, four factors (history of genital infection, partner with urogenital symptoms, ectopy, inflammatory changes on a smear) can be combined to produce an index for predicting CT cervical infection. Others factors (age, no pregnancies, mucopus from the cervical os, inflammatory or dysplasic Pap smear, and signs of upper genital tract infection) are indicators of presumption and can be useful to selectively screen asymptomatic or symptomatic patients.

Adolescent↗
PubMed1988

Kinetic properties of two plasmid-mediated beta-lactamases from Klebsiella pneumoniae with strong activity against third-generation cephalosporins.

We determined the kinetic constants for two plasmid-mediated beta-lactamases with strong activity against third-generation cephalosporins: CTX-1 and SHV-2. The enzymes had many similar properties: their synthesis was constitutive and they were significantly active against penicillins as well as cephalosporins. The two enzymes thus differed considerably from the chromosomal cephalosporinases, but bore some resemblance to the commonly-encountered plasmid-coded penicillinases, such as TEM beta-lactamases. Moreover, like the TEM enzymes, the plasmid-mediated CTX-1 and SHV-2 enzymes were highly sensitive to the action of the inhibitors clavulanic acid and sulbactam. These inhibitors protected cefotaxime from hydrolysis by these enzymes. Both CTX-1 and SHV-2 lacked activity against the cephamycins, cefoxitin, latamoxef (moxalactam) and cefotetan. The CTX-1 and SHV-2 enzymes had a low activity against oxacillin and were not sensitive to chloride ions. Thus, they were not related to the OXA type beta-lactamases. For the third-generation cephalosporins the rates of hydrolysis were high and thus bore no relation with those observed for the other presently-known beta-lactamases, with perhaps the exceptions of those produced by K. oxytoca. Imipenem was very resistant to the action of these CTX-1 and SHV-2 beta-lactamases.

Cephalosporins↗
PubMed1988

The kinetics of SHV-2 plasmid-mediated beta-lactamase compared to those of the parent enzyme from which it is derived.

Kinetic constants were determined for two closely related plasmid-mediated beta-lactamases: SHV-2 and PIT-2 (also known as SHV-1). These enzymes were synthesized constitutively. They were highly sensitive to the action of the inhibitors clavulanic acid and sulbactam, and they lacked activity against cephamycins and also imipenem. Both enzymes were significantly active against penicillins and first-generation cephalosporins, and the main difference concerned the third-generation cephalosporins: SHV-2 was highly active against these compounds whereas PIT-2 was not.

Anti-Bacterial Agents↗
PubMed1988

[Evaluation of a rapid diagnostic method in Chlamydia trachomatis infections].

This study is based on 526 female patients investigated by gynecologists in an ambulatory practice (G.P.'s). The samples originating from within the uterine neck have been analysed by one so-called "rapid" test (D.I.F.T.) and after culture in McCoy cells. Prevalence by culture is 20.5% and sensitivity is 96.5%, whereas prevalence is only 4.9% and sensitivity about 20.4% for D.I.F.T. For D.I.F.T.-test, the predictive positive value is 76.6%, when the predictive negative value is close to 82.8%. These results give the evidence that the inoculation of uro-genital specimens in cell-cultures still remains the gold standard method for detecting C. trachomatis infections.

Antibodies, Bacterial↗
PubMed1987

[Effects of beta-lactamases on the antibacterial activity of carumonam and aztreonam against Klebsiella sp. in comparison with 4 other beta-lactams].

Carumonam and aztreonam are two similar monocyclic beta lactam antibiotics. We have studied their antibacterial activities on Klebsiella, in comparison with cefotaxime, cefoxitin, cefotetan and imipenem. In the case of K. pneumoniae (53 strains) the antibacterial activities of the two monobactams are very similar. On the contrary, with K. oxytoca (22 strains) carumonam is significantly more active. This situation seems to be justified by an improved stability of carumonam to beta lactamases. In addition, the antibacterial activities of imipenem and of cephamycins remain quite constant within all the strains. Then the antibacterial activity of cefotaxime is fluctuant, which is in relation with a clear susceptibility to the Klebsiella beta lactamases.

Anti-Bacterial Agents↗
PubMed1986

[Klebsiella oxytoca beta-lactamases: study of their action on 3d-generation cephalosporins].

Indole-positive Klebsiella pneumoniae or K. oxytoca are usually resistant to penicillins as a result of the production of a chromosomally-mediated beta-lactamase with a low level of synthesis (specific activity approximately 50 to 100 mU/mg). Although most strains are susceptible to the majority of cephalosporins, some strains exhibit resistance to cephalosporins including third-generation drugs. These resistant strains produce a chromosomally-mediated beta-lactamase with a high level of synthesis (specific activity approximately 5,000 mU/mg or higher). Four beta-lactamases have been identified on the basis of their isoelectric points: pI = 5.5, 5.7, 6.0 and 6.3; nevertheless they have similar kinetic constants, and are inhibited by clavulanic acid. These enzymes hydrolyze most third-generation cephalosporins, in the following order of decreasing velocities: cefoperazone, ceftriaxone, cefotaxime, cefodizime, cefpirome; ceftazidime, and cefoxitin, cefotetan, latamoxef, cephamycins which are totally resistant to these enzymes.

Cephalosporins↗
PubMed1985

[Computerized analysis of activity profiles of beta-lactams].

This study was designed to compare the in vitro activities of recent cephalosporins and other beta-lactams. One of our objectives was to determine whether the microbiologist could use a single cephalosporin for routine antibiotic sensitivity testing. All the strains studied were recovered from outpatients. Sensitivity and/or resistance were evaluated by MIC determination, according to a program developed in our laboratory, using a personal computer. Using special programs, patterns of activities of beta-lactams were determined quantitatively and graphically for each bacterial strain tested. For most strains ceftriaxone, and to a lesser extent moxalactam and cefoperazone, exhibited greater antibacterial activity than the other beta-lactams, except against group D streptococci. For Enterobacteriaceae, cefadroxil is satisfactory in screening for in vitro activity of cephalosporins.

Anti-Bacterial Agents↗
PubMed1982

[Multicenter study on the status of antibiotic and chemotherapy resistance in Switzerland 1979].

In 1979 a three-month multicentre study of resistance of bacteria isolated from humans and animals was carried out in Switzerland with the participation of 22 institutes and laboratories. A total of 23,852 antibiograms were evaluated concerning the following bacteria: Escherichia coi, Klebsiella pneumoniae, Salmonella sp., Serratia marcescens, Proteus (indole-negative), Proteus (indole-positive), Pseudomonas aeruginosa, Staphylococcus aureus, and enterococci (streptococci of Group D). 95.5% of the strains were isolated from human material, almost half being isolated from urine. The remaining 4.5% were obtained from animal material, more than half being isolated from the milk of cows with mastitis. Although the various institutes and laboratories did not use a uniform, standardized method, the results are closely in line with those of similar studies carried out earlier in Switzerland, Germany, Austria and the USA. No pronounced trend in the direction of increased resistance is observable.

Animals↗
PubMed1978

[Epidemiology of resistance factors to antibiotics].

Resistance factors are small independent extrachromosomal DNA molecules (plasmids) conferring resistance on one or more antibiotics to the bacteria which harbour them; in Enterobacteriaceae and other gramnegative bacteria they are transferable by conjugation. The work is reviewed which has been undertaken to underline the importance of the R factors in nature, and more precisely in the current environment of the intestinal bacteria (animal and human gut, sewage) under the selective pressure of antibiotics or otherwise.

Adult↗
PubMed1974

R factor-mediated and chromosomal resistance to ampicillin in Escherichia coli.

Sixty-four ampicillin-resistant strains of Escherichia coli were studied. Six characters were examined: (i) resistance to ampicillin, cephalothin, and carbenicillin, (ii) synergy between ampicillin and cloxacillin, (iii) level of beta-lactamase activity after osmotic shock, (iv) transferability of ampicillin resistance, (v) immunological characterization of the enzyme, and (vi) determination of substrate profiles. One class of strains was found in which synthesis of beta-lactamase is inferred to be plasmid mediated; these strains are highly resistant to ampicillin and carbenicillin, sensitive to cephalothin, do not show synergism between ampicillin and cloxacillin, and reveal a high enzymatic activity after osmotic shock. A second class is formed by strains for which beta-lactamase synthesis is inferred to be chromosomal; these strains present a low resistance level to ampicillin, are sensitive to carbenicillin and resistant to cephalothin, show a synergism between ampicillin and cloxacillin, and reveal a very low enzymatic activity after osmotic shock. These characters may be used to differentiate periplasmic and cell-bound beta-lactamases.

Ampicillin↗