Biomedical subjects

P Chatron

Publications and source records attributed to P Chatron.

4 recordsLinked to original sources

PubMed1997

Novel extended-spectrum TEM-type beta-lactamase from an Escherichia coli isolate resistant to ceftazidime and susceptible to cephalothin.

A novel extended-spectrum TEM-type beta-lactamase was detected in an Escherichia coli isolate which was resistant to ceftazidime and susceptible to cephalothin. The corresponding bla gene was sequenced. The deduced amino acid sequence showed the following three amino acid replacements with respect to the TEM-2 sequence: Glu-->Lys-104, Arg-->Ser-164, and Glu-->Lys-240. Since it confers a ceftazidimase-type resistance phenotype, we propose for this novel enzyme the designation CAZ-9, corresponding to TEM-46 in the sequential numbering scheme of TEM beta-lactamases.

Ceftazidime↗

PubMed1994

Frequency of inhibitor-resistant TEM beta-lactamases in Escherichia coli isolates from urinary tract infections in France.

Over a six-month period in 1993, 2972 non-duplicated isolates of Escherichia coli causing urinary tract infections were collected in a French teaching hospital (n = 785) and in three private laboratories (n = 2187). The resistance rate to amoxycillin-clavulanate combination (MIC > 16 mg/l) was 25.0% in the hospital isolates and 10.0% in the community isolates. Respectively, 27.5% and 45.0% of hospital and community isolates resistant to amoxycillin-clavulanate exhibited an unusual beta-lactam resistance pattern, suggesting inhibitor-resistant TEM (IRT) beta-lactamase production. These isolates were highly resistant to amoxycillin-clavulanate (MIC90 > 1024 mg/L), but were susceptible to cephalosporins (MIC < 32 mg/L). Enzyme extracts of these IRT-producing strains focused at pI 5.2 (n = 100) or 5.4 (n = 53). DNA-DNA hybridization confirmed that the beta-lactamases involved in this resistance mechanism were TEM-1 derived and contained variations in the altered positions described in IRT enzymes. This study shows a total frequency of 4.9% of IRT-producing isolates among E. coli isolated from urine specimens.

Amoxicillin↗

PubMed1992

[Structure an functions of IgG subclasses].

This review first deals with IgG subclasses according to the aspects that ascribe them their common class properties: general structure, enzymatic cleavage, synthesis, Gm allotypes. Then the subclass specific characteristics are described, comparing the main structural features (domains, hinge, disulfide bridges, kappa/lambda ratio). The IgG subclasses are further compared according to their effector functions, stressing those resulting from structural differences: classical pathway of complement activation, binding to Fc receptors, to protein A and to rheumatoid factors. Finally, a survey of the prolific works about antibody functions of IgG subclasses, allows a glimpse of the wide possible applications in this field.

Age Factors↗

PubMedDate not supplied

[Vernal keratoconjunctivitis in the child. Clinical and complementary study apropos of 22 cases].

PURPOSE: Vernal kératoconjunctivitis was studied in a population of 22 children aged 3 to 14 years and followed up in an allergy and ophthalmology outpatient clinic. The role of allergy and the severity of inflammation where assessed by a systematic exploration, which combined a detailed allergy evaluation and blood and lacrimal sampling. MATERIALS AND METHODS: Allergy criteria chosen and recorded in 9 cases are: an increase of total IgE over the higher limit for the age, a positive skin prick test to one allergen, a positive serum specific IgE dosage (> 0.35 IU/mL) of specific IgE. Conjunctival allergy was present in 6 of the 9 children with a positive allergenic provocation test, or with a high local production of total IgE and a lacrimal/serum eosinophilic cationic protein ratio greater than one. RESULTS: Criteria used for supporting the IgE mediated hypersensitivity diagnosis are discussed: they have to be very strict to eliminate false positive results. Allergen involvement can only be evidenced by a specific provocation test. When evidenced as described, limbic or palpebral conjunctivitis had the same frequency. Lacrimal ICAM 1 levels seemed to be higher (p < 0.05) in the severe limbal forms (24.7 +/- 3 pg/mL) than in the palpebral ones (8.1 +/- 6.5 pg/mL). Interpretation of biological parameters evidencing conjunctival inflammation is more difficult. CONCLUSION: Allergic involvement in child vernal keratoconjunctivitis can only be assessed through a detailed evaluation, leading to a specialised ophthalmic and allergic management. A specific treatment can then be established, based on allergen eviction and possibly on specific immunotherapy (5 cases). H1 antihistamin treatments are dedicated only to children with a positive allergic evaluation.

Adolescent↗