[Statistical study of the SIRSCAN computerised camera]

The antibiograms of 1162 bacterial strains, including references, have been performed within four centres. They have been read manually and by the SIRSCAN camera, which yields to 30936 couples of diameters values. A non-concordance, at a 3 mm level, was observed fot 11.14% of the diameters. The mean of difference is 0.82 mm and the standard deviation 3.34 mm. Round Petri dishes gave results less reliable than those obtained with square dishes. A deviation in function of the centres is obtained for wild-strains as for the references. For the whole population a S/R discordance (sensible/résistant confusion) is obtained for 1.76% of the diameters. This value drops to 0.93% for enterobacteriaceae, P. aeruginosa and S. aureus (968 strains).

[Determination of the isoelectric point of beta-lactamases isolated from 67 Klebsiella oxytoca strains and phenotype behaviour against eight beta-lactam antibiotics]

Klebsiella oxytoca is naturally resistant to aminopenicillins and carboxypenicillins by production of a chromosomal beta-lactamase but susceptible to third generation cephalosporins. The third generation cephalosporins activity may be reduced by: overproduction of the chromosomally encoded beta-lactamase or an extended-spectrum beta-lactamase. These activity modification are rarely found in the hospital of Aix-en-Provence (France). The activity modification rate of K. oxytoca resistant by one of these mechanisms between 1986 and 1991 are 3.6% for chromosomally encoded beta-lactamase overproduction and 0.7% for acquisition of an extended-spectrum beta-lactamase. We have determined the isoelectric point (pI) by isoelectrofocusing of the beta-lactamases isolated from 67 K. oxytoca and the activity of 8 beta-lactams has been studied by disk-diffusion. 51 wild strains, 14 overproducing strains (including 2 in vitro mutants) and 2 strains with extended-spectrum beta-lactamase were studied. For every wild strain, we observed only one band except for two strains with two bands (pl 5.4 + 6.3 and pl 5.6 + 7.7). The isoelectric points for the other strains are comprised between pl 5.25 and pl 8.2: 22 pl 7.7; 13 pl 5.25; 4 pl 5.6; 4 pl 6.3; 2 pl 6.6; 2 pl 8.1 and 2 pl 8.2. In the strains with chromosomally encoded beta-lactamase overproduction we observed several bands in each extract and only the major band was considered. The isoelectric point of in vitro mutant strains with beta-lactamase overproduction was the same that the wild strains. We observed 3 pl: 5.25 - 1 pl: 5.6 - 3 pl 6.3 and 5 pl 7.7.(ABSTRACT TRUNCATED AT 250 WORDS)

[In vitro effect of cefixime against 200 strains of Branhamella catarrhalis. Comparison with cefotaxime]

The in vitro activity of cefixime was tested against 200 strains of Branhamella catarrhalis. Of these strains, 146 had been collected during 1987 from 15 different "Centres hospitaliers généraux", through a multicenter collaborative investigation organized by the "Collège de Bactériologie-Virologie-Hygiène des hôpitaux généraux". The remaining 54 strains were isolated at the "Centre hospitalier", of Aix-en-Provence. The strains originated from: bronchopulmonary collections: 80.2 per cent, sinusitis: 5.6 per cent, conjunctivitis: 4.6 per cent, otitis: 3.5 per cent, blood cultures: 0.5 per cent, miscellaneous: 5.6 per cent. Seventy-three per cent of the strains produced beta-lactamases. MIC determination was performed according to the agar dilution procedure on non-enriched Mueller-Hinton agar (30 hours incubation at 37 degrees C without CO2). The inoculum was 10(5) CFU per spot. Non beta-lactamase producing strains displayed the following MIC 50 and MIC 90 values (mg/l): amoxicillin: 0.03 - 0.125; cefotaxime: 0.06 - 1; cefixime: 0.06 - 0.5. Beta-lactamase producing strains were generally more resistant: amoxicillin: 32 - 128; cefotaxime: 1 - 2, and cefixime: 0.5 - 1.

[In vitro comparative activity of five macrolides against 190 Branhamella catarrhalis strains]

We compared the in vitro activity of 5 macrolides against 190 strains of Branhamella catarrhalis; 48 strains were isolated at Centre Hospitalier, Aix-en-Provence, the 142 others were isolated during 1987, in 15 different Centres-Hospitaliers-Généraux in France. 153 strains were betalactamase producing strains; no difference in susceptibility to erythromycin was observed on betalactamase producing and non producing strains. Three active macrolides against 100% of strains were: erythromycin (MIC 50 = 0.25 mg/l - MIC 90 = 0.50 mg/l), roxithromycin (MIC 50 = 0.50 mg/l - MIC 90 = 0.50 mg/l) and josamycin (MIC 50 = 0.50 mg/l - MIC 90 = 1 mg/l); A lower activity was noted on midecamycin (mic 50 = 2 mg/l - MIC 90 = 2 mg/l) and spiramycin (MIC 50 = 4 mg/l - MIC 90 = 8 mg/l).