[Changes in the antibiotic sensitivity of Haemophilus (H. influenzae and H. parainfluenzae) colonizing the upper respiratory tract of the child]

Haemophilus strains recovered from the upper respiratory tract in children were investigated by three one-month studies, in 1982, 1983 and 1984 respectively. Strains were recovered from nose and throat swabs in children hospitalized in a pediatric department during March/April. H. influenzae and H. parainfluenzae exhibited very different patterns of resistance to antibiotics. Little resistance was found among H. influenzae strains: percentage of ampicillin-resistant (beta-lactamase producing) and/or tetracycline-resistant strains did not exceed 4% and showed no change over the three study years. H. parainfluenzae was considerably more resistant, with percentages of strains resistant to one antibiotic or more reaching 25% in 1982 and 1983 and 36% in 1984. Resistance to ampicillin rose from 20-22% in 1982-1983 to 31% in 1984. Resistance to chloramphenicol emerged in 1984 and was found in 4.5% of strains; these strains were also resistant to ampicillin and tetracycline. Resistance to tetracycline was found in 18% of strains in 1983 and in 14% in 1982 and 1984. In 1983, three cases of meningitis due to an ampicillin-resistant strain (one of which was also resistant to chloramphenicol) were seen. Although one type b ampicillin-resistant strain was isolated in this study, such an occurrence seems difficult to predict and strains infecting the upper respiratory tract apparently do not become invasive under normal conditions. The possibility that H. parainfluenzae may be a reservoir of resistance genes for H. influenzae is considered.

[Presence of plasmids in Neisseria meningitidis]

The plasmid content of twenty-nine Neisseria meningitidis strains, isolated from CSF and blood cultures, was investigated by agarose gel electrophoresis. The strains (twenty-seven from serogroup B and two from serogroup C) were sensitive to antibiotics, but 50% were resistant to sulphonamide (MIC greater than or equal to 16 mg/l). Two serogroup-B strains from CSF harboured an extrachromosomal element. These two cryptic plasmids differed in size: 8.4 Kb for pNMT1 and 82 Kb for pNMT2.

[Antibiotic sensitivity of meningococci isolated from patients and carriers]

Ninety-two strains of Neisseria meningitidis (twenty-four recovered from CSF, four from blood, and sixty-four from oropharyngeal swabs) were tested for susceptibility to penicillin, ampicillin, minocycline, chloramphenicol, rifampicin, erythromycin, spiramycin, josamycin, sulphamethoxazole, and trimethoprim. Antibiotic activity (MIC) was determined by agar dilution. Among the 92 cultures, strains were in the following decreasing order: group B, undefined groups, and group C. 75% of strains recovered from carriers and 50% of those recovered from CSF were susceptible to 8 mg/l of sulphamethoxazole. No strain was susceptible to trimethoprim (MIC 8 mg/l). All strains were susceptible to penicillin (range MICs: 0.007-0.25; mean MIC: 0.06), ampicillin (0.015-0.5; 0.12), minocycline (0.03-0.05; 0.25), chloramphenicol (0.12-4; 0.5). and rifampin (0.007-0.25; 0.015). In vitro activity of macrolides was influenced by culture conditions. With 5 to 10% CO2, MICs were 2 to 4 times greater than those culture conditions. With 5 to 10% CO2, MICs were 2 to 4 times greater than those observed without CO2. Josamycin was more active than erythromycin and spiramycin.

[Inhibitory activity of ampicillin and mecillinam on Haemophilus influenzae]

Mecillinam, an antibiotic of the beta-lactam group, is active against Gram negative bacilli, with the exception of a few species such as Haemophilus influenzae. The activities of ampicillin, mecillinam, and ampicillin-mecillinam combinations at ratios of 1/1, 2/1, 4/1, 1/2 and 1/4, on 21 Haemophilus influenzae strains, were studied by agar dilution and determination of minimal inhibitory concentrations (MIC). Ampicillin at concentrations of 0.12 to 0.25 mg/l was active on susceptible strains. Beta-lactamase-producing strains were inhibited by 4 and 8 mg/l ampicillin. MICs of mecillinam were above 128 mg/l for 19 strains; two strains were susceptible to 2 mg/l. In every case, antibacterial activity was greater with the ampicillin-mecillinam combination than with either one of the antibiotics alone. The maximum antibacterial effect was obtained at ratios of 1/1 and 1/2; in this case, susceptible strains were inhibited by 0.06 mg/l ampicillin. Kinetic evaluation (killing curves) showed that ampicillin has a bactericidal effect at concentrations under the MIC when it is combined with mecillinam at a 1/1 ratio.

New inhibitors of alcohol dehydrogenase: studies in vivo and in vitro in the rat

Two compounds bearing an amide group, p-butoxyphenol acetamide (BPA) and N-(p-butoxybenzyl)formamide (BBF) were studied as inhibitors of alcohol dehydrogenase (ADH) and their action compared with that of 4-methyl-pyrazole (4-MP), a known inhibitor of this enzyme. In vitro studies on pure horse liver ADH showed that BPA and BBF were noncompetitive inhibitors with respect to ethanol and that their Ki values were 22 and 0.14 micrometer, respectively. The apparent Ki values of BPA and BBF for rat liver ADH were found to be 90 and 2.3 micrometers, respectively (noncompetitive inhibition). Several in vivo experiments were carried out in the rat. Administration intraperitoneally of the substance (460 mumol/kg) 1 hr before intraperitoneal injection of alcohol (2 g/kg body weight) led to a significant decrease in ethanol catabolism. Injection of the substances at 460 mumol/kg brought about a decrease in rat liver ADH activity, but the activity of mitochondrial aldehyde dehydrogenase was only decreased in animals treated with BBF.

[Comparative activity of tetracycline, doxycycline and minocycline against Haemophilus]

A total of 90 isolates of Haemophilus were studied for susceptibility to tetracycline, doxycycline and minocycline. In vitro activity was determined by agar dilution method (MIC) and disk diffusion test. Disk diffusion tests were done on chocolate agar and on supplemented Mueller-Hinton agar. MICs rang from greater than or equal to 128 to 0,25, 32 to 0,5 and 32 to 0,25 micrograms/ml for tetracycline, doxycycline and minocycline respectively. Strains can be divided into tetracycline-sensitive strains which are inhibited by concentration less than or equal to 2 micrograms/ml and tetracycline-resistant strains inhibited by greater than or equal to 16 micrograms/ml. Sensitive strains are inhibited by 0,5-1 microgram/ml of doxycycline and 0,25-2 micrograms/ml of minocycline. Resistant strains are inhibited by concentrations from 2 to 32 micrograms/ml of doxycycline and from 0,5 to 32 micrograms/ml of minocycline. All but one resistant strains were inhibited by a concentration of less than or equal to 4 micrograms/ml of minocycline; all but two resistants strains were inhibited by doxycycline at a concentration greater than or equal to 4 micrograms/ml. The correlation coefficients are the following: for tetracycline, r = -0,95; for doxycycline r = -0,83 when disk diffusion test is done on supplemented Mueller-Hinton and r = -0,94 on chocolate agar; for minocycline r = -0,62 on supplemented Muller-Hinton and r = -0,75 on chocolate agar.

[Haemophilus colonization in children: serotypes, biotypes and antibiotic sensitivity]

The occurrence of Haemophilus in throat swabs from 273 hospitalized children aged 0-15 years has been investigated. Haemophilus was detected in 124 children. H. influenzae was observed in 15.7% of the children and 37.6% of the carriers. H. parainfluenzae was observed in 31.8% of the children and 70% of the carriers. The carriage rate of Haemophilus influenzae type b occurred in 6.6% of the children and was not observed in children aged less than six months. One nontypable, biotype II strain of H. influenzae (2.2%) was resistant to ampicillin and tetracycline; one biotype I, type b strain was resistant to tetracycline. Among 90 strains of H. parainfluenzae, 20 were beta-lactamase-producing strains; 80% of these strains were isolated in children aged more than two years. Beta-lactamase-producing Haemophilus was detected in 7.7% of children but only 0.36% of children were carrier of ampicillin-resistant H. influenzae. No chloramphenicol-resistant strain was isolated during this study.

Comparative activity of cefotaxime and selected beta-lactam antibiotics against Haemophilus influenzae and aerobic gram-negative bacilli

The activity of cefotaxime was compared with that of ampicillin, moxalactam, and cefoperozone against 50 isolates of Haemophilus influenzae and with that of ampicillin, carbenicillin, cephalothin, cefoxitin, cefamandole, cefazolin, and several other established and investigational beta-lactam antibiotics against several hundred isolates of gram-negative aerobic enteric bacilli. Minimal inhibitory concentrations of the drugs were determined by the agar plate dilution technique for H. influenzae and by the microtiter broth dilution technique for the other pathogens. Cefotaxime was the most active agent against H. influenzae; it was 20 times more active than ampicillin. It was also the most active agent against Escherichia coli, Klebsiella pneumoniae, nontyphoid Salmonella species, and Yersinia enterocolitica. Cefotaxime was among the most active agents against Enterobacter cloacae, Citrobacter species, Shigella species, Proteus mirabilis, and Acinetobacter calcoaceticus. None of the new cephalosporins or penicillin inhibited greater than 90% of the isolates of Pseudomonas aeruginosa at concentrations of less than or equal to 16 micrograms/ml; these drugs were, however, more active than carbenicillin.

[Effects of chloramphenicol on microsomal reductases associated with lipoperoxidation (author's transl)]

The effects of chloramphenicol treatment to rats, by intraperitoneal way on three consecutive days were studied on various enzymatic systems of hepatic microsomes, implicated in the detoxication reactions non induced or induced by phenobarbital. Chloramphenicol increases the activity of reductases like NADPH cytochrome c reductase and neotetrazolium reductases. It does not appear to modify the activity of the N-demethylase systems or of the cytochrome P 450 level contrarily to phenobarbital. Chloramphenicol decreases the activity of microsomal nitro reductases, the production of malonaldehyde and conjugated dienes in the microsomes currently considered as a reliable estimate of the extent of the lipoperoxidation process. These results suggest that chloramphenicol could act like an antioxdant derivative.

Comparative activities of cefotaxime, a new cephalosporin derivative, and of selected beta-lactam antibiotics against Haemophilus species

The activity of cefotaxime (HR756), a new semi-synthetic cephalosporin, was compared with the activity of ampicillin, carbenicillin, cephalothin, cephaloridine, cefazolin, cefamandole and cefoxitin against 247 strains of Haemophilus sp.; 20 of these strains produce a beta-lactam inactivating enzyme. The minimal inhibitoring concentrations were determined by the agar plate dilution technique. Cefotaxime is not only more active than any other cephalosporin but also than ampicillin, generally estimated the most active drug against Haemophilus sp. Bacteriostatic concentrations of cefotaxime which inhibit 50 and 95% of the strains (BSC50 and BSC95) were 0,009 microgram/ml and 0,03 microgram/ml, respectively, showing an activity 20 times superior to that of ampicillin. Cefotaxime activity was unaffected by the production of beta-lactamase.

[Bactericidal activity of ampicillin, chloramphenicol and gentamicin, alone or in combinations against susceptible and resistant "Haemophilus influenzae" (author's transl)]

Bactericidal activity of three antibiotics, ampicillin, chloramphenicol and gentamicin, alone or in combinations, was determined against susceptible and resistant strains of Haemophilus influenzae. The various antibiotic combinations were studied for the determination of a synergistic or antagonistic effect. The study was done by the checkerboard method. A percentage of survivors inferior or equal to 0.01% of the inoculum represents the bactericidal activity. Ampicillin and chloramphenicol are bactericidal antibiotics against H. influenzae at concentrations of 1 microgram/ml and 4 microgram/ml, respectively. The combination of ampicillin and gentamicin exhibited a synergistic effect against strains sensitive and resistant to ampicillin. The combination of chloramphenicol and gentamicin was synergistic against all strains. Ampicillin and chloramphenicol, when combined, were antagonistic against two strains using a bacteriostatic concentration of chloramphenicol; and against the remaining strains the effects of the combination were indifferent.