Evidence for a true post-beta-lactamase-inhibitor effect of clavulanic acid against Klebsiella pneumoniae and Haemophilus influenzae.

OBJECTIVE: The purpose of this study was to investigate and characterize in vitro the post-beta-lactamase inhibitor effect (PLIE) of clavulanic acid against two beta-lactamase-producing species of bacteria. METHODS: The PLIE was investigated against one strain of Klebsiella pneumoniae and one strain of Haemophilus influenzae. A stationary-phase inoculum of about 107 colony-forming units per mL of each bacterium was pre-exposed for 2 h to clavulanic acid, either alone or in combination with amoxicillin at various concentrations. After pre-exposure, the dilution required to remove the beta-lactamase inhibitor was 1:100 or 1:1000 according to the bacterial species and their susceptibilities to clavulanic acid. Bacteria were counted hourly after drug removal, on solid agar medium. RESULTS: Control cultures exposed to amoxicillin alone after dilution, showed a delay in growth, which may be inherent to the time required to synthesize sufficient beta-lactamase after the dilution steps. Control experiments clearly distinguished the post-antibiotic effect and the growth delay from the PLIE. CONCLUSION: The PLIE could be one of several factors explaining why beta-lactam/beta-lactamase inhibitor combinations remain effective throughout the dosing interval, even if a few hours after in vivo administration, serum concentrations of beta-lactamase inhibitor fall below levels that are active in vitro.

[Pneumococcal antibiotic resistance. Data from 6 regional registries for 1999]. / Résistance du pneumocoque aux antibiotiques. Données de 6 observatoires régionaux pour l'année 1999.

RESISTANCE BY REGION: Resistance varied greatly by region, ranging from 34.2% resistant strains in Alsace to 63.1% in Brittany. The incidence of resistant strains was always higher in children (especially in children aged 1 to 5 years) and in ENT samples. The time course of resistance has varied between regions, as has that of serotypes. CRUCIAL FINDING: In these 6 regions, and despite a high incidence (that varied from one region to another) of reduced susceptibility strains for penicillin G, amoxicillin (19-32%) and cefotaxime (6.5-18.5%), amoxicillin-cefotaxime resistant strains remained very rare (0.2-3.5%).

[Evolution of antibiotic resistance of Streptococcus pneumoniae: results of Alsace observatory in 2005]. / Evolution de la sensibilité de Streptococcus pneumoniae aux antibiotiques: résultats de l'observatoire du pneumocoque Alsace (année 2005).

OBJECTIVES: Between 1st January 2005 and 31st December 2005, 232 strains of Streptococcus pneumoniae were collected in the Alsace county from participating laboratories (one from university hospital, 7 from general hospitals and 12 private laboratories) to assess their susceptibility to penicillin and evaluated serogroups of strains. METHOD: The coordinating centre performed MICs by the reference agar dilution test, interpreted according to CA-SFM breakpoints. Others antibiotics (erythromycin, cotrimoxazole, tetracycline...) were tested by agar diffusion, ATB-PNEUMO gallery or VITEK gallery (BioMérieux, France) by each participating laboratory. Data were processed, using 4th dimension software. RESULTS: Strains were collected from 151 blood samples, 38 ear pus, 11 cerebrospinal fluids, 8 pleural liquids and 24 representative pulmonary samples. The prevalence of pneumococci with decreased susceptibility to penicillin G (PDSP) is 35.1% (pulmonary samples excluded). The rate of PNSP decreases for all types of samples compared with other years of surveillance 2003 (44.0%). The rate of blood samples decreases for first time between the creation of Pneumococcal Observatory. The high-level resistance tend to decrease and began low. The PDSP are rather resistant to erythromycin, cotrimoxazole and fosfomycin. Among the PDSP, the most prevalent serotypes were 14, 19, 6 and 9. CONCLUSION: Among pneumococcal strains, the rate of PDSP tend however to decrease in 2005 compared with 2003. The rate stays inferior to the observed rates in other French counties where the same decreasing is described.

[Bacterial growth delay in E. coli: demonstration and evaluation of the beta-lactamase post-inhibitor effect on 6 strains with different resistance phenotypes]. / Retard de recroissance bactérienne chez E. coli: mise en évidence et évaluation d'un effet postinhibiteur de beta-lactamases sur six souches de phénotypes de résistance différents.

Six E. coli, whose phenotypes of resistance were different, were tested in vitro in order to evaluate a regrowth delay, the post beta-lactamases inhibitor effect (PLIE). This PLIE was investigated after a brief incubation in contact with clavulanic acid (CA) alone or associated with amoxicillin (AMX). After removal of the drugs used during the pre-exposure phase, the bacteria were incubated with AMX at different concentrations. The PLIE was shown not to be in association with any other regrowth delay (post-antibiotic effect or effect inherent to the technical procedures used). A PLIE was evaluated on the five intermediary or high-level beta-lactamases-producing strains. Generally, the duration of the PLIE was prolonged after the CA alone pre-exposure phase and could reach values up to 22 hours. The concentrations of AMX added in cultures previously exposed to sufficient CA concentrations were related to an extended PLIE.

[In vitro demonstration of a true post-beta-lactamases inhibitor effect (PLIE) of clavulanic acid on Klebsiella pneumoniae and Haemophilus influenzae]. / Mise en évidence in vitro d'un véritable effet post-inhibiteur de bêta-lactamases (EPIBLA) de l'acide clavulanique sur Klebsiella pneumoniae et Haemophilus influenzae.

In vivo, serum concentrations of beta-lactamase inhibitors measured during the last part of the dosing interval are below the levels associated with in vitro activity. Nevertheless, beta-lactam plus beta-lactamase inhibitor combinations remain active in vivo throughout the dosing interval. One of the many reasons for this contradiction may be the PLIE. The PLIE can be evaluated only in the light of the postantibiotic effect (PAE). Also, accurate determination of the PLIE requires a careful investigation of all bacterial regrowth delays (BRDs) inherent to the technical procedures used. The purpose of the study reported herein was to determine the true in vitro PLIE of clavulanic acid (CA) against two beta-lactamase-producing strains, a Klebsiella pneumoniae strain (amoxicillin [AMX] MIC > 256 mg/L; CA MIC = 64 mg/L; and AMX + CA MIX = 4 mg/L) and a Haemophilus influenzae strain (AMX MIC = 32 mg/L; CA > 32 mg/L; AMX-CA = 1 mg/L). For each strain, a stationary phase inoculum of 10(7) was preexposed for 2 h to either CA alone or CA + AMX in various concentrations. Dilution to 10(-2) or 10(-3) was performed to eliminate the CA and/or AMX after the preexposition phase. Hourly bacterial counts were done between 0 and 8 h and after 24 h. Control cultures exposed to AMX after dilution showed a growth delay possibly ascribable to the time needed for bacteria to produce a large enough amount of beta-lactamases. Control experiments were done to unequivocally differentiate PLIE from PAE and BRD. The true PLIE values thus obtained ranged from 0 to 4.5 h for K. pneumoniae and from 0 to 15 h for H. influenzae. For both strains, a PLIE was demonstrated after exposure to CA alone.

[Chronic experimental bacteremia in Yucatan micropigs]. / Bactériémie chronique expérimentale du microporc Yucatan.

The Yucatan micropig has been used to develop an experimental model of chronic bacteremia. This animal exhibits clinical and biological characteristics that are close to those in humans, and the pharmacokinetic behaviours of many classes of drugs in this model are similar to those in man. Six adult female were intravenously inoculated with a mean Escherichia coli inoculum of 5.1 x 10(9) bacteria. During five days of spontaneous evolution, the medical follow-up includes biological, clinical and bacteriological parameters. A systemic inflammatory syndrome, a sepsis, an organ insufficiency and positive blood cultures mimic the human disease. In all animals there is an adynamia, a lack of motor coordination, an anorexia, a tachypnea, a fever, a leuconeutropenia followed by an hyperleucocytosis, an anemia, a thrombopenia, an acute tubulonephritis and an elevated sedimentation rate. In some cases, there is an increase of the C reactive protein, in others, an increase of IL-6 and IL-8. At day five, all animals are alive, and five micropigs have positive blood cultures. This chronic, reproducible model is thus suitable for further antibacterial treatments evaluations.