Anne Jacolot

Efficacy of β-Lactams for Treating Experimentally Induced Pneumonia Due to a Carbapenem-Hydrolyzing Metallo-β-Lactamase-Producing Strain of Pseudomonas aeruginosa

ABSTRACT A rat pneumonia model was established with a Pseudomonas aeruginosa strain that produced the plasmid-encoded metallocarbapenemase VIM-2. A significant decrease in lung bacterial titers was observed when imipenem, cefepime, ceftazidime, and piperacillin-tazobactam were given at the highest doses recommended for humans, despite their high MICs. Aztreonam at high doses produced a similar decrease in bacterial titers.

Efficacies of Imipenem, Meropenem, Cefepime, and Ceftazidime in Rats with Experimental Pneumonia Due to a Carbapenem-Hydrolyzing β-Lactamase-Producing Strain of Enterobacter cloacae

ABSTRACT The antibacterial activities of imipenem-cilastatin, meropenem-cilastatin, cefepime and ceftazidime againstEnterobacter cloacae NOR-1, which produces the carbapenem-hydrolyzing β-lactamase NmcA and a cephalosporinase, and against one of its in vitro-obtained ceftazidime-resistant mutant were compared by using an experimental model of pneumonia with immunocompetent rats. The MICs of the β-lactams with an inoculum of 5 log10 CFU/ml were as follows for E. cloacae NOR-1 and its ceftazidime-resistant mutant, respectively: imipenem, 16 and 128 μg/ml, meropenem, 4 and 32 μg/ml, cefepime, <0.03 and 1 μg/ml, and ceftazidime, 1 and 512 μg/ml. The chromosomally located cephalosporinase and carbapenem-hydrolyzing β-lactamase NmcA were inducible by cefoxitin and meropenem inE. cloacae NOR-1, and both were stably overproduced in the ceftazidime-resistant mutant. Renal impairment was induced (uranyl nitrate, 1 mg/kg of body weight) in rats to simulate the human pharmacokinetic parameters for the β-lactams studied. Animals were intratracheally inoculated with 8.5 log10 CFU of E. cloacae, and therapy was initiated 3 h later. At that time, animal lungs showed bilateral pneumonia containing more than 6 log10 CFU of E. cloacae per g of tissue. Despite the relative low MIC of meropenem for E. cloacae NOR-1, the carbapenem-treated rats had no decrease in bacterial counts in their lungs 60 h after therapy onset compared to the counts for the controls, regardless of whether E. cloacae NOR-1 or its ceftazidime-resistant mutant was inoculated. A significant decrease in bacterial titers was observed for the ceftazidime-treated rats infected with E. cloacae NOR-1 only. Cefepime was the only β-lactam tested effective as treatment against infections due to E. cloacae NOR-1 or its ceftazidime-resistant mutant.

Animal model methodology: immunocompetent or leucopenic rats, which is the best? Results from a model of experimental pneumonia due to derepressed cephalosporinase-producing Enterobacter cloacae.

Background: The aim of this study was to compare the bactericidal activity of cefepime plus amikacin against experimental pneumonia induced by a stably derepressed cephalosporinase-producing Enterobacter cloacae strain in immunocompetent and leucopenic rats. Methods: Sixty Wistar rats were used. Leucopenia was induced in half of them by a single intravenous administration of 30 mg/kg cyclophosphamide, while the remaining rats received the same volume of saline. All rats were infected 96 h later by tracheal instillation of 8 log10 colony-forming units of E. cloacae. Twelve rats (6 immunocompetent and 6 leucopenic) were sacrificed 6 h later to assess the initial bacterial burden to the lungs. Then, the remaining 48 rats received a combination of 60 mg/kg cefepime twice a day and 25 mg/kg amikacin once a day given intraperitoneally or the same volume of saline. Six rats per group (leucopenic or not, treated or not) were sacrificed 12 and 30 h after therapy started. Results: Spontaneous bacterial clearance with time was observed only in immunocompetent rats. Compared to untreated animals, antibiotic administration induced a decrease in lung bacterial titres in immunocompetent and leucopenic rats. The difference was statistically significant only in leucopenic rats. Conclusions: The use of leucopenic rats reduced spontaneous bacterial clearance in the lungs and increased the bactericidal effect of the antibiotic combination and ultimately the confidence in the reliability of the results.

Monitoring of 8-methoxypsoralen during extracorporeal photochemotherapy: evidence for a "first-dose" effect.

Therapeutic monitoring of 8-methoxypsoralen (8-MOP) was studied in 12 patients (age range 43-85 years, weight range 48-76 kg) treated for Sezarys syndrome by extracorporeal photochemotherapy (ECP) for 14-41 months. Before the beginning of each ECP cycle (2 sessions on consecutive days at about 4-week intervals), a blood sample was drawn to determine the 8-MOP plasma concentration 2 h after drug ingestion. Plasma 8-MOP levels were measured using a high-performance liquid chromatography method with spectrophotometric detection. Monitoring parameters (dose, 2-h plasma 8-MOP concentration) showed important interindividual and intraindividual variations. The 8-MOP dose ranged from 0.57 to 1.04 mg/kg. Intraindividual variations of 2-h 8-MOP levels ranged from 21% to 75%. Of the 652 measurements, 13% were < 100 ng/ml, the therapeutic threshold for effective ECP; in three of the seven patients, increasing the dose obtained levels exceeding the therapeutic threshold, i.e, the absorption was not saturable. Orthogonal regression analysis between plasma 8-MOP concentrations measured in two consecutive ECP sessions showed a first-dose effect: the 2-h plasma 8-MOP concentration was significantly lower after the first administration than after the second (approximately 1.26-fold). Because 8-MOP has been proven to be a potent suicide inhibitor of drug metabolism in rats and humans, it is possible that 8-MOP had an inhibitory effect on its own metabolism within the therapeutic dose range for ECP, which would explain in part the inter- and intraindividual variability in 8-MOP kinetics and first-dose effect.

Preliminary hazard analysis applied to outsourcing sterile chemotherapy preparations

Background Our hospital organization raised the possibilities of outsourcing their sterile pediatric chemotherapy preparations to another hospital conditional on analyzing the potential hazardous events that need to be anticipated. Methods The study was conducted by a multidisciplinary working group from September 2015 to January 2016 with the support of a risk manager. A list of hazardous situations that could occur during outsourcing process was assessed. First, a map of hazardous situations was developed by crossing outsourcing processes divided into phases classified as critical or not. Second, a map of risk was established by crossing potential consequences of these hazardous situations and elaborating corrective actions to reduce the initial risks. Results The map of hazardous situations identified 183 relevant hazardous situations, 78 of which were considered high priority and 154 scenarios were developed. Slightly more than half of these hazardous situations concerned information system (30%), human resources (14%), and management (11%). The generic hazards of information system and human generated 37 (24%) and 41 (27%) scenarios, respectively. To reduce critical risks, 33 corrective actions were proposed. Working time required was estimated at 35 days. The subcontractor personnel for this new organization included an estimated extra time of 0.7-pharmacist working day and 1.4-pharmacy dispenser working day. Conclusions The preliminary hazard analysis method appeared to apply to our system of outsourcing sterile cytotoxic preparations in another hospital. Regardless, this analysis is complex and requires time and expertise.

How to solve the problem of spontaneous bacterial clearance when testing new antibiotic treatment: results on experimental pneumonia due to a derepressed cephalosporinase‐producing Enterobacter cloacae

Because the magnitude of spontaneous bacterial clearance can be similar or even higher than treatment effect, depending upon experimental model and bacterial strain used, this work investigated the value of rendering rats immunosuppressed to facilitate bacterial implantation and reduce spontaneous bacterial clearance. In a first step, rats received a single intravenous cyclophosphamide dose 4 days before infection. Three different doses were tested: 10, 20, and 40 mg/kg. After modeling with NONMEM V, the cyclophosphamide dose required to maintain white blood cell count <1.0 × 103/μL from day 4 to day 5 was 30 mg/kg. In a second step, influence of immunosuppression on lung bacterial titers was characterized. Rats were given one of the three intravenous cyclophosphamide doses (0, 10, 30 mg/kg), and after 4 days, they were infected by tracheal injection of 8.9 ± 0.1 log10 cfu Enterobacter cloacae before being sacrificed at different times. Bacteria in homogenized lungs were quantitatively cultured on Drigalski agar. Bacterial lung count was closely influenced by the grade of induced leukopenia. A single intravenous 30 mg/kg cyclophosphamide dose 4 days before infection suppressed the spontaneous clearance of E. cloacae for at least 30 h without significantly increasing animal mortality; this result seems to be linked to a white blood cell count maintained lower than 1.0 × 103/μL for all the time. This modified animal model could be contributive in the evaluation of antibacterial agents, especially to simulate the behavior of intensive care unit immunocompromised patients.