Antoine Andremont

Liposomes and Nanoparticles in the Treatment of Intracellular Bacterial Infections

The treatment of infections caused by obligate or facultative intracellular microorganisms is difficult because most of the available antibiotics have either poor intracellular diffusion and retention or reduced activity at the acidic pH of the lysosomes. The need for antibiotics with greater intracellular efficacy led to the development of endocytosable drug carriers, such as liposomes and nanoparticles, which mimic the entry path of the bacteria by penetrating the cells into phagosomes or lysosomes. This Review assesses the potential of liposomes and nanoparticles in the targeted antibiotic therapy of intracellular bacterial infections and diseases and the pharmaceutical advantages and limitations of these submicron delivery systems.

Intracellular visualization of ampicillin-loaded nanoparticles in peritoneal macrophages infected in vitro with Salmonella typhimurium.

Intracellular targeting of ampicillin by means of polyisohexylcyanoacrylate (PIHCA) nanoparticles was studied in murine peritoneal macrophages infected with Salmonella typhimurium. The intracellular distribution of actively endocytosed nanoparticles was visualized by transmission electron microscopy and confocal microscopy. Nanoparticles were either isolated or closely associated with bacteria within phagosomes or phagolysosomes. Thus the potential of ampicillin-loaded nanoparticles .in targeting of intracellular bacteria is demonstrated. Consequently, ampicillin, which usually penetrates into cells at a low level, is directly carried in, when loaded on nanoparticles, and brought into contact with intracellular bacteria.

Surveillance of intestinal colonization and of infection by vancomycin-resistant enterococci in hospitalized cancer patients

OBJECTIVE: To study epidemiologic features of and risk factors for intestinal colonization and infection by vancomycin-resistant enterococci (VRE) in cancer patients. METHODS: During a 41-month period, over 7600 fecal samples and all samples from sterile sites from hospitalized cancer patients were screened for VRE. Species were identified and isolates analyzed by pulsed-field gel electrophoresis (PFGE) of SmaI DNA restriction fragments. Antibiotic resistance was characterized by MIC determinations, and polymerase chain reaction for vanA, vanB, and vanC1 genes. Plasmid contents were analyzed before and after PstI and HindIII restriction, and by Southern hybridization with a vanA probe. Two case-control studies were performed to identify risk factors for colonization or infection by VRE, respectively. RESULTS: Eighty-two isolates were recovered from 81 patients. Most (72%) isolates were Enterococcus faecium VanA/vanA, with 37 different PFGE types, each of which was found in only one to four patients, except for type P1, which was found in 20 patients hospitalized over a 3-month period in the pediatric wards. Plasmid analysis suggested that only two types of plasmid were carrying gene vanA, as part of a transposon related to transposon Tn 1546 from reference strain E. faecium BM4147. Seventy-seven patients were colonized during the study period. Six of them became infected. Four patients were infected but not colonized. Only one patient died during the course of infection, but intestinal colonization persisted for months in the survivors. Case-control analysis revealed that cephalosporin treatment was a significant risk factor for colonization. No significant risk factor for infection was found in colonized patients. CONCLUSION: Colonization by VRE was mostly endemic and the colonized patients were not often infected. However, when clustered cases of colonization occurred, they were then associated with an increased rate of infection.

Non-nephrotoxic empiric antimicrobial therapy in febrile neutropenic cancer patients

We evaluated the efficacy of piperacillin-pefloxacin as a non-nephrotoxic antibiotic combination in febrile neutropenic cancer patients treated with nephrotoxic chemotherapy. 40 patients: 34 with solid tumours and 6 with non-Hodgkin lymphoma, were treated during 55 episodes with: piperacillin 4 g intravenously every 8 h and pefloxacin 400 mg intravenously every 12 h. If the patient remained febrile after 72 h, 1 g vancomycin intravenously was added every 12 h. The mean duration of neutropenia was 7 days (range 3-13). Infection was microbiologically documented in 13 episodes (8 gram-positive cocci and 7 gram-negative bacilli). Temperature became normal in 38 patients with piperacillin-pefloxacin and 12 further episodes were resolved by the addition of vancomycin. 2 patients had an early change of antibiotics because of clinical deterioration, there were 2 protocol violations and 1 patients temperature became normal after the addition of amphotericin. Neither septic death nor toxicity were observed. We conclude that this empirical treatment is active and safe and warrants further comparative trials.

Measurement of inhibition zone diameter in disk susceptibility tests by computerized image analysis.

This paper presents an application of computerized image analysis in microbiology. This application permits the automatic detection and diameter measurement of inhibition zones in disk susceptibility tests. Each inhibition zone boundary was extracted according to an edge detection method based on the Students t-test and a priori knowledge (geometry, densitometry). Evaluation of the method was performed by comparing the results from an image analyser and a trained observer. For this purpose, we used kappa statistics and obtained a close agreement (a kappa coefficient equal to 0.84) on a set of about 600 inhibition zones. The results encourage us to develop the method further to include the detection of antagonism and synergism.