Mouse model of colonization of the digestive tract with Acinetobacter baumannii and subsequent pneumonia

AIM

Implementing a mouse model of Acinetobacter baumannii (AB) digestive colonization and studying the propensity of an intestinal reservoir of AB to be at the origin of pneumonia.

MATERIALS & METHODS

After a disruption of the digestive flora by piperacillin-tazobactam, two multidrug-resistant AB strains were intranasally inoculated to two cohorts of ten mice daily. For each strain, five mice were rendered transiently neutropenic.

RESULTS & CONCLUSION

One strain persisted several weeks in the digestive tract, even after stopping piperacillin-tazobactam injections, leading to the hypothesis that some AB strains can authentically colonize the gut. Most of the immunocompromised mice experienced clinical signs and positive lung cultures, which were associated with positive spleen cultures, an argument in favor of bacterial translocation.

Wide spread of OXA-23-producing carbapenem-resistant Acinetobacter baumannii belonging to clonal complex II in different hospitals in Lebanon

OBJECTIVES

To investigate the molecular epidemiology of Acinetobacter baumannii strains isolated from different hospitals in Lebanon.

METHODS

A total of 119 non-duplicate Acinetobacter strains were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and partial rpoB gene sequencing. Antibiotic susceptibility testing was performed by disc diffusion method and all identified carbapenem-resistant isolates were investigated by PCR assays for the presence of the carbapenemase-encoding genes. Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were used for molecular typing.

RESULTS

Of the 119 A. baumannii isolates, 76.5% were resistant to carbapenems. The most common carbapenemase was the OXA-23-type, found in 82 isolates. The study of population structure using MLST revealed the presence of 30 sequence types (STs) including 18 new ones, with ST2 being the most commonly detected, accounting for 61% of the isolates typed. PFGE performed on all strains of ST2 identified a major cluster of 53 isolates, in addition to three other minor clusters and ten unique profiles.

CONCLUSIONS

This study highlights the wide dissemination of highly related OXA-23-producing carbapenem-resistant A. baumannii belonging to the international clone II in Lebanon. Thus, appropriate infection control measures are recommended in order to control the geographical spread of this clone in this country.

Antibacterial action of lipid nanocapsules containing fatty acids or monoglycerides as co-surfactants

Lipid nanocapsules (LNCs) are a new generation of biomimetic nanocarriers obtained via a phase inversion temperature method and have an oily core of medium-chain triglycerides that is surrounded by a shelf containing a lipophilic surfactant (lecithin) and a hydrophilic surfactant macrogol 15-hydroxystearate. The aim of the present study was to produce LNCs with antibacterial activity by replacing lecithin with other lipophilic surface active compounds, namely medium-chain fatty acids and their 1-monoglycerides, which are known to have antimicrobial properties. Fatty acids and monoglycerides were found to affect the properties of LNCs, such as particle size and zeta potential. Incorporation of a co-surfactant decreased significantly particle size (p⩽0.0039). Furthermore, incorporation of either lecithin or fatty acids with at least 10 carbon atoms yielded LNCs with the zeta potential significantly more negative than that of LNCs composed solely of triglycerides and macrogol 15 hydroxystearate (p⩽0.0310). Moreover, they were capable of decreasing the phase inversion temperature. The activity of the LCNs against Gram-positive S. aureus, including a methicillin-resistant strain, increased with increases in the length of the hydrocarbon tail. Monoglyceride-LNCs were found to be more active than the corresponding fatty acids. The opposite behaviour was observed for Gram-negative bacteria, whereby only caproic acid- and caprylic acid-LNCs were found to be active against these organisms. The monoglyceride-LNCs were bactericidal, and they killed in a time-dependent manner. Fatty acid-LNCs killed in a concentration-dependent manner. A haemolysis assay was performed to obtain preliminary information on the safety of the tested LNCs. In the case of fatty acid-LNCs, the concentrations at which bacterial growth was inhibited were similar to the haemolytic concentrations. However, monoglyceride-LNCs showed antibacterial action at concentrations much lower than those at which haemolysis was observed. In conclusion, monoglyceride-LNCs are promising candidates as carriers for the encapsulation of antibacterial agents, particularly against S. aureus.

Diversity of Acinetobacter species isolated from different environments in Lebanon: a nationwide study

Aim: To investigate the extrahospital reservoirs of Acinetobacter spp. in Lebanon. Materials & methods: Two thousand three hundred and sixty-one samples from different ecological niches were analyzed by culture methods. Species identification was confirmed by rpoB-gene sequencing. Multilocus sequence typing was used to characterize the Acinetobacter baumannii clones. Results & conclusion: Acinetobacter spp. were detected in 14% of environmental samples and 8% of food samples. Furthermore, 9% of animals and 3.4% of humans were colonized. Non-baumannii Acinetobacter were the most common species isolated and newly susceptible A. baumannii clones were detected. Interestingly, 21 isolates were not identified at the species level and were considered as putative novel species. To our knowledge, this is the largest epidemiological study investigating the epidemiology of Acinetobacter spp. outside hospitals.

Stress Conditions Induced by Carvacrol and Cinnamaldehyde on Acinetobacter baumannii

Acinetobacter baumannii has emerged as a major cause of nosocomial infections. The ability of A. baumannii to display various resistance mechanisms against antibiotics has transformed it into a successful nosocomial pathogen. The limited number of antibiotics in development and the disengagement of the pharmaceutical industry have prompted the development of innovative strategies. One of these strategies is the use of essential oils, especially aromatic compounds that are potent antibacterial molecules. Among them, the combination of carvacrol and cinnamaldehyde has already demonstrated antibacterial efficacy against A. baumannii. The aim of this study was to determine the biological effects of these two compounds in A. baumannii, describing their effect on the rRNA and gene regulation under environmental stress conditions. Results demonstrated rRNA degradation by the carvacrol/cinnamaldehyde mixture, and this effect was due to carvacrol. Degradation was conserved after encapsulation of the mixture in lipid nanocapsules. Results showed an upregulation of the genes coding for heat shock proteins, such as groES, groEL, dnaK, clpB, and the catalase katE, after exposure to carvacrol/cinnamaldehyde mixture. The catalase was upregulated after carvacrol exposure wich is related to an oxidative stress. The combination of thiourea (hydroxyl radical scavenger) and carvacrol demonstrated a potent bactericidal effect. These results underline the development of defense strategies of the bacteria by synthesis of reactive oxygen species in response to environmental stress conditions, such as carvacrol.

Lipid-Based Liquid Crystals As Carriers for Antimicrobial Peptides: Phase Behavior and Antimicrobial Effect

The number of antibiotic-resistant bacteria is increasing worldwide, and the demand for novel antimicrobials is constantly growing. Antimicrobial peptides (AMPs) could be an important part of future treatment strategies of various bacterial infection diseases. However, AMPs have relatively low stability, because of proteolytic and chemical degradation. As a consequence, carrier systems protecting the AMPs are greatly needed, to achieve efficient treatments. In addition, the carrier system also must administrate the peptide in a controlled manner to match the therapeutic dose window. In this work, lyotropic liquid crystalline (LC) structures consisting of cubic glycerol monooleate/water and hexagonal glycerol monooleate/oleic acid/water have been examined as carriers for AMPs. These LC structures have the capability of solubilizing both hydrophilic and hydrophobic substances, as well as being biocompatible and biodegradable. Both bulk gels and discrete dispersed structures (i.e., cubosomes and hexosomes) have been studied. Three AMPs have been investigated with respect to phase stability of the LC structures and antimicrobial effect: AP114, DPK-060, and LL-37. Characterization of the LC structures was performed using small-angle X-ray scattering (SAXS), dynamic light scattering, ζ-potential, and cryogenic transmission electron microscopy (Cryo-TEM) and peptide loading efficacy by ultra performance liquid chromatography. The antimicrobial effect of the LCNPs was investigated in vitro using minimum inhibitory concentration (MIC) and time-kill assay. The most hydrophobic peptide (AP114) was shown to induce an increase in negative curvature of the cubic LC system. The most polar peptide (DPK-060) induced a decrease in negative curvature while LL-37 did not change the LC phase at all. The hexagonal LC phase was not affected by any of the AMPs. Moreover, cubosomes loaded with peptides AP114 and DPK-060 showed preserved antimicrobial activity, whereas particles loaded with peptide LL-37 displayed a loss in its broad-spectrum bactericidal properties. AMP-loaded hexosomes showed a reduction in antimicrobial activity.

Reservoirs of Non-baumannii Acinetobacter Species

Acinetobacter spp. are ubiquitous gram negative and non-fermenting coccobacilli that have the ability to occupy several ecological niches including environment, animals and human. Among the different species, Acinetobacter baumannii has evolved as global pathogen causing wide range of infection. Since the implementation of molecular techniques, the habitat and the role of non-baumannii Acinetobacter in human infection have been elucidated. In addition, several new species have been described. In the present review, we summarize the recent data about the natural reservoir of non-baumannii Acinetobacter including the novel species that have been described for the first time from environmental sources and reported during the last years.

Molecular analysis of Acinetobacter baumannii strains isolated in Lebanon using four different typing methods

This study analyzed 42 Acinetobacter baumannii strains collected between 2009–2012 from different hospitals in Beyrouth and North Lebanon to better understand the epidemiology and carbapenem resistance mechanisms in our collection and to compare the robustness of pulsed field gel electrophoresis (PFGE), multilocus sequence typing (MLST), repetitive sequence-based PCR (rep-PCR) and bla_OXA-51 sequence-based typing (SBT). Among 31 carbapenem resistant strains, we have detected three carbapenem resistance genes: 28 carried the bla_OXA-23 gene, 1 the bla_OXA-24 gene and 2 strains the bla_OXA-58 gene. This is the first detection of bla_OXA-23 and bla_OXA-24 in Lebanon. PFGE identified 11 types and was the most discriminating technique followed by rep-PCR (9 types), bla_OXA-51 SBT (8 types) and MLST (7 types). The PFGE type A'/ST2 was the dominant genotype in our collection present in Beyrouth and North Lebanon. The clustering agreement between all techniques was measured by adjust Wallace coefficient. An overall agreement has been demonstrated. High values of adjust Wallace coefficient were found with followed combinations: PFGE to predict MLST types  = 100%, PFGE to predict bla_OXA-51 SBT = 100%, bla_OXA-51 SBT to predict MLST = 100%, MLST to predict bla_OXA-51 SBT = 84.7%, rep-PCR to predict MLST = 81.5%, PFGE to predict rep-PCR = 69% and rep-PCR to predict bla_OXA-51 SBT = 67.2%. PFGE and MLST are gold standard methods for outbreaks investigation and population structure studies respectively. Otherwise, these two techniques are technically, time and cost demanding. We recommend the use of bla_OXA-51 SBT as first typing method to screen isolates and assign them to their corresponding clonal lineages. Repetitive sequence-based PCR is a rapid tool to access outbreaks but careful interpretation of results must be always performed.

Current molecular methods in epidemiological typing of Acinetobacter baumannii

ABSTRACT 

The emergence of Acinetobacter baumannii during recent decades as an important nosocomial pathogen responsible of worldwide, intensively documented, outbreaks has resulted in a need for effective epidemiological typing methods. Throughout the years, many typing methods for A. baumannii epidemiological studies have been proposed from phenotypic to molecular methods. Currently, the use of phenotypic typing methods have declined considerably and been progressively replaced by molecular methods. In this review, we introduce the current molecular methods available for A. baumannii typing. Each method has its own advantages and disadvantages, and the selection of an appropriate genotyping method depends on studied objectives. This review sheds light on questions in different epidemiological settings and most molecular methods used to fit these objectives.

First report of blaNDM-1-producing Acinetobacter baumannii isolated in Lebanon from civilians wounded during the Syrian war

OBJECTIVES

The emergence of carbapenem-resistant Acinetobacter baumannii has been observed worldwide. We describe the first detection of A. baumannii carrying the blaNDM-1 gene in Lebanon, isolated from Syrian patients wounded during the civil war.

METHODS

Four carbapenem-resistant A. baumannii strains isolated in 2012 in the Tripoli Government Hospital, Lebanon, from civilians wounded during the Syrian war, were analysed. Susceptibility was determined by disk diffusion testing, and resistance to carbapenems was confirmed by Etest. The presence of blaOXA-23-like, blaOXA-24-like, blaOXA-58-like, blaOXA-143-like, and blaNDM was investigated by PCR. Clonal relationships were studied by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and blaOXA-51 sequence-based typing.

RESULTS

All isolates harboured the blaNDM-1 gene and were negative for other tested carbapenemases. They all belonged to the sequence type 85 and formed a single cluster by PFGE. Finally, blaOXA-51-like gene sequencing revealed the presence of the blaOXA-94 variant in all four isolates.

CONCLUSION

These findings show that Syria constitutes a reservoir for NDM-1-producing bacteria. These results also highlight the need for effective measures to stop the threatening spread of such strains.

High prevalence of closely-related Acinetobacter baumannii in pets according to a multicentre study in veterinary clinics, Reunion Island

Our objective was to study the carriage of Acinetobacter baumannii (AB) in pets in Reunion Island (RI), a French territory in Indian Ocean. Overall, 138 pets were sampled (rectum, mouth, wounds if applicable) in 9 veterinary clinics (VC). The prevalence of AB carriage was 6.5% (95%CI; 2.4, 10.6) and 9 carriers were identified from 4 VC. Hospitalization in a VC and antimicrobial treatment administered within the 15 preceding days were significantly associated with AB carriage (P<0.01 and P<0.05, respectively). Despite the VC in which animals have been sampled were located all around RI, most isolates (8/9) were closely-related (>90% similarity by pulsed-field gel electrophoresis). Additional studies are needed to improve the understanding about interactions between the different reservoirs of AB in RI.

Discordance in the minimal inhibitory concentrations of ertapenem for Enterobacter cloacae: Vitek 2 system versus Etest and agar dilution methods

Our objective was to compare the ertapenem minimal inhibitory concentrations (MICs) for Enterobacter cloacae isolates categorized intermediate or resistant to ertapenem when measured with the Vitek 2 system, with the MICs for these isolates when measured by two methods performed in agar medium: the Etest and agar plate dilution method (APDM). Overall, 50 E. cloacae isolates were included in the study. The mean MIC of ertapenem was 2.92±1.77μg/ml according to the Vitek 2 system, 0.94±0.84μg/ml according to the Etest strips, and 0.93±0.62μg/ml according to the APDM. Furthermore, the MICs determined by the Vitek 2 system were higher than the MICs determined by the two other methods for 96% of strains. Lastly, according to the Etest strips and APDM, 42% of E. cloacae were susceptible to ertapenem. No carbapenemase was identified by the screening method used. Using the Vitek 2 system to determine ertapenem MICs for E. cloacae can have potential consequences in terms of additional carbapenemase-detecting tests and antimicrobial therapy. It would be interesting to determine if the Vitek 2 system is more effective for the detection of carbapenemase producers with low-level carbapenem resistance than the two methods performed in agar medium.

Reservoirs of Acinetobacter baumannii outside the hospital and potential involvement in emerging human community-acquired infections

The objective of the present report was to review briefly the potentially community-acquired Acinetobacter baumannii infections, to update information on the reservoirs of A. baumannii outside the hospital, and to consider their potential interactions with human infections. Most reports on potentially community-acquired A. baumannii have been published during the last 15 years. They concern community-acquired pneumonia, infections in survivors from natural disasters, and infected war wounds in troops from Iraq and Afghanistan. Although the existence of extra-hospital reservoirs of A. baumannii has long been disputed, the recent implementation of molecular methods has allowed the demonstration of the actual presence of this organism in various environmental locations, in human carriage, in pets, slaughter animals, and human lice. Although the origin of the A. baumannii infections in soldiers injured in Southwestern Asia is difficult to determine, there are some arguments to support the involvement of extra-hospital reservoirs in the occurrence of community-acquired infections. Overall, the emergence of community-acquired A. baumannii infections could be associated with interactions between animals, environment, and humans that are considered to be potentially involved in the emergence or re-emergence of some infectious diseases.

Investigation of Acinetobacter baumannii resistance to carbapenems in Marseille hospitals, south of France: a transition from an epidemic to an endemic situation

Carbapenem-resistant Acinetobacter baumannii infections are a worldwide endemic nosocomial threat. Between December 2010 and April 2011, an increase of carbapenem-resistant A. baumannii infections occurred in several Marseille University Hospitals. The aim of this study was to investigate the increase of carbapenem-resistant A. baumannii infections and to characterize the mechanisms of carbapenem resistance. The increase was detected by a homemade computer surveillance program, known as EPIMIC, that monitors antibiotic resistance profiles on a weekly basis. During this period, positive samples of carbapenem-resistant A. baumannii were retrieved from patients hospitalized in different units. Genotyping of the isolates was performed using pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST), and carbapenemase gene analyses were performed to detect the presence of carbapenemases and to determine the relationships of the isolates. Carbapenem-resistant A. baumannii were isolated in a total of 11 patients who were hospitalized in different hospitals units. We identified the presence of the bla(OXA23-like) carbapenemase-encoding gene in all of the isolates and found four major PFGE groups and different MLST groups. These results demonstrate a current evolution in the A. baumannii epidemiology in Marseille with a switch from an epidemic situation to an endemic situation and with several circulating clones.

Correlation between glove use practices and compliance with hand hygiene in a multicenter study with elderly patients

In a study conducted in 11 health care settings for elderly patients, we demonstrated a significant negative correlation between the proportion of glove use outside any risk of exposure to body fluids and compliance with hand hygiene (P < .02). This result underscores a major limitation of strategies for controlling the spread of multidrug-resistant bacteria that recommend systematic glove use for each contact with carriers or their environment.

Cell surface properties of two differently virulent strains of Acinetobacter baumannii isolated from a patient

The aim of this study was to unravel, by focusing on cell surface properties, the underlying virulence factors contributing to the difference in the pathogenicity observed in two Acinetobacter baumannii strains isolated from the same patient. The two strains were phenotypically different: (i) a mucoid strain (AB-M), highly virulent in a mouse model of pneumonia, and (ii) a nonmucoid strain (AB-NM), moderately virulent in the same model. The study of the cell surface properties included the microbial adhesion to solvents method, the measurement of the electrophoretic mobility of bacteria, the analysis of biofilm formation by calcofluor white staining, the adherence to silicone catheters, and scanning electron microscopy. The AB-NM strain was more hydrophobic, more adherent to silicone catheters, and produced more biofilm than the AB-M strain. Scanning electron microscopy showed bacterial cells with a rough surface and the formation of large cell clusters for AB-NM whereas the AB-M strain had a smooth surface and formed only a few cell clusters. Contrary to the results of most previous studies, cell surface properties were not correlated to the virulence described in our experimental model, indicating that mechanisms other than adherence may be involved in the expression of A. baumannii virulence.

Differences in Acinetobacter baumannii strains and host innate immune response determine morbidity and mortality in experimental pneumonia

Despite many reports documenting its epidemicity, little is known on the interaction of Acinetobacter baumannii with its host. To deepen our insight into this relationship, we studied persistence of and host response to different A. baumannii strains including representatives of the European (EU) clones I–III in a mouse pneumonia model. Neutropenic mice were inoculated intratracheally with five A. baumannii strains and an A. junii strain and at several days morbidity, mortality, bacterial counts, airway inflammation, and chemo- and cytokine production in lungs and blood were determined. A. baumannii RUH875 and RUH134 (EU clone I and II, respectively) and sporadic strain LUH8326 resulted in high morbidity/mortality, whereas A. baumannii LUH5875 (EU clone III, which is less widespread than clone I and II) caused less symptoms. A. baumannii type strain RUH3023^T and A. junii LUH5851 did not cause disease. All strains, except A. baumannii RUH3023^T and A. junii LUH5851, survived and multiplied in the lungs for several days. Morbidity and mortality were associated with the severity of lung pathology and a specific immune response characterized by low levels of anti-inflammatory (IL-10) and specific pro-inflammatory (IL-12p40 and IL-23) cytokines at the first day of infection. Altogether, a striking difference in behaviour among the A. baumannii strains was observed with the clone I and II strains being most virulent, whereas the A. baumannii type strain, which is frequently used in virulence studies appeared harmless.

Measurement of hand hygiene compliance and gloving practices in different settings for the elderly considering the location of hand hygiene opportunities during patient care

We monitored hand hygiene and gloving practices by direct observation in 8 health care settings for elderly persons in western France. Compliance with hand hygiene was better than that reported by previous studies, was better for single contacts and before or after a series of successive contacts than inside series, and was closely related to gloving practices. Practices differed among the settings.

Impact of a multi-faceted training intervention on the improvement of hand hygiene and gloving practices in four healthcare settings including nursing homes, acute-care geriatric wards and physical rehabilitation units

AIMS

To assess the impact of a multi-faceted training program on the compliance with hand hygiene and gloving practices.

BACKGROUND

Hand hygiene is considered as the cornerstone of the prevention of hospital-acquired infections. Several studies have enhanced the poor effectiveness of training programs in improving hand hygiene compliance.

DESIGN

A before-after evaluation study.

METHODS

The study was conducted in four healthcare settings before and after an intervention program which included the performance feedback of the first evaluation phase, three six-h training sessions, the assessment of hand hygiene performance with teaching boxes and the organisation of one full-day session devoted to institutional communication around hand hygiene in each setting. Hand hygiene compliance and quality of hand rubbing were evaluated. Hand hygiene opportunities were differentiated into extra-series opportunities (before or after a single contact and before the first contact or after the last contact of a series of consecutive contacts) and intra-series opportunities (from the opportunity following the first contact to the opportunity preceding the last in the same series).

RESULTS

Overall, 969 contacts corresponding to 1,470 hand hygiene opportunities (760 during the first phase and 710 during the second) were observed. A significant improvement of observed practices was recorded for the hand hygiene compliance in intra-series opportunities (39·0% vs. 19·0%; p < 10(-5) ), the proportion of gloves worn if indicated (71·4% vs. 52·0%; p < 0·001) and the quality of hand rubbing (85·0% vs. 71·9%; p < 10(-5) ).

CONCLUSIONS

Some of the performances measured for both hand hygiene and gloving practices were improved. We plan to extend this investigation by performing a qualitative study with experts in behavioural sciences to try improving practices for which adherence was still weak after the training program such as hand hygiene in intra-series opportunities.

RELEVANCE TO CLINICAL PRACTICE

This study underscored the usefulness of implementing contextualised training programs, while more traditional courses have shown little impact.

Epidemiology and antimicrobial resistance of Streptococcus pneumoniae in France in 2007: data from the pneumococcus surveillance network

Antimicrobial resistance of Streptococcus pneumoniae in France is closely monitored by the pneumococcus surveillance network, founded in 1995, which collects data from regional observatories (Observatoire Régionaux du Pneumocoque [ORP]). In 2007, 23 ORPs analyzed the antibiotic susceptibility of 5,302 isolates of S. pneumoniae recovered in France from cerebrospinal fluid, blood, middle ear fluid, and pleural fluid, as well as from adult respiratory samples. The study showed that 38.2% of the strains were nonsusceptible to penicillin, 19.3% nonsusceptible to amoxicillin, and 10.5% nonsusceptible to cefotaxime. The percentage of pneumococcus nonsusceptible to penicillin varied according to both the sample and the age of the patient (child/adult): blood (27.8%/32.5%), cerebrospinal fluid (33.7%/34.6%), middle ear fluid (60.2%/27.5%), and pleural fluid (50.0%/31.0%). Between 2003 and 2007, the frequency of penicillin resistance in invasive pneumococcal disease gradually decreased from 46.4% to 29.0% in children and from 43.8% to 32.7% in adults. This decrease coincided with the introduction of a seven-valent pneumococcal conjugate vaccine into immunization programs and with a general reduction in levels of antibiotic consumption in France.

Comparative in vitro activity of Meropenem, Imipenem and Piperacillin/tazobactam against 1071 clinical isolates using 2 different methods: a French multicentre study

BACKGROUND

Meropenem is a carbapenem that has an excellent activity against many gram-positive and gram-negative aerobic, facultative, and anaerobic bacteria. The major objective of the present study was to assess the in vitro activity of meropenem compared to imipenem and piperacillin/tazobactam, against 1071 non-repetitive isolates collected from patients with bacteremia (55%), pneumonia (29%), peritonitis (12%) and wound infections (3%), in 15 French hospitals in 2006. The secondary aim of the study was to compare the results of routinely testings and those obtained by a referent laboratory.

METHOD

Susceptibility testing and Minimum Inhibitory Concentrations (MICs) of meropenem, imipenem and piperacillin/tazobactam were determined locally by Etest method. Susceptibility to meropenem was confirmed at a central laboratory by disc diffusion method and MICs determined by agar dilution method for meropenem, imipenem and piperacillin/tazobactam.

RESULTS

Cumulative susceptibility rates against Escherichia coli were, meropenem and imipenem: 100% and piperacillin/tazobactam: 90%. Against other Enterobacteriaceae, the rates were meropenem: 99%, imipenem: 98% and piperacillin/tazobactam: 90%. All Staphylococci, Streptococci and anaerobes were susceptible to the three antibiotics. Against non fermeters, meropenem was active on 84-94% of the strains, imipenem on 84-98% of the strains and piperacillin/tazobactam on 90-100% of the strains.

CONCLUSIONS

Compared to imipenem, meropenem displays lower MICs against Enterobacteriaceae, Escherichia coli and Pseudomonas aeruginosa. Except for non fermenters, MICs90 of carbapenems were <4 mg/L. Piperacillin/tazobactam was less active against Enterobacteriaceae and Acinetobacter but not P. aeruginosa. Some discrepancies were noted between MICs determined by Etest accross centres and MICs determined by agar dilution method at the central laboratory. Discrepancies were more common for imipenem testing and more frequently related to a few centres. Overall MICs determined by Etest were in general higher (0.5 log to 1 log fold) than MICs by agar dilution.

High content screening identifies decaprenyl-phosphoribose 2' epimerase as a target for intracellular antimycobacterial inhibitors

A critical feature of Mycobacterium tuberculosis, the causative agent of human tuberculosis (TB), is its ability to survive and multiply within macrophages, making these host cells an ideal niche for persisting microbes. Killing the intracellular tubercle bacilli is a key requirement for efficient tuberculosis treatment, yet identifying potent inhibitors has been hampered by labor-intensive techniques and lack of validated targets. Here, we present the development of a phenotypic cell-based assay that uses automated confocal fluorescence microscopy for high throughput screening of chemicals that interfere with the replication of M. tuberculosis within macrophages. Screening a library of 57,000 small molecules led to the identification of 135 active compounds with potent intracellular anti-mycobacterial efficacy and no host cell toxicity. Among these, the dinitrobenzamide derivatives (DNB) showed high activity against M. tuberculosis, including extensively drug resistant (XDR) strains. More importantly, we demonstrate that incubation of M. tuberculosis with DNB inhibited the formation of both lipoarabinomannan and arabinogalactan, attributable to the inhibition of decaprenyl-phospho-arabinose synthesis catalyzed by the decaprenyl-phosphoribose 2′ epimerase DprE1/DprE2. Inhibition of this new target will likely contribute to new therapeutic solutions against emerging XDR-TB. Beyond validating the high throughput/content screening approach, our results open new avenues for finding the next generation of antimicrobials.

Tuberculosis is still a major threat to global health. The disease in humans is caused by a bacterium, Mycobacterium tuberculosis, and treatment of an infected individual requires more than six months of chemotherapy. Because such a long course of treatment is required, compliance is low, which can result in the development of multidrug resistant strains (MDR-TB) and even extremely resistant strains (XDR-TB). Identifying new drug targets and potential lead therapeutic compounds are needed to combat MDR-XDR-TB. We developed a new type of assay based on the visualization of mycobacterium replication within host cells and applied it for the search of compounds that are able to chase the pathogen from its hideout. As a result, we found 20 new series of drug candidates that are effective against the bacilli in its hiding place, potentially addressing a crucial aspect in the resilience of the disease. We also showed that one series of compounds acts by inhibiting a key enzyme required for the synthesis of an essential component from the mycobacterial cell wall that is not targeted by any of the commercially available antituberculosis drugs. Altogether, our results pave the way for development of the next generation of antibacterial agents.

Infection et rupture de varice œsophagienne au cours de la cirrhose

Endotoxemia and bacterial infection are frequent in patients with cirrhosis. They alter systemic and splanchnic hemodynamics, worsen coagulation disorders, impair liver function and thus may induce variceal bleeding. In variceal bleeding, bacterial infection favours failure to control bleeding, early rebleeding, and death. In patients with cirrhosis and variceal bleeding, antibiotic-prophylaxis decreases bacterial infection and the incidence of early rebleeding, and, more important, significantly decreases the death rate in these patients.

Impact of the reinforcement of a Methicillin-Resistant Staphylococcus aureus Control Programme: A 3-year evaluation by several indicators in a French University Hospital

Our objective was to evaluate the impact of the reinforcement of a methicillin-resistant Staphylococcus aureus (MRSA) control programme and to assess the impact of risk adjustment on the interpretation of data. A stepwise, retrospective analysis of 3-year prospectively collected data was performed in a 600-bed French teaching hospital in the Parisian area. A reinforcement of a pre-existing programme for limiting the spread of MRSA was implemented in 2002 and 2003 by increasing the frequency of the feedback of surveillance data, by using alcohol-based disinfectants, and by increasing patient screening. Different indicators were used to follow the change over time of MRSA transmission: the proportion of MRSA acquired in our hospital, the incidence of newly acquired MRSA/1,000 patient-days (PD) (incidence of newly acquired MRSA), the incidence of newly acquired MRSA isolated in at least one clinical specimen/1,000 PD (incidence of newly acquired clinical MRSA), and a risk-adjusted indicator, the incidence of newly acquired-MRSA isolated in at least one clinical specimen/1,000 PD of carriers identified at admission (incidence related to the risk of acquisition). The change over time of these indicators was studied with the chi-square test for trend. During the study, all indicators decreased significantly, with a mean drop of 0.07/1,000 PD for the incidence of newly acquired clinical MRSA, and a mean drop of 3.0/1,000 PD for the incidence related to the risk of acquisition. The proportion of MRSA acquired in our hospital decreased from 49.3% in 2002 to 24.1% in 2004. Concurrently, between 2002 and 2004, the number of patients screened on admission to hospital or at the time of intra-hospital transfer increased by 31% and the consumption of waterless alcohol-based hand disinfectants increased by 244%. The decreasing trend of all indicators emphasizes the effectiveness of the reinforcement of our MRSA control programme. From 2002 to 2004, the trend of the indicator related to the risk of acquisition over time is similar to those of other indicators. Further studies should be useful to assess if risk-adjustment is absolutely necessary when tracking rates within a single institution.

Consideration of age at admission for selective screening to identify methicillin-resistant Staphylococcus aureus carriers to control dissemination in a medical ward

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has become an increasingly important pathogen responsible for hospital-acquired infections. Our study was to evaluate the efficiency of our selective screening program for methicillin-resistant Staphylococcus aureus (MRSA) carriers at admission to nonintensive care units.

METHODS

During 6 months, all patients were screened at admission to an internal medicine ward, at which time they were classified as patients at risk of carriage (PRC) and those with no known risk factor. The amplitude of cross transmission was estimated using various indicators during this universal screening period and during the same calendar period of the preceding year (selective screening).

RESULTS

The prevalence of MRSA carriage at admission was 5.5%. Among the 22 carriers identified, only 10 were PRC. Age >80 years was significantly associated with MRSA carriage upon admission (OR, 3.5; P < .01). All estimation indicators of MRSA dissemination amplitude were significantly lower during universal screening (relative risks varied from 2.79 to 26.4 according to indicators), demonstrating the need to broaden our criteria defining PRC.

CONCLUSION

Adding patients >80 years of age to our PRC definition would increase screening sensitivity (15 carriers identified for 128 patients sampled) and would enable early implementation of barrier precautions for the additional carriers identified.

Evaluation of a Strategy of Screening Multiple Anatomical Sites for Methicillin-Resistant Staphylococcus aureus at Admission to a Teaching Hospital

We compared the sensitivity of screening with nasal culture alone with that of a multiple-site screening method for the identification of carriers of methicillin-resistant Staphylococcus aureus at hospital admission. If nasal cultures alone had been used during the 1-year study, 27.0% of carriers of methicillin-resistant S. aureus would have been missed, which corresponds to 560 theoretical isolation days. If rectal screening had not been used, 431 theoretical isolation days would have been missed, and, if axillary screening had not been used, 99 theoretical isolation days would have been missed.

Control and Outcome of a Large Outbreak of Colonization and Infection with Glycopeptide-Intermediate Staphylococcus aureus in an Intensive Care Unit

BACKGROUND

Glycopeptide-intermediate Staphylococcus aureus (GISA) is emerging as a cause of nosocomial infection and outbreaks of infection and colonization in intensive care units (ICUs). We describe an outbreak of GISA colonization/infection and the ensuing control measures in an ICU and investigate outcomes of the affected patients.

METHODS

We describe an outbreak of GISA colonization and infection that affected 21 patients in a medical ICU at a tertiary care teaching hospital, as well as the measures taken to eradicate the GISA strain.

RESULT

Recognition of the outbreak was difficult. Infections, all of which were severe, were diagnosed in 11 of 21 patients. Patient isolation and barrier precautions failed when used alone. Addition of a stringent policy of restricted admissions, twice daily environmental cleaning, and implementation of hand decontamination with a hydroalcoholic solution led to outbreak termination. This was associated with increases in workload, despite a marked decrease in the number of admissions.

CONCLUSION

This first description of a large outbreak of GISA colonization and infection underlines the importance of routine GISA-strain detection when methicillin-resistant S. aureus is isolated. Outbreak control may be difficult to achieve.

Influence of fluoride, hydrogen peroxide and lactic acid on the corrosion resistance of commercially pure titanium

Titanium is widely used in dental implantology and orthopaedics due to its excellent corrosion resistance and mechanical properties. However, it has been reported that Ti is sensitive to F(-), H(2)O(2) and lactic acid. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the corrosion resistance of CP-Ti disks after 9 days immersion in different test solutions, based on artificial saliva containing F(-) (0.5% and 2.5%), H(2)O(2) (0.1% and 10%) and/or lactic acid. Because activated macrophages and bacteria can also release locally some of these oxidative compounds, we investigated the role of these cells when plated onto titanium disks. The surface roughness (R(a)) was highly increased when titanium disks were immersed in artificial saliva containing F(-), H(2)O(2) and lactic acid. After 21 days of cell culture, R(a) was significantly increased on disks incubated with activated-J774.2 cells or Streptococcus mitis. AFM appeared to be more sensitive than SEM in evaluating the corrosion of the titanium. Chemical species, either environmental or those released by macrophages and bacteria, can provoke a marked attack of the titanium surface.

Accuracy of delayed (24 hours) processing of bronchoalveolar lavage for diagnosing bacterial pneumonia

OBJECTIVE

Pneumonia in the intensive care unit is associated with a high mortality rate. Diagnostic accuracy is mandatory to improve prognosis. However, in many hospitals, samples from the respiratory tract cannot be immediately processed bacteriologically around the clock. This may complicate therapeutic choice based on invasive diagnostic procedures. We evaluated the effect of storing bronchoalveolar lavage fluid at 4 degrees C for 24 hrs on direct examination and culturing for diagnosing pneumonia.

DESIGN

Prospective, paired comparison study.

SETTING

Intensive care unit in a university hospital.

PATIENTS

A total of 93 bronchoalveolar lavages were performed on 66 intensive care unit patients who were suspected to have bacterial pneumonia.

INTERVENTION

Each sample was divided into two; one half was processed immediately (H0), and the other was processed after refrigeration at 4 degrees C for 24 hrs (H24).

MEASUREMENTS AND MAIN RESULTS

All negative H0 culture samples (n = 31) were also negative for pathogens in H24 samples. Sixty two bronchoalveolar lavage cultures yielded one or more microorganisms, giving a total of 113 microorganisms in one or both samples. The results of positive cultures at H0 and H24 for the culturing diagnostic threshold of 10 colony forming units/mL agreed well (Kappa coefficient, 0.84); agreement was even better (Kappa coefficient, 0.85) when possible contaminants were excluded. The bias calculated as the mean difference between paired culture results was 0.195 +/- 1.31 (Delta log). When considering the accepted threshold of 10 colony forming units/mL, specificity at H24 compared to H0 was excellent (100%), but sensitivity was slightly lower (80%).

CONCLUSION

Delayed processing of bronchoalveolar lavage sampling is an acceptable alternative when immediate culturing cannot be performed because it enables antibiotic administration.

The Impact of Methicillin Resistance on the Outcome of Poststernotomy Mediastinitis Due toStaphylococcus aureus

The impact of methicillin resistance on morbidity and mortality among patients with severe Staphylococcus aureus infection remains highly controversial. We retrospectively analyzed patients with mediastinitis due to methicillin-susceptible S. aureus (MSSA; 145 patients) or methicillin-resistant S. aureus (MRSA; 73 patients) who were treated with closed drainage using Redon catheters. Initial empirical antibiotic therapy was appropriate for every patient. Patients with MRSA mediastinitis were older, had higher disease severity scores at admission to the intensive care unit (ICU), and had longer periods of MRSA incubation. Multivariate analysis revealed that ICU mortality was associated with age of > or =65 years, incubation time of < or =15 days, bacteremia, higher Acute Physiology and Chronic Health Evaluation II score, and receipt of mechanical ventilation > or =2 days after surgical debridement, but not with methicillin resistance. After adjustment, durations of mechanical ventilation and Redon catheter drainage were similar for both groups (for patients infected with MRSA, only the time to mediastinal effluent sterilization remained longer). Methicillin resistance did not significantly affect ICU mortality among patients with poststernotomy mediastinitis who benefited from optimal treatments.

Carriage of methicillin-resistant Staphylococcus aureus among hospital employees: prevalence, duration, and transmission to households

OBJECTIVE

To assess the prevalence and duration of methicillin-resistant Staphylococcus aureus (MRSA) carriage among hospital employees and transmission to their households.

DESIGN

A point-prevalence survey of MRSA carriage (nasal swabbing) of staff and patients throughout the hospital; a prevalence survey of MRSA carriage in 2 medical wards, with carriers observed to estimate carriage duration; and evaluation of transmission to MRSA-positive workers' families. All MRSA isolates were analyzed by pulsed-field gel electrophoresis. During the study, no MRSA outbreak was detected among hospitalized patients.

SETTING

A 600-bed, public tertiary-care teaching hospital near Paris.

RESULTS

Sixty MRSA carriers were identified among 965 healthcare providers (prevalence, 6.2%; CI95, 4.7%-7.7%). Prevalence was higher in staff from clinical wards than from elsewhere (9.0% vs 2.1%; P < .0001). Identity of isolates from employees and patients varied from 25% in medical wards to 100% in the long-term-care facility. MRSA carriage was identified in 14 employees from 2 medical wards (prevalence, 19.4%; CI95, 10.3%-28.5%). Prevalence depended on the length of service in these wards. Transmission to households was investigated in 10 MRSA-positive workers' families and was found in 4. All isolates from each family were identical.

CONCLUSIONS

Few data are available concerning the prevalence of MRSA carriers among hospital employees in the absence of an outbreak among patients. MRSA transmission between patients and employees likely depends on the frequency and duration of exposure to MRSA-positive patients and infection control measures employed. Frequent transmission of MRSA from colonized healthcare workers to their households was documented.

Infectious and inflammatory dissemination are affected by ventilation strategy in rats with unilateral pneumonia

OBJECTIVE

To evaluate the effect of V(T) reduction and alveolar recruitment on systemic and contralateral dissemination of bacteria and inflammation during right-side pneumonia.

DESIGN

Interventional animal study. SETTING. University hospital research laboratory.

SUBJECTS

A total of 54 male Wistar rats.

INTERVENTIONS

One day after right lung instillation of 1.4x10(7) Pseudomonas aeruginosa, rats were left unventilated or ventilated for 2 h at low V(T) (6 ml/kg) with different strategies of alveolar recruitment: no PEEP, 8 cm H(2)O PEEP, 8 cm H(2)O PEEP in a left lateral position, 3 cm H(2)O PEEP with partial liquid ventilation, or high V(T) (set such as end-inspiratory pressure was 30 cm H(2)O) without PEEP (ZEEP). After ventilation the lungs, spleen and liver were cultivated for bacterial counts. Global bacterial dissemination was scored considering the percentage of positive spleen, liver and left lung cultures. TNF-alpha was assayed in plasma before and after mechanical ventilation.

MEASUREMENTS AND RESULTS

All rats had right-side pneumonia with similar bacterial counts. All mechanical ventilation strategies, with the exception of low V(T)-PEEP 8, promoted contralateral lung dissemination. Overall bacterial dissemination was less in non-ventilated controls (22%) and low V(T)-PEEP 8 (22%) than in high V(T)-ZEEP (67%), low V(T)-PEEP 8 in left lateral position (59%) and low V(T)-ZEEP (56%) ( p<0.05). Partial liquid ventilation prevented systemic bacterial translocation, but at the expense of contralateral bacterial seeding. Plasma TNF-alpha concentration increased significantly after mechanical ventilation with no PEEP at both high and low V(T).

CONCLUSIONS

Our results suggest that PEEP might reduce the risk of ventilation-induced bacterial and inflammatory mediator dissemination during pneumonia.

[Update on Acinetobacter baumannii]

RESISTANCE TO IMIPENEM: The increase in the prevalence of A. baumannii resistance is worrying because of the diversity of the enzymes implicated in the resistance and its epidemic diffusion that is always difficult to handle. BROAD SPECTRUM BETA-LACTAMASE: Still rare in Acinetobacter, a broad spectrum beta-lactamase has been demonstrated in a strain isolated during a urinary infection and at the origin of an outbreak.

RISK FACTORS

Other than the classic risk factors, a survey regrouping the data from 28 Spanish hospitals showed that hospitalisation in an intensive care unit and the administration of an inappropriate antibiotherapy are two risk factors of mortality during Acinetobacter infections.

DEPENDING ON THE PRODUCTION OF SLIME

An antibiotherapy must be administered earlier in strains producing slime than in strains that do not. TO FIGHT ACINETOBACTER: It is essential to break the epidemic chain. In addition to this priority measure, a policy of correct antibiotic use must be installed.

[Acinetobacter, a nosocomial pathogen. Contribution of experimental models]

EPIDEMIOLOGY

The increasing importance of Acinetobacter as a nosocomial pathogen responsible for outbreaks in intensive care units has been pointed out for twenty years. Today Acinetobacter infections are essentially pneumonia in patients under mechanical ventilation.

EXPERIMENTAL MODELS

Most clinical isolates are resistant to b-lactam antibiotics as well as to other drugs. Animal models represent an essential step between in vivo testing an<d clinical studies, necessary to understand physiopathology, pharmacology and efficacy of therapy. The virulence of clinical isolates of Acinetobacter spp has been studied in a mouse model of systemic infection. Pharmacological studies and efficacy of antibiotics have been studied in a mouse model of Acinetobacter pneumonia.

HUMAN THERAPEUTICS

The majority of strains are multi-resistant to antibiotics and the infections they cause are difficult to treat. Isolated or combined Sulbactam has often been used with success.

[Treatment of genital infections in gynecology]

Choice of antimicrobial agents and length of therapy of infections of the female genital tract and chemotherapy are presented with particular mention to their side effects. Clinical approach and antibiotic regimens of pelvic inflammatory diseases are discussed.

Accuracy of delayed cultures of plugged telescoping catheter samples for diagnosing bacterial pneumonia

OBJECTIVE

It is not always feasible to culture immediately bacteriologic samples of protected pulmonary specimens on a 24-hr basis before starting antibiotic treatment. We have evaluated the effect of delaying the culture of immediate plugged telescoping catheter (PTC) samples performed before starting antibiotherapy.

DESIGN

Prospective paired comparisons study.

SETTING

Intensive care unit in a university hospital.

PATIENTS

Ninety-nine PTCs were performed on 68 intensive care unit patients suspected of nosocomial or community- acquired bacterial pneumonia.

INTERVENTION

PTC samples were divided into two aliquots: one for immediate (H0) analysis and one for storage at 4 degrees C (H24) for 24 hrs before being cultured.

MEASUREMENTS AND MAIN RESULTS

The results from these delayed cultures (H24) were compared with those from immediate ones (H0). All negative H0 samples (n = 59) were also negative at H24. Forty PTCs yielded one or more microorganisms, with a total of 69 microorganisms in one or both samples. H0 and H24 cultures were concordant in 119 of 128 (97.9%) cases (kappa coefficient value 0.79) with a threshold of 103 colony-forming units (cfu)/mL. Agreement between paired cultures was very good. The bias calculated as the mean difference between paired culture results was 0.128 +/- 1.024 (Deltalog). Concordance using the 103 cfu/mL threshold (102/107 cases, kappa coefficient value 0.82) and agreement were enhanced (0.067 +/- 0.645) when possible contaminants were excluded (n = 21).

CONCLUSIONS

Storing PTC specimens for 24 hrs at 4 degrees C is an acceptable alternative when culturing cannot be performed immediately. This allows starting antibiotic treatment without any delay.

An outbreak of imipenem-resistant Acinetobacter baumannii in critically ill surgical patients

OBJECTIVE

To describe an outbreak of imipenem-resistant Acinetobacter baumannii (IR-Ab) and the measures for its control, and to investigate risk factors for IR-Ab acquisition.

DESIGN

An observational and a case-control study.

SETTING

A surgical intensive care unit (ICU) in a university tertiary care hospital.

METHODS

After admission to the ICU of an IR-Ab-positive patient, patients were prospectively screened for IR-Ab carriage upon admission and then once a week. Environmental cleaning and barrier safety measures were used for IR-Ab carriers. A case-control study was performed to identify factors associated with IR-Ab acquisition. Cases were patients who acquired IR-Ab. Controls were patients who were hospitalized in the ICU at the same time as cases and were exposed to IR-Ab for a similar duration as cases. The following variables were investigated as potential risk factors: baseline characteristics, scores for severity of illness and therapeutic intervention, presence and duration of invasive procedures, and antimicrobial administration.

RESULTS

Beginning in May 1996, the outbreak involved 17 patients over 9 months, of whom 12 acquired IR-Ab (cases), 4 had IR-Ab isolates on admission to the ICU, and 1 could not be classified. Genotypic analysis identified two different IR-Ab isolates, responsible for three clusters. Ten of the 12 nosocomial cases developed infection. Control measures included reinforcement of barrier safety measures, limitation of the number of admissions, and thorough environmental cleaning. No new case was identified after January 1997. Eleven of the 12 cases could be compared to 19 controls. After adjustment for severity of illness, a high individual therapeutic intervention score appeared to be a risk factor for IR-Ab acquisition.

CONCLUSION

The outbreak ended after strict application of control measures. Our results suggest that high work load contributes to IR-Ab acquisition.

In vivo activity of levofloxacin alone or in combination with imipenem or amikacin in a mouse model of Acinetobacter baumannii pneumonia

We evaluated the in vivo activity of levofloxacin alone or in combination with imipenem or amikacin in a mouse model of Acinetobacter baumannii pneumonia using a susceptible strain and one with low-level resistance (MIC/MBC of levofloxacin: 0.06/0.06 and 4/4 mg/L, respectively). As demonstrated previously with other pathogens, the AUC/MIC ratio predicted the efficacy of fluoroquinolones against A. baumannii. This parameter correlated with bactericidal effect and survival. Combination therapy did not enhance the efficacy of levofloxacin.

Nosocomial bacteremia in HIV patients: the role of peripheral venous catheters

A retrospective case-control study compared 40 human immunodeficiency virus (HV)-infected patients with 43 nosocomial bacteremias (NB) to 77 HIV-infected patients without NB. Presence of a peripheral venous catheter (PVC) was associated with occurrence of NB and was significantly more frequent in NB without an identified source. PVCs probably are an underestimated source of NB in HIV-infected patients.

Control of staphylococcal adhesion to polymethylmethacrylate and enhancement of susceptibility to antibiotics by poloxamer 407

We studied the antiadhesive effect of Poloxamer 407 (P407), together with modifications in the antimicrobial susceptibility of residual adherent staphylococci. Bacterial adherence was markedly inhibited (77% to more than 99.9%) whether polymethylmethacrylate was exposed to P407 before or during the adherence assay. Furthermore, residual adherent staphylococci appeared to be more susceptible to antibiotic activity, suggesting that combination of P407 with antibiotics could be a promising approach to the prevention of infection of foreign material.