Introduced in the 1980s, carbapenem antibiotics have served as the last line of defense against multidrug-resistant Gram-negative organisms. Over the last decade, carbapenem-resistant Enterobacteriaceae (CRE) have emerged as a significant public health threat. This review summarizes the molecular genetics, natural history, and epidemiology of CRE and discusses approaches to prevention and treatment.
Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae is a pathogen causing an epidemic of carbapenem-resistant Enterobacteriaceae (CRE) in healthcare settings in developed countries. The spread is primarily by patient-to-patient transmission. Understanding the mode of spread is important for designing effective control measures. We studied CRE dissemination by quantifying environmental contamination from the vicinity of 34 carriers using selective contact plates. We examined rectal CRE concentrations and clinical characteristics and correlated these with environmental contamination. Eight (24%) carriers were non-spreaders: no CRE was detected in their vicinity. Faecal continence was the only independent predictor of being a non-spreader. Among the 26 spreaders, we identified a distinct group of six (18%) super-spreaders who accounted for 79% of environmental colonies detected. Super-spreaders were likely to have high rectal CRE concentrations and to have been admitted with respiratory disease. CRE spread to the environment follows the 20/80 rule: 20% of carriers are responsible for 80% of shedding and may play a central role in CRE transmission.
In the last decade, the global emergence of carbapenem resistance in Enterobacteriaceae has posed great concern to public health. Data concerning the role of environmental contamination in the dissemination of carbapenem-resistant Enterobacteriaceae (CRE) are currently lacking. Here, we aimed to examine the extent of CRE contamination in various sites in the immediate surroundings of CRE carriers and to assess the effects of sampling time and cleaning regimens on the recovery rate. We evaluated the performance of two sampling methods, CHROMAgar KPC contact plate and eSwab, for the detection of environmental CRE. eSwab was followed either by direct plating or by broth enrichment. First, 14 sites in the close vicinity of the carrier were evaluated for environmental contamination, and 5, which were found to be contaminated, were further studied. The environmental contamination decreased with distance from the patient; the bed area was the most contaminated site. Additionally, we found that the sampling time and the cleaning regimen were critical factors affecting the prevalence of environmental CRE contamination. We found that the CHROMAgar KPC contact plate method was a more effective technique for detecting environmental CRE than were eSwab-based methods. In summary, our study demonstrated that the vicinity of patients colonized with CRE is often contaminated by these organisms. Using selective contact plates to detect environmental contamination may guide cleaning efficacy and assist with outbreak investigation in an effort to limit the spread of CRE.
Inoculation with Azospirillum brasilense exerts beneficial effects on plant growth and crop yields. In this study, a comparative analysis of maize (Zea mays) root inoculated or not inoculated with A. brasilense strains was performed in two soils. Colonization dynamics of the rhizobacteria were tracked in various root compartments using 16S rRNA-targeted probes and 4',6'diamidino-2-phenylindole staining, and the structure of bacterial populations in the same samples was analyzed by denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction products of the 16S rRNA gene. Based on whole cell hybridization, a large fraction of the bacterial community was found to be active in both the rhizoplane-endorhizosphere and rhizosphere soil compartments, in both soil types. A DGGE fingerprint analysis revealed that plant inoculation with A. brasilense had no effect on the structural composition of the bacterial communities, which were also found to be very similar at the root tip and at zones of root branching. However, rhizobacterial populations were strongly influenced by plant age, and their complexity decreased in the rhizoplane-endorhizosphere in comparison to rhizosphere soil. A clone library generated from rhizosphere DNA revealed a highly diverse community of soil and rhizosphere bacteria, including an indigenous Azospirillum-like organism. A large proportion of these clones was only distantly related to known species.
It is more convenient and practical to collect rectal swabs than stool specimens to study carriage of colon pathogens. In this study, we examined the ability to use rectal swabs rather than stool specimens to quantify Klebsiella pneumoniae carbapenemase (KPC)-producing carbapenem-resistant Enterobacteriaceae (CRE). We used a quantitative real-time PCR (qPCR) assay to determine the concentration of the bla KPC gene relative to the concentration of 16S rRNA genes and a quantitative culture-based method to quantify CRE relative to total aerobic bacteria. Our results demonstrated that rectal swabs are suitable for quantifying the concentration of KPC-producing CRE and that qPCR showed higher correlation between rectal swabs and stool specimens than the culture-based method. Klebsiella pneumoniae carbapenemase (KPC)-type enzymes are -lactamases, capable of hydrolyzing all known -lactam antibiotics (1). The spread of the bla KPC genes has led to the emergence of carbapenem-resistant Enterobacteriaceae (CRE), mostly K. pneumoniae, as important nosocomial pathogens causing outbreaks in various parts of the world (2). Infections by these pathogens are severe, with an estimated case fatality rate of 35%, and thus considered a clinical and public health threat (3).Active surveillance of high-risk patients has been advocated in areas where CRE are endemic or where there are ongoing outbreaks (4). Although stool samples are considered the "gold standard" specimen for studying gut bacteria in general (5, 6) and for detecting CRE in particular (7), hospital epidemiologists, clinical microbiologists, and researchers frequently use rectal swabs due to practical considerations, such as ease of collection, handling, and processing (8-11). Several studies compared the qualitative sensitivity of rectal swabs versus stool specimens for the recovery and detection of various pathogens, such as Campylobacter fetus subsp. jejuni, vancomycin-resistant Enterococcus faecium (VRE), and Lawsonia intracellularis, by culturing and/or molecular quantification methods (12)(13)(14). These studies had mixed results, with some studies reporting comparable test sensitivity with either sample type (12-14) and others reporting significantly lower sensitivity with rectal swabs (15, 16). For quantitative testing, rectal swabs are believed to be inadequate due to the high variation in the quantity of fecal material on each swab and the difficulties in determining this quantity (17)(18)(19)(20).As the human colon flora is a diverse ecosystem, which is populated by both anaerobic and aerobic microorganisms (21), development of quantitative methods, such as culture-and quantitative real-time PCR (qPCR)-based techniques is important for studying the bacterial composition of this complex ecosystem. The use of these methods can lead to a thorough knowledge about gastrointestinal community composition, the effects of antibiotics, and their roles in health and disease.Here, we suggest an alternate methodology for quantifying pathogens that would overcome the pr...
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