Molecular Approaches to Detection of Bacteria in Critical Care Patients

DOI: 10.1007/978-3-540-49433-1_5

ABSTRACT For over 100 years clinical medicine has relied on culture-based techniques to define infections in patients. However, over
the past 30 years, it has become clear that culture-independent methods more completely describe both microbial diversity
and community dynamics and the importance of such interactions in states of health and disease has been revealed [1, 2]. Furthermore, the use of culture-based techniques has clouded our understanding of the pathogenesis of human infections.
The concept that one species causes infection by entering the host, defeating the host’s defense system and multiplying to
a threshold that allows it to cause injury is probably only applicable for a small subset of microbes, e.g., bioterror agents.
The new emerging paradigm in microbial pathogenesis is that many organisms, such as Streptococcus pneumoniae, already exist in bacterial communities of the oro- and nasopharynx of most healthy individuals and that a change in their
virulence gene expression and/or an increase in numbers permitting dissemination cause symptoms of infection [3]. The molecular signals that bring about these shifts in pathogen physiology are not fully understood; however, given the
importance of bacterial cell-to-cell signaling (quorum sensing) it is possible that shifts in bacterial community composition
may lead to emergence and dominance of pre-existing pathogenic species within the community. This hypothesis is supported
by the finding that within hours of their admission to the intensive care unit (ICU), critically ill patients exhibit dramatic
changes in the bacterial communities colonizing their oro- and nasal pharynx [4, 5].

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    ABSTRACT: Knowledge of the determinant factors responsible for the presence of antimicrobial-resistant pathogens in severe nursing home-acquired pneumonia (NHAP) is deemed essential for antibiotic selection. Data for institutionalized patients with cases of severe pneumonia confirmed by culture of protected bronchoalveolar lavage fluid samples (> or =10(3) cfu/mL) during a 36-month period were analyzed. A classification tree with a sensitivity of 100% was developed using binary recursive partitioning to predict which patients are unlikely to have drug-resistant pathogen (DRP)-related pneumonia. Of the 88 patients who satisfied the inclusion criteria, 17 had at least 1 DRP recovered from the lower respiratory tract. The predictor variables were the Activity of Daily Living score and previous use of antibiotics. Prospective application of the model in 47 patients over a 24-month period yielded a sensitivity of 100% (95% confidence interval [CI], 71.3%-100%) and a specificity of 69.4% (95% CI, 51.9%-83.6%). The use of the tree may provide a more rational basis for selecting initial therapy for severe NHAP after it is validated in a large prospective study.
    Clinical Infectious Diseases 09/2004; 39(4):474-80. DOI:10.1086/422317 · 9.42 Impact Factor
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    ABSTRACT: Several recent studies provide evidence that the oral cavity may influence the initiation and/or the progression of lung diseases such as pneumonia and chronic obstructive pulmonary disease (COPD). Studies have shown that poor oral hygiene and periodontal disease may foster colonization of the oropharyngeal region by respiratory pathogens, particularly in hospital or nursing home patients. If aspirated, these pathogens can cause pneumonia, one of the most common respiratory infections, especially in institutionalized subjects. Other cross-sectional epidemiologic studies point to an association between periodontal disease and COPD. This systematic review examines the literature to determine if interventions that improve oral hygiene reduce the rate of pneumonia in high-risk populations. Do periodontal diseases or other indicators of poor oral health influence the initiation/progression of pneumonia or other lung diseases? MEDLINE, pre-MEDLINE, MEDLINE Daily Update, and the Cochrane Controlled Trials Register were searched to identify published studies that related variables associated with pneumonia and other lung disease to periodontal disease. Searches were performed for articles published in English from 1966 through March 2002. Randomized controlled clinical trials (RCTs), longitudinal, cohort, and case-control studies were included. Study populations included patients with any form of pneumonia or chronic obstructive pulmonary disease (COPD) and periodontal disease, as measured by assessments of gingival inflammation, probing depth, clinical attachment level, and/or radiographic bone loss, or oral hygiene indices. Limited to studies of humans. The summary statistics used to analyze the RCTs included weighted mean differences in rates of disease between control and intervention groups. For cohort studies that measured differences in rates of disease between groups with and without oral disease, weighted mean differences, relative risks, or odds ratios were compared. A meta-analysis was performed on the 5 intervention studies to determine the relationship between oral hygiene intervention and rate of pneumonia in institutionalized patients. Of the initial 1,688 studies identified, 36 satisfied all inclusion criteria and were read. Of these, 21 (11 case-control and cohort studies [study population 1,413] and 9 RCTs [study population 1,759]) were included in the analysis. 1. A variety of oral interventions improving oral hygiene through mechanical and/or topical chemical disinfection or antibiotics reduced the incidence of nosocomial pneumonia by an average of 40%. 2. Several studies demonstrated a potential association between periodontal disease and COPD. 1. Oral colonization by respiratory pathogens, fostered by poor oral hygiene and periodontal diseases, appears to be associated with nosocomial pneumonia. 2. Additional large-scale RCTs are warranted to provide the medical community with further evidence to institute effective oral hygiene procedures in high-risk patients to prevent nosocomial pneumonia. 3. The results associating periodontal disease and COPD are preliminary and large-scale longitudinal and epidemiologic and RCTs are needed.
    Annals of Periodontology 01/2004; 8(1):54-69. DOI:10.1902/annals.2003.8.1.54
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    ABSTRACT: Oral health is influenced by oral microbial flora, which are concentrated in dental plaque. Dental plaque provides a microhabitat for organisms and an opportunity for adherence of the organisms to either the tooth surface or other microorganisms. In critically ill patients, potential pathogens can be cultured from the oral cavity. These microorganisms in the mouth can translocate and colonize the lung, resulting in ventilator-associated pneumonia. The importance of oral care in the intensive care unit has been noted in the literature, but little research is available on mechanical or pharmacological approaches to reducing oral microbial flora via oral care in critically ill adults. Most research in oral care has been directed toward patients' comfort; the microbiological and physiological effects of tooth brushing in the intensive care unit have not been reported. Although 2 studies indicated reductions in rates of ventilator-associated pneumonia in cardiac surgery patients who received chlorhexidine before intubation and postoperatively, the effects of chlorhexidine in reducing ventilator-associated pneumonia in other populations of critically ill patients or its effect when treatment with the agent initiated after intubation have not been reported. In addition, no evaluation of the effectiveness of pharmacological and mechanical interventions relative to each other or in combination has been published. Additional studies are needed to develop and test best practices for oral care in critically ill patients.
    American Journal of Critical Care 02/2004; 13(1):25-33; discussion 34. · 1.60 Impact Factor