http://www.bio21.bas.bg/ibf/PC_review.pdf

Phases and phase transitions of the phosphatidylcholines

Background: Necrotizing fasciitis is a life-threatening soft-tissue infection primarily involving the superficial fascia. The present report describes the clinical presentation and microbiological characteristics of this condition as well as the determinants of mortality associated with this uncommon surgical emergency.

Methods: The medical records of eighty-nine consecutive patients who had been admitted to our institution for necrotizing fasciitis from January 1997 to August 2002 were reviewed retrospectively.

Results: The paucity of cutaneous findings early in the course of the disease makes the diagnosis difficult, and only thirteen of the eighty-nine patients had a diagnosis of necrotizing fasciitis at the time of admission. Preadmission treatment with antibiotics modified the initial clinical picture and often masked the severity of the underlying infection. Polymicrobial synergistic infection was the most common cause (forty-eight patients; 53.9%), with streptococci and enterobacteriaceae being the most common isolates. Group-A streptococcus was the most common cause of monomicrobial necrotizing fasciitis. The most common associated comorbidity was diabetes mellitus (sixty-three patients; 70.8%). Advanced age, two or more associated comorbidities, and a delay in surgery of more than twenty-four hours adversely affected the outcome. Multivariate analysis showed that only a delay in surgery of more than twenty-four hours was correlated with increased mortality (p < 0.05; relative risk = 9.4).

Conclusions: Early operative debridement was demonstrated to reduce mortality among patients with this condition. A high index of suspicion is important in view of the paucity of specific cutaneous findings early in the course of the disease.

Level of Evidence: Prognostic study, Level II-1 (retrospective study). See Instructions to Authors for a complete description of levels of evidence.

Necrotizing Fasciitis: Clinical Presentation, Microbiology, and Determinants of Mortality

SUMMARY This review begins with a discussion of the large family of Staphylococcus aureus and beta-hemolytic streptococcal pyrogenic toxin T lymphocyte superantigens from structural and immunobiological perspectives. With this as background, the review then discusses the major known and possible human disease associations with superantigens, including associations with toxic shock syndromes, atopic dermatitis, pneumonia, infective endocarditis, and autoimmune sequelae to streptococcal illnesses. Finally, the review addresses current and possible novel strategies to prevent superantigen production and passive and active immunization strategies.

Staphylococcal and Streptococcal Superantigen Exotoxins

Background: Klebsiella pneumoniae is an opportunistic pathogen and leading cause of hospital-associated infections. Intensive care unit (ICU) patients are particularly at risk. Klebsiella pneumoniae is part of the healthy human microbiome, providing a potential reservoir for infection. However, the frequency of gut colonization and its contribution to infections are not well characterized. Methods: We conducted a 1-year prospective cohort study in which 498 ICU patients were screened for rectal and throat carriage of K. pneumoniae shortly after admission. Klebsiella pneumoniae isolated from screening swabs and clinical diagnostic samples were characterized using whole genome sequencing and combined with epidemiological data to identify likely transmission events. Results: Klebsiella pneumoniae carriage frequencies were estimated at 6% (95% confidence interval [CI], 3%-8%) among ICU patients admitted direct from the community, and 19% (95% CI, 14%-51%) among those with recent healthcare contact. Gut colonization on admission was significantly associated with subsequent infection (infection risk 16% vs 3%, odds ratio [OR] = 6.9, P < .001), and genome data indicated matching carriage and infection isolates in 80% of isolate pairs. Five likely transmission chains were identified, responsible for 12% of K. pneumoniae infections in ICU. In sum, 49% of K. pneumoniae infections were caused by the patients' own unique strain, and 48% of screened patients with infections were positive for prior colonization. Conclusions: These data confirm K. pneumoniae colonization is a significant risk factor for infection in ICU, and indicate ~50% of K. pneumoniae infections result from patients' own microbiota. Screening for colonization on admission could limit risk of infection in the colonized patient and others.

/pdf/gastrointestinal-carriage-is-a-major-reservoir-of-klebsiella-1y4ver225w.pdf

Gastrointestinal Carriage Is a Major Reservoir of Klebsiella pneumoniae Infection in Intensive Care Patients.

We have identified an unusual group of viridans group streptococci that resemble Streptococcus pneumoniae. DNA-DNA homology studies suggested that a subset of these isolates represent a novel species that may be included in the S. oralis-S. mitis group of viridans group streptococci. We suggest that this novel species be termed Streptococcus pseudopneumoniae. A combination of phenotypic and genetic reactions allows its identification. S. pseudopneumoniae strains do not have pneumococcal capsules, are resistant to optochin (inhibition zones, less than 14 mm) when they are incubated under an atmosphere of increased CO2 but are susceptible to optochin (inhibition zones, >14 mm) when they are incubated in ambient atmospheres, are not soluble in bile, and are positive by the GenProbe AccuProbe Pneumococcus test. The bile solubility test is more specific than the optochin test for identification of S. pneumoniae. Genetic tests for pneumolysin (ply) and manganese-dependent superoxide dismutase (sodA) and identification tests with a commercial probe, AccuProbe Pneumococcus, do not discriminate between the new species and S. pneumoniae.

Accuracy of Phenotypic and Genotypic Testing for Identification of Streptococcus pneumoniae and Description of Streptococcus pseudopneumoniae sp. nov.

Necrotizing fasciitis, which is a severe and uncommon infection involving the subcutaneous tissues, is usually caused by group A streptococci. To our knowledge, however, group B streptococci (Streptococcus agalactiae) have been reported to cause necrotizing fasciitis in only 4 instances (2 involving neonates) over the past 4 decades. We report 3 cases of group B streptococcal necrotizing fasciitis in adults that occurred in southern Ontario and Quebec within a 10-month period. All 3 patients had significant underlying illness, and all required surgical debridement in addition to antibiotic therapy. One of the cases fulfilled the criteria for streptococcal toxic shock–like syndrome. Group B streptococcus has been recognized as a frequent cause of serious disease in adults. It has become evident over the past decade that invasive streptococcal infections are on the increase. We speculate that group B streptococcus has recently acquired an increased ability to cause necrotizing fasciitis and suggest that this may represent the emergence of a new clinical syndrome in adults.

https://jamanetwork.com/HttpHandlers/ArticlePdfHandler.ashx?journal=INTEMED&articleId=1105575&pdfFileName=ico71147.pdf

Group B Streptococcal Necrotizing Fasciitis and Streptococcal Toxic Shock–Like Syndrome in Adults

Intermixing of dipalmitoylphosphatidylcholine with phospho- and sphingolipids bearing highly asymmetric hydrocarbon chains

To determine the optimal media for optochin susceptibility testing of Streptococcus pneumoniae, we measured inhibition zones for 72 S. pneumoniae and 22 Streptococcus viridans isolates on three blood-containing media. Because 15.3, 0, and 22.2% of S. pneumoniae organisms were misidentified on Columbia agar, Trypticase soy agar (TSA), and Mueller-Hinton agar, respectively, each containing sheep blood, we recommend that TSA-sheep blood agar be used.

Optochin Revisited: Defining the Optimal Type of Blood Agar for Presumptive Identification of Streptococcus pneumoniae

Exchangeable phospho- and sphingolipid probes (phosphatidylcholine, -ethanolamine, -serine, and -glycerol, phosphatidic acid, sphingomyelin, cerebroside, and sulfatide) have been synthesized in which one acyl chain is substituted with a fluorescent bimanyl, 7-(dimethylamino)coumarin-3-yl, or diphenyl-hexatrienyl group. The distribution of these probes between two different populations of lipid vesicles can be readily monitored by fluorescence intensity measurements, as described by Nichols and Pagano [Nichols, J. W., & Pagano, R. E. (1982) Biochemistry 21, 1720-1726], when one of the vesicle populations contains a low mole fraction of a nonexchangeable quencher, (12-DABS)-18-PC. The probes examined in this study exchange between phospholipid vesicles on a time scale of minutes, with kinetics indicating that the transfer process takes place by diffusion of probe monomers through the aqueous phase. As expected, lipid probes with different charges differ markedly in their equilibrium distributions between neutral and charged lipid vesicles. However, probes with different polar headgroups differ only modestly in their relative affinities for vesicles composed of "hydrogen-bonding" lipids (PE and PS) vs "non-hydrogen-bonding" lipids (PC and PG or O-methyl-PA). Probes with different headgroups also show modest, albeit reproducible, differences in their relative affinities for cholesterol-containing vs cholesterol-free PC/PG vesicles. Our results suggest that lipids with different headgroup structures may mix more nearly ideally in liquid-crystalline lipid bilayers than would be predicted from previous analyses of the phase diagrams for binary lipid mixtures.

Partitioning of exchangeable fluorescent phospholipids and sphingolipids between different lipid bilayer environments.

Bacterial resistance to antibiotics is an increasing problem in Canada and worldwide1–4 Vancomycin-resistant enterococci (VRE) are strains of Enterococcus faecium or Enterococcus faecalis that contain genes conferring resistance to vancomycin5,6Escherichia coli (E coli), Klebsiella pneumonia (K pneumonia), and other gram-negative bacteria may produce the enzymes known as extended spectrum beta-lactamases (ESBLs) These have the ability to inactivate beta-lactam antibiotics such as penicillin, ampicillin, and the cephalosporins7,8

The presence and growth (colonization) of VRE and ESBL-producing micro-organisms in the gastrointestinal tract is usually of no consequence for the host; but under certain circumstances — such as immunosuppression, gastrointestinal surgery, or physical debilitation — they may serve as a source of infection for the carrier These hosts may also serve as a reservoir for the transmission of VRE and ESBL-producing organisms to other persons9,10

Results from the Canadian Nosocomial Infection Surveillance Program showed that, from 1999 to 2005, the rate of VRE colonization and VRE infection increased from 037 to 132 cases, and from 002 to 005 cases, respectively, per 1,000 patients admitted to hospital11 The laboratory-based Canadian Ward Surveillance Study in 2008 found that ESBL-producing E coli were identified in all Canadian geographic regions, and that 49% of E coli isolates were ESBL producers12

Specific prevention and control measures for antibiotic-resistant organisms (AROs) include screening (a process to identify persons colonized with AROs) and isolation of the carriers Hospital infection prevention and control strategies have been developed in some Canadian jurisdictions,13–16 and these are compatible with other national and international documents17,18 Non-specific strategies for controlling ARO transmission and infection include hand hygiene, environmental cleaning, antimicrobial stewardship, and bundled practices such as those to prevent central line-associated blood stream infections

Antibiotic-resistant organisms, such as VRE and ESBL-producers, lead to the increased use of hospital resources due to extended hospital stays, laboratory tests, physician consultations, medications if a VRE or ESBL-related infection were to arise, and the need to adhere to infection prevention and control measures to prevent the further spread of these pathogens19 Some of the increased resource usage results from the morbidity caused by VRE or ESBL-producing organism infections, while some is a consequence of control strategies For example, it may be harder to transfer a patient to a rehabilitation facility if the patient is currently in isolation, which will in and of itself prolong the length of stay

The objective of this systematic review is to evaluate the clinical evidence for the effectiveness of screening, isolation, and decolonization strategies for persons colonized or infected with VRE and ESBL-producing organisms in acute and long-term care facilities The health services impact of these strategies will be discussed


Objective

The objective of the report is to answer the following research questions: 


What is the clinical evidence on the effectiveness of selective versus universal versus no screening of patients (adult and pediatric) for VRE or ESBL-producing organisms?


What is the clinical evidence on the effectiveness of patient isolation for VRE or ESBL-producing organisms?


What is the clinical evidence on the impact of isolation on the patient?


What is the clinical evidence for the effectiveness of decolonizing patients known to be carrying VRE or ESBL-producing organisms?


What is the clinical evidence on the effectiveness of additional precautions in the operating room or post-anesthesia recovery room in patients colonized with VRE or ESBL-producing organisms?


What is the health services impact of screening, isolating, and decolonizing patients known to be carrying VRE or ESBL-producing organisms on blocked beds, cancelled or limited surgeries, or the range of services a facility can provide?







Methods
For the clinical evidence, an information specialist performed the literature search using a peer-reviewed search strategy Methodological filters were applied to limit retrieval to health technology assessments, systematic reviews, meta-analyses, randomized controlled trials, and non-randomized studies Trials were eligible for inclusion if they involved adults or pediatric patients in acute or long-term care facilities, with VRE or ESBL-producing organisms; compared the effectiveness of screening, isolation, and decolonization with no screening, no isolation, and no decolonization; and reported outcomes related to detection, transmission, and infection of VRE or ESBL-producing organisms

The information specialist also conducted a search on the health services impact of the related main search concepts, using the same methodology as for the clinical evidence Trials were eligible for inclusion if they involved adults or pediatric patients in acute or long-term care facilities with VRE or ESBL-producing organisms and discussed the impact of screening, isolation, and decolonization of these patients on hospital resources

Regular alerts were established to update the search until the publication of the final report

Grey literature (literature that is not commercially published) was identified by searching relevant sections of the Grey Matters checklist (http://cadthca/resources/grey-matters)

Screening, Isolation, and Decolonization Strategies for Vancomycin-Resistant Enterococci or Extended Spectrum Beta-Lactamase Producing Organisms: A Systematic Review of the Clinical Evidence and Health Services Impact

Michael A. Gardam

Papers

Group B Streptococcal Necrotizing Fasciitis and Streptococcal Toxic Shock–Like Syndrome in Adults

Intermixing of dipalmitoylphosphatidylcholine with phospho- and sphingolipids bearing highly asymmetric hydrocarbon chains

Optochin Revisited: Defining the Optimal Type of Blood Agar for Presumptive Identification of Streptococcus pneumoniae

Partitioning of exchangeable fluorescent phospholipids and sphingolipids between different lipid bilayer environments.

Screening, Isolation, and Decolonization Strategies for Vancomycin-Resistant Enterococci or Extended Spectrum Beta-Lactamase Producing Organisms: A Systematic Review of the Clinical Evidence and Health Services Impact