F. Kate Gould

Guidelines for the diagnosis and antibiotic treatment of endocarditis in adults: a report of the Working Party of the British Society for Antimicrobial Chemotherapy

The BSAC guidelines on treatment of infectious endocarditis (IE) were last published in 2004. The guidelines presented here have been updated and extended to reflect developments in diagnostics, new trial data and the availability of new antibiotics. The aim of these guidelines, which cover both native valve and prosthetic valve endocarditis, is to standardize the initial investigation and treatment of IE. An extensive review of the literature using a number of different search criteria has been carried out and cited publications used to support any changes we have made to the existing guidelines. Publications referring to in vitro or animal models have only been cited if appropriate clinical data are not available. Randomized, controlled trials suitable for the development of evidenced-based guidelines in this area are still lacking and therefore a consensus approach has again been adopted for most recommendations; however, we have attempted to grade the evidence, where possible. The guidelines have also been extended by the inclusion of sections on clinical diagnosis, echocardiography and surgery.

Development and Evaluation of a Chromogenic Agar Medium for Methicillin-Resistant Staphylococcus aureus

ABSTRACT We describe here the development and evaluation of MRSA ID, a new chromogenic agar medium for the specific isolation and identification of methicillin-resistant Staphylococcus aureus (MRSA). We used S. aureus ID (bioMérieux, La Balme Les Grottes, France) and supplemented it with various antimicrobials, including cefoxitin, ciprofloxacin, oxacillin, and methicillin. Cefoxitin proved to be superior to the other antimicrobials for the selection of MRSA from other strains of S. aureus. MRSA ID (consisting of S. aureus ID supplemented with 4 mg of cefoxitin/liter) was evaluated by the use of 747 swabs from various clinical sites. All specimens were also cultured on CHROMagar MRSA and oxacillin resistance screening agar base (ORSAB) and in selective mannitol broth (SMB). A total of 85 MRSA strains were isolated by a combination of all methods. After 22 to 24 h of incubation, 80% of the MRSA strains were isolated as green colonies on MRSA ID, compared with 59 and 62% of the strains that were isolated as colored colonies on CHROMagar MRSA and ORSAB, respectively. After 48 h of incubation, 89, 72, and 78% of the MRSA strains were isolated on MRSA ID, CHROMagar MRSA, and ORSAB, respectively. Sixty-five percent of the strains were isolated by growth in SMB. The specificities of MRSA ID, CHROMagar MRSA, ORSAB, and SMB were 99.5, 99.3, 97.9, and 92.8%, respectively, after 22 to 24 h of incubation. We conclude that MRSA ID is a sensitive and specific medium for the isolation and identification of MRSA.

Guidelines (2008) for the prophylaxis and treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections in the United Kingdom

These evidence-based guidelines are an updated version of those published in 2006. They have been produced after a literature review of the treatment and prophylaxis of methicillin-resistant Staphylococcus aureus (MRSA). The guidelines aim to complement those recently published for the antibiotic treatment of common and emerging community-onset MRSA infections in the UK. The guidelines have reviewed and updated, where appropriate, previous recommendations, taking into account any changes in the UK epidemiology of MRSA, ongoing national surveillance data and the value of new antistaphylococcal agents licensed for use in UK practice. Emerging therapies that have not been licensed for UK use are not reviewed, but their future potential role has been mentioned where deemed appropriate. Recommendations are given for the treatment of common infections caused by MRSA, elimination of MRSA from carriage sites and prophylaxis of surgical site infection.

Lung transplantation for patients with cystic fibrosis and Burkholderia cepacia complex infection: A single-center experience

BACKGROUND Pre-operative infection with organisms from the Burkholderia cepacia complex (BCC), particularly B cenocepacia, has been linked with a poorer prognosis after transplantation compared to patients with cystic fibrosis (CF) without this infection. Therefore, many transplant centers do not list these patients for transplantation. METHODS We report the early and long-term results of a cohort of lung transplant recipients with CF and pre-operative BCC infection. Patients with pre-transplantation BCC infection were identified by case-note review. BCC species status was assigned by polymerase chain reaction (PCR)-based techniques. Survival rates were compared to recipients with CF without BCC infection. Survival rates in BCC subgroups were also compared, and then further analyzed pre- and post-2001, when a new immunosuppressive and antibiotic regime was introduced for such patients. RESULTS Two hundred sixteen patients with CF underwent lung transplantation and 22 had confirmed pre-operative BCC infection, with 12 of these being B cenocepacia. Nine B cenocepacia-infected recipients died within the first year, and in 8 BCC sepsis was considered to be the cause of death. Despite instituting a tailored peri-operative immunosuppressive and microbiologic care approach for such patients, post-transplantation BCC septic deaths occurred frequently in those with pre-transplantation B cenocepacia infection. In contrast, recipients infected with other BCC species had significantly better outcomes, with post-transplantation survival comparable to other recipients with CF. CONCLUSIONS Mortality in patients with B cenocepacia infection was unacceptably high and has led to our center no longer accepting patients with this condition onto the lung transplant waiting list. Long-term survival in the non-B cenocepacia BCC group was excellent, without high rates of acute rejection or bronchiolitis obliterans syndrome (BOS) longer term, and these patients continue to be considered for lung transplantation.

Evaluation of S. aureus ID, a New Chromogenic Agar Medium for Detection of Staphylococcus aureus

ABSTRACT S. aureus ID (bioMérieux, La Balme Les Grottes, France) is a new chromogenic agar medium designed to enable the isolation of staphylococci and the specific identification of Staphylococcus aureus. S. aureus produces green colonies on this medium due to production of α-glucosidase. To evaluate this medium, a total of 350 wound swabs were cultured onto S. aureus ID, CHROMagar Staph. aureus, and conventional media routinely used in our laboratory. After 18 to 20 h of incubation, 96.8% of strains formed green colonies on S. aureus ID compared with 91.1% of strains forming mauve colonies on CHROMagar Staph. aureus. A total of 94.3% of strains were recovered within 18 to 20 h with conventional media. The sensitivity was increased after 48 h of incubation to 98.7, 96.2, and 95.6% with S. aureus ID, CHROMagar Staph. aureus, and conventional media, respectively. A total of 97.4% of green colonies on S. aureus ID were confirmed as S. aureus compared with 94.4% of mauve colonies on CHROMagar Staph. aureus. We conclude that S. aureus ID is a highly sensitive and specific medium for the isolation and identification of S. aureus from wound swabs.

Bacterial colonization of the donor lower airways is a predictor of poor outcome in lung transplantation

OBJECTIVE At the time of lung transplant, we routinely perform bronchoalveolar lavage (BAL) of the donor lungs on the recipient operating table immediately before implantation, for bacterial and fungal cultures. We sought to determine whether the results correlate with the outcome. METHODS We retrospectively analysed 115 consecutive cadaveric lung transplants (single lung: 42; bilateral lung: 63; heart-lung: 10) performed over 4 years. RESULTS Fifty-three (46%) grafts had positive BAL (bacteria: 33; fungus: 10; mixed: 10) and 62 (54%) were negative. Recipients with donor BAL culture positive for bacteria had lower mean oxygenation index in the first 6 h compared with those with negative bacterial culture (36.5+/-14.73 vs. 44.1+/-16.79 kPa) (P=0.019). They also had longer median intensive treatment unit stay (2.5 vs. 1.5 days) (P=0.035), and median time of mechanical ventilation (37.5 vs. 23.0 h) (P=0.008), as well as inferior 6-month, 1-year, 2-year and 4-year cumulative survival (79, 77, 74, 60% vs. 93, 92, 88, 79% respectively) (P=0.04). There was no difference in the above parameters between recipients with Gram-negative (n=18) and recipients with Gram-positive bacteria (n=19) in the donor BAL. Incidence of acute rejection within the first 2 weeks and time of onset of bronchiolitis obliterans syndrome (BOS) were similar in the bacteria-positive and bacteria-negative groups. Recipients with donor BAL positive for fungi alone had similar outcome with the negatives. There was no difference in the donor oxygenation index and age, recipient age, transplant type and ischaemic time between compared groups. There was a significant difference in the median length of donor mechanical ventilation between donors with Gram-positive and donors with Gram-negative bacteria in the BAL (24 vs. 48 h) (P=0.01), as well as between donors with fungi alone in the BAL and donors with negative BAL (67 vs. 48 h) (P=0.04). CONCLUSIONS Donor lungs with lower airways colonized with bacteria result in inferior recipient outcome. Bacterial colonization of the donor lower airways could therefore be used as a marker of donor lung injury, but evidence from a prospective study is necessary.

Evaluation of a Chromogenic Culture Medium for Isolation of Clostridium difficile within 24 Hours

ABSTRACT Rapid and effective methods for the isolation of Clostridium difficile from stool samples are desirable to obtain isolates for typing or to facilitate accurate diagnosis of C. difficile-associated diarrhea. We report on the evaluation of a prototype chromogenic medium (ID C. difficile prototype [IDCd]) for isolation of C. difficile. The chromogenic medium was compared using (i) 368 untreated stool samples that were also inoculated onto CLO medium, (ii) 339 stool samples that were subjected to alcohol shock and also inoculated onto five distinct selective agars, and (iii) standardized suspensions of 10 C. difficile ribotypes (untreated and alcohol treated) that were also inoculated onto five distinct selective agars. Two hundred thirty-six isolates of C. difficile were recovered from 368 untreated stool samples, and all but 1 of these strains (99.6%) were recovered on IDCd within 24 h, whereas 74.6% of isolates were recovered on CLO medium after 48 h. Of 339 alcohol-treated stool samples cultured onto IDCd and five other selective agars, C. difficile was recovered from 218 samples using a combination of all media. The use of IDCd allowed recovery of 96.3% of isolates within 24 h, whereas 51 to 83% of isolates were recovered within 24 h using the five other media. Finally, when they were challenged with pure cultures, all 10 ribotypes of C. difficile generated higher colony counts on IDCd irrespective of alcohol pretreatment or duration of incubation. We conclude that IDCd is an effective medium for isolation of C. difficile from stool samples within 24 h.

The structure and proinflammatory activity of the lipopolysaccharide from Burkholderia multivorans and the differences between clonal strains colonizing pre and posttransplanted lungs

The Burkholderia cepacia complex is a group of Gram-negative bacteria that are opportunistic pathogens for humans especially in cystic fibrosis patients. Lipopolysaccharide (LPS) molecules are potent virulence factors of Gram-negative bacteria organisms essential for bacterial survival. A complete analysis of the bacterial lipopolysaccharide structure to function relationship is required to understand the chemical basis of the inflammatory process. We have therefore investigated the structures of lipopolysaccharides from clonally identical Burkholderia multivorans strains (genomovar II) isolated pre- and post-lung transplantation through compositional analysis, mass spectrometry, and 2D NMR spectroscopy. We tested the LPS proinflammatory activity as a stimulant of human myelomonocytic U937 cell cytokine induction and assessed TLR4/MD2 signaling. Marked changes between the paired strains were found in the lipid A-inner core region. Such structural variations can contribute to the bacterial survival and persistence of infections despite the loss of a CF milieu following lung transplantation.

Linezolid: safety and efficacy in special populations

Linezolid has been in general use in the UK since 2000. Although toxicity, particularly haematological and neurological, has been an issue, linezolid has proved to be an effective alternative to glycopeptides in the treatment of Gram-positive infections. Since its original licence for the treatment of skin and soft tissue infections and pneumonia, there have been reports of its successful use in the treatment of bone and joint infections, endocarditis, and other difficult-to-treat infections.

A novel chromogenic medium for isolation of Pseudomonas aeruginosa from the sputa of cystic fibrosis patients

BACKGROUND A novel chromogenic medium for isolation and identification of Pseudomonas aeruginosa from sputa of cystic fibrosis (CF) patients was evaluated and compared with standard laboratory methods. METHODS One hundred sputum samples from distinct CF patients were cultured onto blood agar (BA), Pseudomonas CN selective agar (CN) and a Pseudomonas chromogenic medium (PS-ID). All Gram-negative morphological variants from each medium were subjected to antimicrobial susceptibility testing, and identification using a combination of biochemical and molecular methods. RESULTS P. aeruginosa was isolated from 62 samples after 72 h incubation. Blood agar recovered P. aeruginosa from 56 samples (90.3%) compared with 59 samples (95.2%) using either CN or PS-ID. The positive predictive value of PS-ID (98.3%) was significantly higher than growth on CN (88.5%) for identification of P. aeruginosa (P<0.05). CONCLUSIONS PS-ID is a promising medium allowing for the isolation and simultaneous identification of P. aeruginosa from sputa of CF patients.