Retrospective analysis of 49 cases of brain abscess and review of the literature.

The case records of 49 patients discharged from St George's Hospital, London, between December 2000 and March 2004 with the diagnosis of brain abscess were reviewed in order to document the epidemiology, causes, treatment, and prognostic factors associated with brain abscess. Brain abscess occurred at all ages, more frequently in men than in women. Headache and altered mental status were common presenting symptoms. The frontal lobe was the most common site. Streptococcal infection was seen most commonly, but staphylococcal infection predominated in cases following neurosurgery. Computed tomography provided sufficient diagnostic information in most cases. All but five patients had early surgical drainage. Cefotaxime and metronidazole were used most often for empirical therapy. Thirty-nine patients recovered fully or had minimal incapacity. Five patients died. Patients with underlying cranial neoplasms or medical conditions had a worse outcome than those with a contiguous focus of infection or post-traumatic abscess. Changes in disease pattern were determined by comparison to a literature review. A PubMed search of the literature using the keywords "brain abscess" was undertaken, and identified papers and relevant citations were reviewed. Compared to earlier series, there was a marked decrease in the number of cases of brain abscess secondary to otitis media and congenital heart disease. There was an increase in the number of cases of brain abscess secondary to neurosurgery and trauma. Changes in the epidemiology of predisposing conditions for brain abscess are associated with changes in the patient population and causative organisms. Though still a potentially fatal infection, there have been recent improvements in diagnosis, treatment, and outcome.

The objective assessment of international collaboration between pathology laboratories.

Collaboration between clinical laboratories in different countries is widespread but rarely subject to critical analysis. We developed a management tool for assessing the quality of an international pathology laboratory collaboration. Key areas of activity were identified and relevant performance indicators were established. There was no evidence of improved staff morale arising from the project but research, education, equipment, protocols and ethics activities all had demonstrable outputs. Identification of suboptimal performance in areas of the project allowed effective improvement planning. International collaboration may consume significant resources. Objective assessment should be used to measure performance and to enhance quality.

Glucose in bronchial aspirates increases the risk of respiratory MRSA in intubated patients.

BACKGROUND: The risk of nosocomial infection is increased in critically ill patients by stress hyperglycaemia. Glucose is not normally detectable in airway secretions but appears as blood glucose levels exceed 6.7-9.7 mmol/l. We hypothesise that the presence of glucose in airway secretions in these patients predisposes to respiratory infection. METHODS: An association between glucose in bronchial aspirates and nosocomial respiratory infection was examined in 98 critically ill patients. Patients were included if they were expected to require ventilation for more than 48 hours. Bronchial aspirates were analysed for glucose and sent twice weekly for microbiological analysis and whenever an infection was suspected. RESULTS: Glucose was detected in bronchial aspirates of 58 of the 98 patients. These patients were more likely to have pathogenic bacteria than patients without glucose detected in bronchial aspirates (relative risk 2.4 (95% CI 1.5 to 3.8)). Patients with glucose were much more likely to have methicillin resistant Staphylococcus aureus (MRSA) than those without glucose in bronchial aspirates (relative risk 2.1 (95% CI 1.2 to 3.8)). Patients who became colonised or infected with MRSA had more infiltrates on their chest radiograph (p<0.001), an increased C reactive protein level (p<0.05), and a longer stay in the intensive care unit (p<0.01). Length of stay did not determine which patients acquired MRSA. CONCLUSION: The results imply a relationship between the presence of glucose in the airway and a risk of colonisation or infection with pathogenic bacteria including MRSA.

Antibody response to pneumolysin and to pneumococcal capsular polysaccharide in healthy individuals and Streptococcus pneumoniae infected patients.

BACKGROUND: Animal experiments have shown that antibodies against capsular polysaccharide enhance phagocytosis of pneumococcal bacteria and that antibodies against pneumolysin are anti-inflammatory and prevent pneumococcal invasion. It is not known if an antibody response to pneumolysin can be acquired from natural exposure to pneumococcal bacteria or how the concentration of pneumolysin antibody at the mucosal surface compares with that of antibodies against pneumococcal capsular polysaccharide. This study used an equal potency method to measure specific antibody concentrations against pneumolysin and pneumococcal capsular polysaccharides in order to facilitate comparative estimates of concentrations in saliva and serum. The results may provide experimental information as a basis for an improved pneumococcal vaccine strategy. RESULTS: Healthy individuals had higher IgM and IgG antibody concentrations against capsular polysaccharide than against pneumolysin in both saliva and serum, but for IgA the converse was true. Patients with acute pneumococcal infection had significantly lower concentrations of specific IgG antibodies against both antigens than the healthy group. These patients also had significantly higher concentrations of IgM antibody against both antigens than the healthy control group. DISCUSSION: Healthy individuals acquire a comparatively lower concentration of antibody to pneumolysin than to pneumococcal capsular polysaccharides from natural exposure to pneumococcal bacteria. Patients infected by pneumococcal bacteria have lower specific IgG antibody concentrations to both antigens than healthy individuals. These findings support the view that pneumolysin could potentially be used as a vaccine. For enhanced effectiveness, it could be used as a supplement to Pneumovax((R))II rather than as a replacement. The two acquired antibodies, i.e. to pneumolysin and to capsular polysaccharide, could then play their protective roles at different stages in the course of pneumococcal infection, and together contribute to an effective immune defence against Streptococcus pneumoniae.

Management and outcome of bloodstream infections due to Candida species in England and Wales.

This two-year prospective hospital population-based study of candidaemia is the first to be conducted in the UK. It was carried out on behalf on the British Society for Medical Mycology (BSMM) as part of the European Confederation of Medical Mycology (ECMM) epidemiological survey of candidaemia. Six hospitals in England and Wales acted as sentinel hospitals. Main outcome measures were hospital population-based incidence and 30-day mortality. There were 18.7 episodes of candidaemia per 100,000 finished consultant episodes or 3.0/100,000 bed days and 45.4% cases occurred in intensive care unit (ICU) patients. Candida albicans was isolated in 64.7% of confirmed cases. The majority of isolates were sensitive to standard antifungal agents, including fluconazole. The overall 30-day mortality was 26.4% and removal of the central venous catheter was associated with a significant reduction in mortality. In conclusion, the incidence of candidaemia in England and Wales is similar to that of the USA, the majority of isolates remain sensitive to commonly used antifungal agents and mortality associated with this infection appears to be falling.

Strategy for diagnosis of congenital toxoplasmosis: evaluation of methods comparing mothers and newborns and standard methods for postnatal detection of immunoglobulin G, M, and A antibodies.

In a study involving 14 laboratories supported by the European Community Biomed 2 program, we evaluated immunologic methods for the postnatal diagnosis of congenital toxoplasmosis (CT). Among babies born to mothers who seroconverted to positivity for toxoplasmosis during pregnancy, we analyzed 55 babies with CT on the basis of persistent anti-Toxoplasma immunoglobulin G (IgG) at 1 year of life and 50 control babies without anti-Toxoplasma IgG at 1 year of life in the absence of curative treatment with pyrimethamine-sulfonamides. We tested in-house methods such as the enzyme-linked immunofiltration assay (ELIFA) or Immunoblotting (IB) for the detection of IgG or IgM; these methods allowed comparison of the immunologic profiles of the mothers and the infants. We compared ELIFA and IB with a commercial enzyme immunoassay (EIA) or in-house immunosorbent agglutination assay (ISAGA) for the detection of IgM or IgA. The performances of combinations of methods were also assessed. A cumulative sensitivity of 98% during a 1-year follow-up was obtained with the ELIFA plus ISAGA combination. Only one case of CT was missed by the ELIFA plus ISAGA combination, whereas three cases were missed by the IB plus ISAGA combination, even though 48% of patients with CT were treated with pyrimethamine-sulfonamides, which are known to inhibit antibody neosynthesis. A similar performance was obtained with either ELIFA or IB in combination with EIA. The difference in performance between ELIFA plus ISAGA and IB plus ISAGA was not statistically significant (P = 0.31), and we conclude that both combinations of tests can be used for the diagnosis of CT in newborns.

The past and present role of the Sabin-Feldman dye test in the serodiagnosis of toxoplasmosis.

The dye test for the detection of Toxoplasma-specific antibodies was first described by Sabin and Feldman 50 years ago. The test is highly specific and sensitive and considerable information is available on the development and persistence of dye test antibodies after primary Toxoplasma infection. However, the test uses live Toxoplasma gondii and is now only employed in a few laboratories. It is still the reference method for the serodiagnosis of toxoplasmosis, and a multicentre study comparing dye test results between different laboratories was much needed. We report in this article the results of a multicentre evaluation of the test involving nineteen laboratories in eight countries. The study revealed overall satisfactory standardization between the laboratories, but there were differences in the test protocols, the use of reference/standard preparations and the interpretation of results. There is still no agreement on the level of dye test values which reflect infection with the parasite, and conversion from titres to international units (IUs) did not improve standardization. However, the results indicated that a value of > 4 IU or a titre of 1:16 met the definition of positivity of most participants. We recommend that the dye test be retained as a reference method and that interlaboratory standardization be improved by the use of a common protocol and the expression of results in titres.

Misdiagnosis of toxoplasma infection by PCR: fears unfounded.

A nested PCR based diagnostic assay for the detection of toxoplasmosis was devised in 1990 and was used successfully among a battery of tests for the clinical diagnosis of Toxoplasma gondii infection since 1991. However, it was reported that the assay produced false positive diagnoses with Nocardia asteroides infection. Investigation of this phenomenon showed that although cross reactivity with some unrelated organisms may be observed when altered conditions are employed, the assay does not lead to misdiagnosis if performed under the appropriate, stringent conditions.

Cross contamination of blood cultures associated with a multiple use venting device.

AIM: To investigate cross contamination of blood cultures associated with multiple use venting devices, which are widely used in clinical microbiology laboratories to reduce labour costs. METHODS: Systematic analysis of 13,880 blood culture results in a large teaching hospital where multiple use venting devices were employed. RESULTS: Nine series of potential cross contamination were identified in a 12 month period. Four series involved coagulase negative staphylococci and were unlikely to represent true cross contamination. Five series involved blood cultures which had significant bacterial growth at the time of venting. CONCLUSIONS: Multiple use venting devices can be associated with cross contamination of blood cultures. This may result from contamination of the internal lumen of the venting device which is not exposed to the biocide. Medical microbiologists should consider the possibility of cross contamination associated with venting procedures when interpreting blood culture results. Further development of multiple use venting devices is required to reduce the risk of cross contamination of cultures.

Risk factors for acquisition of gentamicin-resistant enterococcal infection: a case-controlled study.

High-level gentamicin-resistant enterococci present problems in the treatment of infected patients, especially as synergy between penicillin and gentamicin is lost. Previous studies have suggested various risk factors for the acquisition of these enterococci. A case-controlled study was performed on 17 patients infected with resistant enterococci and 26 infected with sensitive strains who attended a London hospital. The key risk factors for acquisition of infection with high-level gentamicin-resistant enterococci were found to be prior prolonged antibiotic treatment, use of five or more antibiotics, and the presence of a urinary catheter. It is proposed that infection control measures should be targeted at patients at higher risk. In addition, control of antibiotic usage in a hospital may help to prevent acquisition and spread of these organisms.

Quantitation of Toxoplasma gondii DNA in a competitive nested polymerase chain reaction.

AIM: To quantify Toxoplasma gondii DNA using a specially constructed artificial template as competitor in a nested polymerase chain reaction (PCR). METHODS: The diagnostic assay was a nested PCR employing four primers that amplify part of the single copy gene for the P30 major surface antigen in T gondii. An artificial competitor containing the four primer binding sites was made first by creating a 216 bp deletion in the native 914 bp full length PCR product using restriction enzyme digestion, ligation of selected digestion fragments, and cloning the ligation product into an E coli plasmid vector for production. Competitive nested PCR using three different quantities of T gondii genomic DNA with four corresponding 10-fold dilutions of the artificial competitor was then performed, and the results visualised with agarose gel electrophoresis. A standard curve was drawn by plotting the T gondii to competitor ratio readings against log10 of the competitor readings. RESULTS: The band intensities on agarose gel showed quantitative amplification in competitive nested PCR. The amount of competitor required to achieve equal molar amounts of PCR products is calculated by reading off the value of the competitor where the T gondii to competitor ratio equals 1 on the standard curves. CONCLUSIONS: Competitive PCR is possible with a nested assay, and quantitative amplification is well preserved. The use of an artificial competitor containing the same primer binding sites as the target enables the absolute amount of T gondii DNA in unknown samples to be estimated. In addition, the competitor simultaneously serves as a control for detecting false negative results of failed reactions in individual assay runs.

Detection of Toxoplasma gondii in cured meats.

Congenital toxoplasmosis is associated with acute maternal infection acquired during or shortly before the pregnancy. The mother's infection is initiated by the ingestion of one of the life forms of the parasite but the relative importance of the different sources of toxoplasmosis are not established. Recent epidemiological studies have confirmed ingestion of raw meats as a risk factor but also identified consumption of cured meats as being associated with acute toxoplasmosis in pregnancy. There is little existing information concerning the efficiency of commercial curing processes for inactivating Toxoplasma gondii. We sought to detect the presence of T. gondii in ready-to-eat cured meat samples by amplification of the parasite's P30 gene using the polymerase chain reaction (PCR). In addition, tissue culture was used in order to isolate viable parasites. Laboratory inoculated specimens were used to assess the sensitivity of each method. PCR was able to detect parasite contamination down to a level of 5 x 10(3) trophozoites/g while viable toxoplasma could be detected in tissue culture at a level of 10(3) trophozoites/g cured meat. The high salt content of some cured meats limited sensitivity of the PCR assay by inhibition of the polymerase enzyme and reduced the sensitivity of tissue culture due to osmotic pressure causing cytopathic effect. However viable T. gondii was detected in one out of 67 ready-to-eat cured meat samples. Our results highlight the need for improved methods for detecting toxoplasma contamination of food. Health implications of consuming cured meats in pregnancy require careful consideration.