Cross-reactivity in the Platelia™ Aspergillus enzyme immunoassay caused by blastomycosis.

It is well known that cross reactions with other fungal pathogens including Histoplasma capsulatum can occur with the use of the Platelia™ Aspergillus galactomannan assay. We report two patients with confirmed blastomycosis whose bronchoalveolar lavage (BAL) fluid tested positive for Aspergillus galactomannan despite no evidence of aspergillosis.

Multicenter evaluation of the LightCycler methicillin-resistant Staphylococcus aureus (MRSA) advanced test as a rapid method for detection of MRSA in nasal surveillance swabs.

The rate of methicillin-resistant Staphylococcus aureus (MRSA) infection continues to rise in many health care settings. Rapid detection of MRSA colonization followed by appropriate isolation can reduce transmission and infection. We compared the performance of the new Roche LightCycler MRSA advanced test to that of the BD GeneOhm MRSA test and culture. Double-headed swabs were used to collect anterior nasal specimens from each subject. For both tests, DNA was extracted and real-time PCR was performed according to manufacturer's instructions. For culture, one swab of the pair was plated directly to CHROMagar MRSA. The swab paired with the BD GeneOhm MRSA test was also placed into an enrichment broth and then plated to CHROMagar MRSA. Colonies resembling staphylococci were confirmed as S. aureus by standard methods. Discrepant specimens had further testing with additional attempts to grow MRSA as well as sample amplicon sequencing. Agreement between results for the two swabs was 99.3% for those with valid results. A total of 1,402 specimens were tested using direct culture detection of MRSA as the gold standard; 187 were culture positive for MRSA. The LightCycler MRSA advanced test had relative sensitivity and specificity of 95.2% (95% confidence interval [CI]: 91.1% to 97.8%) and 96.4% (95% CI: 95.2% to 97.4%), respectively. The BD GeneOhm assay had relative sensitivity and specificity of 95.7% (95% CI: 91.7% to 98.1%) and 91.7% (95% CI: 90.0% to 93.2%), respectively. Following discrepancy analysis, the relative sensitivities of the LightCycler MRSA advanced test and the BD GeneOhm MRSA assay were 92.2 and 93.2%, respectively; relative specificities were 98.9 and 94.2%, respectively. Specificity was significantly better (P<0.001) with the LightCycler MRSA advanced test. The sensitivity of direct culture was 80.4%. The LightCycler MRSA advanced test is a useful tool for sensitive and rapid detection of MRSA nasal colonization.

Evaluation of a real-time polymerase chain reaction assay using analyte-specific reagents for detection of methicillin-resistant Staphylococcus aureus nasal carriage.

OBJECTIVE: To validate a real-time polymerase chain reaction (PCR) assay for the detection of methicillin-resistant Staphylococcus aureus (MRSA) that is capable of accommodating 30 patient samples in a single batch without compromising the level of sensitivity and specificity associated with PCR testing. STUDY DESIGN: A real-time PCR analyte-specific reagent (ASR) assay was compared to conventional culture methods using dual swab samples collected from the nares of 151 patients. RESULTS: Of the 151 specimens, 49 (32%) were positive for MRSA by PCR, whereas 40 (26%) were positive by culture methods. The Roche LightCycler 2.0 (Roche Diagnostics, Indianapolis, Indiana, U.S.A.) and its associated ASRs were capable of analyzing 30 patient samples and 2 controls in < 2 hours. Current data suggest that 4-10% of our patient specimens harbor both coagulase negative Staphylococcus and S aureus in the same sample. Samples such as this are reflexed to culture, only 24% of which contain MRSA. Efficiency in the laborato-ry was greatly improved. The sensitivity, specificity, positive predictive value and negative predictive value were 100%, 92%, 82% and 100%, respectively. CONCLUSION: The Roche LightCycler 2.0 PCR platform is a sensitive and efficient screening method for determining the nasal carriage of MRSA with a rapid turnaround time in the clinical laboratory.

Pulmonary histoplasmosis.

Pulmonary manifestations of histoplasmosis were last reviewed in Seminars in 2004. This review highlights the management of the most common clinical syndromes, emphasizing recognition, diagnosis, and treatment. The reader is referred to the earlier review for subjects not fully addressed herein. Knowledge of the utility of serological testing is essential, particularly when antigen tests and cultures are negative. Antigen testing is most useful in patients with more diffuse pulmonary involvement and those with progressive disseminated disease due to the high fungal burden. Detection of antigen in bronchoalveolar lavage fluid may be particularly helpful in certain circumstances. Guidelines for antifungal therapy have been updated and will be discussed for pulmonary syndromes.

Gastrointestinal histoplasmosis.

Gastrointestinal histoplasmosis (GIH) is an uncommon disease with protean manifestations. It may occur as a result of mediastinal histoplasmosis or in the setting of progressive dissemination. GIH may be misdiagnosed as inflammatory bowel disease, malignancy, or other intestinal diseases leading to inappropriate therapies and unnecessary surgical interventions. Patients with bowel obstruction, perforation, or bleeding, and systemic findings suggestive of histoplasmosis should be evaluated for GIH. This is especially true for immunosuppressed patients, especially those with AIDS. Diagnosis first requires consideration of histoplasmosis in the differential in patients with the above types of gastrointestinal abnormalities, and second, familiarity with a battery of mycologic and serologic tests. Progressive disseminated histoplasmosis (PDH) is lethal if left untreated, and treatment is highly effective. This review will focus on the clinical and histopathologic features of GIH, the approach to diagnosis, and recommendations for treatment.

Pathogenic differences between North American and Latin American strains of Histoplasma capsulatum var. capsulatum in experimentally infected mice.

Clinical differences in histoplasmosis between North America and Brazil prompted investigation of experimental infection with representative strains. Mortality was higher with Latin American strains, and lung pathology showed large necrotizing granuloma with prominent neutrophilic infiltration. Chronic disease was unique to the North American strain.

Pulmonary histoplasmosis syndromes: recognition, diagnosis, and management.

Pulmonary manifestations are the hallmark of histoplasmosis. Clinical syndromes range from asymptomatic infection to diffuse alveolar disease causing respiratory difficulty and even death. Serologic tests for antibodies and antigen detection are especially helpful in the diagnosis of histoplasmosis but are frequently overlooked. Detection of Histoplasma capsulatum antigen in bronchoalveolar lavage fluid may be particularly helpful in patients with acute pulmonary histoplasmosis or disseminated disease with pulmonary involvement. Topics of special importance for pulmonary disease specialists include the approach to the exclusion of histoplasmosis in the evaluation of patients with suspected sarcoidosis, differentiation of pulmonary histoplasmosis and malignancy in those with lung masses or mediastinal lymphadenopathy, and recognition and management of chronic pulmonary and mediastinal manifestations of histoplasmosis. Although histoplasmosis is mild and self-limited in most healthy individuals, antifungal therapy is indicated in those with acute diffuse pulmonary infection, chronic pulmonary histoplasmosis, progressive disseminated disease, and perhaps mediastinal adenitis accompanied by obstructive symptoms. Antifungal therapy to prevent reactivation of histoplasmosis during immunosuppressive therapy, or transition of mediastinal adenitis to fibrosing mediastinitis, although controversial, is not recommended. Several new drugs active against H. capsulatum offer alternatives in patients failing or intolerant of current therapies.