Comparison of traditional gas chromatography (GC), headspace GC, and the microbial identification library GC system for the identification of Clostridium difficile.

Three gas chromatography (GC) methods were compared for the identification of 52 clinical Clostridium difficile isolates, as well as 17 non-C. difficile Clostridium isolates. Headspace GC and Microbial Identification System (MIS) GC, an automated system which utilizes a software library developed at the Virginia Polytechnic Institute to identify organisms based on the fatty acids extracted from the bacterial cell wall, were compared against the reference method of traditional GC. Headspace GC and MIS were of approximately equivalent accuracy in identifying the 52 C. difficile isolates (52 of 52 versus 51 of 52, respectively). However, 7 of 52 organisms required repeated sample preparation before an identification was achieved by the MIS method. Both systems effectively differentiated C. difficile from non-C. difficile clostridia, although the MIS method correctly identified only 9 of 17. We conclude that the headspace GC system is an accurate method of C. difficile identification, which requires only one-fifth of the sample preparation time of MIS GC and one-half of the sample preparation time of traditional GC.

Using the microbiology laboratory in the diagnosis of pneumonia.

Pneumonia/influenza is one of the top ten leading causes of mortality in the United States each year. The identification of the etiologic agent responsible for lower respiratory tract infection plays an important role in the proper management of this clinical problem. The specimens submitted for evaluation are obtained in diverse ways and include expectorated sputum, material from transtracheal and bronchoscopic procedures, pleural fluid and lung aspirates, and biopsy of actual lung tissue. Processing of material can include stained smears, aerobic and anaerobic cultures, and special processing techniques for fungal, viral, Pneumocystis carinii, Legionella, mycobacterial, and mycoplasma identification. Modifications of smear preparation techniques and application of the new DNA probe technology are providing the opportunity for rapid microbiologic testing of clinical specimens with increased sensitivity and specificity, often obviating the need for invasive diagnostic procedures. Laboratory methodology is continually undergoing technological change, and optimal care of the patient with pneumonia requires close cooperation between the attending physician and the clinical laboratory.

Selenomonas bacteraemia--case report and review of the literature.

Selenomonas species are crescent shaped Gram-negative bacilli with a characteristic tuft of flagella located on the concave surface. They are normally found in human gingiva or the rumen of herbivores. The first case of Selenomonas bacteraemia to be reported in a patient immunocompromised by malignant disease is described and the two previously reported cases of Selenomonas bacteraemia as reviewed. The importance of careful anaerobic culturing to recover the organism and special diagnostic techniques to classify the bacteria as Selenomonas species are emphasised. These organisms may cause serious human disease including bacteraemia.