Molecular typing of methicillin-resistant Staphylococcus aureus by PCR-RFLP and its usefulness in an epidemiological study of an outbreak.

A new convenient molecular typing method, simultaneous polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) analysis, for three different genes of methicillin-resistant Staphylococcus aureus (MRSA) was evaluated using 35 isolates of MRSA and comparing results with those previously reported for sequencing-based spa typing. Twenty-nine isolates of the most frequent protein A (spa) type were discriminated into 6 different types by PCR-RFLP. In contrast, spa typing could discriminate only 1 of the 19 most frequent PCR-RFLP-type isolates. The discriminatory powers of the two methods were equal for the other isolates. These results suggest that PCR-RFLP has the advantages of both relative easiness and greater discriminatory power than spa typing. We also report the case of a suspected outbreak in which PCR-RFLP was sufficient for ruling out the possibility of an outbreak. Thus, PCR-RFLP is preferable as a preliminary screening method for epidemiological studies of nosocomial infection caused by MRSA.

Gamma heavy chain disease screening showing a discrepancy between electrophoretic and nephelometric determinations of serum gamma globulin concentration.

A 75-year-old woman with rheumatoid arthritis showed a discrepancy between the reduced level of serum gamma globulin on cellulose acetate electrophoresis and the normal level of serum IgG determined by laser nephelometry. Although no M-peak was detectable on cellulose acetate electrophoresis, immunoelectrophoresis of the patient's serum revealed a monoclonal protein reacting with anti-IgG antiserum but not with anti-kappa or anti-lambda light chain antiserum. Western blotting of the patient's serum showed abnormal low-molecular-weight gamma chains. Thus, the patient was diagnosed with gamma heavy chain disease. A comparison of gamma globulin levels determined by different methods may be useful when screening for this disease.

[Determination of fractal dimension using digital nuclear image of lymphocyte].

Microscopic morphological findings in smeared and stained blood cells are difficult to be characterized quantitatively. However, a recent progress in digital image processing has been enabled to express some of these findings quantitatively. In this report, we propose the usefulness to determine "box" fractal dimension of nuclear image of lymphocyte. Fractal dimension was determined in digital 256-grayscale images of normal, atypical and leukemic lymphocytes by a box-counting method after extracting a nuclear image out of a cellular image, binalyzing and thinning it. The results suggest that fractal dimensions of nuclear images are mainly correlated with changes in chromatin appearance. Fractal dimension could be a useful quantitative parameter for cytological differentiation between normal and atypical lymphocytes.

[An elderly case with Listeria monocytogenes sepsis and pulmonary non-tuberculous mycobacterial infection].

A 88-year-old woman, who had lived in a nursing home, was admitted to our hospital because of the suspicion of pulmonary tuberculosis. She had a cough, fever and diarrhea on admission. She suffered from sepsis because Listeria monocytogenes was isolated from only the blood culture twice. We immediately administered imipenem/cilastatin to her on admission. She simultaneously had pulmonary non-tuberculous mycobacterial infection because the chest roentgenogram showed a cavity in the right upper lung field and Mycobacterium intracellulare was isolated from the sputum many times. She was treated with isoniazid, rifampicin and clarithromycin for the pulmonary non-tuberculous mycobacterial infection. Her condition improved soon after the administration of IPM/CS but a low grade fever and cough persisted. L. monocytogenes and M. intracellulare are important pathogens in the elderly because cell-mediated immunity mainly works as host defenses against both organisms.

[Elimination of electrocardiogram artifacts from electroencephalogram records by using the simultaneously recorded electrocardiograph data].

We developed a simple method to eliminate electrocardiogram (ECG) artifacts from electroencephalogram (EEG) records by using simultaneously recorded ECG data. The raw EEG data, the real EEG data and the ECG data were regarded as multi-dimensional vectors Ea, Er and C, respectively. Also, the ECG data, with reduced amplitude whose coefficient was denoted as 'k', were assumed to be overlapped on the real EEG. These assumptions introduced the equations [Ea = Er + k.C], [Er.C = 0] and finally [k = Ea. C/C.C]. This calculation method was implemented by a Macintosh computer using data exported from digital EEG recordings (sampled at 200 Hz with 16-bit resolution). In several subjects, sampling intervals of 5 or 10 seconds for calculation succeeded in eliminating ECG artifacts. However, regardless of the sampling interval, this elimination condition was not always efficient in several other subjects, including a brain-dead patient. It was suggested that the ECG data used were insufficient for the calculation, because only one hand-to-hand reference was used for simultaneous recording, as usual. This one ECG reference was able to express only one ECG projection. Then two other hand-to-foot references of ECG were added to the recordings, and the elimination procedure was performed using all of the simultaneously recorded ECG data at the three references. Consequently, elimination was much improved in most subjects, including the brain-dead patient. Our method may be useful for eliminating ECG artifacts without changing reference electrodes.