Epidemic spread of a single clone of methicillin-resistant Staphylococcus aureus among injection drug users in Zurich, Switzerland

We describe an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) among injection drug users (IDUs). From August 1994 through December 1999, we registered 31 IDUs with MRSA infections (12 with soft-tissue infection, 7 with pneumonia [fatal in 1], 7 with endocarditis [fatal in 1], 2 with osteomyelitis, 2 with septic arthritis, and 1 with ulcerative tonsillitis), with a marked increase in the number of IDUs registered during 1998 and 1999. Of 31 patients, 15 (48%) were infected with human immunodeficiency virus. A point-prevalence study among IDUs who frequented outpatient facilities in Zurich revealed an MRSA carriage rate of 10.3% (range, 0%-28.6%) in various facilities. In all but 1 case, pulsed-field gel electrophoresis banding patterns of isolates obtained from these patients were indistinguishable from isolates of the initial 31 IDUs registered. Risk factors for MRSA carriage were disability and prior hospitalization in a hospice. In summary, MRSA became endemic in IDUs in Zurich as a result of the spread of a single clone. This clone caused major morbidity and was responsible for a lethal outcome in 2 cases.

[99mTc-MIBI characterization of breast microcalcifications. Correlations with scintigraphic and histopathologic findings]

INTRODUCTION

Microcalcifications which do not belong to focal lesions are a difficult diagnostic problem to solve with mammography. We investigated the yield of 99mTc-Sestamibi (MIBI) scintigraphy in the assessment of the benign or malignant nature of these lesions and compared nuclear medicine with histologic and immuno-histochemical findings.

MATERIAL AND METHODS

Twenty-seven areas of microcalcifications (0.3-5 cm in largest diameter) were considered; no solid masses or cysts were detected by mammography and sonography. The mammographic features of these microcalcifications were suggestive of malignancy in 3 cases and of benignity in 14; the diagnosis was questionable in the other 10 cases. MIBI scintigraphy was considered positive for malignancy when there was tracer uptake in the breast. Cytologic samples of all lesions were obtained with fine-needle aspiration under stereotactic guidance. Histology was performed in the 13 lesions considered malignant or dubious at mammography, independent of their cytology; histology was combined with immunohistochemical tests to assess intracellular mitochondria count and the number of vessels. The other 14 lesions, which were benign at mammography and cytology, were followed-up yearly for two years, and no change in clinical or radiological findings was demonstrated.

RESULTS

Histology diagnosed 8 ductal carcinomas (3 invasive carcinomas and 5 carcinomas in situ) and 5 benign lesions (1 sclerosing adenosis and 4 fibrocystic diseases, 3 of them associated with ductal hyperplasia). Scintigraphy was positive in 4/8 malignant lesions (3/3 invasive carcinomas, 1-3.5 cm in largest diameter; 1/5 carcinomas in situ, 5 cm in largest diameter) and negative in 4/5 benign lesions (we had one false positive in a fibrocystic disease associated with ductal hyperplasia). Tracer uptake was observed in all lesions with a high intracellular mitochondria count, except for 2 carcinomas in situ (0.3 and 0.8 cm in largest diameter, respectively); no benign or malignant lesion was well vascularized. Scintigraphy was negative also in the other 14 benign lesions with no histology.

CONCLUSIONS

99mTc-MIBI scintigraphy was able to characterize both invasive ductal carcinomas and benign lesions, which results hold even though our series was small because of the selection criteria we used. Thus, all invasive ductal carcinomas were identified and we had only one false positive (1/19) in benign lesions. In contrast, the technique was inadequate in carcinomas in situ, probably because their size and biological patterns vary greatly. Thus, scintigraphy was negative in 4/5 lesions (all < 1 cm O) and positive in only 1/5 (5 cm O). Therefore we conclude that 99mTc-MIBI scintigraphy cannot replace stereotactically-guided fine-needle aspiration in breast microcalcifications with questionable mammographic findings.

[Is mammography useful in the detection of breast cancer in women 35 years of age or younger?]

Breast cancer in women 35 years old or younger is unusual. It accounts for 1-3.6% of all breast cancers but is the leading cause of cancer mortality in women 15-35 years old. The diagnostic delay, with T2 or more advanced cancer at clinical presentation, is due to the patient's age and the opinion of low mammographic reliability for cancer diagnosis in this age group. To assess the usefulness of mammography in breast cancer patients aged 35 years or younger, we reviewed the clinical, mammographic and histologic data of 65 cancers collected in 7 breast diagnosis and counseling centers in Lombardy. Fifty-three patients (81.5%) were referred for a palpable breast mass, which was a T2 or more advanced cancer in 23 cases. Mammography showed malignant patterns (spiculated opacities, clusters of microcalcifications, casting, branching and ductal type calcifications) in 31 patients (47.7%). Mammography was not definitive but correctly suggested further examinations in 30 women and it had only 4 false negatives. Ultrasonography performed in 43 patients was negative in 3 (7%), pathologic and pathognomonic for cancer in 27 (62.8%) and pathologic but not indicative of malignancy in 13 (20.2%). The cytologic or histologic diagnosis of breast cancer was made under US guidance in 24 cases. In women aged 35 years or younger mammography was effective in identifying breast cancers; US and fine-needle aspiration biopsy (FNAB) complete mammography. We believe that mammography can be a valuable screening tool in young women at high risk for breast cancer because of family history.

[Color Doppler ultrasonography versus angiography in leg aneurysms]

The authors compared color-Doppler US with angiographic findings in the study of peripheral lower limbs aneurysms. Twelve cases were observed over a 2-year period of time. In each case, the combination of B-mode and color-Doppler US permitted the accurate evaluation of the aneurysm and of the possible compression of adjacent vessels. Angiography, which was considered the gold standard, detected only 8 of 12 cases; in 3 of 8 cases, the actual diameter of the aneurysm was under estimated. The simultaneous visualization of vessel wall and of intraluminal blood flow proved color-Doppler US to be superior to the gold standard in these cases. The authors conclude that color-Doppler US may become the new reference standard in the diagnosis and follow-up of peripheral aneurysms.

[Imaging of the breast treated with quadrantectomy and radiotherapy. Interpretative difficulties in diagnosing asymptomatic recurrences]

This study was aimed at evaluating the incidence of breast carcinoma recurrences in a group of female patients treated with QU.A.RT. July 1989 to December 1990, 111 asymptomatic patients underwent physical examination, mammography (in both cranio-caudal and 45 degrees oblique projections), and US with 7.5 and 10 MHz probes. The study population was made of patients operated between 1984 and 1989 and subsequently treated with radiotherapy. Twenty-seven cases with suspect mammographic and US findings were selected and submitted to cytology with needle biopsy under US or stereotaxic guidance. Ten of them exhibited recurrences (9%) at cytology. Of the extant 17 cases, 5 had inflammatory lesions, 1 had liponecrosis, and 11 patients presented with no pathologic cells. The interpretative difficulties of mammographic and US findings were also examined. Problems were found to be related to both correct execution of the technique due to the treatment the breast is submitted to (volumetric reduction and structural distortion) and to correct image interpretation. Therefore we conclude that the two diagnostic methods be combined for they are complementary in the early detection of breast carcinoma recurrence.

[Tropical splenomegaly: echographic picture]

Tropical splenomegaly is a pathologic condition due to multiple causes, endemic malaria being the major one. Twenty-eight black patients, 10 males and 18 females, residing in a tropical area, were investigated with US. The morphological features and major diameters of the spleen were studied and the splenic volumetric index (IVS) was calculated. Typical features were the presence of small intraparenchymal calcifications (46%) and the enlargement of splenic vessels, with US wall reinforcement (75%). No nodular lesions were detected, but increased frequency of organ lobulation was observed. A definite and uniform increase in splenic diameters was seen in all cases; IVS in particular was greater than the accepted confidence limit (21.5 +/- 6.5). This characteristic features should help the echographist to recognize this condition for they supply useful clinical information.

[Value of echographic examination in the study of osteomyelitis]

Beside conventional radiology and bone scintigraphy, an important role is played in the diagnosis of osteomyelitis by sonography (US). This technique is especially useful to detect fluid collections in the soft tissues adjacent to the bone. Ten patients with osteomyelitis were examined: in 8 cases the presence of fluid collections was demonstrated, which were sometimes spreading along the bone axis and sometimes localized in a single site. The collection was subperiosteal in all cases. Sonography proved thus useful in providing further information on the bone affected with osteomyelitis.

[Role of echography in the diagnosis of ovarian tumors]

The role of sonography is evaluated in the diagnosis of ovarian tumors. Real-time US proves more sensitive than gynecological examination in the diagnosis of ovarian diseases. As yet, however, no correlation has been found between histological findings and US appearance. An accurate review of the relative literature and of our results lead us to the conclusion that sonography does not significantly affect the early diagnosis of ovarian tumors.