Fitness and dissemination of disinfectant-selected multiple-antibiotic-resistant (MAR) strains of Salmonella enterica serovar Typhimurium in chickens.

OBJECTIVES: The aims of this study were to determine whether strains of Salmonella enterica serovar Typhimurium which had acquired low-level multiple antibiotic resistance (MAR) through repeated exposure to farm disinfectants were able to colonize and transmit between chicks as easily as the parent strain and, if such strains were less susceptible to fluoroquinolones, would high-level resistance be selected after fluoroquinolone treatment. METHODS: Two mutants were compared with the isogenic parent. In the first experiment, day-old chicks were co-infected with both the parent and a mutant to determine their relative fitness. In the second experiment, parent and mutant strains (in separate groups of chicks) were assessed for their ability to transmit from infected (contact) to non-infected (naive) birds and with respect to their susceptibility to fluoroquinolone treatment. Birds were regularly monitored for the presence of Salmonella in caecal contents. Replica plating was used to monitor for the selection of antibiotic-resistant strains. RESULTS: The parent strain was shown to be significantly fitter than the two mutants and was more rapidly disseminated to naive birds. Antibiotic treatment did not preferentially select for the two mutants or for resistant strains. CONCLUSIONS: The disinfectant-exposed strains, although MAR, were less fit, less able to disseminate than the parent strain and were not preferentially selected by therapeutic antibiotic treatment. As such, these strains are unlikely to present a greater problem than other salmonellae in chickens.

Randomized clinical trial comparing radioisotope occult lesion localization and wire-guided excision for biopsy of occult breast lesions.

BACKGROUND: Accurate localization of impalpable breast lesions that require biopsy is important. This randomized trial compared radioisotope occult lesion localization (ROLL) with the standard hooked-wire technique. METHODS: Ninety-five patients were randomized to receive either ROLL or wire localization of an occult breast lesion. Correct placement of isotope was confirmed by mammography and a hand-held gamma probe was used to guide the surgical excision. Radiological, surgical and pathological data were compared for accuracy, duration and ease of technique, and histopathological diagnosis. Procedure-related pain was also assessed. RESULTS: Of the 95 patients entered, 48 were randomized to ROLL and 47 to wire localization. Two ROLL procedures failed. Marking was accurate in 46 of 48 ROLL procedures and 44 of 47 of wire localizations (P = 0.242). Difficulty in localization (Likert score 2.6 for ROLL versus 4.4 for wire localization; P < 0.001) and the degree of surgical difficulty (2.6 versus 4.0; P < 0.001) were significantly less for ROLL. ROLL was associated with less pain (score 2.7 versus 3.6; P = 0.012). There were no significant differences in mean duration of operation, specimen weight, need for intraoperative re-excision or second therapeutic operation. CONCLUSION: ROLL and wire-guided localization were similarly effective for breast biopsy, but ROLL was easier for both radiologist and surgeon, and less painful for the patient.

Molecular mechanisms underlying a unique intermediate phase of memory in aplysia.

Short- and long-term synaptic facilitation induced by serotonin at Aplysia sensory-motor (SN-MN) synapses has been widely used as a cellular model of short- and long-term memory for sensitization. In recent years, a distinct intermediate phase of synaptic facilitation (ITF) has been described at SN-MN synapses. Here, we identify a novel intermediate phase of behavioral memory (ITM) for sensitization in Aplysia and demonstrate that it shares the temporal and mechanistic features of ITF in the intact CNS: (1) it declines completely prior to the onset of LTM, (2) its induction requires protein but not RNA synthesis, and (3) its expression requires the persistent activation of protein kinase A. Thus, in Aplysia, the same temporal and molecular characteristics that distinguish ITF from other phases of synaptic plasticity distinguish ITM from other phases of behavioral memory.

Predicting invasion in mammographically detected microcalcification.

AIM: To identify pre-operative factors which predict presence of invasive disease within mammographically detected malignant microcalcification. MATERIALS AND METHODS: A retrospective analysis was undertaken of 116 serial stereotactic core needle biopsies (SCNBs) performed on malignant mammographic calcification. Final surgical pathology was correlated with pre-operative features (clinical, radiological and core histology) in an attempt to predict the presence of an invasive component. RESULTS: Thirty-eight clusters contained invasive carcinoma. The sensitivity of SCNB for invasion was 55%. Clinical features, calcium morphology and cluster size were not shown to be predictive of invasive disease. Ductal carcinoma in situ (DCIS) of high grade on core histology and increasing number of calcifications were predictive of increased risk of invasion (high grade core biopsy DCIS and > 40 calcifications 48% invasive at surgical histology; high grade core biopsy DCIS and < 40 calcifications 15% invasive; non-high grade core biopsy DCIS 0% invasive). CONCLUSIONS: Identification of those clusters diagnosed as DCIS by percutaneous biopsy which are likely to harbour an invasive component is possible. It would seem reasonable to consider staging the axilla at therapeutic surgery in these patients.

When have mammographic calcifications been adequately sampled at needle core biopsy?

AIMS: To determine if the number of flecks of calcification retrieved at stereotaxic core needle biopsy or the number of core samples obtained containing calcification are related to biopsy sensitivity, and to determine how many calcifications or cores containing calcification the radiologist should aim to retrieve when sampling mammographic microcalcification. MATERIALS AND METHODS: A retrospective review was performed of core specimen radiographs from 57 consecutive patients who had stereotaxic core needle biopsies of impalpable malignant microcalcifications without an associated mammographic mass. The total number of calcifications retrieved and the numbers of cores containing calcification were correlated with findings at core and surgical histology. RESULTS: Increasing retrieval of calcification elements visible on specimen radiography was associated with increasing sensitivity of the biopsy. Five or more flecks of calcium gave an absolute sensitivity of 100%. Increasing numbers of core samples obtained containing radiographically demonstrable calcification was also associated with increasing sensitivity. Three or more cores containing calcium resulted in a 100% absolute sensitivity for malignancy. CONCLUSION: To ensure adequate sampling of calcification at core biopsy, an optimum of either three or more cores containing calcium or five or more flecks of calcium in total is required. Achieving this target ensures a high pre-operative diagnosis rate for malignant microcalcifications.Bagnall, M. J. C. (2000). Clinical Radiology 55, 548-553.

Lower-limb deep venous thrombosis: direct MR imaging of the thrombus.

PURPOSE: To determine the feasibility of diagnosing deep venous thrombosis (DVT) with direct three-dimensional magnetic resonance (MR) imaging of the thrombus. MATERIALS AND METHODS: Eighteen patients with proved DVT at conventional venography were evaluated with a magnetization-prepared three-dimensional blood- and fat-suppressed MR imaging sequence. The presence and extent of thrombosis on the MR images were compared with the findings at conventional venography. RESULTS: At MR imaging, DVT was visualized in 17 of the 18 patients. MR imaging demonstrated greater proximal extent of the thrombosis in four patients, asymptomatic contralateral thrombosis in one, involvement of the deep femoral vein in five, and involvement of the superficial venous system in three. CONCLUSION: Direct MR imaging of clots appears capable of demonstrating venographically diagnosed DVT. This MR imaging technique is noninvasive, quick, and repeatable and allows a survey of the whole lower-limb venous system. Detection of thrombosis relies on the formation of methemoglobin, which appears to be sufficiently rapid to allow use of this technique in the clinical setting. Changes in the signal from clot over time may allow estimation of the age of the thrombus.