Ayako Takahashi

Detection of a Variant Metallo-β-Lactamase, IMP-10, from Two Unrelated Strains of Pseudomonas aeruginosa and an Alcaligenes xylosoxidans Strain

ABSTRACT The gene blaIMP-10 of a variant metallo-β-lactamase, IMP-10, had a single base replacement of G by T at nucleotide 145, which led to an amino acid alteration of Val49 to Phe compared to the IMP-1 enzyme, indicating that IMP-10 was a point mutation derivative of IMP-1. Highly purified enzymes revealed that IMP-10 was different from IMP-1 in its extremely low hydrolyzing activities for penicillins, such as benzylpenicillin, ampicillin, and piperacillin.

Presence of Pseudomonas putida Strains Harboring Plasmids Bearing the Metallo-β-Lactamase Gene blaIMP in a Hospital in Japan

ABSTRACT To determine the persistence and spread of antibiotic-resistant strains in Gunma University Hospital, 83 Pseudomonas putida strains (each from a different patient) were isolated from January 1997 through December 2001. Of the 83 strains isolated, 27 were resistant to carbapenems. All 27 produced metallo-β-lactamase and were found to be PCR positive for the blaIMP gene. Most (22 strains) were primarily isolated from the wards (W7 [9 strains] and W4 [8 strains]). Another five blaIMP-positive P. putida strains from wards W7 and W4 were obtained by swabbing around the water pipes. A total of 32 blaIMP-positive P. putida strains were assessed by pulsed-field gel electrophoresis (PFGE) and testing of drug susceptibility to 10 chemotherapeutic agents. Both PFGE and MIC patterns revealed that there were long-term resident strains among inpatients and hospital environments. The blaIMP genes of 22 of 32 strains were all transferable to a recipient strain of Pseudomonas aeruginosa by conjugation or transformation and conferred resistance to carbapenems and cephems. The blaIMP plasmids were conjugally transmissible among P. aeruginosa strains and mediated resistance to amikacin as well as β-lactams. Ten of the 22 plasmids mediated additional resistance to gentamicin and tobramycin. Plasmids with identical DNA and drug resistance patterns were found in P. putida strains with identical PFGE patterns and with different PFGE patterns. We presumed that P. putida was one of the resident species in inpatients and especially in hospital environments, spreading drug resistance genes via plasmids among P. putida strains and supplying them to more pathogenically important species, such as P. aeruginosa.

Gliomatosis cerebri evaluated by 18Fα-methyl tyrosine positron-emission tomography

Gliomatosis cerebri is a rare condition in which an infiltrative glial neoplasm spreads through the brain with preservation of the underlying structure. CT and MRI show diffuse abnormal density or signal, without mass effect, and because these findings are nonspecific, it is difficult to make a definitive diagnosis. Our purpose was to assess the usefulness of a new tumour-detecting amino acid tracer for positron-emission tomography (PET), L-[3-18F] α-methyl tyrosine (FMT), in patients with gliomatosis cerebri. We performed FMT PET, fluorodeoxyglucose FDG PET and MRI eight patients with gliomatosis cerebri and six with non-neoplastic disease, whose MRI also showed diffuse high signal on T2-weighted images. Standardised uptake (SUV) of FMT and FDG in the area of gliomatosis was obtained and the tumour-to-normal cortex (T/N) ratio of this was compared. The tumours were shown on FMT PET as areas of increased uptake, except in one patient with severe intracranial hypertension. There were significant differences between the SUV of FMT and the T/N ratio of FMT in patients and in controls (both P<0.01), and between the T/N ratio of FMT and FDG in patients (P <0.01). Increased uptake of FMT PET strongly suggests neoplasia. FMT PET is valuable for differentiating gliomatosis cerebri from non-neoplastic diseases showing similar diffuse high signal on T2-weighted images and little contrast enhancement.

Added value of contrast-enhanced CISS imaging in relation to conventional MR images for the evaluation of intracavernous cranial nerve lesions.

IntroductionThe normal cranial nerves (CNs) of the cavernous sinus can be clearly demonstrated using contrast-enhanced constructive interference in steady-state (CISS) magnetic resonance imaging (MRI). This study used the method to evaluate pathological CNs III, IV, V1, V2, and VI in cavernous sinuses affected by inflammatory and neoplastic diseases.MethodsMR images from 17 patients with diseases involving the cavernous sinuses and/or causing neuropathy in CNs III–VI were retrospectively evaluated. The patients were divided into inflammatory (n = 11) and neoplastic (n = 6) groups. We defined CNs as abnormal when they exhibited enlargement or enhancement. CNs were evaluated using both contrast-enhanced CISS and T1-weighted MRI.ResultsIn the inflammatory group, abnormal CNs were identified by contrast-enhanced CISS MRI in 13 of 25 symptomatic CNs (52%) in eight patients, but in only two CNs (8%) in two patients by contrast-enhanced T1-weighted MRI. In the neoplastic group, both sequences of contrast-enhanced CISS and T1-weighted MRI detected abnormalities in the same three of eight symptomatic CNs (37.5%), i.e., the three CNs were all in the same patient with adenoid cystic carcinoma.ConclusionContrast-enhanced CISS MRI is useful for detecting CN abnormalities in inflammatory pathological conditions of the cavernous sinuses.

Anatomic analysis of computed tomography images obtained during fluoroscopic computed tomography-guided percutaneous lumbar sympathectomy

PurposeThe fluoroscopic computed tomography (CT)-guidance technique increases the accuracy and safety of needle placement for percutaneous lumbar sympathectomy. The aim of the present study was to provide anatomic data from CT images and to discuss the safest route for needle insertion.MethodsWe retrospectively analyzed CT images that were obtained from 25 patients (14 men, 11 women; 37—89 years of age [mean, 68.4 years]) during fluoroscopic CT-guided percutaneous lumbar sympathectomy. The anatomy around the inserted needle was measured and the correlations between patient characteristics and the procedure-related distances were assessed.ResultsThe distance from the midline (spinous process) to the entry point and the depth to the target site correlated with body size, especially height and weight. The maximal distance from midline to the insertion point in the range of safe needle insertion at L2 was less than 7.0 cm in approximately 20% of the patients.ConclusionThe present study was performed to determine the anatomic details required to guide safe percutaneous lumbar sympathectomy based on CT images. The use of CT guidance is recommended for lumbar sympathectomy, especially at the L2 spinal level.

Wave-like appearance of diffuse pachymeningeal enhancement associated with intracranial hypotension

Diffuse pachymeningeal enhancement on magnetic resonance (MR) imaging is important in identifying spontaneous and secondary intracranial hypotension (IH) [cerebrospinal fluid (CSF) hypovolemia] in patients with postural headache, because CSF pressure at lumbar puncture is variable. We examined the pachymeningeal enhancement pattern in patients with IH. MR imaging findings of pachymeningeal enhancement were examined before and after treatment in seven consecutive patients with spontaneous IH and one patient with IH after lumbar puncture. Diffuse non-nodular dural enhancement was observed in all patients. Characteristic thick, uninterrupted, enhancement was observed, mainly in the dura of the frontal, temporal, and retroclival regions, and the tentorium. Thin and uninterrupted, or partially interrupted, enhancement was observed, mainly in the parieto-occipital region and cerebellar convexity. Curved linear enhancement was observed along the calvarium of all patients. A wave-like appearance, a clear pattern of dural unevenness parallel to the brain, was detected in the frontal and temporal regions, near the base, in all patients. A wave-like appearance, especially in the frontal and temporal base, may be a characteristic MR imaging indicator of IH.

Incidentally detected parafalcine chondrosarcoma

SummaryParafalcine chondrosarcoma is extremely rare, and may be difficult to differentiate preoperatively from falx meningioma. An 18-year-old woman presented with a parafalcine chondrosarcoma incidentally detected as a small lesion 2 years before admission, suggesting falx meningioma. Brain computed tomography and magnetic resonance imaging just before admission revealed the parafalcine lesion had increased by about nine times in volume during the last 2 years. Single-photon emission computed tomography (SPECT) after intravenous administration of both thallium-201 chloride (201TlCl) and N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) demonstrated no abnormal uptake of either tracer. Histological examination revealed classic low-grade chondrosarcoma. Parafalcine chondrosarcoma should be considered at this site if relatively rapid growth is observed. SPECT using 201TlCl and 123I-IMP may be useful to discriminate parafalcine low-grade chondrosarcoma from meningioma or other tumours originating in this region.

Non-Contrast Renal MR Angiography: Value of Subtraction of Tagging and Non-Tagging Technique.

PURPOSE The aim of this study was to examine the usefulness of the subtraction technique of non-contrast renal magnetic resonance angiography (MRA) between tagged and non-tagged data collection. MATERIAL AND METHODS We performed renal MRA on eleven healthy volunteers using a 3T MRI unit. For renal MRA, a three dimensional balanced type steady-state free precession (SSFP) sequence (True FISP, Siemens) was used with diaphragmatic navigator gating. We tried to acquire selective arterial images by subtracting black-blood images (tagged images, on which arterial longitudinal magnetization was nearly zero by selective inversion of upper-stream aortic flow) from bright-blood images (non-tagged images, on which arterial flow is bright due to inflow effect). For analysis, two radiologists independently evaluated the visual quality of the axial and coronal targeted maximum intensity projection images (MIP) of original bright-blood MRA and subtraction MRA. RESULTS Visualization of the main stem of the renal arteries and their 1st branches were satisfactory on both techniques, and there was no statistically significant difference. The score of 2nd branch appeared superior with the subtraction method, but only the right side showed a statistically significant difference (P <0.01). Visualization of small intraparenchymal arteries was significantly superior with subtraction method on both sides. CONCLUSION We tried to improve selective demonstration of renal arterial branches using subtraction technique. Although full sequence optimization was not performed, this pilot study showed this technique to be slightly time-consuming but superior in visualization of peripheral branches and possibly more sensitive in detecting small vessel abnormalities.