Chyi-Liang Chen

Risk factors and outcome analysis of acinetobacter baumannii complex bacteremia in critical patients.

Objectives:Acinetobacter baumannii complex bacteremia has been identified increasingly in critical patients admitted in ICUs. Notably, A. baumannii complex bacteremia has a high mortality rate, yet the risk factors associated with mortality remain unclear and controversial. Design:Retrospective study. Setting:All adult ICUs at a tertiary care medical center. Patients:All patients with A. baumannii complex bacteremia admitted in 2009–2010. Interventions:None. Measurements and Main Results:Risk factors for mortality were analyzed. Bacterial isolates were identified by 16S-23S ribosomal RNA intergenic spacer region sequencing for genospecies and genotyped by pulsed-field gel electrophoresis. Carbapenemase genes were detected by polymerase chain reaction and sequencing. A total of 298 patients met the inclusion criteria, including 73 (24.5%) infected by imipenem-resistant A. baumannii complex. The overall 30-day mortality was 33.6% (100 of 298). Imipenem-resistant A. baumannii complex bacteremia specifically showed a high mortality (69.9%) and was associated with prior use of broad-spectrum antibiotics for more than 5 days for treating ventilator-associated pneumonia before the occurrence of bacteremia. Mortality was associated with inappropriate initial antimicrobial therapy, which was correlated with imipenem-resistant A. baumannii complex but not with any specific genospecies. ISAba1–blaOXA-23–ISAba1 (Tn2006) was found in most (66.7%, 40 of 68) imipenem-resistant A. baumannii (genospecies 2) and also spread beyond species border to all imipenem-resistant genospecies 3 (2), 13TU (2), and 10 (1). Conclusions:For critical patients with A. baumannii complex infection, ventilator-associated pneumonia in particular, the selective pressure from prior use of broad-spectrum antibiotics for 5 days or more increased risk of subsequent imipenem-resistant A. baumannii complex bacteremia. To reduce mortality, rapid identification of imipenem-resistant A. baumannii complex and early initiation of appropriate antimicrobial therapy in these high-risk patients are crucial.

Hypoplasia of the internal carotid artery with intercavernous anastomosis.

Abstract We report a symptomatic case of unilateral hypoplasia of the internal carotid artery with an intercavernous anastomosis, a very rare developmental anomaly. The symptoms were caused by occlusion of the proximal middle cerebral artery which possibly related to the haemodynamic stress caused by the anomalous intercavernous anastomosis.

Imipenem heteroresistance induced by imipenem in multidrug-resistant Acinetobacter baumannii: mechanism and clinical implications.

Acinetobacter baumannii has emerged as a major pathogen causing nosocomial infections, particularly in critical patients admitted to the Intensive Care Unit. Increasing resistance to carbapenems in A. baumannii has been observed worldwide. Here we report the clinical impact and mechanism of imipenem heteroresistance (imipenem minimum inhibitory concentration of 6-32 μg/mL with the presence of resistant cells inside the inhibition zone of Etest strips or disks) in multidrug-resistant A. baumannii (MDR-AB). To identify risk factors associated with the emergence of imipenem heteroresistance, a retrospective case-control study was undertaken involving cases with subsequent clinical isolates of the same genotype showing loss of imipenem susceptibility and matched controls with isolates belonging to imipenem-susceptible MDR-AB. The molecular mechanism of heteroresistance was examined. From April 2006 to March 2007, 126 consecutive isolates of MDR-AB were identified from 29 patients. Switch from imipenem susceptibility to heteroresistance was more likely to occur in successive MDR-AB derived from patients who had been exposed to imipenem (length of use 10.9 ± 6.5 days for cases vs. 5.3 ± 4.8 days for controls; P=0.02). An insertion sequence (ISAba1) was found in the promoter region of a class C β-lactamase gene (bla(ADC-29)) in most imipenem-heteroresistant MDR-AB isolates. In vitro experiments indicated that imipenem heteroresistance, which was associated with overexpression of bla(ADC-29), could be induced by imipenem. Carbapenem use was the only risk factor identified for the emergence of carbapenem-heteroresistant MDR-AB. Physicians should weigh the benefits and risks of each carbapenem-based treatment in managing carbapenem-susceptible MDR-AB infection.

Spinal MR findings in spontaneous intracranial hypotension

Abstract. Whole spine magnetic resonance (MR) imaging was used to evaluate the shape, size, signal intensity, and enhancement of the spinal spaces in a series of six patients with spontaneous intracranial hypotension (SIH). In all patients varying degrees of shrunken dural sacs, expanded extradural spaces with delayed homogeneous enhancement, and distended epidural venous plexuses were noted. In 83% (5/6) of patients, the MR signal of the expanded extradural space was similar to that of cerebrospinal fluid; 17% (1/6) showed an excessive fat deposit in the epidural space. Sixty-seven percent (4/6) of patients had a visible peridural membrane. After relief of the symptoms, one patient (1/4) showed persistence of the spinal abnormalities even though the brain abnormalities disappeared. In conclusion, the spinal MR findings of SIH, like its brain counterpart, are characteristic. In cases with clinical suspicion but without support from brain MR imaging, spinal MR imaging may be helpful in establishing the diagnosis.

Enhanced cervical MRI in identifying intracranial dural arteriovenous fistulae with spinal perimedullary venous drainage

Abstract Diagnosis of an intracranial dural arteriovenous fistula (DAVF) with spinal perimedullary venous drainage is challenging because the presenting symptoms are usually related to dysfunction of the spine, not of the brain. Repeated spinal angiograms are usually performed before the diagnosis is finally made by cerebral angiography. We report two cases of intracranial DAVFs with spinal perimedullary venous drainage. In both cases contrast-enhanced cervical MRI demonstrated dilated lower brainstem and upper spinal veins, which, we believe, is a good indicator of the existence of such drainage. We suggest that, in cases with perimedullary serpentine enhancement on thoracic or lumbar MR images, additional Gd-enhanced cervical spinal MR imaging should be performed. The simple process of tracing the veins upwards may avoid a lot of unnecessary examinations and delay in the diagnosis.

Spontaneous spinal epidural haematomas with repeated remission and relapse

Abstract We present a case of spontaneous spinal epidural haematoma (SSEH) with a rare clinical course of repeated spontaneous recovery and relapse. The patient suffered three episodes of upper-back pain of sudden onset followed by sensory and motor dysfunction after weight lifting. In the first two episodes, the neurological deficits recovered spontaneously and completely. In the last episode, paraplegia persisted even after emergency surgery. Serial studies with computed tomographic (CT) myelography and magnetic resonance imaging (MRI) demonstrated the remitting and relapsing course of the SSEHs. The possible causes of the SSEHs and the mechanisms of spontaneous recovery are discussed.

Extracranial distal aneurysm of posterior inferior cerebellar artery

Abstract An unusual aneurysm arising from an extracranial lateral medullary segment of the posterior inferior cerebellar artery (PICA) is reported. The origin of the PICA was also extracranial, 10 mm below the foramen magnum. The aneurysm was not seen on three-vessel angiography. The literature is reviewed with regard to the clinical and radiological features of such aneurysms. Occipital and nuchal headache with an altered level of consciousness, intraventricular haemorrhage, and hydrocephalus are suggestive of such aneurysm. The need for four-vessel angiography is again stressed.

Suprasellar and infrasellar craniopharyngioma with a persistent craniopharyngeal canal: case report and review of the literature.

Abstract Craniopharyngiomas are usually confined to the sellar and suprasellar regions; infrasellar craniopharyngioma is rare. From an embryological point of view, this unusual localisation can be explained by Erdheims theory that these tumours can arise anywhere along the craniopharyngeal canal (CPC). However, there has been no proof of this theory, because the CPC is usually obliterated during the 12th week of gestation. I present a case of supra- and infrasellar craniopharyngiomas with a persistent CPC. Imaging demonstrated an intimate relationship between the infrasellar tumour and the CPC, supporting Erdheims view.

Central gadolinium enhancement of an acute spontaneous spinal epidural haematoma

Spontaneous spinal epidural haematoma (SSEH) is uncommon, but central gadolinium (Gd) enhancement of the haematoma is even rarer. To our knowledge, only one case has been reported, but no explanation was given concerning the mechanism of this enhancement. We present a case of SSEH with unusual central Gd enhancement which we believe is due to oozing from the injured posterior internal venous plexuses. Therefore, although rare, central Gd enhancement of an epidural mass should not rule out the possibility of a haematoma.

A glimpse into evolution and dissemination of multidrug-resistant Acinetobacter baumannii isolates in East Asia: a comparative genomics study

Clonal dissemination is characteristic of the important nosocomial pathogen Acinetobacter baumannii, as revealed by previous multi-locus sequence typing (MLST) studies. However, the disseminated phyletic unit is actually MLST sequence type instead of real bacterial clone. Here we sequenced the genomes of 13 multidrug-resistant (MDR) A. baumannii strains from Taiwan, and compared them with that of A. baumannii from other East Asian countries. Core-genome phylogenetic tree divided the analyzed strains into three major clades. Among them, one ST455 clade was a hybrid between the ST208 clade and the other ST455 clade. Several strains showed nearly identical genome sequence, but their isolation sources differed by over 2,500 km and 10 years apart, suggesting a wide dissemination of the phyletic units, which were much smaller than the sequence type. Frequent structural variation was detected even between the closely related strains in antimicrobial resistance elements such as AbaRI, class I integron, indicating strong selection pressure brought by antimicrobial use. In conclusion, wide clonal dissemination and frequent genomic variation simultaneously characterize the clinical MDR A. baumannii in East Asia.