Comparison of screening methods for detection of extended-spectrum beta-lactamases and their prevalence among Escherichia coli and Klebsiella species in Hong Kong

Three tests, the disk diffusion test, the double-disc synergy test and the inhibitor-potentiated disc diffusion test, were compared for their abilities to detect production of extended-spectrum beta-lactamases (ESBL) in 702 Escherichia coli and 472 Klebsiella spp. strains from four hospitals. Eleven percent E. coli and 13% Klebsiella spp. were found to produce ESBL. As an indicator of ESBL activity, the sensitivities of the five extended-spectrum beta-lactams were as follows: cefotaxime (100%), cefpodoxime (99.3%), ceftriaxone (98.6%), aztreonam (93%) and ceftazidime (57.7%) when interpreted using the National Committee for Clinical Laboratory Standards criteria. Their positive predictive values ranged from 67.8-83.8%. Both the inhibitor-potentiated disc diffusion test and the double-disc synergy test (at three inter-disc widths of 20, 25 and 30 mm) were capable of identifying all the ESBL-producers. However, at a single inter-disc width of 30 mm, the double-disc synergy test has limited sensitivity (83.8%). As a second test for confirming ESBL activity in strains with reduced susceptibility to beta-lactams, the inhibitor-potentiated disc diffusion test is therefore a simple and reliable option.     

Assessment of HBV persistent infection in an adult population in Taiwan

In order to study the prevalence of hepatitis B virus (HBV) in the adult population of Taiwan, we screened for the presence of HBV DNA in 205 blood samples from adult (20-59-year-old) volunteers. According to the serological markers of HBV, samples were divided into three groups: group I (173 subjects) was negative for both HBsAg and HBeAg; group II (14 subjects) was positive for both HBsAg and HBeAg; and group III consisted of 18 subjects who were HBsAg-positive but HBeAg-negative. Plasma HBV DNA was not detected in group I, but it was found in 85.7% and 11.8% of samples in group II and group III, respectively. A free-form HBV DNA was found in 14.3% of the leukocyte samples in group II. Furthermore, an integrated form of HBV DNA was detected in the leukocytes of two cases of group I who remained healthy based on clinical data. HBV DNA was also detected in the spermatozoa and liver cells of one of the cases.     

An improved technique for monitoring the drinking behavior of mice

A set of calibrated lickometers provides continuous, quantitative monitoring of fluid consumption. It has been used in our laboratory at four levels of temporal resolution: 24 hr, 1 hr, 6 min, and for counting of individual licks. Convenient features are mounting of the licking tube-bottle assembly on the cage top (which permits the use of disposable plastic cages with litter) and automated collection of data with microcomputers.     

Optimization of 3-D hepatocyte culture by controlling the physical and chemical properties of the extra-cellular matrices

Hepatocytes are anchorage-dependent cells sensitive to microenvironment; the control of the physicochemical properties of the extra-cellular matrices may be useful to the maintenance of hepatocyte functions in vitro for various applications. In a microcapsule-based 3-D hepatocyte culture microenvironment, we could control the physical properties of the collagen nano-fibres by fine-tuning the complex-coacervation reaction between methylated collagen and terpolymer of hydroxylethyl methacrylate-methyl methacrylate-methylacrylic acid. The physical properties of the nano-fibres were quantitatively characterized using back-scattering confocal microscopy to help optimize the physical support for hepatocyte functions. We further enhanced the chemical properties of the collagen nano-fibres by incorporating galactose onto collagen, which can specifically interact with the asialoglycoprotein receptor on hepatocytes. By correlating a range of collagen nano-fibres of different physicochemical properties with hepatocyte functions, we have identified a specific combination of methylated and galactosylated collagen nano-fibres optimal for maintaining hepatocyte functions in vitro. A model of how the physical and chemical supports interplay to maintain hepatocyte functions is discussed.     

Comparative in vitro activity of the new erythromycin derivative dirithromycin against gram-positive bacteria isolated from cancer patients

The in vitro activity of dirithromycin (LY-237216), a new macrolide erythromycin derivative, was compared to that of four other agents (clarithromycin, erythromycin, roxithromycin, clindamycin) against 334 gram-positive isolates obtained from cancer patients. Dirithromycin was similar in potency and antimicrobial spectrum to the other agents tested. It was very active against beta-haemolytic streptococci andStreptococcus pneumoniae, and moderately active against penicillin and methicillin susceptibleStaphylococcus aureus, Bacillus spp.,Listeria monocytogenes andCorynebacterium jeikeium. Erythromycin resistant organisms were also resistant to dirithromycin.     

Acidic pH and increasing [Ca(2+)] reduce the swelling of mucins in primary cultures of human cervical cells

BACKGROUND: Cervical mucus is a heterogeneous mixture of water, ions and mucins that form a hydrophilic polymer gel. Mucins, the main components of mucus, are condensed inside secretory granules and swell to become a hydrogel after exocytosis. Using human cervical secretory cell primary cultures, the effect of [Ca(2+)] and [H(+)] on the swelling velocity of mucin granules was investigated in vitro. METHODS and RESULTS: Immunocytochemistry demonstrated that estrogen and progesterone receptors were expressed in cultured secretory cells along with mucins type 1, 4, 5AC and 5B. Exocytosis of secretory cells, recorded by videomicroscopy, showed that during swelling, the radius of the secretory granule matrix followed first-order kinetics. An increase in extracellular [Ca(2+)] from 1 to 4 mmol/l or a reduction in pH from 7.4 to 6.5 was seen to produce a significant decrease in the velocity of swelling of the secretory granule matrix. CONCLUSIONS: The inverse relationship observed between the diffusion of the granular matrix and the extracellular [Ca(2+)] or [H(+)] suggested that changes in cation concentration might drastically affect the swelling characteristics of mucins and provide a control mechanism for the observed viscoelastic properties of mucus.     

Cell adhesion-related proteins as specific markers of sponge cell types involved in allogeneic recognition

Sponge immunocyte identification is of interest to comparative immunologists since characterizing these cells will allow investigations into the mechanisms of non-self recognition in the oldest animal phylum. Here, we report that polyclonal antibodies raised against the core protein of a proteoglycan involved in cell adhesion in the marine sponge Microciona prolifera are specific markers for archaeocytes, the totipotent sponge cells. Archaeocytes are mobilized upon allogeneic contact and they accumulate in the contact zone. A second type of cell, the gray cells, are specifically recognized by monoclonal antibodies raised against CD44, a hyaluronan receptor. Gray cells do also accumulate in the contact area. Specific staining of a third sponge cell type, the rhabdiferous cells, shows that these do not accumulate upon allografting. These specific cell markers allow tracking of archaeocytes and gray cells, and show that they play an active role in sponge allogeneic reactions.     

Altered GABAB receptor immunoreactivity in the gerbil hippocampus induced by baclofen and phaclofen, not seizure activity

The present study was performed to determine whether the effects induced by GABA(B) receptor-acting drugs would be related with the alteration in GABA(B) receptor expression in the hippocampus using Mongolian gerbil, a genetic epilepsy model. The distribution patterns of both GABA(B) receptor 1A/B and GABA(B)receptor 2 immunoreactivities were similarly detected in the hippocampi of normal and seizure-prone gerbils. Following baclofen (GABA(B) receptor agonist) or phaclofen (GABA(B) receptor antagonist) treatment, GABA(B) receptor immunoreactivities were decreased or increased by dose-dependent manners, respectively. Vigabatrin (GABA transaminase inhibitor) or 3-mercaptopropionic acid (GAD inhibitor) treatment did not affect GABA(B) receptor expressions. These findings suggest that GABA(B) receptor expression in the gerbil hippocampus may be altered by baclofen or phaclofen treatment.     

Detection of T suppressor cells in patients with organ allografts

Specific immunosuppression of host's immune response to donor HLA antigens has been a major goal to clinical transplantation. Recent evidence has been accumulating to show that a distinct population of T cells expressing the CD8(+) CD28(-) phenotype display suppressor function and inhibit Th activation and proliferation by modulating the APC function. To assess the presence of Ts in transplant recipient's circulation, we have developed a flow cytometry method that measures the expression of costimulatory molecules on donor APC exposed to recipient Th and Ts. Our results demonstrate that quantitation of the capacity of CD8(+) CD28(-) T cells from patient circulation to suppress the activation of costimulatory molecules (CD80, CD86) on donor APC offers a reliable tool for monitoring specific immunosuppression against the graft in solid organ transplantation.