Evaluation of in vitro serial antibiotic elution from meropenem-impregnated polymethylmethacrylate beads after ethylene oxide gas and autoclave sterilization.

OBJECTIVES: To determine the elution properties of meropenem and to compare the elutions of meropenem-impregnated polymethylmethacrylate (PMMA) beads without sterilization (P-M-C) to those sterilized with steam (P-M-A) and ethylene oxide gas (P-M-EO). METHODS: A commercial bead mould was used to produce four groups of beads: one group without antibiotic (negative control), and three groups of meropenem-impregnated beads: P-M-C, P-M-A, and P-M-EO. The beads were placed in a phosphate buffered solution and eluent samples were collected. Concentrations of the antibiotic in eluent samples from the two sterilized groups and the control beads were determined using a microbiological assay at 1, 3, 6 and 12 hours and at 1, 2, 3, 6, 9, 12, 15, 18, 22, 26, and 30 days. RESULTS: The microbiological assay resulted in no zone of inhibition at all time periods for the P-M-A samples and the samples of PMMA without antimicrobial. The meropenem concentration on the eluent remained above 4 mcg/ml for 15 days in the P-M-C group and until day 18 for P-M-EO group. There was no statistical difference in AUC0-∞ (p<0.318), however significance did occur for MRT (p<0.005) when comparing P-M-C and P-M-EO with the later being higher. DISCUSSION: The meropenem incorporated in the PMMA beads eluted effectively and gradually decreased after the 24 hour peak, but remained above the concentration level of 4 mcg/ml for 15 days in the P-M-C group and until day 18 for P-M-EO group. Ethylene oxide does not adversely affect meropenem's elution from PMMA beads.

Chemiluminescent enzyme immunoassay for detection of PCR-amplified enterotoxin A from Clostridium perfringens.

A PCR protocol was developed for the rapid and specific detection of Clostridium perfringens strains harboring the enterotoxin A gene in artificially contaminated ground beef. A biotinylated primer pair was designed for amplification of a 750 bp fragment of the C. perfringens enterotoxin A gene. A combination of 4 h enrichment incubation and nucleic acid extraction, followed by 2 h of PCR amplification allowed detection at levels below 10 CFU of freshly grown cells in raw and cooked beef samples. PCR amplified products were confirmed by a Southern hybridization assay using a digoxigenin-labeled internal probe, and two hybridization ELISA protocols (PCR-ELISA) applying a streptavidin capture step for the hybridized PCR products. Both enzyme immunoassays utilized chemiluminescent detection with Lumiphos 530TM as substrate, after hybridization to an internal digoxigenin-labeled probe or a 5' conjugated alkaline phosphatase-labeled probe. The PCR-ELISA resulted in faster confirmation of the PCR products while providing a level of sensitivity comparable to Southern hybridization, and has potential for development into an automated method.

Nonradioactive colony hybridization assay for detection and enumeration of enterotoxigenic Clostridium perfringens in raw beef.

A DNA probe endolabeled with digoxigenin by PCR was developed to detect and enumerate enterotoxigenic Clostridium perfringens in raw beef. After 2 h of hybridization, membranes were developed by using an anti-digoxigenin-alkaline phosphatase conjugated antibody. The resulting chromogenic reaction allowed us to detect and enumerate < or = 10 CFU of C. perfringens per g.

Postnatal development of a cholinergic influence on neuroleptic-induced catalepsy.

The development of cholinergic influence on neuroleptic-induced catalepsy was investigated in 10-, 15- and 20-day-old rat pups. It was found that the antimuscarinic atropine was ineffective in decreasing the catalepsy produced by spiroperidol treatment at 10 and 15 days. By day 20, however, atropine attenuated cataleptic behavior in a dose-dependent manner. Atropine alone was shown paradoxically to elicit mild to moderate cataleptic responses in 10- and 15-day-olds, but not at day 20. Clozapine by itself produced the same age dependent pattern of catalepsy response as the spiroperidol and atropine combination treatment. These results suggest that cholinergic mechanisms which interact antagonistically with the dopamine systems underlying cataleptic behavior are not functionally mature until after day 15 in the rat.

Dopaminergic antagonism and catalepsy in the developing rat.

The cataleptic effect of the dopaminergic blockers spiroperidol and haloperidol was investigated in developing rats. Both neuroleptics were found to produce less catalepsy in 15 day old rats than in either 10 or 20 day old animals. It is proposed that the decrement in catalepsy occurring between 10 and 15 days of age is related to increased dopaminergic activity in the neostriatum. The reversal of this phenomenon by 20 days may be a consequence of maturation of cholinergic local circuit neurons.

Body weight and regulatory deficits following unilateral nigrostriatal lesions.

Unilateral nigrostriatal lesions were performed in rats by punctate injection of 6-hydroxydopamine. Lesioned animals exhibited anorexia and weight loss for 7-11 days after surgery. These animals then displayed normal rate of weight gain. However, there was a chronic depression of body weight in the lesioned animals relative to sham controls, evident for over two months after 6-hydroxydopamine administration. Unilateral nigrostriatal damage also produced major deficits in the animals' water intake in tests of prandial drinking, response to water deprivation, and response to osmotic challenge. The relationship of nigrostriatal damage to the "lateral hypothalamic syndrome" and the role of dopaminergic neurons in regulation and ingestive behaviors are discussed.

Lack of stimulation by high amphetamine doses following a low dose of spiperone.

The locomotor stimulant and stereotypic effects of amphetamine were investigated in rats pretreated with the specific dopaminergic blocker spiperone (0.25 mg/kg). Amphetamine doses from 8.0 to 64.0 mg/kg failed to stimulate behavior significantly and consistently after spiperone treatment. These results suggest the possibility of non-competitive antagonism by spiperone at dopaminergic synapses.

Postnatal development of dopaminergic and cholinergic catalepsy in the rat.

The cataleptic response to various doses of the dopamine-receptor antagonist spiperone and the cholinergic agonist pilocarpine was investigated in rats of different ages. Spiperone produced catalepsy in rats 1, 5 and 10 days old, and also in adults. Pilocarpine produced catalepsy in 15- and 20-day old rats, as well as in adults, but not in 10-day old animals. These results suggest that dopaminergic neurons involved in catalepsy are already functional in neonates. Cholinergic substrates of catalepsy, on the other hand, appear to reach functional maturity after the second week of life.