In vitro antimicrobial efficacy of a silver alginate dressing on burn wound isolates.

OBJECTIVE: To test the antimicrobial effectiveness of a silver alginate dressing on opportunistic pathogens, namely meticillin-sensitive Staphylococcus aureus (MSSA) and meticillin-resistant Staphylococcus aureus (MRSA), Klebsiella spp., Enterococcus faecalis, Enterococcus faecium, Pseudomonas aeruginosa, Escherichia coli, Enterobacter sakazakii, Enterobacter cloacae, Serratia marcescens, Chryseobacterium indologenes, Proteus vulgaris and Acinetobacter baumannii. METHOD: In total, 40 microorganisms were isolated from patients attending three burn centres in the US and evaluated for their susceptibility to a silver alginate wound dressing, employing a corrected zone of inhibition assay, conducted on Mueller Hinton agar (MHA). RESULTS: The sizes of the corrected zones of inhibition varied between and within genera. For example, all Acinetobacter baumannii strains were found to be sensitive to ionic silver at pH 7, with a mean of 2.8mm, compared with 3.5mm at pH 5.5. The silver alginate dressing also demonstrated activity on all strains of Enterobacter and Escherichia coli, with susceptibility to the silver alginate dressing enhanced at pH 5.5. For Enterococcus spp. the average corrected zone of inhibition at pH 7 was 3.6mm, versus 4.9mm at pH 5.5. All strains of Pseudomonas aeruginosa were found to be sensitive to the silver alginate dressing. The average corrected zone of inhibition was 6.9mm at pH 7, compared with 8mm at pH 5.5. For MRSA and Staphylococcus aureus, it ranged from 4.5mm to 7.5mm at pH 7. When the pH was decreased to 5.5, the corrected zone of inhibition increased. CONCLUSION: This study demonstrates the activity of a silver alginate dressing on a wide range of burn isolates, including antibiotic-resistant bacteria, isolated from three different burn centres in the US. It also highlights the possible importance of pH and its potential effects on antimicrobial performance and microbial susceptibility. However, more extensive testing is required to substantiate this. CONFLICT OF INTEREST: SLP is employed by Advanced Medical Solutions Ltd.

A comparison of the antimicrobial efficacy of two silver-containing wound dressings on burn wound isolates.

OBJECTIVE: To evaluate and compare the efficacy of a silver alginate (SA) dressing and a silver carboxymethyl cellulose (SCMC) dressing on burn isolates grown within the quasi/non-biofilm state and the biofilm phenotypic states. METHOD: Antimicrobial activity was tested using 46 burn wound isolates with a corrected zone of inhibition (CZOI) assay on agar (quasi/non-biofilm) and poloxamer (biofilm). RESULTS: All Gram-negative and positive isolates evaluated were found to be sensitive to both silver containing wound dressings, although superior antimicrobial activity was observed for a select number of specific bacteria when grown in the quasi/non-biofilm phenotypic state, for the SCMC dressing. However, the majority of isolates demonstrated reduced sensitivity to silver when grown as a biofilm, compared with growth in the quasi/non-biofilm phenotypic state. Both dressings demonstrated equivalent antimicrobial activity on Gram-negative isolates grown in the biofilm phenotypic state. For the Gram-positive isolates growing in the biofilm phenotypic state, there appeared to be greater sensitivity to the SA dressing compared with the SCMC dressing, although this result was not statistically significant. CONCLUSION: This study demonstrated the antimicrobial effectiveness of an SA and SCMC dressing in inhibiting the growth of burn isolates residing in both the quasi/non-biofilm and biofilm phenotypic states. It also suggests the SA dressing could be more effective on Gram-positive isolates grown in the biofilm phenotypic state, compared with SCMC dressing.

Lipomas of the internal auditory canal.

Lipoma of the internal auditory canal is a rare tumor that may be confused clinically with the much more common vestibular schwannoma. We present two cases of lipoma of the internal auditory canal. The clinical presentation is indistinguishable from that of vestibular schwannomas. The high signal intensity on T1-weighted magnetic resonance imaging, both with and without contrast, is consistent with other reports of lipoma. Review of the literature shows that lipomas of the internal auditory canal are histopathologically similar to lipomas of the cerebellopontine angle. The symptoms, erosive effect on the auditory canal, and gross appearance of this uncommon tumor are sometimes difficult to differentiate from those of a vestibular schwannoma. The diagnosis can be established by intraoperative examination of frozen sections.

Central versus peripheral effects on temperature preference and body temperature following alteration of 5-HT in maturing mice.

Experiments were designed to distinguish between central and peripheral effects on temperature preference and body temperature of drugs injected intraperitoneally (IP) in infant mice ranging in age from 3 to 10 days postpartum. These compared a drug restricted to the periphery ("peripheral" drug) with a drug of similar action that reaches the central nervous system (CNS) as well as the periphery. Two different classes of drugs were utilized to test central versus peripheral actions independently with drugs that have different modes of action: 1-aromatic amino acid inhibitors and serotonin receptor antagonists. Although the decarboxylase inhibitor NSD 1015, which reaches the central nervous system from IP injection, can significantly decrease temperature preference (Tpref), the peripheral inhibitor carbidopa had no significant effects on Tpref or on body temperature (Tb). Furthermore, pretreatment with NSD 1015 prevented the elevation of Tpref produced by the serotonin precursor 5-hydroxytryptophan (5-HTP); however carbidopa pretreatment had no effect on the increased Tpref produced by 5-HTP. In other experiments, the peripheral serotonin antagonist BW 501C was not able to prevent elevated Tpref produced by 5-HTP, although the specific 5-HT2 antagonist pirenperone, which reaches the CNS as well as the periphery, blocks the 5-HTP elevation of Tpref. Taking all of these results together, we conclude that the changes in Tb and Tpref following these treatments require a decarboxylase inhibitor or 5-HT antagonist that reaches the CNS. However, the well known and potent peripheral vasoconstrictor action of serotonin requires that peripheral effects of drugs be considered when manipulations are not restricted to the CNS.