Inactivation of the bacterial pathogens Staphylococcus pseudintermedius and Acinetobacter baumannii by butanoic acid.

AIMS: This study was performed to evaluate the efficacy of butanoic acid against bacterial pathogens including Acinetobacter baumannii and Staphylococcus pseudintermedius. METHODS AND RESULTS: Vegetative bacteria were exposed to butanoic acid in vitro and log reduction was quantified using viable count assays. The maximum (8 and 9) log inactivation was determined by qualitatively assaying for growth/no-growth after a 48-h incubation (37°C). Membrane integrity after exposure to butanoic acid was determined by propidium iodide staining, scanning electron microscopy, membrane depolarization and inductively coupled plasma analysis. Cytosolic pH was measured by 5-(6-)carboxyfluorescein succinimidyl ester. CONCLUSIONS: Inhibitory concentrations of butanoic acid ranged between 11 and 21 mmol l-1 for Gram-positive and Gram-negative species tested. The maximum log reduction of A. baumannii was achieved with a 10-s exposure of 0·50 mol l-1 of butanoic acid. Staphylococcus pseudintermedius required 0·40 mol l-1 of butanoic acid to achieve the same level of reduction in the same time period. Inactivation was associated with membrane permeability and acidification of the cytosol. SIGNIFICANCE AND IMPACT OF THE STUDY: Antibiotic resistance among bacterial pathogens necessitates the utilization of novel therapeutics for disinfection and biological control. These results may facilitate the development of butanoic acid as an effective agent against a broad-spectrum of antibiotic-resistant bacterial pathogens.

Microbial cometabolism of sucralose, a chlorinated disaccharide, in environmental samples.

During the rapid mineralization in soil of sucralose (4-chloro-4-deoxy-alpha, D-Galactopyranosyl-1,6-dichloro-1,6-dideoxy-beta, D-fructofuranoside), a metabolic product was formed that appears to be the corresponding unsaturated aldehyde. During the slow and incomplete mineralization of sucralose in lake water, which was not increased by the addition of nitrogen and phosphorus, the same compound was produced. That product was further metabolized by microorganisms in lake water and soil. Mineralization was also slow in sewage under aerobic conditions, but organic products were not detected. Little or no CO2 was formed from the disaccharide in flooded soil or anaerobic sewage. Bacteria in culture did not use sucralose as a carbon source but did convert it to the presumed unsaturated aldehyde, 1,6-dichloro-1,6-dideoxy-D-fructose and possibly the uronic acid of sucralose. Sucralose carbon was not incorporated into cells of two sucralose-metabolizing bacteria or the microbial biomass of sewage or lake water. The chlorinated disaccharide was slowly metabolized by a galactose oxidase preparation. It is concluded that the chlorinated sugar is acted on microbiologically by cometabolism.

Interactions between Shewanella colwelliana, Oyster Larvae, and Hydrophobic Organophosphate Pesticides.

Shewanella colwelliana (strain D) is a periphytic estuarine bacterium that forms biofilms beneficial to oyster set. Our study examined whether these and other films concentrated two hydrophobic, organophosphate pesticides, Abate and malathion, that are detected in Chesapeake Bay oyster waters. Both biofilms and purified exopolysaccharide of S. colwelliana did not adsorb more of the Abate or malathion than could be accounted for by adsorption to control surfaces. Similar results were obtained by using Deleya marina, Hyphomonas MHS3, and autochthonous biofilms. Conversely, decapsulated S. colwelliana D cells, prepared in the laboratory, bioconcentrated Abate. Significantly, the S. colwelliana D biofilms exposed to Abate did not inhibit the settlement and metamorphosis of Crassostrea gigas larvae.

Factors influencing bacterial production of inducers of settlement behavior of larvae of the oysterCrassostrea gigas.

Dissolved chemical inducers of settlement behavior of veliger larvae of the oysterCrassostrea gigas are found in supernatants of both pigmented species of bacteria (Alteromonas colwelliana, Vibrio cholerae strain HTX) as well as nonpigmented bacteria (Excherichia coli, Vibrio cholerae strain 596-B). Usually less than 10% of veligers exhibited settlement behavior in response to supernatants from the early bacterial growth phases, whereas 30-90% of larvae responded when exposed to supernatant from late-log and stationary phase cultures. Percentages of larvae exhibiting settlement behavior were inversely correlated with oxygen levels in the culture. Furthermore, the behavioral response decreased with pigment formation, suggesting that quantities of noxious compounds such as quinones may build up in the supernatants of cultures of pigmented bacteria. Tyrosinase, an enzyme that converts L-tyrosine to L-DOPA in the first step of melanogenesis, was detected both in the bacterial pellet and the supernatant during growth of the pigmented species. The enzyme is not required for the production of settlement inducer as the nonpigmented speciesE. coli andV. cholerae (596-B) also released inducer into the supernatant and had no detectable tyrosinase. The data suggest either that there is more than one inducer of settlement behavior found in bacterial supernatants or that the inducer is not L-DOPA or an L-DOPA-mimetic associated with the melanin biochemical pathway.