Anti-Candida and anti-quorum sensing activity of airborne microorganisms detected by a rapid method

Abstract INTRODUCTION: Introducing new antibiotics to the clinic is critical. METHODS: We adapted a plate method described by Kawaguchi and coworkers in 20131 for detecting inhibitory airborne microorganisms. RESULTS: We obtained 51 microbial colonies antagonist to Chromobacterium violaceum, purified and retested them, and of these, 39 (76.5%) were confirmed. They comprised 24 bacteria, 13 fungi, and 2 yeasts. Among the fungi, eight (61.5%) produced active extracts. Among the bacterial, yeast, and fungal strains, 17 (44.7%) and 12 (31.6%) were active against Candida albicans and Candida parapsilosis, respectively. CONCLUSIONS: The proposed screening method is a rapid strategy for discovering potential antibiotic producers.

Composition, anti-quorum sensing and antimicrobial activity of essential oils from Lippia alba

Many Gram-negative pathogens have the ability to produce N-acylhomoserine lactones (AHLs) as signal molecules for quorum sensing (QS). This cell-cell communication system allows them to coordinate gene expression and regulate virulence. Strategies to inhibit QS are promising for the control of infectious diseases or antibiotic resistant bacterial pathogens. The aim of the present study was to evaluate the anti-quorum sensing (anti-QS) and antibacterial potential of five essential oils isolated from Lippia alba on the Tn-5 mutant of Chromobacterium violaceum CV026, and on the growth of the gram-positive bacteria S. aureus ATCC 25923. The anti-QS activity was detected through the inhibition of the QS-controlled violacein pigment production by the sensor bacteria. Results showed that two essential oils from L. alba, one containing the greatest geranial:neral and the other the highest limonene:carvone concentrations, were the most effective QS inhibitors. Both oils also had small effects on cell growth. Moreover, the geranial/neral chemotype oil also produced the maximum zone of growth inhibition against S. aureus ATCC 25923. These data suggest essential oils from L. alba have promising properties as QS modulators, and present antibacterial activity on S. aureus.

A fatal case of Chromobacterium violaceum septicemia in Hong Kong.

Chromobacterium violaceum causes a rare infection in human, usually in tropical or subtropical areas. We report a fatal case of C. violaceum infection affecting a 40-year-old previously healthy man in Hong Kong. He presented with a wound infection and lymphadenitis. Despite multiple antibiotic treatment, including ciprofloxacin, he succumbed shortly after admission to the hospital. We report the epidemiological investigation findings and discuss the possible sources of infection. Physicians should be alert to this rare but fatal infection. Injury prevention and proper wound care should be emphasized to the public.

Drug resistance in Chromobacterium violaceum

Chromobacterium violaceum is a free-living bacterium commonly found in aquatic habitats of tropical and subtropical regions of the world. This bacterium is able to produce a large variety of products of biotechnological and pharmacological use. Although C. violaceum is considered to be non-pathogenic, some cases of severe infections in humans and other animals have been reported. Genomic data on the type strain ATCC 12472(T) has provided a comprehensive basis for detailed studies of pathogenicity, virulence and drug resistance genes. A large number of open reading frames associated with various mechanisms of drug resistance were found, comprising a remarkable feature of this organism. Amongst these, beta-lactam (penicillin and cephalosporin) and multidrug resistance genes (drug efflux pumps) were the most numerous. In addition, genes associated with bacitracin, bicyclomycin, chloramphenicol, kasugamycin, and methylenomycin were also found. It is postulated that these genes contribute to the ability of C. violaceum to compete with other bacteria in the environment, and also may help to explain the common drug resistance phenotypes observed in infections caused by this bacterium