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.

Patrones de resistencia antimicrobiana en uropatógenos gramnegativos aislados de pacientes ambulatorios y hospitalizados Cartagena, 2005-2008 / Antimicrobial resistance pattern for gram-negative uropathogens isolated from hospitalised patients and outpatients in Cartagena, 2005-2008

Objetivo Determinar el patrón de resistencia antimicrobiana de bacterias patógenas asociadas a infecciones urinarias en pacientes ambulatorios y hospitalizados. Métodos Se realizó un estudio descriptivo entre febrero de 2005 y noviembre de 2008 en el Laboratorio Clínico de la Universidad de San Buenaventura, Cartagena. La susceptibilidad antimicrobiana fue evaluada con el método de difusión en agar empleado la técnica de Kirby Bauer aplicando procedimientos normalizados. Resultados Del total de muestras de orina analizadas (1 384) durante el período de estudio, 32,9 por ciento (455) fueron urocultivos positivos, la mayoría de éstos (81,4 por ciento) provenían de mujeres. Los agentes bacterianos más frecuentes fueron Escherichia. coli (60,1 por ciento), Klebsiella pneumoniae (6,9 por ciento), Pseudomonas aeruginosa (6,6 por ciento), Proteus mirabilis (5,4 por ciento) y Acinetobacter baumannii (1,4 por ciento). Los aislamientos gramnegativos mostraron una alta resistencia a la ampicilina (84,3100 por ciento), amoxacilina/ácido clavulánico (66,5 80,0 por ciento) y ciprofloxacina (40,057,9 por ciento). Conclusión Las bacterias gramnegativas fueron los principales agentes asociados a infecciones urinarias en esta población siendo E. coli el aislamiento más frecuente. La interpretación de los perfiles de susceptibilidad encontrados permite considerar como prudente la administración empírica de cefalosporinas de tercera generación como tratamiento inicial de las infecciones urinarias en esta población.

Objective Determining the microbial aetiology spectrum and antibiotic resistance pattern of uropathogens causing urinary tract infections in hospitalised patients and outpatients. Methods A descriptive study was carried out between February 2005 and November 2008 at the San Buenaventura University's Clinical Laboratory in Cartagena. Antibiotic sensitivity was determined by the Kirby Bauer method. Results Out of the total specimens (1,384) analysed over the four-year study period, 455 of the urine samples (32.9 percent) were culture positive, most (81.4 percent) having come from females. The bacterium isolated most frequently was Escherichia coli (60.1 percent) followed by Klebsiella pneumoniae (6.9 percent), Pseudomonas aeruginosa (6.6 percent), Proteus mirabilis (5.4 percent) and Acinetobacter baumannii (1.4 percent). The Gram-negative isolates displayed a high level of resistance to ampicillin (range 84.3100 percent), amoxicillin/clavulanic acid (range 66.580 percent) and ciprofloxacin (range 4057.9 percent). Conclusion Gram-negative bacteria were responsible for urinary tract infections in the patients involved in this study. The most commonly isolated bacteria were E. coli. Empirical administration of a third-generation cephalosporin for initial treatment of urinary tract infections in this population appears prudent from the perspective of antimicrobial susceptibility.