Delftia acidovorans secretes substances that inhibit the growth of Staphylococcus epidermidis through TCA cycle-triggered ROS production.

The proportion of Staphylococcus aureus in the skin microbiome is associated with the severity of inflammation in the skin disease atopic dermatitis. Staphylococcus epidermidis, a commensal skin bacterium, inhibits the growth of S. aureus in the skin. Therefore, the balance between S. epidermidis and S. aureus in the skin microbiome is important for maintaining healthy skin. In the present study, we demonstrated that the heat-treated culture supernatant of Delftia acidovorans, a member of the skin microbiome, inhibits the growth of S. epidermidis, but not that of S. aureus. Comprehensive gene expression analysis by RNA sequencing revealed that culture supernatant of D. acidovorans increased the expression of genes related to glycolysis and the tricarboxylic acid cycle (TCA) cycle in S. epidermidis. Malonate, an inhibitor of succinate dehydrogenase in the TCA cycle, suppressed the inhibitory effect of the heat-treated culture supernatant of D. acidovorans on the growth of S. epidermidis. Reactive oxygen species production in S. epidermidis was induced by the heat-treated culture supernatant of D. acidovorans and suppressed by malonate. Further, the inhibitory effect of the heat-treated culture supernatant of D. acidovorans on the growth of S. epidermidis was suppressed by N-acetyl-L-cysteine, a free radical scavenger. These findings suggest that heat-resistant substances secreted by D. acidovorans inhibit the growth of S. epidermidis by inducing the production of reactive oxygen species via the TCA cycle.

Resistencia antimicrobiana en cepas de Pseudomonas aeruginosa aisladas de aguas termales de la provincia del Chimborazo, Ecuador / Antimicrobial resistance in strains Pseudomonas aeruginosa isolated from termal waters at Chimborazo, Ecuador

La intervención humana en los manantiales de aguas termales ha traído su contaminación microbiológica y química. El uso indiscriminado de los antimicrobianos, han desembocado en la contaminación de diversos ambientes acuáticos con estas sustancias y con bacterias resistentes a las mismas. En este sentido el objetivo del presente trabajo fue conocer la resistencia antimicrobiana en cepas de Pseudomonas aeruginosa aisladas de aguas termales de la región del Chimborazo, Ecuador. Se analizaron 12 muestras de agua termal procedentes de baños de la Provincia del Chimborazo. Las muestras consistieron de un volumen de 0,5 litro de agua de cada manantial. El aislamiento de Pseudomonas aeruginosa se realizó por la técnica de filtración en membrana, utilizando filtros de acetato de celulosa de 0,45 µm de poro, un volumen de muestra de 100 ml y el agar Cetrimida. Las cepas aisladas se identificaron siguiendo los esquemas de MacFadden (2004) y Barrow y Feltham (1993), complementados con las pruebas bioquímicas de las galerías API (bioMerieux). El perfil de resistencia a los antibióticos se determinó por el método de difusión de Kirby y Bauer (1966) interpretándose según el CLSI (2014). Se identificaron 15 cepas de Pseudomonas aeruginosa. Todas las cepas fueron resistentes a los antibióticos Ampicilina y Ampicilina-Sulbactam, y cinco fueron multiresistentes a seis antibióticos (Ampicilina, Ampicilina-Sulbactam, Amikacina, Ceftazidime, Cefepime y Ciprofloxacina). Los resultados nos señalan la necesidad de realizar estudios del resistoma de los ecosistemas de las aguas termales, para determinar la presencia de genes de resistencias en las bacterias autóctonas

Human intervention in the hot springs has brought its microbiological and chemical contamination. The indiscriminate use of antimicrobials, have resulted in the contamination of various aquatic environments with these substances and bacteria The objectives were meet antimicrobial resistance in Pseudomonas aeruginosa strains isolated from hot springs in the region of Chimborazo, Ecuador. 12 samples of thermal water baths from Chimborazo Province were analyzed. Samples consisted of a volume of 0.5 liters of water. Pseudomonas aeruginosa isolation was performed by the membrane filtration technique using cellulose acetate filter 0.45 um pore, a sample volume of 100 ml and Cetrimide agar. The isolates were identified following schemes MacFadden (2004) and Barrow and Feltham (1993), supplemented with biochemical tests of API (bioMerieux) galleries. The profile of antibiotic resistance was determined by the method of dissemination of Kirby and Bauer (1966) and the results were interpreted according the CLSI (2014). 15 strains of Pseudomonas aeruginosa were identified. All strains were resistant to ampicillin and ampicillin - Sulbactam antibiotics and five were multidrug resistant to six antibiotics (Ampicillin, ampicillin-Sulbactam, amikacin, ceftazidime, cefepime and ciprofloxacin). The results show us the need for studies of resistoma ecosystems hot springs, to determine the presence of resistance genes in indigenous bacteria