Proteus mirabilis secretes factors that affect Klebsiella pneumoniae growth and survival in urine

GALVÁN, ESTELA M; MATEYCA, CELESTE

Córdoba

Congreso; LII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2016

SAIB

K. pneumoniae(Kp) andP. mirabilis(Pm) are gram-negative bacteria that cause urinary tract infections in individuals with long-term indwelling catheters. Previous studies showed that Pm outcompeted Kp in both Kp-Pm mixed biofilms and planktonic cultures in artificial urine medium (AUM). It is known that Pm produces a urease that hydrolyses urea to CO2and NH3 increasing the urine pH.We aim to study the factors involved in this competitive interaction between Kp and Pm. The ability of each strain to grow in single and mixed cultures was evaluated by counting colony forming units. The pH and NH3 concentration was also monitored. In single cultures both Kp and Pm did grow, while in mixed cultures Kp viability decreased 105-fold. A gradual increase of pH and NH3 was observed in mixed cultures, with maximal values of 9.3 and 135 mM, respectively. Cell-free supernatants from mixed cultures were able to drastically affect Kp growth (105-fold decrease). Evaporation of NH3 from the supernatant abolished its detrimental effect over Kp. When evaporated supernatants were adjusted to pH 9.3 a 10-fold decrease on Kp viability was found. However, Kp viable cell counts did not decrease in AUM buffered to pH 9.3. These results suggest that ammonia produced by Pm in AUM, and not the alkalinization by itself, is the major agent responsible for the competitive interaction between Kp and Pm.