Stenotrophomonas maltophilia ISOLATES FROM CYSTIC FIBROSIS PATIENTS IN ARGENTINA: GENOTYPIC AND PHENOTYPIC CHARACTERIZATION

ALCARAZ ELIANA; SCHINERO AGOSTINA; GARCÍA CARLOS; FRIEDMAN LAURA; DI CONZA JOSÉ; CENTRÓN DANIELA; PASSERINI DE ROSSI BEATRIZ

Congreso; XII Congreso Argentino de Microbiología General. SAMIGE.; 2017

Stenotrophomonas maltophilia (Sm) is a nosocomial multidrug-resistant pathogen. Respiratory tract colonization by Sm is commonly seen in cystic fibrosis (CF) patients, but its pathogenic role has not been fully established. However, chronic Sm colonization should be considered as a chronic infection because of the associated specific immune response to Sm. The aim of this study was to characterize eight Sm isolates obtained between 2014-2016 from sputum of three CF patients attending hospitals in Argentina: 5 isolates from a 22-year-old female (1318, 1321, 1326, 1336 and 1340) and B8 from a 5-year-old female (Buenos Aires City), and SF2 and SF3 from a 14-year-old male (Santa Fe City). The reference strain K279a isolated from the blood of an oncologic patient was included. ERIC-PCR revealed a great diversity among the isolates. However, two isolates (1318 and 1326) belong to the same cluster. Biofilm formation and phenotypic traits associated to biofilm development (swimming, twitching and EPS production) were studied. Biofilm formation and EPS (extracellular matrix) production were evaluated in microtiter plates. The biomass, quantified by measuring the OD540 of crystal violet, ranged from 0.49 to 1.51. Among the studied isolates, only 1336, SF2 and SF3 formed strong biofilms as well as K279a. The other Sm CF isolates produced low amounts of biomass and EPS. Only SF2, SF3 and K279a showed high levels of EPS production. With respect to swimming and twitching motilities, SF2 and SF3 produced diameters similar to those of K279a, while the other isolates do not posses these types of motility. Phenotypic and genotypic characteristics related to proteolytic and nitrate reduction abilities were also investigated. Detection of narG (coding for the membrane-bound nitrate reductase) and stmPr-1 (coding for the extracellular alkaline serine protease) genes by PCR was done with primers designed in this study. All the isolates but 1336 amplified for stmPr-1. However, only B8, SF2, SF3 and K279a produced zones of hydrolysis on casein agar plates, suggesting that the other Sm isolates could have mutations in stmPr-1. On the other hand, the nitrate reductase activity was only detected in K279a. However, narG was detected in K279a and SF2, suggesting that SF2 could have mutations in this gene. In conclusion, the 5 isolates collected sequentially from a female patient do not posses motility (associated to flagellum or type IV pili) nor proteolytic activity, and only 2 isolates belong to the same cluster. Four of them formed biofilms with lower biomass and EPS production than the non-CF K279a strain. Thus, they expressed lower virulence factors than K279a. In contrast, the 2 isolates collected from a male patient showed a profile similar to K279a. None of the CF-recovered isolates showed nitrate reductase activity that supports growth in the absence of oxygen. This is the first report on characterization of Sm recovered from CF patients in Argentina. More studies on a possible Sm adaptation to CF airways are needed.