Antimicrobial susceptibility pattern of Stenotrophomonas species isolated from Mexico

Background: Stenotrophomonas species are multi-resistant bacteria with ability to cause opportunistic infections. Objective: We isolated 45 Stenotrophomonas species from soil, sewage and the clinic with the aim of investigating their susceptibility to commonly used antimicrobial agents. Methodology: The identities of isolates were confirmed with 16S rRNA gene sequence and MALDI-TOF analysis. Anti-mi- crobial resistance, biofilm production and clonal diversity were also evaluated. The minimum inhibitory concentration technique as described by Clinical & Laboratory Standards Institute: CLSI Guidelines (CLSI) was employed for the evaluation of isolate susceptibility to antibiotics. Result: Forty-five Stenotrophomonas species which include 36 environmental strains and 9 clinical strains of S. maltophilia were considered in this study. 32 (88.9 %) environmental strains were identified to be S. maltophilia, 2 (5.6 %) were Stenotrophomonas nitritireducens, and 2 (5.6 %) cluster as Stenotrophomonas spp. Stenotrophomonas isolates were resistant to at least six of the antibiotics tested, including Trimethoprim/Sulfamethoxazole (SXT). Conclusion: Environmental isolates from this study were resistant to SXT which is commonly used for the treatment of S. maltophilia infections. This informs the need for good public hygiene as the environment could be a reservoir of multi-resistant bacteria. It also buttresses the importance of surveillance study in the management of bacterial resistance. Keywords: Stenotrophomonas; environmental; biochemical characterization; clonal diversity; anti-microbial susceptibility.

Aislamiento e identificación de microorganismos potencialmente amilolíticos y celulolíticos de suelos de humedales de Bogotá

Las amilasas y celulasas de origen microbiano se han utilizado desde hace más de tres décadas en la industria; el aislamiento de cepas microbianas nativas productoras de enzimas es el punto de partida para aprovechar la biodiversidad microbiana para la obtención de enzimas con propiedades para la obtención de nuevos productos en la optimización de procesos industriales. El objetivo de este trabajo, fue aislar, a partir de suelo de cinco humedales en Bogotá, cepas microbianas con capacidad para producir enzimas amilolíticas y celulolíticas. Se realizó la medición de halos de hidrólisis en agar almidón y agar carboximetilcelulosa. Se determinaron las unidades enzimáticas (U/ml/min) por medio de azúcares reductores por la técnica de DNS. Se seleccionaron cuatro cepas de Bacillus subtillis amiloliquefaciens productoras de amilasas con actividades entre 752±33 y 480 ± 35 U/ml/min a 60ºC y cinco cepas celulolíticas identificadas como Bacillus subtillis amiloliquefaciens, Stenotrophomonas nitritireducens y Yersinia massiliensis, capaces de producir celulasas con actividades enzimáticas entre 19.11 ± 2.3 y 13.82 ± 2.5 UA/ml/min a 50ºC. Con estos resultados se demostró que a partir de suelos de humedales, se pueden recuperar microrganismos con capacidad de producción enzimática, como punto de partida para una posterior aplicación en procesos industriales.

Screening for endophytic nitrogen-fixing bacteria in Brazilian sugar cane varieties used in organic farming and description of Stenotrophomonas pavanii sp. nov.

A Gram-negative, rod-shaped, non-spore-forming and nitrogen-fixing bacterium, designated ICB 89T, was isolated from stems of a Brazilian sugar cane variety widely used in organic farming. 16S rRNA gene sequence analysis revealed that strain ICB 89T belonged to the genus Stenotrophomonas and was most closely related to Stenotrophomonas maltophilia LMG 958T, Stenotrophomonas rhizophila LMG 22075T, Stenotrophomonas nitritireducens L2T, [Pseudomonas] geniculata ATCC 19374T, [Pseudomonas] hibiscicola ATCC 19867T and [Pseudomonas] beteli ATCC 19861T. DNA–DNA hybridization together with chemotaxonomic data and biochemical characteristics allowed the differentiation of strain ICB 89T from its nearest phylogenetic neighbours. Therefore, strain ICB 89T represents a novel species, for which the name Stenotrophomonas pavanii sp. nov. is proposed. The type strain is ICB 89T ( = CBMAI 564T = LMG 25348T).

Stenotrophomonas daejeonensis sp. nov., isolated from sewage

A Gram-stain-negative, motile, aerobic bacterial strain, designated MJ03T, was isolated from sewage and was characterized taxonomically by using a polyphasic approach. Comparative 16S rRNA gene sequence analysis showed that strain MJ03T belongs to the family Xanthomonadaceae, class Gammaproteobacteria, and was related most closely to Stenotrophomonas acidaminiphila AMX 19T (97.9 % sequence similarity), Stenotrophomonas humi R-32729T (97.1 %), Stenotrophomonas nitritireducens L2T (96.9 %), Stenotrophomonas maltophila ATCC 13637T (96.8 %) and Stenotrophomonas terrae R-32768T (96.7 %). The G+C content of the genomic DNA of strain MJ03T was 64.7 mol%. The detection of a quinone system with ubiquinone Q-8 as the predominant component and a fatty acid profile with iso-C15 : 0, iso-C11 : 0, iso-C14 : 0, iso-C17 : 1 ω9c, iso-C11 : 0 3-OH and iso-C13 : 0 3-OH as major components supported the affiliation of strain MJ03T to the genus Stenotrophomonas. However, levels of DNA–DNA relatedness between strain MJ03T and the type strains of five closely related species of the genus Stenotrophomonas ranged from 11 to 34 %, showing clearly that the isolate represents a novel genospecies. Strain MJ03T could be differentiated clearly from its phylogenetic neighbours on the basis of several phenotypic, genotypic and chemotaxonomic features. Therefore, strain MJ03T is considered to represent a novel species of the genus Stenotrophomonas, for which the name Stenotrophomonas daejeonensis sp. nov. is proposed. The type strain is MJ03T (=KCTC 22451T =JCM 16244T).

Stenotrophomonas ginsengisoli sp. nov., isolated from a ginseng field

A Gram-negative, non-spore-forming, rod-shaped bacterium, designated strain DCY01T, was isolated from soil from a ginseng field in South Korea and was characterized in order to determine its taxonomic position. 16S rRNA gene sequence analysis revealed that strain DCY01T belonged to the Gammaproteobacteria and was most closely related to Stenotrophomonas koreensis KCTC 12211T (98.4 % similarity), Stenotrophomonas humi R-32729T (97.2 %), Stenotrophomonas terrae R-32768 (97.1 %), Stenotrophomonas maltophilia DSM 50170T (96.9 %) and Stenotrophomonas nitritireducens DSM 12575T (96.8 %). Chemotaxonomic analyses revealed that strain DCY01T possessed a quinone system with Q-8 as the predominant compound, and iso-C15 : 0 (28.2 %), C16 : 0 10-methyl (13.2 %), iso-C15 : 1 F (10.8 %) and C15 : 0 (7.5 %) as major fatty acids, corroborating assignment of strain DCY01T to the genus Stenotrophomonas. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The results of DNA–DNA hybridization and physiological and biochemical tests clearly demonstrated that strain DCY01T represents a species distinct from recognized Stenotrophomonas species. Based on these data, DCY01T (=KCTC 12539T=NBRC 101154T) should be classified as the type strain of a novel species of the genus Stenotrophomonas, for which the name Stenotrophomonas ginsengisoli sp. nov. is proposed.

Bacterium-Based NO2− Biosensor for Environmental Applications

ABSTRACT A sensitive NO2 − biosensor that is based on bacterial reduction of NO2 − to N2O and subsequent detection of the N2O by a built-in electrochemical N2O sensor was developed. Four different denitrifying organisms lacking NO3 − reductase activity were assessed for use in the biosensor. The relevant physiological aspects examined included denitrifying characteristics, growth rate, NO2 − tolerance, and temperature and salinity effects on the growth rate. Two organisms were successfully used in the biosensor. The preferred organism was Stenotrophomonas nitritireducens, which is an organism with a denitrifying pathway deficient in both NO3 − and N2O reductases. Alternatively Alcaligenes faecalis could be used when acetylene was added to inhibit its N2O reductase. The macroscale biosensors constructed exhibited a linear NO2 − response at concentrations up to 1 to 2 mM. The detection limit was around 1 μM NO2 −, and the 90% response time was 0.5 to 3 min. The sensor signal was specific for NO2 −, and interference was observed only with NH2OH, NO, N2O, and H2S. The sensor signal was affected by changes in temperature and salinity, and calibration had to be performed in a system with a temperature and an ionic strength comparable to those of the medium analyzed. A broad range of water bodies could be analyzed with the biosensor, including freshwater systems, marine systems, and oxic-anoxic wastewaters. The NO2 − biosensor was successfully used for long-term online monitoring in wastewater. Microscale versions of the NO2 − biosensor were constructed and used to measure NO2 − profiles in marine sediment.