Molecular analysis of bacterial microbiota associated with oysters (Crassostrea gigas and Crassostrea corteziensis) in different growth phases at two cultivation sites.

Microbiota presumably plays an essential role in inhibiting pathogen colonization and in the maintenance of health in oysters, but limited data exist concerning their different growth phases and conditions. We analyzed the bacterial microbiota composition of two commercial oysters: Crassostrea gigas and Crassostrea corteziensis. Differences in microbiota were assayed in three growth phases: post-larvae at the hatchery, juvenile, and adult at two grow-out cultivation sites. Variations in the microbiota were assessed by PCR analysis of the 16S rRNA gene in DNA extracted from depurated oysters. Restriction fragment length polymorphism (RFLP) profiles were studied using Dice's similarity coefficient (Cs) and statistical principal component analysis (PCA). The microbiota composition was determined by sequencing temperature gradient gel electrophoresis (TGGE) bands. The RFLP analysis of post-larvae revealed homology in the microbiota of both oyster species (Cs > 88 %). Dice and PCA analyses of C. corteziensis but not C. gigas showed differences in the microbiota according to the cultivation sites. The sequencing analysis revealed low bacterial diversity (primarily ß-Proteobacteria, Firmicutes, and Spirochaetes), with Burkholderia cepacia being the most abundant bacteria in both oyster species. This study provides the first description of the microbiota in C. corteziensis, which was shown to be influenced by cultivation site conditions. During early growth, we observed that B. cepacia colonized and remained strongly associated with the two oysters, probably in a symbiotic host-bacteria relationship. This association was maintained in the three growth phases and was not altered by environmental conditions or the management of the oysters at the grow-out site.

[Genotypying of clinical isolates of Helicobacter pylori by cagA, vacA and babA2 virulence associated genes. First detection of a babA2 positive strain in Chilean patients]. / Genotipificación de aislados clínicos de Helicobacter pylori en base a genes asociados a virulencia cagA, vacA y babA2. Primer aislamiento de una cepa babA2 positiva en pacientes chilenos.

BACKGROUND: Helicobacter pylori-associated gastroduodenal diseases depends on host characteristics, environmental conditions and bacterial virulence factors, such as cagA, vacA y babA2 gene products. Moreover, peptic ulcer disease has been related with cagA+, vacAs1m1 strains, while metaplasia and gastric cancer has been associated to cagA+, vacAs1 and babA2+ H pylori strains. Gene babA2 has not yet been described in clinical isolates from Chilean patients. AIM: To investigate the presence of cagA, vacA (s and m) and babA2 genes in clinical isolates of H pylori from Chilean patients. MATERIAL AND METHODS: Sixty six isolates from 41 patients were genotyped by PCR, using primers for s1a, s1b, s2, m1, m2, cagA and babA2 genes as previously described. RESULTS: cagA gene was detected in 16 isolates (24.2%) while vacAs1a, vacAs1b, vacAs2, vacAm1 and vacAm2 were detected in 28 (42.4%), 14 (21.2%), 17 (25.8%), 21 (31.8%) and 29 isolates (43.9%), respectively. One isolate (1.5%) was babA2 positive, being the first isolate with this genotype described in Chile. Besides the babA2+ genotype this clinical isolate also presented cagA+ and vacAs1a which has been related with metaplasia or gastric cancer. Five isolates showed an ulcerogenic profile cagA+, vacAs1m1. CONCLUSIONS: The results presented indicate the prevalence of vacAs1m1 genotype among the clinical isolates analyzed, and a low frequency of babA2 genotype.

[Resistance to gentamicin, amikacin and ciprofloxacin among nosocomial isolates of klebsiella pneumoniae subspecie pneumoniae producing extended spectrum beta-lactamases]. / Resistencia a gentamicina, amikacina y ciprofloxacina en cepas hospitalarias de klebsiella pneumoniae subespecie pneumoniae productoras de beta-lactamasas de espectro extendido.

BACKGROUND: Klebsiella pneumoniae is a pathogenic bacterium frequently isolated from nosocomial samples, specially the subspecie pneunonlae, with extensive antibiolic resistance profiles, including third generation cepbhalosporiis, aminoglycosides and quinolones. This is specially true for those strains producing extended spectrum beta lactamases (ESBL). AIM: To investigate the susceptibility to gentamicin, amikacin and ciprofloxacin and the presence of some aminogloycoside modifying enzyme (AMEs) among nosocomial strains of K pneumoniae subspecie pneumoniae producing ESBL. MATERIAL AND METHODS: The antibiotic resistant patterns and the level of resistance (minimal inhibitory concentration, MIC) of 100 strains, isoklted from sel ,eal bospitals of dcifferent Chilean cities, were deterl,in,ed. Tbe presence of some aminoglycosides modifying enzyme (AMEs) was investigated by PCR. RESULTS: Sixty five percent of strains were resistant to gentamicin, 47% were resistant to amikacin, and 29% were resistant to ciprofloxacin. The most frequent AMEs genes detected were the aac(6')-Ib gene (6'N-Acetyltransferase type Ib enzyme) in 69% of strains, conferring resistance to amikacin, kanamycin, tobramycin, and nieoniycin, and the gene aac(3)-IIa (3-Acetyltransferase type 3-IIa enzyme), in 36% of strains, conferring resistance to gentamlicin. CONCLUSIONS: Among nosocomial strains of K pneumoniae subspecie pneumoniae isolaterd from Chilean hospitals, there is an association between the production of ESBL and the resistance to others antimicrobial agents, especially aminoglycosides. Nevertheless, 71% of isolates are susceptible to ciprofloxacin.