A habilidade de uma cepa de Lactobacillus rhamnosus isolada de um recém-nascido saudável de reduzir as consequências patológicas para o hospedeiro após infecção experimental por Salmonella enterica subsp. enterica sorov. Typhimurium foi avaliada em camundongos gnotobióticos e convencionais. Os camundongos convencionais receberam 0,1mL de leite probiótico por dia (0,8 log unidade formadora de colônia), 10 dias antes do desafio oral com S. Typhimurium (5,0 log unidade formadora de colônia), e continuaram recebendo probiótico até o término do experimento. O tratamento com probiótico nos camundongos gnotobióticos consistiu em uma única dose de leite probiótico no início do experimento e desafio oral após 10 dias (3,0 log unidade formadora de colônia). Em termos histopatológicos e morfométricos, a proteção foi observada no fígado e nos intestinos nos animais gnotobióticos e convencionais, respectivamente. No entanto, a população de S. Typhimurium foi similar em ambos os grupos tratado e controle de animais gnotobióticos. Desta forma, conclui-se que a proteção conferida pela cepa de L. rhamnosus contra o desafio experimental S. Typhimurium foi observada em diferentes sítios anatômicos nos animais convencionais e gnotobióticos e que essa proteção não foi devido à redução da população de S. Typhimurium nos intestinos.

The ability of a Lactobacillus rhamnosus strain isolated from a healthy breast-fed human newborn to reduce the pathological consequences for the host due to an experimental oral infection with Salmonella enterica subsp. enterica serov. Typhimurium in vivo was determined using gnotobiotic and conventional mice. Conventional mice received 0.1mL probiotic milk (8.0 log colony-forming unit) daily for 10 days before the oral pathogenic challenge (5.0 log colony-forming unit). Then probiotic treatment was continued until the end of the experiment. Probiotic treatment in germ-free mice consisted of a single dose of the probiotic milk at the beginning of the experiment and a challenge with S. Typhimurium 10 days later (3.0 log colony-forming unit). A protective effect was observed in both gnotobiotic and conventional animals in terms of histopathologic and morphometric data, but in different anatomical sites. This protection was observed in liver and intestines, respectively, for gnotobiotic and conventional mice. However, S. Typhimurium populations were similar in the feces of both treated and control gnotobiotic mice. We conclude that a protective effect of L. rhamnosus against experimental S. Typhimurium was observed. This protection was not due to the reduction of the population of pathogenic bacteria in the intestine.

Puba or carimã is a Brazilian staple food obtained by spontaneous submerged fermentation of cassava roots. A total of 116 lactobacilli and three cocci isolates from 20 commercial puba samples were recovered on de Man, Rogosa and Sharpe agar (MRS); they were characterized for their antagonistic activity against foodborne pathogens and identified taxonomically by classical and molecular methods. In all samples, lactic acid bacteria were recovered as the dominant microbiota (7.86 ± 0.41 log10 CFU/g). 16S-23S rRNA ARDRA pattern assigned 116 isolates to the Lactobacillus genus, represented by the species Lactobacillus fermentum (59 isolates), Lactobacillus delbrueckii (18 isolates), Lactobacillus casei (9 isolates), Lactobacillus reuteri (6 isolates), Lactobacillus brevis (3 isolates), Lactobacillus gasseri (2 isolates), Lactobacillus nagelii (1 isolate), and Lactobacillus plantarum group (18 isolates). recA gene-multiplex PCR analysis revealed that L. plantarum group isolates belonged to Lactobacillus plantarum (15 isolates) and Lactobacillus paraplantarum (3 isolates). Genomic diversity was investigated by molecular typing with rep (repetitive sequence)-based PCR using the primer ERIC2 (enterobacterial repetitive intergenic consensus). The Lactobacillus isolates exhibited genetic heterogeneity and species-specific fingerprint patterns. All the isolates showed antagonistic activity against the foodborne pathogenic bacteria tested. This antibacterial effect was attributed to acid production, except in the cases of three isolates that apparently produced bacteriocin-like inhibitory substances. This study provides the first insight into the genetic diversity of Lactobacillus spp. of puba.

Lactobacilli isolated from the vaginal tract of women with and without bacterial vaginosis (BV) were identified and characterized for the production of antagonists. Bacterial samples were isolated from healthy women (N = 16), from patients with clinical complaints but without BV (N = 30), and from patients with BV (N = 32). Identification was performed using amplified ribosomal DNA restriction analysis. Production of antagonistic compounds was evaluated by the double-layer diffusion technique using Gram-positive (N = 9) and Gram-negative bacteria (N = 6) as well as yeast (N = 5) as indicator strains. Of a total of 147 isolates, 133 were identified as pertaining to the genus Lactobacillus. Lactobacillus crispatus was the species most frequently recovered, followed by L. johnsonii and L. jensenii. Statistical analysis showed that L. crispatus was more frequent in individuals without BV (P < 0.05). A higher production of antagonists was noted in L. crispatus isolates from healthy women (P < 0.05). More acidic local pH and higher H2O2 production by isolated lactobacilli from healthy women suggest these mechanisms as the possible cause of this antagonism. In conclusion, a significant correlation was detected between the presence and antagonistic properties of certain species of Lactobacillus and the clinical status of the patients.