PCR ribotyping and arbitrarily primed PCR for the comparison of enterotoxigenic Bacteroides fragilis strains from two Polish university hospitals

Multi-omics reveals the particle size effect of nanoplastics on the hepatopancreas and intestinal toxicity of crustacean model Neospoda palmata

Nano-plastics (NPs) have emerged as prevalent contaminants in aquatic ecosystems, gaining significant research interest. Nonetheless, limited research has addressed the toxicity mechanisms associated with PS-NPs (polystyrene nanoplastics) of varying particle sizes. In this investigation, genotoxicity, growth patterns, hepatopancreatic damage, and intestinal flora alterations in freshwater shrimp Neocaridina palmata (Shen 1948), subjected to 35 days PS-NPs exposure (two size PS-NPs: 75 nm and 200 nm were used for this experiment, and five concentrations were set: 0 mg/L, 0.5 mg/L, 2.5 mg/L, 5 mg/L, and 10 mg/L concentrations PS-NP concentrations were examined using RNA sequencing, histopathological analyses, enzyme activity assessments, and 16S rRNA sequencing. Noteworthy variations in differentially expressed genes (DEGs) were identified across groups exposed to different PS-NPs sizes. We observed that PS-NPs predominantly instigated cellular component-related processes and induced apoptosis and oxidative stress across tissues via the mitochondrial pathway. Although the 200 nm-PS-NPs are stronger than the 75 nm-PS-NPs in terms of fluorescence intensity, 75 nm-PS-NPs are more likely to promote apoptosis than 200 nm-PS-NPs. PS-NPs impeded standard energy provision in N. palmata, potentially contributing to decreased body length and weight. Moreover, PS-NPs inflicted damage on intestinal epithelial and hepatopancreatic tissues and significantly modified intestinal microbial community structures. Specifically, PS-NPs-induced intestinal damage was marked by a decline in some probiotics (notably Lactobacilli) and a surge in pathogenic bacteria. Moreover, supplementing N. palmata with Lactobacilli appeared ameliorate oxidative stress and strengthen energy metabolism. Our findings provided valuable insights into crustacean toxicity mechanisms when subjected to PS-NPs and the potential risks that different PS-NPs sizes posed to terrestrial ecosystems.

Low rate of carriage of macrolide-resistant group B streptococci in pregnant women in The Netherlands

OBJECTIVES

To describe prevalence of phenotypic and genotypic macrolide-resistance among GBS isolates in pregnant women and explore the possibility of clonal spread of resistant GBS isolates in a multicultural population.

STUDY DESIGN

Antimicrobial resistance patterns of 107 GBS isolates obtained from asymptomatic pregnant women were determined using E-tests. Macrolide resistance genes mef(A), erm(TR) and erm(B) were determined with PCR and a subset of 39 isolates, including the 8 isolates harbouring macrolide resistance genes, was subjected to RAPD analysis to detect clonal spreading.

RESULTS

Resistance to erythromycin and clindamycin was found in 8% and 7%, respectively. Macrolide resistance genes mef(A), erm(TR) and erm(B) were found in 1, 2 and 5 isolates, respectively; only five of these eight isolates exhibited both genotypic as well as phenotypic resistance. One genotype occured in 36% of the subset.

CONCLUSIONS

Earlier reports on prevalence of phenotypic resistance were confirmed. Among the susceptible isolates one clonal type of GBS was clearly predominant; one of the resistant isolates shared its genotype. When such clonal types acquire resistance traits in the future, GBS disease may become harder to control.

bft gene subtyping in enterotoxigenic Bacteroides fragilis isolated from children with acute diarrhea

Enterotoxigenic Bacteroides fragilis (ETBF) strains are associated with diarrhea disease in farm animals and young children. In this study, the bft gene subtyping from ETBF strains recovered from one immunodeficient and two immunocompetent children with diarrhea were determined. Thirteen ETBF strains were isolated and by using a multiplex-PCR their bft subtypes were determined. All 13 ETBF strains harbored the bft-1 subtype and by AP-PCR they were clustered in the same group I. This study shows that ETBF strains can be present in acute diarrhea and that bft-1 subtype is often present in these organisms. However, further studies are needed to evaluate the role of this bft-1 subtype in the pathogenesis of diarrhea.

Genetic variation in 16S-23S rDNA internal transcribed spacer regions and the possible use of this genetic variation for molecular diagnosis of Bacteroides species

The structural variation in 16S-23S rDNA internal transcribed spacer regions (ITS) among Bacteroides species was assessed by PCR amplification and sequencing analysis, and its possible use for molecular diagnosis of these species was evaluated. Ninety strains of the genus Bacteroides, including the species B. distasonis, B. eggerthii, B. fragilis, B. ovatus, B. thetaiotaomicron, B. uniformis and B. vulgatus, produced one to three ITS amplification products with sizes ranging from 615 to 810 bp. Some Bacteroides strains could be differentiated at species level on the basis of ITS amplification patterns and restriction fragment length polymorphism (RFLP) analysis using a four-nucleotide-recognizing enzyme, Msp I. The results of sequence analysis of ITS amplification products revealed genes for Ile-tRNA and Ala-tRNA in all strains tested. The nucleotide sequence, except for that in tRNA-coding regions, was highly variable and characteristic for each species, but a common sequence among B. fragilis, B. thetaiotaomicron and B. ovatus was observed. A digoxigenin-labeled oligonucleotide probe (named FOT1), which was designed from this conserved sequence, specifically hybridized to the ITS amplification products from B. fragilis, B. thetaiotaomicron and B. ovatus. These results suggest that the ITS region is a useful target for the development of rapid and accurate techniques for identification of Bacteroides species.

Genotyping of Bacteroides fragilis isolates from stool specimens by arbitrarily-primed-PCR

In order to determine genetic relatedness of Bacteroides fragilis isolates from different clinical sources, arbitrarily primed polymerase chain reaction (PCR) (AP-PCR) was used to compare 17 strains isolated from patients with inflammatory bowel disease (IBD) and 20 strains isolated from foals with diarrhea. Three reference ATCC strains were also analyzed. Eighteen unique types were identified with a 22-mer arbitrary primer (ERIC-2) among the 20 patient isolates. Types 1 (enterotoxigenic) and 9 (nonenterotoxigenic), were each found in the stools of two patients. All other isolates showed a distinct and unique DNA banding pattern indicating a high degree of genotypic variability. Eleven types were identified among the foal isolates. Type 20, a nonenterotoxigenic type, was present in 30% of the foals. No correlation was found between the human and horse isolates. No clear relationship between a disease state (diarrhea or IBD) and specific types was observed. AP-PCR will be useful as a rapid method to determine genetic relatedness and in future epidemiologic studies of diarrheal diseases due to B. fragilis.

Vaginal carriage of enterotoxigenic Bacteroides fragilis in pregnant women

Bacteroides fragilis is an anaerobic bacterial species that is involved in gynecological infections and pathology. The incidence of vaginal carriage is largely unknown, and in order to study this, 120 pregnant women attending a general hospital for delivery were examined. Cultures were positive for eight of these women (6.6%). Interestingly, potential clonal relatedness could be demonstrated among several of the nonenterotoxigenic B. fragilis strains. Among the strains, only one produced metalloprotease enterotoxin. The presence of the gene for the metalloprotease, giving rise to the pathogenic effect on cultured eukaryotic HT29/C1 cells, was confirmed by a newly designed specific PCR assay. The enterotoxigenic B. fragilis (ETBF) strain was analyzed with the help of arbitrarily primed PCR (AP-PCR) and PCR-mediated ribotyping. The ETBF strain was shown to be genetically different compared to several other strains obtained from diverse sources. Our data indicate a relatively high vaginal B. fragilis carriage rate among pregnant women in Warsaw, Poland. Although neither ETBF nor B. fragilis colonization presented a clinical problem, the possible genetic relatedness among the colonizing B. fragilis strains indicates the need for additional research in the field of ETBF transmission and molecular epidemiology.