Prevalence of Antimicrobial Resistance and Respective Genes among Bacillus spp., a Versatile Bio-Fungicide

Antibiotic resistance characterization, virulence factors and molecular characteristics of Bacillus species isolated from probiotic preparations in China

OBJECTIVES

The aim of this study was to determine the phenotypic and molecular characteristics of antibiotic-resistant Bacillus spp. isolated from probiotic preparations in China.

METHODS

Bacillus strains were isolated from probiotic preparations and then identified using 16S rDNA sequencing. Drug sensitivity tests were conducted to determine their susceptibility to seven antibiotics. Whole genome sequencing was performed on the most resistant strains, followed by analysis of their molecular characteristics, resistance genes, and virulence factors.

RESULTS

In total, we isolated 21 suspected Bacillus species from seven compound probiotics, which were identified by 16S rDNA as 12 Bacillus licheniformis, six Bacillus subtilis and three Bacillus cereus. The determination of antimicrobial susceptibility showed widespread resistance to chloramphenicol (95.2%), erythromycin (85.7%) and gentamicin (42.9%). Whole genome sequencing of seven resistant strains revealed that J-6-A (Bacillus subtilis) and J-7-A (Bacillus cereus) contained a plasmid. The resistance gene analysis revealed that each strain contained more than ten resistance genes, among which J-7-A was the most. The streptomycin resistance gene strA was detected in all strains. The chloramphenicol resistance genes ykkC and ykkD were found in J-1-A to J-5-A and were first reported in Bacillus subtilis. The erythrocin resistance gene ermD was detected in strains J-1-A to J-4-A. There were also more than 15 virulence factors and gene islands (GIs) involved in each strain.

CONCLUSIONS

These results confirm the potential safety risks of probiotics and remind us to carefully select probiotic preparations containing strains of Bacillus species, especially Bacillus cereus, to avoid the potential spread of resistance and pathogenicity.

Isolation and identification of a new Bacillus glycinifermentans strain from date palm rhizosphere and its effect on barley seeds under heavy metal stress

Soil contamination by heavy metals is one of the major problems that adversely decrease plant growth and biomass production. Inoculation with the plant growth-promoting rhizobacteria (PGPR) can attenuate the toxicity of heavy metals and enhancing the plant growth. In this study, we evaluated the potential of a novel extremotolerant strain (IS-2 T) isolated from date palm rhizosphere to improve barley seedling growth under heavy metal stress. The species-level identification was carried out using morphological and biochemical methods combined with whole genome sequencing. The bacterial strain was then used in vitro for inoculating Hordeum vulgare L. exposed to three different Cr, Zn, and Ni concentrations (0.5, 1, and 2 mM) in petri dishes and different morphological parameters were assessed. The strain was identified as Bacillus glycinifermentans species. This strain showed high tolerance to pH (6-11), salt stress (0.2-2 M), and heavy metals. Indeed, the minimum inhibitory concentrations at which bacterium was unable to grow were 4 mM for nickel, 3 mM for zinc, more than 8 mM for copper, and 40 mM for chromium, respectively. It was observed that inoculation of Hordeum vulgare L. under metal stress conditions with Bacillus glycinifermentans IS-2 T stain improved considerably the growth parameters. The capacity of the IS-2 T strain to withstand a range of abiotic stresses and improve barley seedling development under lab conditions makes it a promising candidate for use as a PGPR in zinc, nickel, copper, and chromium bioremediation.

Probiotic Potential of Bacillus sp. 62A Isolated from a Marine Extreme Environment

Antimicrobial resistance is an important health concern globally, and probiotics are considered an alternative to minimize it. The present study examined the in vitro probiotic characteristics and in vivo immunomodulatory potential of Bacillus sp. 62A - an extremophile bacterium. Bacillus sp. 62A was evaluated in vitro for its cytotoxicity, hemolytic activity, antibiotic susceptibility, and resistance to gastrointestinal conditions (bile salts, low pH, and intestinal adherence). Additionally, the immunomodulatory effect of Bacillus sp. 62A was studied in mice. The animals were supplemented daily with phosphate-buffered saline (control) and Bacillus sp. 62A at 1 × 108 colony forming units (CFU). Samples were taken on days 5 and 10. Isolated splenocytes were challenged with Escherichia coli for immunological analyses and immune-related gene expression. Serum and feces were collected for IgA and IgG determination. Bacillus sp. 62A did not show cytotoxicity, hemolytic activity, or resistance to antibiotics. Furthermore, the bacterium has autoaggregation and intestinal adhesion capacities and grows in the presence of bile salts and low pH. Bacillus supplementation in mice improved respiratory burst activity, nitric oxide production, and IL-1β and IL-6 gene expressions, mainly at 10 days. After E. coli challenge, Bacillus supplementation in mice induced an anti-inflammatory response through a decrease in immunological parameters and an increase in IL-10 gene expression. Moreover, serum IgA and IgG and fecal IgG augmented in supplemented mice. In conclusion, Bacillus sp. 62A has biosafe and immunomodulatory probiotic potential.

Editorial for Special Issue-''Research Progress and Applications of Natural Products"

This Special Issue (S [...].

Prevalence and Antibiotic Resistance of Bacillus sp. Isolated from Raw Milk

Milk, due to its diversity in terms of its nutritional content, is an important element of the human diet, as well as a good medium for the development of bacteria. The genus Bacillus contains ubiquitous aerobic, rod-shaped, endospore-producing gram-positive bacteria. Representatives of the Bacillus cereus group and the Bacillus subtilis group contribute to shortening the shelf life of milk and dairy products by degrading milk components and its additives. They also produce a number of heat-stable toxins and can cause a number of ailments, mainly in the digestive system. The aim of this research was to identify Bacillus sp. strains isolated from raw milk and to determine their antibiotic resistance. Strains isolated from raw milk samples (n = 45) were identified by MALDI-TOF MS. Ninety strains of Bacillus sp. were identified, for which the antibiotic resistance phenotype was determined. A total of 90 strains of Bacillus were classified in five groups (the Bacillus cereus group (n = 35), B. licheniformis (n = 7), the B. subtilis group (n = 29), B. pumilus (n = 16), and Bacillus sp. (n = 3). All isolates were susceptible to chloramphenicol and meropenem. The antibiotic resistance profiles of the tested groups of Bacillus spp. differed from each other, which is of particular concern in relation to multidrug-resistant representatives of the B. cereus group resistant to cefotaxime (94.29%), ampicillin (88.57%), rifampicin (80%), and norfloxacin (65.71%). Our study provides data on the prevalence and antibiotic sensitivity of Bacillus sp. In raw milk, suggesting a potential risk to health and the dairy industry.