The Bacillus virulome in endophthalmitis

Novel Anti-Microbial/Anti-Inflammatory Combination Improves Clinical Outcome of Bacillus cereus Endophthalmitis

Purpose

The purpose of this study was to explore the therapeutic potential of the novel combination of Bacillus bacteriophage lysin (PlyB) and a synthetic TLR2/4 inhibitor (oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, OxPAPC) in the treatment of experimental Bacillus cereus endophthalmitis.

Methods

C57BL/6J mice were injected with 100 colony forming units (CFUs) Bacillus cereus to induce endophthalmitis. Two hours postinfection, groups of mice were treated with either PlyB, PlyB with OxPAPC, or the groups were left untreated to serve as a control. A group of uninfected mice was injected with only PlyB to serve as a treatment control. Eight hours post-treatment, infected/treated mice were analyzed for bacterial counts, retinal function, histology, and inflammation.

Results

Groups treated with PlyB alone or PlyB/OxPAPC showed significantly reduced bacterial loads compared with untreated eyes. Compared with untreated eyes, PlyB and PlyB/OxPAPC-treated eyes retained significant A-wave and B-wave function. PlyB/OxPAPC-treated eyes retained greater A- and B-wave function compared with eyes treated with PlyB alone. Histology showed that retinal structures were well preserved, and retinal layers were distinguishable in eyes treated with PlyB and PlyB/OxPAPC. Ninety-five percent of infiltrating CD45+ cells in infected untreated eyes were Ly6G+/Ly6C+ neutrophils. Infected eyes treated with PlyB and PlyB/OxPAPC had significantly reduced numbers of CD45+ immune cells compared with untreated eyes. Eyes treated with PlyB/OxPAPC had a significantly lower number of neutrophils than eyes treated with PlyB alone.

Conclusions

These results demonstrated that the novel combination of bacteriophage lysin and TLR2/4 inhibitor was a successful treatment option for treating experimental Bacillus cereus endophthalmitis.

Genomic Insights into the Pathogenicity and Drug-Resistance of a Bacillus cereus Isolated from Human Teeth

Background

Bacillus cereus is a common bacterium found in the environment. Some strains can cause food poisoning, and very few can cause clinically severe infections, leading to death. Here, we characterized the genome sequence of B. cereus LIN78 isolated from teeth with deep caries and compared it with those of 25 other related species.

Methods

Third-generation sequencing technology, bacteriological analyses, biochemistry, and mass spectrometry were applied to characterize the drug-resistance genes and virulence factors of B. cereus LIN78.

Results

The complete genome sequence of B. cereus Lin78 consists of 5647 genes distributed on a circular chromosome, a 393 kbp plasmid, and 928 pseudogenes (37.4% of whole-genome DNA). The LIN78 genome contains 14 sets of 16s, 23s, and 5s ribosomal RNA operons; 106 tRNA genes, one tmRNA, 12 genomic islands, six prophases, 64 repeats; 37 antibiotic-resistant genes; and 1119 putative virulence genes, including enterotoxins and cytolysins. The B. cereus LIN78 genome carries multiple copies of non-ribosomal polypeptide synthetase (NRPS) and post-translationally modified peptides (RiPPs). Phylogenetic analysis of the 26 B. cereus strains showed that B. cereus LIN78 is evolutionarily closely related to B. thuringiensis ATCC 10792 and B. cereus ATCC 14579.

Conclusion

The newly isolated B. cereus carries many virulence genes, including enterotoxins and hemolysins, similar to B. anthracis, and multiple antibiotic resistance genes. These findings suggest that the strain has a potential risk of causing disease. Our studies are vital for further exploration of the evolution of B. cereus, its pathogenic mechanisms, and the control and treatment of bacterial infections.

Ocular trauma from Lawn mower accidents: Clinical insights, visual outcomes and microbial profiles

AIMS

To characterize the clinical features of ocular trauma resulting from lawn mower, identify determinants of unfavorable final visual acuity (FVA), and assess the spectrum of microbial in posttraumatic endophthalmitis.

METHODS

This retrospective study enrolled patients who experienced ocular trauma due to lawn mower at Zhongshan Ophthalmic Center from January 2013 to August 2021. Demographics, clinical features, isolated microorganisms, risk factors influencing reduced visual acuity, treatment regimens, and utilization of eyewear were collected.

RESULTS

The study included 140 participants (140 eyes) (49.47 ± 12.03 years, 95% male). The predominant injury manifestations were penetrating globe injuries (75.7%) and intraocular foreign bodies (51.4%). Endophthalmitis occurred in 35 cases (25%) and Bacillus cereus (23.5%) was the primary pathogen, followed by Staphylococcus epidermidis (11.8%) and Streptococcus species (11.8%). Following the initial assessment, where 77.9% of patients had initial visual acuity (IVA) at grade IV (ranging from light perception to 4/200) and only 0.7% attained grade I (better than 20/40), post-treatment results revealed that 5.7% achieved FVA at grade I, with a concurrent decrease in patients with grade IV vision to 64.3%. Multivariate logistic regression revealed that injury protection (p < 0.001, OR = 0.237, 95% CI = 0.126-0.446), IVA (p = 0.001, OR = 4.102, 95% CI = 1.730-9.729), and retinal detachment (p = 0.042, OR = 8.105, 95% CI = 1.075-61.111) were significant independent risk factors impacting FVA.

CONCLUSION

Lawn mower often cause severe ocular injuries, with high-velocity metal foreign bodies that can lead to infections, most commonly caused by Bacillus cereus. Correct use of protective gear, initial vision assessment, and detecting retinal detachment are crucial for visual prognosis.

An Investigation of Quorum Sensing Inhibitors against Bacillus cereus in The Endophytic Fungus Pithomyces sacchari of the Laurencia sp

Bacillus cereus, a common food-borne pathogen, forms biofilms and generates virulence factors through a quorum sensing (QS) mechanism. In this study, six compounds (dankasterone A, demethylincisterol A3, zinnimidine, cyclo-(L-Val-L-Pro), cyclo-(L-Ile-L-Pro), and cyclo-(L-Leu-L-Pro)) were isolated from the endophytic fungus Pithomyces sacchari of the Laurencia sp. in the South China Sea. Among them, demethylincisterol A3, a sterol derivative, exhibited strong QS inhibitory activity against B. cereus. The QS inhibitory activity of demethylincisterol A3 was evaluated through experiments. The minimum inhibitory concentration (MIC) of demethylincisterol A3 against B. cereus was 6.25 μg/mL. At sub-MIC concentrations, it significantly decreased biofilm formation, hindered mobility, and diminished the production of protease and hemolysin activity. Moreover, RT-qPCR results demonstrated that demethylincisterol A3 markedly inhibited the expression of QS-related genes (plcR and papR) in B. cereus. The exposure to demethylincisterol A3 resulted in the downregulation of genes (comER, tasA, rpoN, sinR, codY, nheA, hblD, and cytK) associated with biofilm formation, mobility, and virulence factors. Hence, demethylincisterol A3 is a potentially effective compound in the pipeline of innovative antimicrobial therapies.

Virulence-related genotypic differences among Bacillus cereus ocular and gastrointestinal isolates and the relationship to endophthalmitis pathogenesis

Background

Bacillus cereus (Bc) can cause self-limiting gastrointestinal infections, but when infecting the eye, can cause rapid and irreversible blindness. This study investigated whether clinical ocular and gastrointestinal Bc isolates differed in terms of virulence-related genotypes and endophthalmitis virulence.

Methods

Twenty-eight Bc ocular, gastrointestinal, and laboratory reference isolates were evaluated. Hemolysis assays were performed to assess potential differences in hemolytic activity. The presence of twenty Bc virulence-related genes was assessed by PCR. A subset of ocular and gastrointestinal isolates differing in PCR positivity for 5 virulence genes was compared to strain ATCC14579 in an experimental murine model of endophthalmitis. At 8 hours post infection, retinal function was evaluated by electroretinography, and intraocular bacterial concentrations were determined by plate counts.

Results

Gastrointestinal Bc isolates were more hemolytic than the Bc ocular isolates and ATCC14579 (p < 0.0001). Bc ocular isolates were more frequently PCR-positive for capK, cytK, hblA, hblC, and plcR compared to the gastrointestinal isolates (p ≤ 0.0002). In the endophthalmitis model, mean A-wave retention did not differ significantly between eyes infected with ATCC14579 and eyes infected with the selected ocular or gastrointestinal isolates (p ≥ 0.3528). Similar results were observed for mean B-wave retention (p ≥ 0.0640). Only one diarrheal isolate showed significantly greater B-wave retention when compared to ATCC14579 (p = 0.0303). No significant differences in mean A-wave (p ≥ 0.1535) or B-wave (p ≥ 0.0727) retention between the selected ocular and gastrointestinal isolates were observed. Intraocular concentrations of ATCC14579 were significantly higher than the selected ocular isolate and 3 of the gastrointestinal isolates (p ≤ 0.0303). Intraocular concentrations of the selected ocular isolate were not significantly different from the gastrointestinal isolates (p ≥ 0.1923).

Conclusions

Among the subset of virulence-related genes assessed, 5 were significantly enriched among the ocular isolates compared to gastrointestinal isolates. While hemolytic activity was higher among gastrointestinal isolates, retinal function retention and intraocular growth was not significantly different between the selected ocular and gastrointestinal isolates. These results suggest that Bc strains causing gastrointestinal infections, while differing from ocular isolates in hemolytic activity and virulence-related gene profile, are similarly virulent in endophthalmitis.

Ocular Bacterial Infections: A Ten-Year Survey and Review of Causative Organisms Based on the Oklahoma Experience

Ocular infections can be medical emergencies that result in permanent visual impairment or blindness and loss of quality of life. Bacteria are a major cause of ocular infections. Effective treatment of ocular infections requires knowledge of which bacteria are the likely cause of the infection. This survey of ocular bacterial isolates and review of ocular pathogens is based on a survey of a collection of isolates banked over a ten-year span at the Dean McGee Eye Institute in Oklahoma. These findings illustrate the diversity of bacteria isolated from the eye, ranging from common species to rare and unique species. At all sampled sites, staphylococci were the predominant bacteria isolated. Pseudomonads were the most common Gram-negative bacterial isolate, except in vitreous, where Serratia was the most common Gram-negative bacterial isolate. Here, we discuss the range of ocular infections that these species have been documented to cause and treatment options for these infections. Although a highly diverse spectrum of species has been isolated from the eye, the majority of infections are caused by Gram-positive species, and in most infections, empiric treatments are effective.

Roles of CCL2 and CCL3 in intraocular inflammation during Bacillus endophthalmitis

Bacillus cereus (B. cereus) endophthalmitis is a vision-threatening bacterial infection. Uncontrolled inflammatory responses are the hallmark of this disease which cause irreversible damage to the retina. We recently reported C-X-C chemokines as a vital modulators which impacted the pathogenesis of this disease. Here, we investigated the impact of two highly upregulated C-C chemokines, CCL2 and CCL3, on intraocular inflammation this disease. B. cereus was injected into the eyes of C57BL/6J (WT), CCL2-/-, and CCL3-/- mice to induce endophthalmitis. Infected eyes were examined for bacterial growth, retinal function, and inflammation. Bacterial growth in CCL2-/- and CCL3-/- mice were similar, but retained retinal function was greater in CCL2-/- and CCL3-/- eyes compared to that of C57BL/6J eyes. The retinal architecture of infected eyes of CCL2-/- mice were conserved for a longer period of time than in infected CCL3-/- eyes. Infected CCL2-/- and CCL3-/- eyes had less inflammation than did infected C57BL/6J eyes. Based on these results, we assessed the efficacies of intravitreal anti-CCL2 or anti-CCL3 with or without the antibiotic gatifloxacin. Compared to infected untreated eyes, there was significantly less inflammation and greater retention of retinal function in eyes treated with anti-CCL2 or anti-CCL3 with gatifloxacin. This study showed that B. cereus endophthalmitis in CCL2-/- mice had a better clinical outcome than in CCL3-/- mice. Intravitreal administration of anti-CCL2 and anti-CCL3 with gatifloxacin significantly reduced inflammation and provided protection of retinal function. These results suggest that CCL2 and CCL3 are prospective anti-inflammatory targets that should be tested along with other antibiotics for treating Bacillus and perhaps other forms of endophthalmitis.

C-X-C Chemokines Influence Intraocular Inflammation During Bacillus Endophthalmitis

Purpose

The purpose of this study was to explore the C-X-C chemokines CXCL2 and CXCL10 as potential anti-inflammatory targets for Bacillus endophthalmitis.

Methods

Bacillus endophthalmitis was induced in C57BL/6J, CXCL2^−/−, and CXCL10^−/− mice. At specific times postinfection, eyes were analyzed for Bacillus, retinal function, and inflammation. The efficacies of intravitreal anti-CXCL2 and anti-CXCL10 with or without gatifloxacin in B. cereus endophthalmitis were also assessed using the same techniques.

Results

Despite similar Bacillus growth in eyes of C57BL/6J, CXCL2^−/−, and CXCL10^−/− mice, retinal function retention was greater in eyes of CXCL2^−/− and CXCL10^−/− mice compared to that of C57BL/6J mice. Neutrophil migration into eyes of CXCL2^−/− and CXCL10^−/− mice was reduced to a greater degree compared to that of eyes of C57BL/6J mice. Infected CXCL2^−/− and CXCL10^−/− mouse eyes had significantly less inflammation compared to that of C57BL/6J eyes. Retinal structures in infected eyes of CXCL2^−/− mice were preserved for a longer time than in CXCL10^−/− eyes. Compared to untreated eyes, there was less inflammation and significant retention of retinal function in eyes treated with anti-CXCL2 and anti-CXCL10 with or without gatifloxacin.

Conclusions

For Bacillus endophthalmitis, the absence of CXCL2 or CXCL10 in mice resulted in retained retinal function and less inflammation. The absence of CXCL2 led to a better clinical outcome than the absence of CXCL10. The use of anti-CXCL2 and anti-CXCL10 limited inflammation during B. cereus endophthalmitis. These results highlight the utility of CXCL2 and CXCL10 as potential targets for anti-inflammatory therapy that can be tested in conjunction with antibiotics for improving treating Bacillus endophthalmitis.