The cereus matter of Bacillus endophthalmitis

Impact of microorganism virulence on endophthalmitis outcomes

AIMS

To determine the impact of microorganism virulence on visual outcomes in endophthalmitis.

METHODS

Retrospective, multicentre cohort study of patients presenting with endophthalmitis between 2006 and 2021. A literature review was conducted to divide cultured microorganisms into low and high virulence subcategories.

RESULTS

610 eyes with endophthalmitis were recruited from New Zealand, the UK and Israel. The median age was 69.4 years. The median visual acuity was hand movements at presentation and 20/120 at the final follow-up. Severe visual loss (≤20/200) occurred in 237 eyes (38.9%) at the final follow-up. The culture-positive rate was 48.5% (296 eyes). Highly virulent microorganisms were associated with a 4.48 OR of severe visual loss at the final follow-up (p<0.001) and a 1.90 OR of developing retinal detachment or requiring enucleation or evisceration during the follow-up period (p=0.028). Oral flora were observed in 76 eyes (25.7%), and highly virulent microorganisms were observed in 68 eyes (22.9%). Highly virulent microorganisms were more likely to be found after glaucoma surgery (15 eyes, 34.9%) and vitrectomy (five eyes, 35.7%) compared with intravitreal injections (two eyes, 2.9%) and cataract surgery (22 eyes, 24.2%). On multivariate analysis, the following were associated with poorer visual outcomes: poor presenting vision (p<0.001), glaucoma surgery (p=0.050), trauma (p<0.001), oral microorganism (p=0.001) and highly virulent microorganism (p<0.001).

CONCLUSION

This is the first classification of microorganisms into high and low virulence subcategories that demonstrate highly virulent microorganisms were associated with poor visual outcomes and increased likelihood of retinal detachment and enucleation.

Five-year analysis of isolated pathogens and antibiotic resistance of ocular infections from two large tertiary comprehensive hospitals in east China

AIM

To analyze the spectrum of isolated pathogens and antibiotic resistance for ocular infections within 5y at two tertiary hospitals in east China.

METHODS

Ocular specimen data were collected from January 2019 to October 2023. The pathogen spectrum and positive culture rate for different infection location, such as keratitis, endophthalmitis, and periocular infections, along with antibiotic resistance were analyzed.

RESULTS

We included 2727 specimens, including 827 (30.33%) positive cultures. A total of 871 strains were isolated, 530 (60.85%) bacterial and 341 (39.15%) fungal strains were isolated. Gram-positive cocci (GPC) were the most common ocular pathogens. The most common bacterial isolates were Staphylococcus epidermidis (25.03%), Staphylococcus aureus (7.46%), Streptococcus pneumoniae (4.59%), Corynebacterium macginleyi (3.44%), and Pseudomonas aeruginosa (3.33%). The most common fungal genera were Fusarium spp. (12.74%), Aspergillus spp. (6.54%), and Scedosporium spp. (5.74%). Staphylococcus epidermidis strains showed more than 50% resistance to fluoroquinolones. Streptococcus pneumoniae and Corynebacterium macginleyi showed more than 90% resistance to erythromycin. The percentage of bacteria showing multidrug resistance (MDR) significantly decreased (χ 2=17.44, P=0.002).

CONCLUSION

GPC are the most common ocular pathogens. Corynebacterium macginleyi, as the fourth common bacterium, may currently be the local microbiological feature of east China. Fusarium spp. is the most common fungus. More than 50% of the GPC are resistant to fluoroquinolones, penicillins, and macrolides. However, the proportion of MDR strains has been reduced over time.

Endophthalmitis Caused by Bacillus cereus: Clinical Characteristics, Outcomes and Antibiotic Susceptibility

Bacillus cereus endophthalmitis is a severe vision-threatening disease. This study aimed to analyze the clinical characteristics, antibiotic susceptibility, and risk factors for poor final visual acuity (VA) and enucleation or evisceration (ENEV) outcomes of B. cereus endophthalmitis patients. We retrospectively reviewed 52 cases (52 eyes) of culture-proven B. cereus endophthalmitis at Zhongshan Ophthalmic Center from January 2013 to December 2023. The mean age of the patients was 38.1 ± 20.1 years, and males composed the majority (90.4%) of the sample size; laborers (32.7%) and farmers (19.2%) were the primary occupations of the patients. All cases were caused by ocular trauma. Forty-one of 51 eyes (80.4%) had a final VA worse than the ability to count fingers (CFs), and 15 of the 52 total eyes (28.8%) underwent ENEV. Binary logistic forward (LR) regression analysis demonstrated that red eye (odds ratio [OR], 13.13; 95% confidence interval [CI], 1.58-108.80; p = 0.017), eye pain (OR, 22.87; 95% CI, 1.00-522.72; p = 0.050), and corneal edema/ulcer (OR, 13.13; 95% CI, 1.58-108.80; p = 0.017) were significant risk factors for poor VA outcomes. Conjunctival sac purulent discharge (OR, 10.08; 95% CI, 2.11-48.12, p = 0.004) and white blood cell (WBC) count (OR, 1.35; 95% CI, 1.06-1.72, p = 0.016) were significant risk factors for ENEV outcomes. B. cereus showed susceptibility rates of 100.0% to vancomycin and ofloxacin; 98.0% to levofloxacin; 93.3% to ciprofloxacin; 87.5% to imipenem; and 78.9% to tobramycin. The susceptibility to azithromycin and clindamycin was 66.7% and 50.0%, respectively. In contrast, B. cereus was resistant to penicillin (susceptibility at 3.8%), cefuroxime (5.6%), and cefoxitin (37.1%).

Immunopeptides: immunomodulatory strategies and prospects for ocular immunity applications

Immunopeptides have low toxicity, low immunogenicity and targeting, and broad application prospects in drug delivery and assembly, which are diverse in application strategies and drug combinations. Immunopeptides are particularly important for regulating ocular immune homeostasis, as the eye is an immune-privileged organ. Immunopeptides have advantages in adaptive immunity and innate immunity, treating eye immune-related diseases by regulating T cells, B cells, immune checkpoints, and cytokines. This article summarizes the application strategies of immunopeptides in innate immunity and adaptive immunity, including autoimmunity, infection, vaccine strategies, and tumors. Furthermore, it focuses on the mechanisms of immunopeptides in mediating ocular immunity (autoimmune diseases, inflammatory storms, and tumors). Moreover, it reviews immunopeptides' application strategies and the therapeutic potential of immunopeptides in the eye. We expect the immune peptide to get attention in treating eye diseases and to provide a direction for eye disease immune peptide research.

ACUTE POST-TRAUMATIC ENDOPHTHALMITIS SECONDARY TO BACILLUS PUMILUS / SAFENSIS

PURPOSE

To report a case of post-traumatic endophthalmitis secondary to Bacillus pumilus/safensis .

METHODS

Observational case report of a single patient.

RESULTS

A 62-year-old man presented with a traumatic corneal laceration because of baling wire while working on a sheep farm. Appropriate corneal laceration repair with injection of intravitreal antibiotics (ceftazidime, clindamycin, and vancomycin) was performed. A single organism, identified as B. pumilus or Bacillus safensis, was isolated from the vitreous aspirate. A subsequent pars plana vitrectomy, pars plana lensectomy, anterior capsulotomy, and fluid-air exchange was required because of severe inflammatory reaction from retained lens material, retinal edema, and vitreous opacities. Vision improved from hand motion to 20/60 at the three-month follow-up visit.

CONCLUSION

We describe a case of acute post-traumatic endophthalmitis secondary to B. pumilus/safensis.

Characterization of a cell wall hydrolase with high activity against vegetative cells, spores and biofilm of Bacillus cereus

Bacillus cereus is a prevalent foodborne pathogen that induces food poisoning symptoms such as vomiting and diarrhea. Its capacity to form spores and biofilm enables it to withstand disinfectants and antimicrobials, leading to persistent contamination during food processing. Consequently, it is necessary to develop novel and efficient antimicrobial agents to control B. cereus, its spores, and biofilms. Peptidoglycan hydrolases have emerged as a promising and eco-friendly alternative owing to their specific lytic activity against pathogenic bacteria. Here, we identified and characterized a Lysozyme-like cell wall hydrolase Lys14579, from the genome of B. cereus ATCC 14579. Recombinant Lys14579 specifically lysed B. cereus without affecting other bacteria. Lys14579 exhibited strong lytic activity against B. cereus, effectively lysing B. cereus cell within 20 min at low concentration (10 μg/mL). It also inhibited the germination of B. cereus spores and prevented biofilm formation at 12.5 μg/mL. Moreover, Lys14579 displayed good antimicrobial stability with negligible hemolysis in mouse red blood cells and no cytotoxicity against RAW264.7 cells. Notably, Lys14579 effectively inhibited B. cereus in boiled rice and minced meat in a dose-dependent manner. Furthermore, bioinformatics analysis and point mutagenesis experiments revealed that Glu-47 was the catalytic site, and Asp-57, Gln-60, Ser-61 and Glu-63 were active-site residues related with the cell wall lytic activity. Taken together, Lys14579 could be a promising biocontrol agent against vegetative cells, spores, and biofilm of B. cereus in food industry.

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 microbial dysbiosis and its linkage with infectious keratitis patients in Northwest China: A cross-sectional study

OBJECTIVES

To evaluate the alteration of ocular surface microbiome of patients with infectious keratitis in northwest of China.

METHODS

The corneal scrapings, eyelid margin and conjunctiva samples were collected from 57 participants, who were divided into bacterial keratitis, fungal keratitis, viral keratitis and control group. The V3-V4 region of bacterial 16S rDNA in each sample was amplified and sequenced on the Illumina HiSeq 2500 sequencing platform, and the differences among different groups were compared bioinformatically.

RESULTS

Significant alterations of the microbiome were observed in alpha-diversity and beta-diversity analysis between the keratitis groups and the control group (p < 0.05). There was no significant differences between eyelid margin and conjunctiva samples in Alpha-Diversity analysis, but a significant difference between eyelid margin and corneal scraping samples in the keratitis group (p < 0.05, independent t-test). The abundances of Bacillus, Megamonas, Acinetobacter, and Rhodococcu were significantly elevated, while the abundance of Staphylococcus was decreased in the keratitis group compared to the control group.

CONCLUSIONS

The abundance of the ocular microbiome in patients with bacterial keratitis, fungal keratitis, or viral keratitis was significantly higher than those in the control group. Keratitis patients may have ecological disorder on ocular surface microbiome compared with controls. We believe that the conjunctiva and eyelid margin microbiome combined analysis can more comprehensively reflect the composition and abundance of ocular surface microbiome.

Therapeutic potential of Bacillus phage lysin PlyB in ocular infections

Bacteriophage lytic enzymes (i.e., phage lysins) are a trending alternative for general antibiotics to combat growing antimicrobial resistance. Gram-positive Bacillus cereus causes one of the most severe forms of intraocular infection, often resulting in complete vision loss. It is an inherently β-lactamase-resistant organism that is highly inflammogenic in the eye, and antibiotics are not often beneficial as the sole therapeutic option for these blinding infections. The use of phage lysins as a treatment for B. cereus ocular infection has never been tested or reported. In this study, the phage lysin PlyB was tested in vitro, demonstrating rapid killing of vegetative B. cereus but not its spores. PlyB was also highly group specific and effectively killed the bacteria in various bacterial growth conditions, including ex vivo rabbit vitreous (Vit). Furthermore, PlyB demonstrated no cytotoxic or hemolytic activity toward human retinal cells or erythrocytes and did not trigger innate activation. In in vivo therapeutic experiments, PlyB was effective in killing B. cereus when administered intravitreally in an experimental endophthalmitis model and topically in an experimental keratitis model. In both models of ocular infection, the effective bactericidal property of PlyB prevented pathological damage to ocular tissues. Thus, PlyB was found to be safe and effective in killing B. cereus in the eye, greatly improving an otherwise devastating outcome. Overall, this study demonstrates that PlyB is a promising therapeutic option for B. cereus eye infections.IMPORTANCEEye infections from antibiotic-resistant Bacillus cereus are devastating and can result in blindness with few available treatment options. Bacteriophage lysins are an alternative to conventional antibiotics with the potential to control antibiotic-resistant bacteria. This study demonstrates that a lysin called PlyB can effectively kill B. cereus in two models of B. cereus eye infections, thus treating and preventing the blinding effects of these infections.

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.

qPCR detection of viable Bacillus cereus group cells in cosmetic products

Reference methods for microbiological safety assessments of cosmetics rely on culture methods that reveal colonies of live microorganisms on growth media. Rapid molecular technologies, such as qPCR, detects the presence of target DNA in samples from dead and viable cells. DNA intercalating dyes, such as propidium monoazide (PMAxx), are capable of restricting PCR amplification to viable microbial cells. Here we developed singleplex and multiplex real time (qPCR) assays for the detection of Bacillus cereus (B. cereus) using 16S rRNA and phosphatidylcholine-specific phospholipase C (PLC) gene specific sequences coupled with PMAxx. The limit of detection was determined to be ~ 1 log CFU/ml for 16S rRNA and 3 log CFU/ml for PLC detection in pure culture using an eye shadow isolate, B. cereus 3A. We assessed the inclusivity and exclusivity of our qPCR assays using 212 strains, including 143 members of B. cereus, 38 non- B. cereus. and 31 non-Bacillus species; inclusivity was 100% for the 16S rRNA and 97.9% for the PLC targets; the exclusivity was 100% for 16S rRNA and 98.6% for PLC targets. These qPCR assays were then used to assess samples of commercial cosmetics: one set of liquid face toners (N = 3), artificially contaminated with B. cereus 3A, and one set of powdered cosmetics (N = 8), previously determined to be contaminated with B. cereus. For some samples, test portions were analyzed by qPCR in parallel, with and without PMAxx treatment. All test portions were simultaneously streaked on BACARA plates to confirm viable cells of B. cereus, according to the culture method. We found no difference in sensitivity between the singleplex and the multiplex qPCR assays (P > 0.05). Inoculated samples that did not recover B. cereus on plates still showed amplification of the DNA targets. However, that amplification was significantly delayed in PMAxx -treated samples (P < 0.0001) with C_T value differences of 7.82 for 16S rRNA and 7.22 for PLC. Likewise, amplification delay was significant (P < 0.0001) with inoculated samples that recovered B. cereus on plates with C_T value differences of 2.96 and 2.36 for 16S rRNA and PLC, respectively, demonstrating the presence of dead cells in the samples. All our qPCR results correlated with detection on BACARA plates (kappa, k = 0.99), independently of the presence of PMAxx in the PCR assays. Nevertheless, the amplification threshold with PMAxx dyes was significantly higher than the non-PMAxx dyes. Our findings confirm qPCR can be used for more rapid detection of microorganisms in cosmetics, including B. cereus, and selective detection of viable cells can be improved using PMAxx dyes.

A Rare Case of Bacillus cereus Septic Arthritis

Joint infections are rare in pediatrics, and those caused by Bacillus cereus are practically unheard of. In this case report, we examine a singular case of B. cereus septic arthritis in a child, with the purpose of educating clinicians on the presentation, inpatient and outpatient management, and clinical outcome. We report the case of a previously healthy pediatric patient who presented to the emergency department with symptoms of septic arthritis of the left knee. The orthopedics team performed arthroscopy and debridement, and the synovial fluid culture grew B. cereus. To our knowledge, this is the first case report on septic arthritis caused by B. cereus in the pediatric population. The treatment protocol consisted of intravenous vancomycin for one week, followed by three weeks of oral ciprofloxacin therapy. The patient had an excellent clinical outcome and returned to normal mobility without limitations. Despite being ubiquitous in the environment, extra-intestinal B. cereus infection is exceedingly rare in immunocompetent individuals. It is so rare, in fact, that it is often dismissed as a lab contaminant. In this case, we demonstrated that cooperation between multiple disciplines offers good clinical outcomes for rare infections, especially those in pediatrics.

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.

Risk factors for globe removal after open-globe injury in agricultural regions

This study aimed to identify the prevalence and risk factors for globe removal among patients with open-globe injuries (OGIs) in agricultural regions. A retrospective chart review of patients with OGIs was performed between January 2010 and December 2019. Univariable and multivariable logistic regression models were used to identify the factors associated with globe removal in OGI. This study included 422 patients (422 eyes). The highest prevalence of OGI was observed in the middle age group (> 20 to 40 years). The most common cause of OGIs was agriculture-related injury (54.7%), followed by industry or workplace-related injury (20.4%), and assault (5.0%). Intraocular foreign bodies, endophthalmitis, and panophthalmitis were reported in 57.6%, 28.4%, and 5.7% of cases, respectively. Eight eviscerations and 43 enucleations were performed, accounting for 12.1% of OGIs. The most common indication for globe removal was panophthalmitis. Multivariable analysis revealed that the predictive factors significantly associated with globe removal were assault injuries (adjusted odds ratio (aOR) = 5.53; p = 0.026), presenting logarithm of the minimum angle of resolution visual acuity (aOR = 311.79; p < 0.001), and endophthalmitis and panophthalmitis (aOR = 3.58 and 734.94, respectively; p < 0.001). This knowledge would aid in patient counseling and encourage health promotion.

Genomic characterization of Bacillus cereus sensu stricto 3A ES isolated from eye shadow cosmetic products

BACKGROUND

The Bacillus cereus group, also known as B. cereus sensu lato (s.l.) contains ubiquitous spore-forming bacteria found in the environment including strains from the B. cereus sensu stricto (s.s.) species. They occur naturally in a wide range of raw materials and in consumer products. Characterizing isolates that have survived in consumer products allows us to better understand the mechanisms that permit spores to persist and potentially cause illness. Here we characterize the draft genome sequence of B. cereus s. s. 3A-ES, originally isolated from eye shadow and since investigated in several cosmetic studies and compared it to other top ten published complete genome sequences of B. cereus s.l. members.

RESULTS

The draft genome sequence of B. cereus s.s. 3A ES consisted of an average of 90 contigs comprising approximately 5,335,727 bp and a GC content of 34,988%, and with 5509 predicted coding sequences. Based on the annotation statistics and comparison to other genomes within the same species archived in the Pathosystems Resource Integration Center (PATRIC), this genome "was of good quality. Annotation of B. cereus s.s. 3A ES revealed a variety of subsystem features, virulence factors and antibiotic resistant genes. The phylogenetic analysis of ten B. cereus group members showed B. cereus s.s. 3A-ES to be a closely related homolog of B. cereus s.s. ATCC 14,579, an established reference strain that is not adapted for cosmetic microbiological studies. Survival of 3A-ES in eye shadow could be linked to predicted stress-response genes and strengthened by additional stress-response genes such as VanB-type, VanRB, CAT15/16, BcrA, BcrB, Lsa(B), and recA that are lacking in B. cereus s.s. ATCC 14,579.

CONCLUSION

Our genomic analysis of B. cereus s.s. 3A-ES revealed genes, which may allow this bacterium to withstand the action of preservatives and inhibitors in cosmetics, as well as virulence factors that could contribute to its pathogenicity. Having a well-characterized strain obtained from eye-shadow may be useful for establishing a reference strain for cosmetics testing.

Application of High-Throughput Sequencing Technology in Identifying the Pathogens in Endophthalmitis

Infectious endophthalmitis is an important cause of vision loss worldwide. It is an inflammatory reaction caused by bacteria, fungi, and other micro-organisms and often occurs as a complication of intraocular surgery, especially following cataract surgery or intravitreal injection. The focus of the prevention and treatment of infectious endophthalmitis is the early detection of microbial flora, such as fungi or bacteria. Current identification methods for bacteria include Gram staining-based, culture-based, and polymerase chain reaction (PCR)-based methods. The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry technology is now the standard identification method of bacteria and fungi after their isolation in culture. The remarkable sensitivity of PCR technology for the direct detection of micro-organisms in clinical samples makes it particularly useful in culture-positive and culture-negative endophthalmitis. Furthermore, PCR increases the rate of microorganism detection in intraocular samples by 20% and can provide a microbiology diagnosis in approximately 44.7–100% of the culture-negative cases. This review aims to introduce the development of different methods for the detection and identification of micro-organisms causing endophthalmitis through a literature review; introduce the research status of the first, second, and third-generation sequencing technologies in infectious endophthalmitis; and understand the research status of endophthalmitis microbial flora. For slow-growing and rare micro-organisms, high-throughput sequencing (HTS) offers advantages over conventional methods and provides a basis for the identification of pathogens in endophthalmitis cases with negative culture. It is a reliable platform for the identification of pathogenic bacteria of infectious endophthalmitis in the future and provides a reference for the clinical diagnosis and treatment of infectious endophthalmitis. The application of HTS technology may also be transformative for clinical microbiology and represents an exciting future direction for the epidemiology of ocular infections.

Dynamic Profile of S-Layer Proteins Controls Surface Properties of Emetic Bacillus cereus AH187 Strain

Many prokaryotes are covered by a two-dimensional array of proteinaceous subunits. This surface layers (S-layer) is incompletely characterized for many microorganisms. Here, we studied Bacillus cereus AH187. A genome analysis identified two genes encoding the S-layer proteins SL2 and EA1, which we experimentally confirmed to encode the two protein components of the S-layer covering the surface of B. cereus. Shotgun proteomics analysis indicated that SL2 is the major component of the B. cereus S-layer at the beginning of exponential growth, whereas EA1 becomes more abundant than SL2 during later stages of stationary growth. Microscopy analysis revealed the spatial organization of SL2 and EA1 at the surface of B. cereus to depend on their temporal-dynamics during growth. Our results also show that a mutant strain lacking functional SL2 and EA1 proteins has distinct surface properties compared to its parental strain, in terms of stiffness and hydrophilicity during the stationary growth phase. Surface properties, self-aggregation capacity, and bacterial adhesion were observed to correlate. We conclude that the dynamics of SL2 and EA1 expression is a key determinant of the surface properties of B. cereus AH187, and that the S-layer could contribute to B. cereus survival in starvation conditions.

INCIDENCE AND RISK FACTORS OF POSTOPERATIVE ENDOPHTHALMITIS AFTER PRIMARY SURGICAL REPAIR COMBINED WITH INTRAOCULAR FOREIGN BODY REMOVAL

PURPOSE

To analyze the incidence and risk factors of postoperative endophthalmitis after primary surgical repair and intraocular foreign body (IOFB) removal within 24 hours of injury.

METHODS

The records of all patients treated surgically for open globe injury and IOFB removal at the Eye Hospital of Shandong First Medical University between January 1, 2015, and June 30, 2020, were retrospectively reviewed. Variables included time from injury to operation, cause of injury, details of surgical repair, and follow-up. The incidence and risk factors of endophthalmitis after IOFB removal were studied.

RESULTS

During 5 years, 99 patients with IOFB were reviewed. Of these, 19 patients were diagnosed with endophthalmitis on admission, and 5 were suspected of having endophthalmitis during operation. Fifty-four cases had no clinical signs of endophthalmitis on admission and during operation and were treated with operation within 24 hours after the injury. Two patients (2 of 54; 3.70%) developed endophthalmitis after IOFB removal, and the causative agent in both cases was Bacillus cereus.

CONCLUSION

The incidence of infectious endophthalmitis after primary surgical repair combined with IOFB removal (≤24 hours) was 3.70% in patients who received a series of standard treatments, and B. cereus infection might be a risk factor.

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.

Comparison of causative microorganisms of posttraumatic endophthalmitis with and without retained intraocular foreign bodies

Background

The goals of this work were to report the demographic characteristics of patients with clinically diagnosed endophthalmitis with or without intraocular foreign bodies (IOFBs) and to analyze the causative microorganisms.

Methods

A retrospective analysis was conducted on 1257 patients with clinically diagnosed posttraumatic endophthalmitis who were admitted to Zhongshan Ophthalmic Center between January 1, 2013, and August 31, 2020.

Results

Of the 1257 patients with clinically diagnosed posttraumatic endophthalmitis, 452 (36.0%) patients had IOFBs. Male dominance was more common among the patients with IOFBs than the patients without IOFBs. The average age of the patients with IOFBs was older than that of the patients without IOFBs. The most common microbial pathogens in these two groups were Gram-positive cocci and Gram-negative bacilli. Gram-positive bacilli were more common in the patients with IOFBs than in those without IOFBs (17.9 vs. 9.4%), and Bacillus spp. accounted for 12.6 and 5.5%, respectively. Fungi were less abundant in the patients with IOFBs than in those without IOFBs (8.0 vs. 15.6%).

Conclusions

Patients with IOFBs were mostly male and older than those without IOFBs. Gram-positive bacilli were more common and fungi were less common in patients with IOFBs than in those without IOFBs.

Immune Inhibitor A Metalloproteases Contribute to Virulence in Bacillus Endophthalmitis

Endophthalmitis is a devastating infection that can cause blindness. Over half of Bacillus endophthalmitis cases result in significant loss of useful vision. Bacillus produces many virulence factors that may contribute to retinal damage and robust inflammation. We analyzed Bacillus immune inhibitor A (InhA) metalloproteases in the context of this disease, hypothesizing that InhAs contribute to Bacillus intraocular virulence and inflammation. We analyzed phenotypes and infectivity of wild type (WT), InhA1-deficient (ΔinhA1), InhA2-deficient (ΔinhA2), or InhA1, A2, and A3-deficient (ΔinhA1-3) Bacillus thuringiensis. In vitro analysis of growth, proteolysis, and cytotoxicity were compared. WT and InhA mutants were similarly cytotoxic to retinal cells. Mutants ΔinhA1 and ΔinhA2 entered log phase growth earlier than WT. Proteolysis by the ΔinhA1-3 mutant was decreased, but this strain grew similar to WT in vitro. Experimental endophthalmitis was initiated by intravitreally infecting C57BL/6J mice with 200 CFU of B. thuringiensis WT or InhA mutants. Eyes were analyzed for intraocular Bacillus and myeloperoxidase concentrations, retinal function loss, and gross histological changes. Eyes infected with ΔinhA1 or ΔinhA2 strains contained greater numbers of bacteria than eyes infected with WT throughout the infection course. Eyes infected with single mutants had inflammation and retinal function loss similar to eyes infected with WT strain. Eyes infected with ΔinhA1-3 cleared the infection. RT-PCR results suggested that there may be compensatory expression of the other InhAs in the single InhA mutant. These results indicate that together, the InhA metalloproteases contribute to the severity of infection and inflammation in Bacillus endophthalmitis.

Outcomes and Prognostic Factors of Posttraumatic Endophthalmitis: A Three-Year Retrospective Study

Purpose

To describe the clinical features, management, and outcomes of patients with posttraumatic endophthalmitis (PTE) and to determine risk factors for poor visual prognosis.

Methods

We retrospectively reviewed the medical records of 42 consecutive patients presenting with PTE who were treated at our institution between 2017 and 2019. Each patient's data, including demographic characteristics, ocular injury details, surgical records, patient outcomes, and laboratory results, were collected and analyzed. Multivariate analysis was conducted to determine the factors associated with poor visual outcomes.

Results

In our series, male (n = 36, 85.7%) and patients below 60 years of age (20–40 years, 23.8%; 40–60 years, 57.14%) comprised most of the total cohort. On presentation, 39 (92.8%) of the 42 PTE patients presented best-corrected visual acuity (BCVA) worse than counting fingers. Pars plana vitrectomy (PPV) was performed in all the patients. 59.5% (n = 25) of the patients' BCVA improved after surgery and 33.3% (n = 14) achieved BCVA of 20/200 or better. The rate of evisceration was 7.1% (n = 3). Of the 42 specimens, the culture was positive in 10 (23.8%) eyes. By univariate analysis, factors including sex, occupation, systemic disease, source of trauma, lens injury, silicone oil tamponade, usage of intravitreal antibiotics, BCVA at presentation, and culture positive for any organism did not affect the final visual outcome. The features associated with poor BCVA (grouped as < 20/200 and ≥ 20/200) included older age (P=0.035), corneal-sclera wound (versus sclera wound) (P=0.047), retained intraocular foreign bodies (IOFBs) (P=0.006), treatment > 3 days (versus < 1 day) (P=0.033), and more times of surgeries (P=0.033).

Conclusions

PTE is a severe complication of penetrating globe injuries associated with irreversible visual loss. Our results highlighted the importance of conducting early therapeutic PPV and IOFB removal to achieve better visual outcomes.

Aging, But Not Sex and Genetic Diversity, Impacts the Pathobiology of Bacterial Endophthalmitis

Purpose

Age, sex, and genetics are important biological variables in determining an individual's susceptibility or response to infectious agents; however, their role has not been evaluated in intraocular infections. In this study, we comprehensively examined the impact of these host biological factors in the pathogenesis of experimental bacterial endophthalmitis.

Methods

Endophthalmitis was induced by intravitreal injection of bacteria (Staphylococcusaureus) in the eyes of male and female C57BL/6 mice of different ages: group I (young, 6–8 weeks), group II (mid-age, 18–20 weeks), and group III (old, 1 year). Highly heterogeneous outbred J:DO mice were used for genetic diversity analysis. Eyes were subjected to clinical examination, retinal function testing using electroretinography (ERG), histopathological analysis (hematoxylin and eosin staining), and bacterial burden estimation. The levels of inflammatory mediators were measured using qPCR and ELISA, and the infiltration of neutrophils was determined by flow cytometry.

Results

Both inbred C57BL/6 and diversity outbred (J:DO) mice were equally susceptible to S. aureus endophthalmitis, as evidenced by a time-dependent increase in clinical scores, bacterial burden, intraocular inflammation, and retinal tissue damage, in addition to decreased retinal function. However, no significant differences were observed in disease severity and innate responses in male versus female mice. Older mice (group III) exhibited higher clinical scores coinciding with increased bacterial proliferation and intraocular inflammation, resulting in enhanced disease severity. Moreover, bone-marrow-derived macrophages from old mice exhibited reduced phagocytic activity but increased inflammatory response toward S. aureus challenge.

Conclusions

Age, but not sex, is an important biological variable in bacterial endophthalmitis. Identification of pathways underlying altered innate immunity and impaired bacterial clearance in aging eyes could provide new insights into the pathobiology of intraocular infections in elderly patients.

Posttraumatic Bacillus cereus Endophthalmitis: Clinical Characteristics and Antibiotic Susceptibilities

Purpose

To report the clinical characteristics, antibiotic susceptibilities, and visual outcomes of patients with posttraumatic endophthalmitis caused by Bacillus cereus.

Methods

In this retrospective, noncomparative case series, the medical records of eyes with culture-proven Bacillus cereus endophthalmitis treated from January 2016 to December 2019 at a referral center were reviewed. Clinical features, antibiotic susceptibilities, and visual outcomes were assessed.

Results

A total of 19 eyes of 19 patients were identified. Three patients progressed to orbital cellulitis. Vitrectomy was performed in 13 eyes, and 11 required silicone oil tamponade. Finally, seven eyes underwent silicone oil removal surgery during follow-up. Only two patients retained a visual acuity better than FC. Four patients underwent evisceration, and three patients had NLP. The cultured Bacillus cereus was sensitive to levofloxacin, ofloxacin, tobramycin, and neomycin at 100%.

Conclusions

The visual outcomes of posttraumatic Bacillus cereus endophthalmitis were generally poor regardless of the prophylactic and therapeutic measures administered. Vitrectomy combined with silicone oil tamponade could help to save the eyeball. Bacillus cereus has a good susceptibility to ofloxacin, levofloxacin, tobramycin, and neomycin; therefore, fluoroquinolones and aminoglycosides can be used to treat Bacillus cereus infection.

Intravitreal Injection and Quantitation of Infection Parameters in a Mouse Model of Bacterial Endophthalmitis

Intraocular bacterial infections are a danger to the vision. Researchers use animal models to investigate the host and bacterial factors and immune response pathways associated with infection to identify viable therapeutic targets and to test drugs to prevent blindness. The intravitreal injection technique is used to inject organisms, drugs, or other substances directly into the vitreous cavity in the posterior segment of the eye. Here, we demonstrated this injection technique to initiate infection in the mouse eye and the technique of quantifying intraocular bacteria. Bacillus cereus was grown in brain heart infusion liquid media for 18 hours and resuspended to a concentration 100 colony forming units (CFU)/0.5 µL. A C57BL/6J mouse was anesthetized using a combination of ketamine and xylazine. Using a picoliter microinjector and glass capillary needles, 0.5 µL of the Bacillus suspension was injected into the mid vitreous of the mouse eye. The contralateral control eye was either injected with sterile media (surgical control) or was not injected (absolute control). At 10 hours post infection, mice were euthanized, and eyes were harvested using sterile surgical tweezers and placed into a tube containing 400 µL sterile PBS and 1 mm sterile glass beads. For ELISAs or myeloperoxidase assays, proteinase inhibitor was added to the tubes. For RNA extraction, the appropriate lysis buffer was added. Eyes were homogenized in a tissue homogenizer for 1-2 minutes. Homogenates were serially diluted 10-fold in PBS and track diluted onto agar plates. The remainder of the homogenates were stored at -80 °C for additional assays. Plates were incubated for 24 hours and CFU per eye was quantified. These techniques result in reproducible infections in mouse eyes and facilitate quantitation of viable bacteria, the host immune response, and omics of host and bacterial gene expression.

The Food Poisoning Toxins of Bacillus cereus

Bacillus cereus is a ubiquitous soil bacterium responsible for two types of food-associated gastrointestinal diseases. While the emetic type, a food intoxication, manifests in nausea and vomiting, food infections with enteropathogenic strains cause diarrhea and abdominal pain. Causative toxins are the cyclic dodecadepsipeptide cereulide, and the proteinaceous enterotoxins hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe) and cytotoxin K (CytK), respectively. This review covers the current knowledge on distribution and genetic organization of the toxin genes, as well as mechanisms of enterotoxin gene regulation and toxin secretion. In this context, the exceptionally high variability of toxin production between single strains is highlighted. In addition, the mode of action of the pore-forming enterotoxins and their effect on target cells is described in detail. The main focus of this review are the two tripartite enterotoxin complexes Hbl and Nhe, but the latest findings on cereulide and CytK are also presented, as well as methods for toxin detection, and the contribution of further putative virulence factors to the diarrheal disease.

Innate Immune Interference Attenuates Inflammation In Bacillus Endophthalmitis

Purpose

To explore the consequences of innate interference on intraocular inflammatory responses during Bacillus endophthalmitis.

Methods

Bacillus endophthalmitis was induced in mice. Innate immune pathway activation was interfered by injecting S layer protein-deficient (∆slpA) B. thuringiensis or by treating wild-type (WT)-infected mice with a TLR2/4 inhibitor (WT+OxPAPC). At 10 hours postinfection, eyes were harvested and RNA was purified. A NanoString murine inflammation panel was used to compare gene expression in WT-infected, WT+OxPAPC, ∆slpA-infected, and uninfected eyes.

Results

In WT-infected eyes, 56% of genes were significantly upregulated compared to uninfected controls. Compared to WT-infected eyes, the expression of 27% and 50% of genes were significantly reduced in WT+OxPAPC and ∆slpA-infected eyes, respectively. Expression of 61 genes that were upregulated in WT-infected eyes was decreased in WT+OxPAPC and ∆slpA-infected eyes. Innate interference resulted in blunted expression of complement factors (C3, Cfb, and C6) and several innate pathway genes (TLRs 2, 4, 6, and 8, MyD88, Nod2, Nlrp3, NF-κB, STAT3, RelA, RelB, and Ptgs2). Innate interference also reduced the expression of several inflammatory cytokines (CSF2, CSF3, IL-6, IL-1β, IL-1α, TNFα, IL-23α, TGFβ1, and IL-12β) and chemokines (CCL2, CCL3, and CXCLs 1, 2, 3, 5, 9, and 10). All of the aforementioned genes were significantly upregulated in WT-infected eyes.

Conclusions

These results suggest that interfering with innate activation significantly reduced the intraocular inflammatory response in Bacillus endophthalmitis. This positive clinical outcome could be a strategy for anti-inflammatory therapy of an infection typically refractory to corticosteroid treatment.

Bacillus cereus: Epidemiology, Virulence Factors, and Host-Pathogen Interactions

The toxin-producing bacterium Bacillus cereus is an important and neglected human pathogen and a common cause of food poisoning. Several toxins have been implicated in disease, including the pore-forming toxins hemolysin BL (HBL) and nonhemolytic enterotoxin (NHE). Recent work revealed that HBL binds to the mammalian surface receptors LITAF and CDIP1 and that both HBL and NHE induce potassium efflux and activate the NLRP3 inflammasome, leading to pyroptosis. These mammalian receptors, in part, contribute to inflammation and pathology. Other putative virulence factors of B. cereus include cytotoxin K, cereulide, metalloproteases, sphingomyelinase, and phospholipases. In this review, we highlight the latest progress in our understanding of B. cereus biology, epidemiology, and pathogenesis, and discuss potential new directions for research in this field.

Glycolytic inhibitor 2-deoxyglucose suppresses inflammatory response in innate immune cells and experimental staphylococcal endophthalmitis

Previously, we have shown that Staphylococcus (S) aureus induces a glycolytic response in retinal residential (microglia) and infiltrated cells (neutrophils and macrophages) during endophthalmitis. In this study, we sought to investigate the physiological role of glycolysis in bacterial endophthalmitis using a glycolytic inhibitor, 2-deoxyglucose (2DG). Our data showed that 2DG treatment attenuated the inflammatory responses of mouse bone marrow-derived macrophages (BMDM) and neutrophils (BMDN) when challenged with either live or heat-killed S. aureus (HKSA). Among the inflammatory mediators, 2DG caused a significant reduction in levels of cytokines (TNF-α, IL-1β, IL-6) and chemokines (CXCL1 and CXCL2). Western blot analysis of 2DG treated cells showed downregulation of bacterial-induced MEK/ERK pathways. In vivo, intravitreal administration of 2DG both pre- and post-bacterial infection resulted in a significant reduction in intraocular inflammation in C57BL/6 mouse eyes and downregulation of ERK phosphorylation in retinal tissue. Collectively, our study demonstrates that 2DG attenuates inflammatory response in bacterial endophthalmitis and cultured innate immune cells via inhibition of ERK signaling. Thus glycolytic inhibitors in combination with antibiotics could mitigate inflammation-mediated tissue damage in ocular infections.