A Comparison of Clinical Features between Community-Associated and Healthcare-Associated Methicillin-Resistant Staphylococcus aureus Keratitis

Epigenetic and Drug Response Modulation of Epigalocaten-In-3-Gallate in Staphylococcus aureus with Divergent Resistance Phenotypes

Healthcare-associated methicillin-resistant Staphylococcus aureus infections represent extremely high morbidity and mortality rates worldwide. We aimed to assess the antimicrobial potential and synergistic effect between Epigalocatenin-3-gallate (EGCG) and different antibiotics in S. aureus strains with divergent resistance phenotypes. EGCG exposure effects in epigenetic and drug resistance key modulators were also evaluated. S. aureus strains (n = 32) were isolated from infected patients in a Lisbon hospital. The identification of the S. aureus resistance phenotype was performed through automatized methods. The antibiotic synergistic assay was performed through disk diffusion according to EUCAST guidelines with co-exposure to EGCG (250, 100, 50 and 25 µg/mL). The bacteria’s molecular profile was assessed through FTIR spectroscopy. The transcriptional expression of OrfX, SpdC and WalKR was performed by using qRT-PCR. FTIR-spectroscopy analysis enabled the clear discrimination of MRSA/MSSA strains and the EGCG exposure effect in the bacteria’s molecular profiles. Divergent resistant phenotypes were associated with divergent transcriptional expression of the epigenetic modulator OrfX, particularly in MRSA strains, as well as the key drug response modulators SpdC and WalKR. These results clearly demonstrate that EGCG exposure alters the expression patterns of key epigenetic and drug response genes with associated divergent-resistant profiles, which supports its potential for antimicrobial treatment and/or therapeutic adjuvant against antibiotic-resistant microorganisms.

Staphylococcus aureus Keratitis in Taiwan: Genotyping, Antibiotic Susceptibility, and Clinical Features

Staphylococcus aureus is an important pathogen for keratitis, a vision-threatening disease. We aimed to investigate the genotyping, antibiotic susceptibility, and clinical features of S. aureus keratitis, and to explore the possible role of Panton–Valentine leucocidin (PVL), a major virulence factor of S. aureus. We recruited 49 patients with culture-proven S. aureus keratitis between 2013 and 2017 at Chang Gung Memorial Hospital, Taiwan. PVL gene, multilocus sequence type (MLST), staphylococcal cassette chromosome mec (SCCmec), and pulsed-field gel electrophoresis (PFGE) were performed. Antibiotic susceptibility was verified using disk diffusion/E test. There were 49 patients with S. aureus keratitis; 17 (34.7%) were caused by methicillin-resistant S. aureus (MRSA) and 9 (18.4%) isolates had PVL genes. The predominant genotyping of MRSA isolates was CC59/PFGE type D/SCCmec VT/PVL (+). All methicillin-sensitive S. aureus (MSSA) and approximately 60% MRSA were susceptible to fluoroquinolones. No significant differences in clinical features, treatments, and visual outcomes were observed between MRSA/MSSA or PVL(+)/PVL(−) groups. In Taiwan, approximately one third of S. aureus keratitis was caused by MRSA, mainly community-associated MRSA. Although MRSA isolates were more resistant than MSSA, clinical characteristics were similar between two groups. Fluoroquinolones could be good empiric antibiotics for S. aureus keratitis.

Methicillin-Resistant Staphylococcus aureus Keratitis: Initial Treatment, Risk Factors, Clinical Features, and Treatment Outcomes

PURPOSE

To analyze the clinical characteristics, management choices, and outcomes of cases of methicillin-resistant Staphylococcus aureus (MRSA) keratitis.

DESIGN

Retrospective interventional case series.

METHODS

Fifty-two culture-proven (52 eyes) cases of MRSA keratitis diagnosed and treated at the University of Pittsburgh Medical Center were identified and reviewed.

RESULTS

The mean age was 66.6 ± 19.2 years with a median follow-up time of 147 days. The most prevalent risk factors included a history of ocular surgery (62.5%), topical corticosteroid use (35.4%), and dry eye syndrome (37.5%). There was a high burden of systemic disease (95.8%). The average presenting logarithm of minimal angle of resolution visual acuity was 1.7 ± 0.8 and the average final logarithm of minimal angle of resolution visual acuity was 1.2 + 1.0. Initial antibiotic treatment varied, with 20.8% receiving moxifloxacin alone, 20.8% receiving fortified cefazolin and fortified tobramycin together, and 12.5% receiving fortified vancomycin and fortified tobramycin, although other antibiotics were used during treatment if warranted. Surgical management was often required as 17.3% of eyes perforated: 13.5% required tarsorrhaphy, 5.8% required penetrating keratoplasty, and 1 eye was enucleated. When patients treated with fourth-generation fluoroquinolones were compared with those treated with fortified vancomycin, no difference in final visual acuity, treatment duration, or need for surgery was found.

CONCLUSION

MRSA causes fulminant keratitis often requiring surgical management with poor visual acuity outcomes. Poor ocular surface, topical corticosteroid use, previous ocular surgery, and/or a high burden of systemic disease were identified as common risk factors. Patients treated with fluoroquinolones in our study had comparable outcomes to those treated with fortified vancomycin; however, those treated with fortified vancomycin tended to have more severe ulcers at presentation.

An Evaluation of Staphylococci from Ocular Surface Infections Treated Empirically with Topical Besifloxacin: Antibiotic Resistance, Molecular Characteristics, and Clinical Outcomes

Introduction

Understanding antibiotic resistance and toxin profiles among staphylococcal isolates in ocular infections can aid in therapeutic management and infection prevention strategies. We evaluated in vitro antibiotic resistance patterns and molecular traits of staphylococci isolated from patients with ocular surface infections. We also report on clinical outcomes for these patients following empirical treatment with topical besifloxacin ophthalmic suspension 0.6%.

Methods

This was a small observational study. Participating investigators from three clinical sites collected an initial ocular culture from the affected eye of patients presenting with ocular surface infections with presumed staphylococcal etiology. Clinical outcome data for patients with confirmed staphylococcal infections were collated later through retrospective review of patient medical records. Staphylococcal species identification in ocular cultures, in vitro antibiotic susceptibility testing, and PCR-based determination of methicillin resistance cassettes and toxin genotypes were conducted at a central laboratory. Isolates were categorized as susceptible or resistant based on systemic breakpoints, where available.

Results

Cultures were collected from 43 patients, and staphylococcal infections were confirmed in 25 patients. Two isolates of Staphylococcus aureus and 27 isolates of Staphylococcus epidermidis were identified. Both S. aureus isolates were methicillin-susceptible, lacked the gene encoding Panton-Valentine leukocidin, and carried few enterotoxin genes. Eight (30%) S. epidermidis were methicillin-resistant (MRSE), and 10 (37%) were ciprofloxacin-resistant. All but two MRSE isolates demonstrated multidrug resistance (MDR), and the staphylococcal cassette chromosome mec (SCCmec) type IVa was detected in five of the eight MRSE isolates. Clinical resolution of the ocular surface infection was reported in all 25 patients following treatment with besifloxacin.

Conclusions

In this study, S. aureus contained few toxins, while SCCmec IVa and MDR was predominant among MRSE from ocular surface infections. Despite significant in vitro fluoroquinolone resistance, there were no cases of treatment failure with topical besifloxacin ophthalmic suspension 0.6%.

Funding

Bausch Health US, LLC.

Comparison of Methicillin-Resistant Staphylococcus aureus Isolates from Cellulitis and from Osteomyelitis in a Taiwan Hospital, 2016-2018

Methicillin-resistant Staphylococcus aureus (MRSA) causes superficial infections such as cellulitis or invasive infections such as osteomyelitis; however, differences in MRSA isolates from cellulitis (CL-MRSA) and from osteomyelitis (OM-MRSA) at the same local area remain largely unknown. A total of 221 MRSA isolates including 106 CL-MRSA strains and 115 OM-MRSA strains were collected at Chang-Gung Memorial Hospital in Taiwan between 2016 and 2018, and their genotypic and phenotypic characteristics were compared. We found that OM-MRSA isolates significantly exhibited higher rates of resistance to multiple antibiotics than CL-MRSA isolates. Genotypically, OM-MRSA isolates had higher proportions of the SCCmec type III, the sequence type ST239, and the spa type t037 than CL-MRSA isolates. Besides the multidrug-resistant lineage ST239-t037-SCCmecIII more prevalent in OM-MRSA, higher antibiotic resistance rates were also observed in several other prevalent lineages in OM-MRSA as compared to the same lineages in CL-MRSA. Furthermore, when prosthetic joint infection (PJI) associated and non-PJI-associated MRSA strains in osteomyelitis were compared, no significant differences were observed in antibiotic resistance rates between the two groups, albeit more diverse genotypes were found in non-PJI-associated MRSA. Our findings therefore suggest that deep infections may allow MRSA to evade antibiotic attack and facilitate the convergent evolution and selection of multidrug-resistant lineages.

Molecular epidemiology and resistance profiles among healthcare- and community-associated Staphylococcus aureus keratitis isolates

PURPOSE

To characterize the molecular, epidemiological, and resistance profiles of methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) keratitis isolates.

PATIENTS AND METHODS

We used a combination of standard microbiological techniques and DNA microarray analysis to characterize the molecular and antibiotic resistance profiles of 75 Staphylococcus aureus keratitis isolates collected over an 11-year period (2006-2016).

RESULTS

Two major USA clonal complexes (CC), CC5 (n=30, 40%) and CC8 (n=28, 37.3%), accounted for 77.3% of the collected S. aureus isolates. USA100, traditionally healthcare associated (n=18/47, 38.3%), and USA300, traditionally community associated (n=12/47, 25.5%), were the dominant MRSA strains. Four (22.2%) of the USA100 MRSA isolates were recovered from patients with no prior healthcare exposure. Eleven (91.7%) of the USA300 isolates were recovered from patients with documented healthcare risk factors. MSSA isolates were polyclonal (n=13). Ninety-three percent of MSSA infections were of healthcare origin. Thirty-seven of 61 (60.6%) healthcare- and 11 of 14 (78.6%) community-associated strains were resistant to three or more antibiotic classes. Sixty-eight percent (n=51) of isolates harbored three of more resistance determinants (genes). The Panton-Valentine Leucocidin gene was detected in 11 (14.7%) of the study isolates. The majority (72.7%) of the strains were members of the USA300 MRSA clone.

CONCLUSION

Clonal complexes CC5 and CC8 were the most frequent clones detected among both the MSSA and the MRSA keratitis isolates. USA100 and USA300 clones were the dominant MRSA genotypes. The USA300 MRSA clone has become a leading cause of healthcare-associated keratitis in South Florida. The USA100 MRSA clone has emerged as an increasing cause of community-associated corneal infections in our outpatient population. This shifting epidemiology coupled with the increasing prevalence of multidrug resistance among both MSSA and MRSA keratitis is a cause of concern.

Risk factors for and molecular characteristics of methicillin-resistant Staphylococcus aureus nasal colonization among healthy children in southern Taiwan, 2005-2010

BACKGROUND/PURPOSE

Nasal colonization of Staphylococcus aureus is a well-defined risk factor for subsequent infection. This study investigated the prevalence of methicillin-resistant S. aureus (MRSA) in southern Taiwan and aimed to identify the host factors for S. aureus colonization and the virulence factor of Panton-Valentine Leukocidin (PVL) genes.

METHODS

In a hospital-based study in Kaohsiung from Oct. 2005 to Dec. 2010, we performed nasal swab in the healthy children aged 2-60 months. We examined the relationship between the demographic characteristics and S. aureus nasal colonization. MRSA isolates were further analyzed for antimicrobial susceptibility and molecular characteristics.

RESULTS

Among 3020 healthy children, 840 (27.8%) children had S. aureus nasal colonization. Of 840 isolates, 246 (29.3%) isolates were MRSA. MRSA colonization was significantly associated with age 2-6 months, day care attendance, and influenza vaccination. Breastfeeding was a protective factor against MRSA colonization. Most MRSA isolates were susceptible to trimethoprim-sulfamethoxazole and doxycycline. Ninety-four percent of MRSA isolates carried either type IV staphylococcal cassette chromosome mec (SCCmec) or SCCmec V_T and 87% belonged to the local community strains, namely clonal complex 59/SCCmec IV or V_T. MRSA isolates with PVL-negative was associated with children with passive smoking.

CONCLUSIONS

Between 2005 and 2010, 27.8% and 8.14% of healthy children in southern Taiwan had nasal carriage of S. aureus and MRSA, respectively. Most MRSA isolates were local community strains. Several demographic factors associated with nasal MRSA colonization were identified.

Detection of methicillin-resistant Staphylococcus aureus (MRSA) in clinical samples of patients with external ocular infection

BACKGROUND AND OBJECTIVES

Staphylococcus aureus is the main Gram-positive bacteria isolated from patients with ocular infections. Herein, we describe the pattern of antibiotic resistance, presence of resistance genes including ermA, ermB, ermC, msrA, mecA and the pvl cytotoxin gene in S. aureus isolates collected from patients with external ocular infection.

MATERIALS AND METHODS

In this study, 8 S. aureus isolates were collected from 81 patients that suffered from eye damage. Antibacterial susceptibility of isolates was determined using the Kirby-Bauer disk diffusion method. Resistance genes including ermA, ermB, ermC, msrA, mecA and the pvl virulence gene were detected by PCR method. Staphylococcal cassette chromosome mec (SCCmec) in MRSA isolates were detected by the multiplex-PCR method.

RESULTS

Three isolates were resistant to cefoxitin which is considered MRSA. The mecA gene was identified in MRSA isolates. SCCmec type IV and the pvl gene were detected in one of the MRSA isolates that was recovered from a diabetic patient.

CONCLUSION

The emergence of S. aureus isolates belonging to SCCmec type IV and pvl gene among patients with ocular infection is very serious; therefore, identify genetic characterization of MRSA isolates for empirical therapy and infection control is very important.

Virulence factor activity relationships (VFARs): a bioinformatics perspective

Virulence factor activity relationships (VFARs) - a concept loosely based on quantitative structure-activity relationships (QSARs) for chemicals was proposed as a predictive tool for ranking risks due to microorganisms relevant to water safety. A rapid increase in sequencing capabilities and bioinformatics tools has significantly increased the potential for VFAR-based analyses. This review summarizes more than 20 bioinformatics databases and tools, developed over the last decade, along with their virulence and antimicrobial resistance prediction capabilities. With the number of bacterial whole genome sequences exceeding 241 000 and metagenomic analysis projects exceeding 13 000 and the ability to add additional genome sequences for few hundred dollars, it is evident that further development of VFARs is not limited by the availability of information at least at the genomic level. However, additional information related to co-occurrence, treatment response, modulation of virulence due to environmental and other factors, and economic impact must be gathered and incorporated in a manner that also addresses the associated uncertainties. Of the bioinformatics tools, a majority are either designed exclusively for virulence/resistance determination or equipped with a dedicated module. The remaining have the potential to be employed for evaluating virulence. This review focusing broadly on omics technologies and tools supports the notion that these tools are now sufficiently developed to allow the application of VFAR approaches combined with additional engineering and economic analyses to rank and prioritize organisms important to a given niche. Knowledge gaps do exist but can be filled with focused experimental and theoretical analyses that were unimaginable a decade ago. Further developments should consider the integration of the measurement of activity, risk, and uncertainty to improve the current capabilities.

Ex vivo rabbit and human corneas as models for bacterial and fungal keratitis

PURPOSE

In the study of microbial keratitis, in vivo animal models often require a large number of animals, and in vitro monolayer cell culture does not maintain the three-dimensional structure of the tissues or cell-to-cell communication of in vivo models. Here, we propose reproducible ex vivo models of single- and dual-infection keratitis as an alternative to in vivo and in vitro models.

METHODS

Excised rabbit and human corneoscleral rims maintained in organ culture were infected using 10⁸ cells of Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans or Fusarium solani. The infection was introduced by wounding with a scalpel and exposing corneas to the microbial suspension or by intrastromal injection. Post-inoculation, corneas were maintained for 24 and 48 h at 37 °C. After incubation, corneas were either homogenised to determine colony-forming units (CFU)/cornea or processed for histological examination using routine staining methods. Single- and mixed-species infections were compared.

RESULTS

We observed a significant increase in CFU after 48 h compared to 24 h with S. aureus and P. aeruginosa. However, no such increase was observed in corneas infected with C. albicans or F. solani. The injection method yielded an approximately two- to 100-fold increase (p < 0.05) in the majority of organisms from infected corneas. Histology of the scalpel-wounded and injection models indicated extensive infiltration of P. aeruginosa throughout the entire cornea, with less infiltration observed for S. aureus, C. albicans and F. solani. The models also supported dual infections.

CONCLUSIONS

Both scalpel wounding and injection methods are suitable for inducing infection of ex vivo rabbit and human cornea models. These simple and reproducible models will be useful as an alternative to in vitro and in vivo models for investigating the detection and treatment of microbial keratitis, particularly when this might be due to two infective organisms.