Fluoroquinolone resistance of Staphylococcus epidermidis isolated from healthy conjunctiva and analysis of their mutations in quinolone-resistance determining region

The pathogenicity and virulence of the opportunistic pathogen Staphylococcus epidermidis

The pervasive presence of Staphylococcus epidermidis and other coagulase-negative staphylococci on the skin and mucous membranes has long underpinned a casual disregard for the infection risk that these organisms pose to vulnerable patients in healthcare settings. Prior to the recognition of biofilm as an important virulence determinant in S. epidermidis, isolation of this microorganism in diagnostic specimens was often overlooked as clinically insignificant with potential delays in diagnosis and onset of appropriate treatment, contributing to the establishment of chronic infection and increased morbidity or mortality. While impressive progress has been made in our understanding of biofilm mechanisms in this important opportunistic pathogen, research into other virulence determinants has lagged S. aureus. In this review, the broader virulence potential of S. epidermidis including biofilm, toxins, proteases, immune evasion strategies and antibiotic resistance mechanisms is surveyed, together with current and future approaches for improved therapeutic interventions.

Repurposing MALDI-TOF MS for effective antibiotic resistance screening in Staphylococcus epidermidis using machine learning

The emergence of Staphylococcus epidermidis as a significant nosocomial pathogen necessitates advancements in more efficient antimicrobial resistance profiling. However, existing culture-based and PCR-based antimicrobial susceptibility testing methods are far too slow or costly. This study combines machine learning with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to develop predictive models for various antibiotics using a comprehensive dataset containing thousands of S. epidermidis isolates. Optimized machine learning models utilized feature selection and achieved high AUROC scores ranging from 0.80 to 0.95 while maintaining AUPRC scores up to 0.97. Shapley Additive exPlanations were employed to analyze relevant features and assess the significance of corresponding protein biomarkers while also verifying that predictive power was derived from the detection of proteins rather than noise. Antimicrobial resistance models were validated externally to evaluate model performance outside the original data collection site. The approaches and findings in this study demonstrate a significant advancement in rapid, cost-effective antimicrobial resistance profiling, offering a promising solution for improving treatments for nosocomial infections and being potentially applicable to other microbial pathogens in the future.

Novel Insights into the Antimicrobial and Antibiofilm Activity of Pyrroloquinoline Quinone (PQQ); In Vitro, In Silico, and Shotgun Proteomic Studies

Microbial infections pose a significant global health threat, affecting millions of individuals and leading to substantial mortality rates. The increasing resistance of microorganisms to conventional treatments requires the development of novel antimicrobial agents. Pyrroloquinoline quinone (PQQ), a natural medicinal drug involved in various cellular processes, holds promise as a potential antimicrobial agent. In the present study, our aim was, for the first time, to explore the antimicrobial activity of PQQ against 29 pathogenic microbes, including 13 fungal strains, 8 Gram-positive bacteria, and 8 Gram-negative bacteria. Our findings revealed potent antifungal properties of PQQ, particularly against Syncephalastrum racemosum, Talaromyces marneffei, Candida lipolytica, and Trichophyton rubrum. The MIC values varied between fungal strains, and T. marneffei exhibited a lower MIC, indicating a greater susceptibility to PQQ. In addition, PQQ exhibited notable antibacterial activity against Gram-positive and -negative bacteria, with a prominent inhibition observed against Staphylococcus epidermidis, Proteus vulgaris, and MRSA strains. Remarkably, PQQ demonstrated considerable biofilm inhibition against the MRSA, S. epidermidis, and P. vulgaris strains. Transmission electron microscopy (TEM) studies revealed that PQQ caused structural damage and disrupted cell metabolism in bacterial cells, leading to aberrant morphology, compromised cell membrane integrity, and leakage of cytoplasmic contents. These findings were further affirmed by shotgun proteomic analysis, which revealed that PQQ targets several important cellular processes in bacteria, including membrane proteins, ATP metabolic processes, DNA repair processes, metal-binding proteins, and stress response. Finally, detailed molecular modeling investigations indicated that PQQ exhibits a substantial binding affinity score for key microbial targets, including the mannoprotein Mp1P, the transcriptional regulator TcaR, and the endonuclease PvuRTs1I. Taken together, our study underscores the effectiveness of PQQ as a broad-spectrum antimicrobial agent capable of combating pathogenic fungi and bacteria, while also inhibiting biofilm formation and targeting several critical biological processes, making it a promising therapeutic option for biofilm-related infections.

The Preventive Effect of Gentamicin in the Irrigating Solution on Endophthalmitis Caused by Methicillin-Resistant Staphylococcus epidermidis After Phacoemulsification with Intraocular Lens Implantation in Rabbits

OBJECTIVE

To analyze the effect of gentamicin in the irrigating solution on endophthalmitis caused by methicillin-resistant Staphylococcus epidermidis after phacoemulsification with intraocular lens implantation.

METHODS

Fifteen rabbits were randomly assigned into three groups. During surgery, group A was irrigated with gentamicin-free solution and injected with 100 μL of normal saline postoperatively, group B was irrigated with 80 μg/mL gentamicin and injected with 100 μl of MRSE suspension, group C was irrigated with gentamicin-free solution and injected with 100 μl of MRSE suspension. At different times, corneal endothelial cell count (CEC), inflammation grading，B-scan ultrasonography and histological examination were analyzed.

RESULTS

No endophthalmitis occurred in groups A and B. Group C developed severe endophthalmitis, with massive inflammatory exudation in the vitreous cavity.

CONCLUSION

Irrigating solution containing gentamicin is favorable to reduce the incidence of MRSE endophthalmitis after phacoemulsification with IOL in rabbits.

The impact of oxygen content on Staphylococcus epidermidis pathogenesis in ocular infection based on clinical characteristics, transcriptome and metabolome analysis

Introduction

This study aims to delineate the etiology and prevalence of isolated pathogens, along with the clinical characteristics of endophthalmitis patients over a 9-year period at hospital in Southwest of China. Additionally, we investigating the metabolic and cellular processes related to environmental factors may offer novel insights into endophthalmitis.

Methods

We analyzed data pertaining to endophthalmitis patients treated at the Affiliated Hospital of Yunnan University from 2015 to 2023. According to our clinical data, we conducted an experiment based on transcriptomics and metabolomics analysis to verify whether environmental factors affect behavior of S. epidermidis by culturating S. epidermidis under oxic and microoxic condition.

Results

In this study, 2,712 fungi or bacteria strains have been analyzed, gram-positive bacteria constituted 65.08%, with S. epidermidis being the most predominant species (25.55%). Ophthalmic trauma was the primary pathogenic factor for S. epidermidis ocular infections. Regarding fluoroquinolones, S. epidermidis exhibited the higher resistance rate to levofloxacin than moxifloxacin. Moreover, our investigation revealed that S. epidermidis in microoxic environment increase in energy metabolism, amino acid metabolism, and membrane transport.

Conclusion

Our findings underscore the significance of S. epidermidis as a crucial pathogen responsible for infectious endophthalmitis. It is crucial to exercise vigilance when considering Levofloxacin as the first-line drug for empiric endophthalmitis treatment. The metabolites alteration observed during the commensal-to-pathogen conversion under microoxic condition serve as a pivotal environmental signal contributing to S. epidermidis metabolism remodeling, toward more pathogenic state.

Molecular and Phenotypic Characterization of Ocular Methicillin-Resistant Staphylococcus epidermidis Isolates in Taiwan

Purpose

Staphylococcus epidermidis, a commensal, has emerged as an important opportunistic pathogen, particularly methicillin-resistant S. epidermidis (MRSE). The mechanism behind this transformation remains unclear. This study aimed to investigate the molecular and phenotypic characteristics of MRSE isolated from healthy conjunctiva and ocular infections.

Methods

We collected MRSE isolates from two groups: healthy conjunctiva from patients undergoing cataract surgeries and ocular infections at our hospital. Genotypic analysis included pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec), and biofilm-related genes (icaA, aap, and bhp). Additionally, phenotypic data on biofilm production and antibiotic susceptibility were recorded.

Results

A total of 86 isolates, including 42 from healthy conjunctiva and 44 from ocular infections, were analyzed. MLST identified 21 sequence types (STs), with ST59 being the most frequent (n = 33, 39.5%), followed by ST130 (n = 10, 11.6%), ST57 (n = 6, 7.0%), and ST2 (n = 6, 7.0%). All isolates were categorized in 23 PFGE types, and SCCmec IV was the most prevalent SCCmec type (n = 52, 60.5%). The two sources of isolates exhibited overlapping molecular types and phenotypic traits, although the ocular infection isolates exhibited significantly higher multidrug resistance compared to healthy conjunctiva isolates (P = 0.032). When contrasting ST59 with non-ST59, ST59 displayed a significantly higher presence of aap (100%) and bhp (69.7%) while lacking icaA (0%). ST59 also showed lower susceptibility to fluoroquinolones compared to non-ST59 (42.4%-54.5% vs. 75.5%-83.0%; P < 0.01).

Conclusions

MRSE isolates from healthy conjunctiva and ocular infections demonstrated a degree of resemblance. Specific strains, notably ST59, exhibited distinctive characterizations.

Delayed-onset micrococcus luteus-induced postoperative endophthalmitis several months after cataract surgery: A case report

BACKGROUND

Micrococcus luteus (M. luteus)-induced endophthalmitis is very rare and and may present as either acute or chronic postoperative endophthalmitis. The aim of this study was to report a case of delayed-onset M. luteus-induced endophthalmitis that occurred several months after cataract surgery.

CASE SUMMARY

A 78-year-old man presented with decreased vision, pain and redness in the right eye that had begun 3 days prior. He had undergone cataract surgery 4 mo prior. Visual acuity was counting fingers; slit-lamp examination revealed conjunctival injection, posterior corneal precipitates, anterior chamber inflammation (cell 4+), and hypopyon. Fundus examination revealed moderate vitreous haze. Urgent vitrectomy was performed for suspected infectious endophthalmitis, followed by vitreous irrigation with injections of antibiotics. On the postoperative day 1, anterior chamber cell decreased to 2+ and hypopyon was not observed on slit lamp examination. Six days postoperatively, the patient had recurrent eye pain, and the anterior chamber cell grade increased to 4+; hypopyon recurred in the anterior chamber, and whitish plaque was observed in the lens capsule. Therefore, the patient underwent intraocular lens (IOL) and lens capsule removal, followed by vitreous irrigation, antibiotics injection, and vitrectomy. M. luteus was identified from a lens capsule culture.

CONCLUSION

In cases of delayed-onset M. luteus-induced endophthalmitis, early vitrectomy and removal of the IOL and lens capsule may be necessary.

Antimicrobial resistance profiles and clonal diversity of Staphylococcus epidermidis isolates from pig farms, slaughterhouses, and retail pork

Livestock-associated coagulase-negative staphylococci (CoNS), such as Staphylococcus (S.) epidermidis, have emerged as a significant reservoir of antimicrobial resistance (AMR). In the current study, the AMR profiles and genetic diversity of S. epidermidis isolates obtained from pig farms, slaughterhouses, and retail pork were analyzed. A total of 89 S. epidermidis isolates, comprising 22 methicillin-resistant (MRSE) and 67 methicillin-susceptible S. epidermidis (MSSE) isolates, were assessed to determine (i) the clonal lineages of the isolates [multilocus sequence (MLST), agr, and staphylococcal cassette chromosome mec (SCCmec) types], (ii) the profiles of AMR phenotypes, and (iii) the carriage of genetic factors associated with major AMR phenotypes and zinc chloride resistance. Two dominant clonal lineages of S. epidermidis, ST100 and ST570, were observed on pig farms, especially in healthy pigs. In addition, potential transmission of pig-associated ST100 MRSE-SCCmec V and ST100 MSSE to farm workers was identified. The high prevalence of ST100 and ST570 isolates in pig farms was associated with high levels of AMR and zinc chloride resistance. In relation to resistance phenotypes, higher carriage rates of resistance genes, such as β-lactams (mecA), phenicols (fexA), and tetracyclines [tet(K), tet(L), tet(S), tet(M), and tet(O)], were identified in pig farm-associated isolates. Furthermore, cfr-mediated linezolid resistance was detected in 14 MSSE isolates from pig farms. This study is the first to provide important insights into the clonal structures and AMR profiles of S. epidermidis isolates collected from healthy pigs, carcass/pork samples, and human workers in Korea.

Drug Susceptibility Test and Analysis of Quinolone Resistance Genes in Mycoplasma hyopneumoniae Vaccine Strains and Field Isolates from China

Background

Enrofloxacin is a commonly used animal-specific drug in veterinary clinics. However, this drug has no epidemiological cutoff values (ECVs/ECOFFs) for Mycoplasma hyopneumoniae in CLSI and EUCAST. Defining the epidemiological cutoff values (ECOFFs) of enrofloxacine to Mycoplasma hyopneumoniae (M. hyo) can inform an early detection of bacterial resistance to better manage the resistance prevention and also help in establishing drug resistance breakpoints;.

Methods

We determined the susceptibility breakpoint of M. hyo to enrofloxacin by the American Clinical and Laboratory Standards Institute (CLSI) standard method based on the PCR of vaccine strains and wild strains drug resistance genes;.

Results

Eighty strains of M.hyo isolated in Tibet were moderately sensitive (S) to tetracycline, florfenicol, spiramycin, erythromycin thiocyanate, tilmicosin, tiamulin, lincomycin, clindamycin, ofloxacin, enrofloxacin, gentamicin, amikacin, with MICs below 0.5 μg/mL. For vaccine 168L, RM48, and J strains, the susceptibility to the same antibacterial drugs was lower compared to the Tibetan isolates. The resistance of J strain to erythromycin thiocyanate was confirmed. Gene point mutation was confirmed in Quinolone Resistance Determining Regions (QRDR) of HNSH strain Topoisomerase IV subunit A, this finding is compared with the sequencing results of 168L strain reference sequence (Accession number: CP003131). Arg-Lys amino acid mutation (G921A and G1179A) was confirmed for the increase of MIC value involved in M.hyo to enrofloxacine;.

Conclusion

The cut-off value of M.hyo to enrofloxacin was set as 1 μg/mLby ECOFFinder XL 2010 V2.1.

Antimicrobial resistance and molecular typing of Salmonella in the chicken production chain in Hubei Province, China

Salmonella is a significant foodborne zoonotic pathogen that endangers both human and animal health. The goal of this research is to gain a preliminary understanding of Salmonella contamination and antimicrobial resistance in the chicken production chain in Hubei Province, China. 1149 animal and environmental samples were collected from chicken farms, slaughterhouses, and retail markets in six cities across Hubei Province in China from 2019 to 2020, yielding Salmonella isolation rates of 4.68% (28/598), 12.21% (47/385), and 9.64% (16/166), respectively. Seventeen distinct serotypes were detected among 53 non-clonal Salmonella strains, of which Meleagridis (26.42%, 14/53) was the dominant serotype. Almost half of the strains (49.06%, 26/53) were multi-drug resistant (MDR). Whole-genome sequencing (WGS) showed that 10 resistance genes (tetA, blaTEM, parC, qnrS1, floR, aac(6′)-Iy, aph(6)-Id, aph(3″)-Ib, aac(6′)-Iaa and sul2) and 7 categories of virulence genes were present in all three links in 22 non-clonal dominant serotype strains. It was shown that Salmonella in the chicken production chain in Hubei Province had a high resistance rate to Tetracycline (TET, 73.58%), Ofloxacin (OFL, 69.81%), Florfenicol (FFC, 60.38%) and Ampicillin (AMP, 39.62%) which was consistent with the widespread use of these drugs in the husbandry industry in China. Salmonella ST types determined by MLST and serotypes determined by WGS had a one-to-one correlation. Minimum spanning tree analysis revealed that there was cross contamination of Salmonella in farms and slaughterhouses, slaughterhouses and markets, animal samples and environmental samples. This work provides useful information for the prevention and control of contamination and antimicrobial resistance of Salmonella in the chicken production chain, as well as demonstrating the dependable role of WGS in Salmonella molecular typing.