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Baldwin G, Vingopoulos F, Garg I, Moon JY, Zeng R, Cui Y, Katz R, Le R, Lu ES, Sayah DN, Hassan Z, Kim LA, Elze T, Husain D, Miller JB.
Structure-function associations between contrast sensitivity and widefield swept-source optical coherence tomography angiography in diabetic macular edema. Graefes Arch Clin Exp Ophthalmol 2023;261(11):3113-3124.
AbstractPURPOSE: To evaluate the relationship between contrast sensitivity (CS) and widefield swept-source optical coherence tomography angiography (WF SS-OCTA) vascular metrics in diabetic macular edema (DME) was the purpose. METHODS: This prospectively enrolled cross-sectional observational study included 61 eyes of 48 patients that were tested with the quantitative CS function (qCSF) test on the same day as imaging with WF SS-OCTA (PLEX® Elite 9000, Carl Zeiss Meditec) 3 × 3, 6 × 6, and 12 × 12 mm scans. Outcomes included visual acuity (VA) and multiple qCSF metrics. Vascular metrics included vessel density (VD) and vessel skeletonized density (VSD) in the superficial (SCP) and deep capillary plexus (DCP) and whole retina (WR) and foveal avascular zone (FAZ) parameters. Mixed effects multivariable linear regression models controlling for age, lens status, and diabetic retinopathy stage were performed. Standardized beta coefficients were calculated by refitting the standardized data. RESULTS: SS-OCTA metrics had a significant association with CS and VA. The effect size of OCTA metrics was larger on CS compared to VA. For example, the standardized beta coefficients for VSD and CS at 3 cpd (βSCP = 0.76, βDCP = 0.71, βWR = 0.72, p < 0.001) were larger than those for VA (βSCP = - 0.55, p < 0.001; βDCP = - 0.43, p = 0.004; βWR = - 0.50, p < 0.001). On 6 × 6 mm images, AULCSF, CS at 3 cpd, and CS at 6 cpd were significantly associated with VD and VSD in all three slab types (SCP, DCP, and WR), while VA was not. CONCLUSION: Structure-function associations in patients with DME leveraging the qCSF device suggest microvascular changes on WF SS-OCTA are associated with larger changes in contrast sensitivity than VA.
Baldwin G, Gaier ED, Hennein L.
Isolated Sixth Nerve Palsy and COVID-19: Response. J Neuroophthalmol 2024;
Ballios BG, Pierce EA, Huckfeldt RM.
Gene editing technology: Towards precision medicine in inherited retinal diseases. Semin Ophthalmol 2021;36(4):176-184.
AbstractPurpose: To review preclinical and clinical advances in gene therapy, with a focus on gene editing technologies, and application to inherited retinal disease.Methods: A narrative overview of the literature, summarizing the state-of-the-art in clinical gene therapy for inherited retinal disease, as well as the science and application of new gene editing technology.Results: The last three years has seen the first FDA approval of an in vivo gene replacement therapy for a hereditary blinding eye disease and, recently, the first clinical application of an in vivo gene editing technique. Limitations and challenges in this evolving field are highlighted, as well as new technologies developed to address the multitude of molecular mechanisms of disease.Conclusion: Genetic therapy for the treatment of inherited retinal disease is a rapidly expanding area of ophthalmology. New technologies have revolutionized the field of genome engineering and rekindled an interest in precision medicines for these conditions.
Baniasadi N, Wang M, Wang H, Mahd M, Elze T.
Associations between Optic Nerve Head-Related Anatomical Parameters and Refractive Error over the Full Range of Glaucoma Severity. Transl Vis Sci Technol 2017;6(4):9.
AbstractPURPOSE: To evaluate the associations between optic disc (OD)-related anatomical parameters (interartery angle [IAA] between superior and inferior temporal retinal arteries, OD tilt [TL], rotation [ROT], and torsion [TO], OD surface curvature [CUR], and central retinal vessel trunk entry point location [CRVTL] on OD) and the spherical equivalent of refractive error (SE), and to assess the impact of glaucoma severity on these relationships. METHODS: Cirrus optical coherence tomography (OCT) fundus images and 24-2 visual fields of 438 patients were included. Ellipses were fitted to OD borders. IAA was calculated between marked retinal artery locations on a circle around OD. Blood vessel entry point on OD was marked to locate CRVTL. TL was measured as the angle between the lines fitted to OD clinical boundary and the Bruch's membrane edges on the horizontal B-scans. Ellipse rotation relative to the vertical axis defined ROT. Angle between the long axis of OD and the interartery line defined TO. CUR was determined by the inner limiting membrane on the horizontal B-scans. Linear regression models evaluated by Bayes Factors (BF) were used to determine the covariance structure between the parameters and SE as well as possible impacts of mean deviation (MD). RESULTS: Our results showed that CRVTL had the strongest relationship with SE, followed by ROT, TL, and IAA (BFs: 3.59 × 10(7), 2645, 1126, and 248, respectively). MD did not significantly modulate the relationship between ONH parameters and SE. CONCLUSION: Our results suggest that SE should be considered when interpreting the OD and its circumpapillary region for diagnostic purposes. TRANSLATIONAL RELEVANCE: The reported relationships between OD-related parameters and ametropia may help to decrease false-positive clinical diagnoses of optic neuropathies.
Baniasadi N, Paschalis EI, Haghzadeh M, Ojha P, Elze T, Mahd M, Chen TC.
Patterns of Retinal Nerve Fiber Layer Loss in Different Subtypes of Open Angle Glaucoma Using Spectral Domain Optical Coherence Tomography. J Glaucoma 2016;25(10):865-872.
AbstractPURPOSE OF THE STUDY: The purpose of the study was to determine whether there are different patterns of retinal nerve fiber layer (RNFL) thinning as measured by spectral domain optical coherence tomography (SD-OCT) for 4 subtypes of open angle glaucoma (OAG): primary OAG (POAG), normal tension glaucoma (NTG), pseudoexfoliation glaucoma (PXG), and pigmentary glaucoma (PDG) and to compare them with normal controls. MATERIALS AND METHODS: SD-OCT RNFL thickness values were measured for 4 quadrants and for 4 sectors (ie, superior-nasal, superior-temporal, inferior-nasal, and inferior-temporal). Differences in RNFL thickness values between groups were analyzed using analysis of variance. Paired t tests were used for quadrant comparisons. RESULTS: Two hundred eighty-five participants (102 POAG patients, 33 with NTG, 48 with PXG, 13 with PDG, and 89 normal patients) were included in this study. All 4 subtypes of OAG showed significant RNFL thinning in the superior, inferior, and nasal quadrants as well as the superior-temporal and inferior-temporal sectors (all P-values <0.0001) compared with normals. POAG and NTG patients had greater RNFL thinning inferiorly and inferior-temporally than superiorly (P-values: 0.002 to 0.018 and 0.006, respectively) compared with PXG patients. In contrast, PDG patients had greater RNFL thinning superiorly and superior-nasally than inferiorly compared with other OAG subtypes (ie, POAG, NTG, PXG groups, with P-values: 0.009, 0.003, 0.009, respectively). Of the 4 OAG subtypes, PXG patients exhibited the greatest degree of inter-eye RNFL asymmetry. CONCLUSIONS: This study suggests that SD-OCT may be able to detect significant differences in patterns of RNFL thinning for different subtypes of OAG.
Banks C, Scangas GA, Husain Q, Hatton MP, Fullerton Z, Metson R.
The role of routine nasolacrimal sac biopsy during endoscopic dacryocystorhinostomy. Laryngoscope 2020;130(3):584-589.
AbstractOBJECTIVES/HYPOTHESIS: Most patients who undergo endoscopic dacryocystorhinostomy (DCR) have a diagnosis of idiopathic nasolacrimal duct obstruction. The purpose of this study was to examine the impact of routine biopsy of the lacrimal sac performed at time of DCR on subsequent patient diagnosis and treatment. STUDY DESIGN: Retrospective review. METHODS: The histopathology of nasolacrimal specimens (n = 769), obtained from 654 consecutive patients undergoing endoscopic DCR by a single surgeon over a 30-year period, were reviewed. Specific focus included the identification of unanticipated pathologic findings as they related to pertinent patient demographics, clinical presentation, radiologic findings, and intraoperative observations. RESULTS: The study population was 69.6% female, with an average age of 56.1 ± 18.2 years. Pathological findings of tissue from the nasolacrimal sac, which was routinely sampled in all cases, showed inflammation (n = 566 [73.6%]), normal histology (n = 147 [19.1%]), granulomas (n = 8 [1.0%]), and neoplastic process (n = 7 [0.9%]). Patient history, preoperative CT scan, and/or intraoperative findings alerted the surgeon to the possibility of an unusual diagnosis in 12 of the 15 patients. An unsuspected neoplastic or granulomatous cause of lacrimal obstruction was identified on intraoperative biopsy in three patients (0.46%). CONCLUSIONS: Although neoplastic and granulomatous diseases are relatively rare causes of lacrimal obstruction necessitating DCR surgery, they may be identified by through patient evaluation in most cases and by routine intraoperative biopsy of the lacrimal sac in all cases. LEVEL OF EVIDENCE: 4 Laryngoscope, 130:584-589, 2020.
Banks C, Husain Q, Sacks R, Freitag SK, Bleier BS.
Development of a Modular Cadaveric Endoscopic Orbital Surgery Model. Am J Rhinol Allergy 2020;34(2):183-188.
Bannai D, Adhan I, Katz R, Kim LA, Keshavan M, Miller JB, Lizano P.
Quantifying Retinal Microvascular Morphology in Schizophrenia Using Swept-Source Optical Coherence Tomography Angiography. Schizophr Bull 2022;48(1):80-89.
AbstractBACKGROUND: Retinovascular changes are reported on fundus imaging in schizophrenia (SZ). This is the first study to use swept-source optical coherence tomography angiography (OCT-A) to comprehensively examine retinal microvascular changes in SZ. METHODS: This study included 30 patients with SZ/schizoaffective disorder (8 early and 15 chronic) and 22 healthy controls (HCs). All assessments were performed at Beth Israel Deaconess Medical Center and Massachusetts Eye and Ear. All participants underwent swept-source OCT-A of right (oculus dextrus [OD]) and left (oculus sinister [OS]) eye, clinical, and cognitive assessments. Macular OCT-A images (6 × 6 mm) were collected with the DRI Topcon Triton for superficial, deep, and choriocapillaris vascular regions. Microvasculature was quantified using vessel density (VD), skeletonized vessel density (SVD), fractal dimension (FD), and vessel diameter index (VDI). RESULTS: Twenty-one HCs and 26 SZ subjects were included. Compared to HCs, SZ patients demonstrated higher overall OD superficial SVD, OD choriocapillaris VD, and OD choriocapillaris SVD, which were primarily observed in the central, central and outer superior, and central and outer inferior/superior, respectively. Early-course SZ subjects had significantly higher OD superficial VD, OD choriocapillaris SVD, and OD choriocapillaris FD compared to matched HCs. Higher bilateral (OU) superficial VD correlated with lower Positive and Negative Syndrome Scale (PANSS) positive scores, and higher OU deep VDI was associated with higher PANSS negative scores. CONCLUSIONS AND RELEVANCE: These results suggest the presence of microvascular dysfunction associated with early-stage SZ. Clinical associations with microvascular alterations further implicate this hypothesis, with higher measures being associated with worse symptom severity and functioning in early stages and with lower symptom severity and better functioning in later stages.
Bansal AK, Madhavan R, Agam Y, Golby A, Madsen JR, Kreiman G.
Neural dynamics underlying target detection in the human brain. J Neurosci 2014;34(8):3042-55.
AbstractSensory signals must be interpreted in the context of goals and tasks. To detect a target in an image, the brain compares input signals and goals to elicit the correct behavior. We examined how target detection modulates visual recognition signals by recording intracranial field potential responses from 776 electrodes in 10 epileptic human subjects. We observed reliable differences in the physiological responses to stimuli when a cued target was present versus absent. Goal-related modulation was particularly strong in the inferior temporal and fusiform gyri, two areas important for object recognition. Target modulation started after 250 ms post stimulus, considerably after the onset of visual recognition signals. While broadband signals exhibited increased or decreased power, gamma frequency power showed predominantly increases during target presence. These observations support models where task goals interact with sensory inputs via top-down signals that influence the highest echelons of visual processing after the onset of selective responses.
Bansal AK, Singer JM, Anderson WS, Golby A, Madsen JR, Kreiman G.
Temporal stability of visually selective responses in intracranial field potentials recorded from human occipital and temporal lobes. J Neurophysiol 2012;108(11):3073-86.
AbstractThe cerebral cortex needs to maintain information for long time periods while at the same time being capable of learning and adapting to changes. The degree of stability of physiological signals in the human brain in response to external stimuli over temporal scales spanning hours to days remains unclear. Here, we quantitatively assessed the stability across sessions of visually selective intracranial field potentials (IFPs) elicited by brief flashes of visual stimuli presented to 27 subjects. The interval between sessions ranged from hours to multiple days. We considered electrodes that showed robust visual selectivity to different shapes; these electrodes were typically located in the inferior occipital gyrus, the inferior temporal cortex, and the fusiform gyrus. We found that IFP responses showed a strong degree of stability across sessions. This stability was evident in averaged responses as well as single-trial decoding analyses, at the image exemplar level as well as at the category level, across different parts of visual cortex, and for three different visual recognition tasks. These results establish a quantitative evaluation of the degree of stationarity of visually selective IFP responses within and across sessions and provide a baseline for studies of cortical plasticity and for the development of brain-machine interfaces.
Banskota S, Raguram A, Suh S, Du SW, Davis JR, Choi EH, Wang X, Nielsen SC, Newby GA, Randolph PB, Osborn MJ, Musunuru K, Palczewski K, Liu DR.
Engineered virus-like particles for efficient in vivo delivery of therapeutic proteins. Cell 2022;185(2):250-265.e16.
AbstractMethods to deliver gene editing agents in vivo as ribonucleoproteins could offer safety advantages over nucleic acid delivery approaches. We report the development and application of engineered DNA-free virus-like particles (eVLPs) that efficiently package and deliver base editor or Cas9 ribonucleoproteins. By engineering VLPs to overcome cargo packaging, release, and localization bottlenecks, we developed fourth-generation eVLPs that mediate efficient base editing in several primary mouse and human cell types. Using different glycoproteins in eVLPs alters their cellular tropism. Single injections of eVLPs into mice support therapeutic levels of base editing in multiple tissues, reducing serum Pcsk9 levels 78% following 63% liver editing, and partially restoring visual function in a mouse model of genetic blindness. In vitro and in vivo off-target editing from eVLPs was virtually undetected, an improvement over AAV or plasmid delivery. These results establish eVLPs as promising vehicles for therapeutic macromolecule delivery that combine key advantages of both viral and nonviral delivery.
Bao YK, Xu BY, Friedman DS, Cho A, Foster PJ, Jiang Y, Porporato N, Pardeshi AA, Jiang Y, Munoz B, Aung T, He M.
Biometric Risk Factors for Angle Closure Progression After Laser Peripheral Iridotomy. JAMA Ophthalmol 2023;141(6):516-524.
AbstractIMPORTANCE: Laser peripheral iridotomy (LPI) is the most common primary treatment for primary angle closure disease (PACD). However, there are sparse data guiding the longitudinal care of PAC suspect (PACS) eyes after LPI. OBJECTIVE: To elucidate the anatomic effects of LPI that are associated with a protective outcome against progression from PACS to PAC and acute angle closure (AAC) and to identify biometric factors that predict progression after LPI. DESIGN, SETTING, AND PARTICIPANTS: This was a retrospective analysis of data from the Zhongshan Angle Closure Prevention (ZAP) trial, a study of mainland Chinese people aged 50 to 70 years with bilateral PACS who received LPI in 1 randomly selected eye. Gonioscopy and anterior-segment optical coherence tomography (AS-OCT) imaging were performed 2 weeks after LPI. Progression was defined as the development of PAC or an acute angle closure (AAC) attack. Cohort A included a random mix of treated and untreated eyes, and cohort B included only eyes treated with LPI. Univariable and multivariable Cox regression models were developed to assess biometric risk factors for progression in cohorts A and B. Data were analyzed from January 4 to December 22, 2022. MAIN OUTCOME AND MEASURE: Six-year progression to PAC or AAC. RESULTS: Cohort A included 878 eyes from 878 participants (mean [SD] age, 58.9 [5.0] years; 726 female [82.7%]) of whom 44 experienced progressive disease. In a multivariable analysis, treatment (hazard ratio [HR], 0.67; 95% CI, 0.34-1.33; P = .25) was no longer associated with progression after adjusting for age and trabecular iris space area at 500 μm (TISA at 500 μm) at the 2-week visit. Cohort B included 869 treated eyes from 869 participants (mean [SD] age, 58.9 [5.0] years; 717 female [82.5%]) of whom 19 experienced progressive disease. In multivariable analysis, TISA at 500 μm (HR, 1.33 per 0.01 mm2 smaller; 95% CI, 1.12-1.56; P = .001) and cumulative gonioscopy score (HR, 1.25 per grade smaller; 95% CI, 1.03-1.52; P = .02) at the 2-week visit were associated with progression. Persistent angle narrowing on AS-OCT (TISA at 500 μm ≤0.05 mm2; HR, 9.41; 95% CI, 3.39-26.08; P <.001) or gonioscopy (cumulative score ≤6; HR, 2.80; 95% CI, 1.13-6.93; P =.04) conferred higher risk of progression. CONCLUSIONS AND RELEVANCE: Study results suggest that persistent angle narrowing detected by AS-OCT or cumulative gonioscopy score was predictive of disease progression in PACS eyes after LPI. These findings suggest that AS-OCT and gonioscopy may be performed to identify patients at high risk of developing angle closure who may benefit from closer monitoring despite patent LPI.
Barham R, Rami HE, Sun JK, Silva PS.
Evidence-Based Treatment of Diabetic Macular Edema. Semin Ophthalmol 2017;32(1):56-66.
AbstractDiabetes mellitus is a chronic disease that affects 415 million people worldwide. Despite treatment advances, diabetic eye disease remains a leading cause of vision loss worldwide. Diabetic macular edema (DME) is a common cause of vision loss in diabetic patients. The pathophysiology is complex and involves multiple pathways that ultimately lead to central retinal thickening and, if untreated, visual loss. First-line treatment of DME has evolved from focal/grid laser established by the Early Treatment of Diabetic Retinopathy Study (ETDRS) to intravitreous pharmacologic therapy. Landmark prospective clinical trials examining the effect of intravitreous injections of vascular endothelial growth factor (VEGF) inhibitors in the treatment of DME have demonstrated improved visual outcomes over focal grid laser. This review focuses on the scientific evidence treatment of DME, disease pathophysiology, clinical disease course, current treatment standards, and emerging novel therapeutic approaches.
Barhoumi A, Salvador-Culla B, Kohane DS.
Nonlinear Optics: NIR-Triggered Drug Delivery by Collagen-Mediated Second Harmonic Generation (Adv. Healthcare Mater. 8/2015). Adv Healthc Mater 2015;4(8):1108.
AbstractIn the study presented by D. S. Kohane and co-workers on page 1159, fluorescein molecules are initially bound to collagen fibers through UV-sensitive bonds. Collagen fibers are exposed to NIR light, which is upconverted to UV light through second harmonic generation. The UV-sensitive bonds absorb the upconverted UV light and undergo an irreversible cleavage releasing the fluorescein molecules.
Barhoumi A, Salvador-Culla B, Kohane DS.
NIR-Triggered Drug Delivery by Collagen-Mediated Second Harmonic Generation. Adv Healthc Mater 2015;4(8):1159-63.
AbstractSecond harmonic generation is a process through which nonlinear materials such as collagen can absorb two photons and scatter one with twice the energy. Collagen upconverts 730 nm (near-IR) to 365 nm (UV) through second harmonic generation, which cleaves a molecule bound to collagen via a UV-sensitive linker.
Baris HN, Chan W-M, Andrews C, Behar DM, Donovan DJ, Morton CC, Ranells J, Pal T, Ligon AH, Engle EC.
Complex cytogenetic rearrangements at the DURS1 locus in syndromic Duane retraction syndrome. Clin Case Rep 2013;1(1)
Barrantes PC, Zhou P, MacDonald SM, Ioakeim-Ioannidou M, Lee NG.
Granular Cell Tumor of the Orbit: Review of the Literature and a Proposed Treatment Modality. Ophthalmic Plast Reconstr Surg 2022;38(2):122-131.
AbstractPURPOSE: To document a unique case of granular cell tumor of the orbit, located lateral to and abutting the optic nerve, that benefited from treatment with proton beam irradiation, with a comprehensive review of the literature on granular cell tumor of the orbit. METHODS: Clinicopathologic case report with detailed imaging features and histopathologic and immunohistochemical evaluation for cytoplasmic tumor biomarkers differentiating granular cell tumor (GCT) from it mimicking lesions with relevant literature citations. The authors reviewed 20 cases of orbital GCT from 2011 to 2020 in addition to 40 cases from 1948 to 2011 and included a summary of imaging and clinical features, outcomes, and recommended treatment modalities. RESULTS: A 32-year-old man with 1-year history of left retrobulbar pain and diplopia on lateral gaze, intermittent left eyelid swelling, and a tonic left pupil was found to have a fusiform intraconal mass extending toward the orbital apex and abutting the optic nerve. Histopathologic and immunohistochemical investigations collectively supplied data diagnostic of a GCT with an initial low proliferation rate. GCT is a soft tissue neoplasm that originates in the nervous system and can occur anywhere in the body. This enhancing tumor is isointense to gray matter on T1-weighted MRI, hypointense on T2. After an incisional biopsy, the patient's symptoms persisted, and follow-up imaging several months later revealed further growth of the mass. The impossibility of complete surgical removal prompted the decision to treat with proton beam radiation therapy, which resulted in substantial regression in the size of the residual tumor. Most frequently involving the inferior rectus muscle (42%), orbital GCT is usually benign with only 4 reported cases of malignant orbital GCT (7%). Wide surgical resection with complete removal is usually curative for benign orbital GCT, and proton beam radiation therapy can aid in tumor shrinkage. CONCLUSIONS: GCT should be considered in the differential diagnosis when encountering patients with mass lesions involving the extraocular muscles, peripheral nerves, or less frequently, the optic nerve or orbital apex. Immunohistochemical analysis of biopsied tissue is required for the definitive diagnosis of GCT. Consideration of adjuvant therapies such as proton beam radiation therapy may be appropriate in cases of incomplete surgical resection of benign GCT. Proton beam radiation therapy can be an excellent therapeutic option for symptomatic relief and residual tumor size reduction with an acceptable toxicity profile.
Barrero-Castillero A, Corwin BK, VanderVeen DK, Wang JC.
Workforce Shortage for Retinopathy of Prematurity Care and Emerging Role of Telehealth and Artificial Intelligence. Pediatr Clin North Am 2020;67(4):725-733.
AbstractRetinopathy of prematurity (ROP) is the leading cause of childhood blindness in very-low-birthweight and very preterm infants in the United States. With improved survival of smaller babies, more infants are at risk for ROP, yet there is an increasing shortage of providers to screen and treat ROP. Through a literature review of new and emerging technologies, screening criteria, and analysis of a national survey of pediatric ophthalmologists and retinal specialists, the authors found the shortage of ophthalmology workforce for ROP a serious and growing concern. When used appropriately, emerging technologies have the potential to mitigate gaps in the ROP workforce.
Barrett AM, Houston KE.
Update on the Clinical Approach to Spatial Neglect. Curr Neurol Neurosci Rep 2019;19(5):25.
AbstractPURPOSE OF REVIEW: Spatial neglect is asymmetric orienting and action after a brain lesion, causing functional disability. It is common after a stroke; however, it is vastly underdocumented and undertreated. This article addresses the implementation gap in identifying and treating spatial neglect, to reduce disability and improve healthcare costs and burden. RECENT FINDINGS: Professional organizations published recommendations to implement spatial neglect care. Physicians can lead an interdisciplinary team: functionally relevant spatial neglect assessment, evidence-based spatial retraining, and integrated spatial and vision interventions can optimize outcomes. Research also strongly suggests spatial neglect adversely affects motor systems. Spatial neglect therapy might thus "kick-start" rehabilitation and improve paralysis recovery. Clinicians can implement new techniques to detect spatial neglect and lead interdisciplinary teams to promote better, integrated spatial neglect care. Future studies of brain imaging biomarkers to detect spatial neglect, and real-world applicability of prism adaptation treatment, are needed.
Barros EM, Martin MJ, Selleck EM, Lebreton F, Sampaio JLM, Gilmore MS.
Daptomycin Resistance and Tolerance Due to Loss of Function in Staphylococcus aureus dsp1 and asp23. Antimicrob Agents Chemother 2019;63(1)
AbstractLipopeptide daptomycin is a last-line cell-membrane-targeting antibiotic to treat multidrug-resistant Alarmingly, daptomycin-resistant isolates have emerged. The mechanisms underlying daptomycin resistance are diverse and share similarities with resistances to cationic antimicrobial peptides and other lipopeptides, but they remain to be fully elucidated. We selected mutants with increased resistance to daptomycin from a library of transposon insertions in sequent type 8 (ST8) HG003. Insertions conferring increased daptomycin resistance were localized to two genes, one coding for a hypothetical lipoprotein (SAOUHSC_00362, Dsp1), and the other for an alkaline shock protein (SAOUHSC_02441, Asp23). Markerless loss-of-function mutants were then generated for comparison. All transposon mutants and knockout strains exhibited increased daptomycin resistance compared to those of wild-type and complemented strains. Null and transposon insertion mutants also exhibited increased resistance to cationic antimicrobial peptides. Interestingly, the mutant also showed increased resistance to vancomycin, a cell-wall-targeting drug with a different mode of action. Null mutations in both and resulted in increased tolerance as reflected by reduced killing to both daptomycin and vancomycin, as well as an increased tolerance to surfactant (Triton X-100). Neither mutant exhibited increased resistance to lysostaphin, a cell-wall-targeting endopeptidase. These findings identified two genes core to the species that make previously uncharacterized contributions to antimicrobial resistance and tolerance in .
