Infectious Disease

Gaca AO, Lemos JA. Adaptation to Adversity: the Intermingling of Stress Tolerance and Pathogenesis in Enterococci. Microbiol Mol Biol Rev 2019;83(3)Abstract
SUMMARY is a diverse and rugged genus colonizing the gastrointestinal tract of humans and numerous hosts across the animal kingdom. Enterococci are also a leading cause of multidrug-resistant hospital-acquired infections. In each of these settings, enterococci must contend with changing biophysical landscapes and innate immune responses in order to successfully colonize and transit between hosts. Therefore, it appears that the intrinsic durability that evolved to make enterococci optimally competitive in the host gastrointestinal tract also ideally positioned them to persist in hospitals, despite disinfection protocols, and acquire new antibiotic resistances from other microbes. Here, we discuss the molecular mechanisms and regulation employed by enterococci to tolerate diverse stressors and highlight the role of stress tolerance in the biology of this medically relevant genus.
Gaiha GD, Rossin EJ, Urbach J, Landeros C, Collins DR, Nwonu C, Muzhingi I, Anahtar MN, Waring OM, Piechocka-Trocha A, Waring M, Worrall DP, Ghebremichael MS, Newman RM, Power KA, Allen TM, Chodosh J, Walker BD. Structural topology defines protective CD8 T cell epitopes in the HIV proteome. Science 2019;364(6439):480-484.Abstract
Mutationally constrained epitopes of variable pathogens represent promising targets for vaccine design but are not reliably identified by sequence conservation. In this study, we employed structure-based network analysis, which applies network theory to HIV protein structure data to quantitate the topological importance of individual amino acid residues. Mutation of residues at important network positions disproportionately impaired viral replication and occurred with high frequency in epitopes presented by protective human leukocyte antigen () class I alleles. Moreover, CD8 T cell targeting of highly networked epitopes distinguished individuals who naturally control HIV, even in the absence of protective alleles. This approach thereby provides a mechanistic basis for immune control and a means to identify CD8 T cell epitopes of topological importance for rational immunogen design, including a T cell-based HIV vaccine.
García-Solache M, Lebreton F, McLaughlin RE, Whiteaker JD, Gilmore MS, Rice LB. Homologous Recombination within Large Chromosomal Regions Facilitates Acquisition of β-Lactam and Vancomycin Resistance in Enterococcus faecium. Antimicrob Agents Chemother 2016;60(10):5777-86.Abstract

The transfer of DNA between Enterococcus faecium strains has been characterized both by the movement of well-defined genetic elements and by the large-scale transfer of genomic DNA fragments. In this work, we report on the whole-genome analysis of transconjugants resulting from mating events between the vancomycin-resistant E. faecium C68 strain and the vancomycin-susceptible D344RRF strain to discern the mechanism by which the transferred regions enter the recipient chromosome. Vancomycin-resistant transconjugants from five independent matings were analyzed by whole-genome sequencing. In all cases but one, the penicillin binding protein 5 (pbp5) gene and the Tn5382 vancomycin resistance transposon were transferred together and replaced the corresponding pbp5 region of D344RRF. In one instance, Tn5382 inserted independently downstream of the D344RRF pbp5 gene. Single nucleotide variant (SNV) analysis suggested that entry of donor DNA into the recipient chromosome occurred by recombination across regions of homology between donor and recipient chromosomes, rather than through insertion sequence-mediated transposition. The transfer of genomic DNA was also associated with the transfer of C68 plasmid pLRM23 and another putative plasmid. Our data are consistent with the initiation of transfer by cointegration of a transferable plasmid with the donor chromosome, with subsequent circularization of the plasmid-chromosome cointegrant in the donor prior to transfer. Entry into the recipient chromosome most commonly occurred across regions of homology between donor and recipient chromosomes.

Gilmore MS, Rauch M, Ramsey MM, Himes PR, Varahan S, Manson JM, Lebreton F, Hancock LE. Pheromone killing of multidrug-resistant Enterococcus faecalis V583 by native commensal strains. Proc Natl Acad Sci U S A 2015;112(23):7273-8.Abstract

Multidrug-resistant Enterococcus faecalis possess numerous mobile elements that encode virulence and antibiotic resistance traits as well as new metabolic pathways, often constituting over one-quarter of the genome. It was of interest to determine how this large accretion of mobile elements affects competitive growth in the gastrointestinal (GI) tract consortium. We unexpectedly observed that the prototype clinical isolate strain V583 was actively killed by GI tract flora, whereas commensal enterococci flourished. It was found that killing of V583 resulted from lethal cross-talk between accumulated mobile elements and that this cross-talk was induced by a heptapeptide pheromone produced by native E. faecalis present in the fecal consortium. These results highlight two important aspects of the evolution of multidrug-resistant enterococci: (i) the accretion of mobile elements in E. faecalis V583 renders it incompatible with commensal strains, and (ii) because of this incompatibility, multidrug-resistant strains sharing features found in V583 cannot coexist with commensal strains. The accumulation of mobile elements in hospital isolates of enterococci can include those that are inherently incompatible with native flora, highlighting the importance of maintaining commensal populations as means of preventing colonization and subsequent infection by multidrug-resistant strains.

Gilmore MS, Lebreton F, van Schaik W. Genomic transition of enterococci from gut commensals to leading causes of multidrug-resistant hospital infection in the antibiotic era. Curr Opin Microbiol 2013;16(1):10-6.Abstract
The enterococci evolved over eons as highly adapted members of gastrointestinal consortia of a wide variety of hosts, but for reasons that are not entirely clear, emerged in the 1970s as leading causes of multidrug resistant hospital infection. Hospital-adapted pathogenic isolates are characterized by the presence of multiple mobile elements conferring antibiotic resistance, as well as pathogenicity islands, capsule loci and other variable traits. Enterococci may have been primed to emerge among the vanguard of antibiotic resistant strains because of their occurrence in the GI tracts of insects and simple organisms living and feeding on organic matter that is colonized by antibiotic resistant, antibiotic producing micro-organisms. In response to the opportunity to inhabit a new niche--the antibiotic treated hospital patient--the enterococcal genome is evolving in a pattern characteristic of other bacteria that have emerged as pathogens because of opportunities stemming from anthropogenic change.
Gilmore MS. The CRISPR-Antibiotic Resistance Connection. CRISPR J 2019;2:199-200.
Gilmore MS, Salamzade R, Selleck E, Bryan N, Mello SS, Manson AL, Earl AM. Genes Contributing to the Unique Biology and Intrinsic Antibiotic Resistance of Enterococcus faecalis. mBio 2020;11(6)Abstract
The enterococci, which are among the leading causes of multidrug-resistant (MDR) hospital infection, are notable for their environmental ruggedness, which extends to intrinsic antibiotic resistance. To identify genes that confer this unique property, we used Tn-seq to comprehensively explore the genome of MDR strain MMH594 for genes important for growth in nutrient-containing medium and with low-level antibiotic challenge. As expected, a large core of genes for DNA replication, expression, and central metabolism, shared with other bacteria, are intolerant to transposon disruption. However, genes were identified that are important to that are either absent from or unimportant for and fitness when similarly tested. Further, 217 genes were identified that when challenged by sub-MIC antibiotic levels exhibited reduced tolerance to transposon disruption, including those previously shown to contribute to intrinsic resistance, and others not previously ascribed this role. is one of the few Gram-positive bacteria experimentally shown to possess a functional Entner-Doudoroff pathway for carbon metabolism, a pathway that contributes to stress tolerance in other microbes. Through functional genomics and network analysis we defined the unusual structure of this pathway in and assessed its importance. These approaches also identified toxin-antitoxin and related systems that are unique and active in Finally, we identified genes that are absent in the closest nonenterococcal relatives, the vagococci, and that contribute importantly to fitness with and without antibiotic selection, advancing an understanding of the unique biology of enterococci. Enterococci are leading causes of antibiotic-resistant infection transmitted in hospitals. The intrinsic hardiness of these organisms allows them to survive disinfection practices and then proliferate in the gastrointestinal tracts of antibiotic-treated patients. The objective of this study was to identify the underlying genetic basis for its unusual hardiness. Using a functional genomic approach, we identified traits and pathways of general importance for enterococcal survival and growth that distinguish them from closely related pathogens as well as ancestrally related species. We further identified unique traits that enable them to survive antibiotic challenge, revealing a large set of genes that contribute to intrinsic antibiotic resistance and a smaller set of uniquely important genes that are rare outside enterococci.
Gilmore MS, Lebreton F, Van Tyne D. Dual defensin strategy for targeting Enterococcus faecalis. Proc Natl Acad Sci U S A 2013;110(50):19980-1.
Gise R, Elhusseiny AM, Scelfo C, Mantagos IS. Ocular involvement in recurrent infectious mucocutaneous eruption (RIME): a variation on a theme. J AAPOS 2020;
Gupta M, Jardeleza MSR, Kim I, Durand ML, Kim L, Lobo A-M. Varicella Zoster Virus Necrotizing Retinitis in Two Patients with Idiopathic CD4 Lymphocytopenia. Ocul Immunol Inflamm 2016;24(5):544-8.Abstract

PURPOSE: Progressive outer retinal necrosis (PORN) associated with varicella zoster virus (VZV) is usually diagnosed in HIV positive or immunosuppressed patients. We report two cases of immunocompetent patients with necrotizing viral retinitis found to have idiopathic CD4 lymphocytopenia. METHODS: Clinical presentation, examination, imaging, and laboratory testing of two patients with VZV retinitis are presented. RESULTS: An HIV negative patient with history of herpes zoster presented with rapid loss of vision and examination consistent with PORN. PCR testing confirmed VZV. Lymphocytopenia was noted with a CD4 count of 25/mm(3). A second HIV negative patient presented with blurred vision and lid swelling and was found to have peripheral VZV retinitis confirmed by PCR. Laboratory workup revealed lymphocytopenia with a CD4 count of 133/mm(3). CONCLUSIONS: VZV necrotizing retinitis classic for PORN can occur in HIV negative patients. Idiopathic CD4 lymphocytopenia should be considered healthy patients who develop ocular infections seen in the immunocompromised.

Hamrah P, Sahin A, Dastjerdi MH, Shahatit BM, Bayhan HA, Dana R, Pavan-Langston D. InVivo confocal microscopic changes of the corneal epithelium and stroma in patients with herpes zoster ophthalmicus. Am J Ophthalmol 2015;159(6):1036-1044.e1.Abstract

PURPOSE: To analyze the density and morphology of corneal epithelial cells and keratocytes by in vivo confocal microscopy (IVCM) in patients with herpes zoster ophthalmicus (HZO) as associated with corneal innervation. DESIGN: Prospective, controlled and masked cross-sectional study. METHODS: setting: Single-center study. PATIENTS: Thirty eyes with the diagnosis HZO and their contralateral clinically unaffected eyes, 15 eyes of 15 normal controls. intervention procedures: In vivo confocal microscopy and corneal esthesiometry of the central cornea. MAIN OUTCOME MEASURES: Changes in morphology and density of the superficial and basal epithelial cells and stromal keratocytes, and correlation with corneal sensation. RESULTS: The density of superficial epithelial cells in HZO eyes with severe sensation loss (766.5 ± 25.2 cells/mm(2)) was significantly lower than both healthy control eyes (1450.23 ± 150.83 cells/mm(2)) and contralateral unaffected eyes (1974.13 ± 298.24 cells/mm(2)) (P = .003). Superficial epithelial cell size (1162.5 μm(2)) was significantly larger in HZO eyes with severe loss of sensation, as compared to contralateral (441.46 ± 298.14) or healthy eyes (407.4 ± 47.2μm(2); all P < .05). The density of basal epithelial cells, anterior keratocytes, and posterior keratocytes did not show statistical significance between patients, controls, and contralateral unaffected eyes. Changes in superficial epithelial cell density and morphology correlated strongly with corneal sensation. CONCLUSIONS: In vivo confocal microscopy reveals profound HZO-induced changes in the superficial epithelium, as demonstrated by increase in cell size, decrease in cell density, and squamous metaplasia. We demonstrate that these changes strongly correlate with changes in corneal innervation in eyes affected by HZO.

Haque M, Lei F, Xiong X, Ren Y, Peng H-Y, Wang L, Kumar A, Das JK, Song J. Stem Cell-Derived Viral Antigen-Specific T Cells Suppress HIV Replication and PD-1 Expression on CD4+ T Cells. Viruses 2021;13(5)Abstract
The viral antigen (Ag)-specific CD8+ cytotoxic T lymphocytes (CTLs) derived from pluripotent stem cells (PSCs), i.e., PSC-CTLs, have the ability to suppress the human immunodeficiency virus (HIV) infection. After adoptive transfer, PSC-CTLs can infiltrate into the local tissues to suppress HIV replication. Nevertheless, the mechanisms by which the viral Ag-specific PSC-CTLs elicit the antiviral response remain to be fully elucidated. In this study, we generated the functional HIV-1 Gag epitope SL9-specific CTLs from the induced PSC (iPSCs), i.e., iPSC-CTLs, and investigated the suppression of SL9-specific iPSC-CTLs on viral replication and the protection of CD4+ T cells. A chimeric HIV-1, i.e., EcoHIV, was used to produce HIV replication in mice. We show that adoptive transfer of SL9-specific iPSC-CTLs greatly suppressed EcoHIV replication in the peritoneal macrophages and spleen in the animal model. Furthermore, we demonstrate that the adoptive transfer significantly reduced expression of PD-1 on CD4+ T cells in the spleen and generated persistent anti-HIV memory T cells. These results indicate that stem cell-derived viral Ag-specific CTLs can robustly accumulate in the local tissues to suppress HIV replication and prevent CD4+ T cell exhaustion through reduction of PD-1 expression.
Hodges RR, Li D, Shatos MA, Bair JA, Lippestad M, Serhan CN, Dartt DA. Lipoxin A4 activates ALX/FPR2 receptor to regulate conjunctival goblet cell secretion. Mucosal Immunol 2017;10(1):46-57.Abstract

Conjunctival goblet cells play a major role in maintaining the mucus layer of the tear film under physiological conditions as well as in inflammatory diseases like dry eye and allergic conjunctivitis. Resolution of inflammation is mediated by proresolution agonists such as lipoxin A4 (LXA4) that can also function under physiological conditions. The purpose of this study was to determine the actions of LXA4 on cultured rat conjunctival goblet cell mucin secretion, intracellular [Ca(2+)] ([Ca(2+)]i), and identify signaling pathways activated by LXA4. ALX/FPR2 (formyl peptide receptor2) was localized to goblet cells in rat conjunctiva and in cultured goblet cells. LXA4 significantly increased mucin secretion, [Ca(2+)]i, and extracellular regulated kinase 1/2 (ERK 1/2) activation. These functions were inhibited by ALX/FPR2 inhibitors. Stable analogs of LXA4 increased [Ca(2+)]i to the same extent as LXA4. Sequential addition of either LXA4 or resolvin D1 followed by the second compound decreased [Ca(2+)]i of the second compound compared with its initial response. LXA4 activated phospholipases C, D, and A2 and downstream molecules protein kinase C, ERK 1/2, and Ca(2+)/calmodulin-dependent kinase to increase mucin secretion and [Ca(2+)]i. We conclude that conjunctival goblet cells respond to LXA4 to maintain the homeostasis of the ocular surface and could be a novel treatment for dry eye diseases.

Hong J, Zhong T, Li H, Xu J, Ye X, Mu Z, Lu Y, Mashaghi A, Zhou Y, Tan M, Li Q, Sun X, Liu Z, Xu J. Ambient air pollution, weather changes, and outpatient visits for allergic conjunctivitis: A retrospective registry study. Sci Rep 2016;6:23858.Abstract

Allergic conjunctivitis is a common problem that significantly impairs patients' quality of life. Whether air pollution serves as a risk factor for the development of allergic conjunctivitis remains elusive. In this paper, we assess the relationship between air pollutants and weather conditions with outpatient visits for allergic conjunctivitis. By using a time-series analysis based on the largest dataset ever assembled to date, we found that the number of outpatient visits for allergic conjunctivitis was significantly correlated with the levels of NO2, O3, and temperature, while its association with humidity was statistically marginal. No associations between PM10, PM2.5, SO2, or wind velocity and outpatient visits were seen. Subgroup analyses showed that sex seemed to modify the effects of humidity on outpatient visits for allergic conjunctivitis, but not for NO2, O3, or temperature. People younger than 40 were found to be susceptible to changes of all four parameters, while those older than 40 were only consistently affected by NO2 levels. Our findings revealed that higher levels of ambient NO2, O3, and temperature increase the chances of outpatient visits for allergic conjunctivitis. Ambient air pollution and weather changes may contribute to the worsening of allergic conjunctivitis.

Ibberson CB, Stacy A, Fleming D, Dees JL, Rumbaugh K, Gilmore MS, Whiteley M. Co-infecting microorganisms dramatically alter pathogen gene essentiality during polymicrobial infection. Nat Microbiol 2017;2:17079.Abstract
Identifying genes required by pathogens during infection is critical for antimicrobial development. Here, we use a Monte Carlo simulation-based method to analyse high-throughput transposon sequencing data to determine the role of infection site and co-infecting microorganisms on the in vivo 'essential' genome of Staphylococcus aureus. We discovered that co-infection of murine surgical wounds with Pseudomonas aeruginosa results in conversion of ∼25% of the in vivo S. aureus mono-culture essential genes to non-essential. Furthermore, 182 S. aureus genes are uniquely essential during co-infection. These 'community dependent essential' (CoDE) genes illustrate the importance of studying pathogen gene essentiality in polymicrobial communities.
Ing EB, Xu QA, Salimi A, Torun N. Physician deaths from corona virus (COVID-19) disease. Occup Med (Lond) 2020;70(5):370-374.Abstract
BACKGROUND: The COVID-19 pandemic has caused much morbidity and mortality to patients but also health care providers. AIMS: We tabulated the cases of physician deaths from COVID-19 associated with front-line work in hopes of mitigating future events. METHODS: On 15 April 2020, a Google internet search was performed using the keywords 'doctor', 'physician', 'death', 'COVID' and 'coronavirus' in English and Farsi, and Chinese using the Baidu search engine. The age, sex and medical speciality of physicians who died from COVID-19 in the line of duty were recorded. Individuals greater than 90 years of age were excluded. RESULTS: We found 278 physicians who died with COVID-19 infection, but complete details were missing for 108 individuals. The average age of the physicians was 63.7 years with a median age of 66 years, and 90% were male (235/261). General practitioners and emergency room doctors (108/254), respirologists (5/254), internal medicine specialists (13/254) and anaesthesiologists (6/254) comprised 52% of those dying. Two per cent of the deceased were epidemiologists (5/254), 2% were infectious disease specialists (4/254), 6% were dentists (16/254), 4% were ENT (9/254) and 3% were ophthalmologists (8/254). The countries with the most reported physician deaths were Italy (121/278; 44%), Iran (43/278; 15%), Philippines (21/278; 8%), Indonesia (17/278; 6%), China (16/278; 6%), Spain (12/278; 4%), USA (12/278; 4%) and UK (11/278;4%). CONCLUSIONS: Physicians from all specialities may die from COVID. Lack of personal protective equipment was cited as a common cause of death. Consideration should be made to exclude older physicians from front-line work.
Inomata T, Kitazawa K, Kuno T, Sung J, Nakamura M, Iwagami M, Takagi H, Midorikawa-Inomata A, Zhu J, Fujimoto K, Okumura Y, Miura M, Fujio K, Hirosawa K, Akasaki Y, Kuwahara M, Dana R, Murakami A. Clinical and Prodromal Ocular Symptoms in Coronavirus Disease: A Systematic Review and Meta-Analysis. Invest Ophthalmol Vis Sci 2020;61(10):29.Abstract
Purpose: This systematic review aimed to determine currently reported clinical and prodromal ocular symptoms in patients with coronavirus disease 2019 (COVID-19). Methods: An online article search was performed in PubMed and EMBASE. Altogether 15 studies (retrospective, prospective, or case studies) involving 1533 patients with COVID-19, reporting on ocular symptoms, and with outcome data available were identified. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses reporting guidelines were followed. Study-specific estimates (incidence rates of ocular symptoms in patients with COVID-19) of cases were combined using one-group meta-analysis in a random-effects model. Results: Of all included studies, 11.2% (95% confidence interval, 5.5-16.9; 78/1526 cases) reported ocular symptoms. The most common ocular finding was conjunctivitis. Prodromal ocular symptoms occurred in 12.5% (13/104 cases) of patients with COVID-19. Positive real-time polymerase chain reaction results were obtained for 16.7% (10/60 cases) of conjunctival samples and 0% (0/17 cases) of tear samples. Twelve ocular conjunctival swab samples tested positive for SARS-CoV-2. Ten cases were from subjects showing ocular symptoms (16.7%, 10/60 cases), and the remaining two cases were from subjects without ocular manifestation (1.8%, 2/113 cases). Limitations included the short study period, small sample size, findings were limited to the Asian population, only seven articles included ophthalmologic examination details, and there is currently no consensus on COVID-19 management. Conclusions: Ocular symptoms may occur in the presymptomatic phase as a prodromal symptom (12.5%, 13/104 cases), suggesting the possibility of viral transmission from the conjunctiva.
Inomata T, Ono K, Matsuba T, Shiang T, Di Zazzo A, Nakatani S, Yamaguchi M, Ebihara N, Murakami A. Pre-banking microbial contamination of donor conjunctiva and storage medium for penetrating keratoplasty. Jpn J Ophthalmol 2017;Abstract
PURPOSE: The aims of this study were to investigate the incidence of positive donor tissue cultures before transfer to preservation medium (Optisol™-GS) for penetrating keratoplasty, to verify the efficacy of antibiotics contained in Optisol™-GS by examining the drug susceptibility and to assess the relationship between the results of our microbial assessments as well as donor factors and the incidence of contamination. METHODS: We conducted a retrospective, cross-sectional study using Juntendo Eye Bank records for all corneal transplantations. Two hundred donor conjunctiva harvestings and storage medium (EP-II(®)) cultures were performed between July 2008 and June 2011. We analyzed the associations between donor factors (age, gender, history of cataract surgery, death-to-preservation interval, cause of death) and contamination rates using multivariate analysis by the generalized estimating equation model. RESULTS: We obtained positive bacterial cultures from 154 of the 200 eyes (77.0%). The isolated bacteria were indigenous, such as coagulase-negative Staphylococci, Corynebacterium sp., and methicillin-resistant Staphylococcus aureus (MRSA). There was significant resistance to levofloxacin (18 eyes, 9.0%) and gentamicin (12 eyes, 6.0%), and no vancomycin-resistant bacteria were detected. The donor factors did not correlate with the prevalence of bacterial contamination in our criteria. CONCLUSIONS: Pre-banking microbial assessment allows for microbial detection, bacterial susceptibility and resistance testing. This is useful for developing preservation mediums containing effective spectrum antibiotic agents for high quality control of corneal banking.
Ismail AM, Cui T, Dommaraju K, Singh G, Dehghan S, Seto J, Shrivastava S, Fedorova NB, Gupta N, Stockwell TB, Halpin R, Madupu R, Heim A, Kajon AE, Romanowski EG, Kowalski RP, Malathi J, Therese KL, Madhavan HN, Zhang Q, Ferreyra LJ, Jones MS, Rajaiya J, Dyer DW, Chodosh J, Seto D. Author Correction: Genomic analysis of a large set of currently-and historically-important human adenovirus pathogens. Emerg Microbes Infect 2018;7(1):208.Abstract
The original publication of this article [1] was missing the below author that made contributions to the research and the published article.
Ismail AM, Lee JS, Dyer DW, Seto D, Rajaiya J, Chodosh J. Selection Pressure in the Human Adenovirus Fiber Knob Drives Cell Specificity in Epidemic Keratoconjunctivitis. J Virol 2016;90(21):9598-9607.Abstract

Human adenoviruses (HAdVs) contain seven species (HAdV-A to -G), each associated with specific disease conditions. Among these, HAdV-D includes those viruses associated with epidemic keratoconjunctivitis (EKC), a severe ocular surface infection. The reasons for corneal tropism for some but not all HAdV-Ds are not known. The fiber protein is a major capsid protein; its C-terminal "knob" mediates binding with host cell receptors to facilitate subsequent viral entry. In a comprehensive phylogenetic analysis of HAdV-D capsid genes, fiber knob gene sequences of HAdV-D types associated with EKC formed a unique clade. By proteotyping analysis, EKC virus-associated fiber knobs were uniquely shared. Comparative structural modeling showed no distinct variations in fiber knobs of EKC types but did show variation among HAdV-Ds in a region overlapping with the known CD46 binding site in HAdV-B. We also found signature amino acid positions that distinguish EKC from non-EKC types, and by in vitro studies we showed that corneal epithelial cell tropism can be predicted by the presence of a lysine or alanine at residue 240. This same amino acid residue in EKC viruses shows evidence for positive selection, suggesting that evolutionary pressure enhances fitness in corneal infection, and may be a molecular determinant in EKC pathogenesis. IMPORTANCE: Viruses adapt various survival strategies to gain entry into target host cells. Human adenovirus (HAdV) types are associated with distinct disease conditions, yet evidence for connections between genotype and cellular tropism is generally lacking. Here, we provide a structural and evolutionary basis for the association between specific genotypes within HAdV species D and epidemic keratoconjunctivitis, a severe ocular surface infection. We find that HAdV-D fiber genes of major EKC pathogens, specifically the fiber knob gene region, share a distinct phylogenetic clade. Deeper analysis of the fiber gene revealed that evolutionary pressure at crucial amino acid sites has a significant impact on its structural conformation, which is likely important in host cell binding and entry. Specific amino acids in hot spot residues provide a link to ocular cell tropism and possibly to corneal pathogenesis.