|Year : 2022 | Volume
| Issue : 1 | Page : 8-14
The role of Type III secretion system in the pathogenesis of Pseudomonas aeruginosa microbial keratitis
Justin J Yang1, Kai-Si Claire Tsuei2, Elizabeth P Shen3
1 Department of Chemistry; Department of Computer Science, Trinity College of Arts and Sciences, Duke University, North Carolina, USA
2 Department of Ophthalmology, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, New Taipei, Taiwan
3 Department of Ophthalmology, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, New Taipei; College of Medicine, Tzu Chi University, Hualien; Department of Ophthalmology, National Taiwan University Hospital and College of Medicine, National Taiwan University, Taipei, Taiwan
|Date of Submission||17-Feb-2021|
|Date of Decision||11-Mar-2021|
|Date of Acceptance||17-Mar-2021|
|Date of Web Publication||11-May-2021|
Elizabeth P Shen
Department of Ophthalmology, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, 289, Jianguo Road, Xindian District, New Taipei
Source of Support: None, Conflict of Interest: None
Pseudomonas aeruginosa is the most commonly isolated Gram-negative pathogen causing sight-threatening microbial keratitis (MK). Contact lens wear is the most significant risk factor associated with pseudomonal MK. Understanding the pathogenesis of MK due to P. aeruginosa and its interactions with contact lenses is crucial in preventing these often rapidly progressive and highly antibiotic-resistant infections. Bacterial virulence factor Type III secretion system (T3SS) has significant interplays between contact lens material, antibiotic sensitivity, disinfectant selectivity, and bacterial cell invasion. Depending on the T3SS exotoxins produced, P. aeruginosa strains are divided into cytotoxic or invasive strains. Cytotoxic strains are relatively resistant to commercial disinfectants, while invasive strains are more antibiotic resistant. Therefore, contact lens wearers are more predisposed to cytotoxic P. aeruginosa infections, and patients with trauma or previous surgery are more prone to infection by invasive strains. Previous studies with mutant P. aeruginosa strains unable to produce T3SS exotoxins were more susceptible to disinfectants and less able to adhere to soft contact lenses, indicating an essential role of T3SS in bacterial virulence. Invasion of P. aeruginosa intracellularly was found to be associated with control of scaffold protein IQ-domain GTPase-activating protein 1 (IQGAP1) and human corneal epithelial cell tight junctions. Knockdown of IQGAP1 strengthened tight junctions that prevented intracellular survival of invasive P. aeruginosa strains and enhanced corneal epithelial cell survival. These novel findings of the vital role of T3SS in the pathogenesis of pseudomonal MKs will provide new guidelines in both prevention and treatment of this common eye-blinding infection.
Keywords: Contact lens, IQ-domain GTPase-activating protein 1, Microbial keratitis, Pseudomonas aeruginosa, Type III secretion system
|How to cite this article:|
Yang JJ, Tsuei KS, Shen EP. The role of Type III secretion system in the pathogenesis of Pseudomonas aeruginosa microbial keratitis. Tzu Chi Med J 2022;34:8-14
|How to cite this URL:|
Yang JJ, Tsuei KS, Shen EP. The role of Type III secretion system in the pathogenesis of Pseudomonas aeruginosa microbial keratitis. Tzu Chi Med J [serial online] 2022 [cited 2022 Jan 21];34:8-14. Available from: https://www.tcmjmed.com/text.asp?2022/34/1/8/315867
| Introduction|| |
Microbial keratitis (MK) due to Pseudomonas aeruginosa causes severe ocular morbidity that may result in blindness if not treated promptly and appropriately . P. aeruginosa, an opportunistic pathogen commonly found in our environment, is the most commonly isolated Gram-negative organism causing MK, particularly among contact lens wearers . The incidence of this contact lens-related microbial keratitis (CLMK) is approximately 3.5–20.9 per 10,000 wearers, varying due to contact lens material and wearing schedules ,,. With young emmetropic individuals wearing cosmetic color-tinted contact lenses, the incidence of CLMK is unfortunately expected to increase ,.
Ongoing research to understand the complex interaction between contact lens material, the initiation mechanisms of CLMK, and the bacterial–host immune response has continued to shed light into the perplex mechanisms causing MK. As our study and other previous studies have shown, contact lens material significantly affects the amount of bacterial adhesion ,,,. Virulence factors of the bacterium may also influence its propensity to adhere ,,,. Among the multitude of virulence factors, the Type III secretion system (T3SS), a contact-dependent protein secretion pathway secreting exotoxins, has been associated with significant host cell damage and thus clinical disease ,,. In this article, we review the present understanding of the complex interactions between P. aeruginosa with contact lenses material in the initiation process of the pathogenesis of CLMK.
| Pathogenesis of Pseudomonas aeruginosa microbial keratitis|| |
Pseudomonal keratitis often presents as a rapidly progressive stromal ulceration with overlying epithelial defect. The stromal ulceration may lead to severe and often rapid stromal melting, resulting in corneal perforation and visual loss ,. The development of CLMK commences with bacterial contamination and subsequent bacterial adhesion to contact lenses, rendering prolonged exposure of the cornea to microbial pathogens [Figure 1] ,,. Since P. aeruginosa is an opportunistic organism, the establishment of an infection requires a compromised state of the host. Trauma due to abrasion or hypoxic injury due to contact lens wear had been proposed to cause epithelial breakdown and thus allow ensuing pseudomonal invasion ,,. To increase the oxygen permeability to the cornea during contact lens wear, silicone hydrogel materials were developed and were found to have at least 6 times greater oxygen permeability than conventional hydrogel lenses . Nevertheless, daily wear of silicone hydrogel contact lenses still had about 6 times greater risk of corneal infection than daily wear or daily disposable conventional soft contact lens . Clearly, factors other than hypoxia must be involved. Therefore, besides the contact lens material itself, the interaction of bacterial virulence factors with host defenses or immunity had been previously studied.
|Figure 1: Proposed pathogenesis of pseudomonal keratitis. Complex interaction between bacterial virulence factor Type III secretion system, contact lens, and host immune response occurs during the initiation process of Pseudomonas aeruginosa keratitis. Understanding of these complex interactions may help to develop prevention strategies and target therapy|
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| Pseudomonal Type III secretion system|| |
T3SS exoenzymes were found to be important virulence factors inducing P. aeruginosa keratitis ,,,. The T3SS is a specialized protein export system that forms a needle-like complex between bacterial and host cells for the transport and secretion of four exotoxins, ExoS, ExoU, ExoT, and ExoY [Figure 2] . The T3SS is encoded by 36 genes in five operons, which correspond to five functional components: the needle-like complex, the translocation apparatus, the regulatory proteins, the chaperones, and the effector proteins . Structurally, the needle-like complex is a hollow filament about 60–120 nm long and 6–10 nm wide and serves as a tube through which secreted factors are transported . The translocation apparatus is composed of proteins that form pores on the host's cell membrane. The needle-like complex connects with these pores, which then accept the effector proteins transported by the needle-like complex and deliver it across the host's cell membrane. A structural component of the needle complex, PscC protein is located on the outer membrane of P. aeruginosa and has been shown to be essential in effector transport [Figure 2] ,. Mutations in the PscC protein result in loss of bacterial virulence and also T3SS exotoxin secretion ,,. The expression of the T3SS usually requires close cell contact in vivo or low calcium growth conditions in vitro ,,. Contamination of contact lenses with adhering bacteria thus provides a chance for relatively close contact with the corneal epithelium to induce the T3SS in vivo. After T3SS activation, the chaperone proteins which bind to effector proteins before secretion facilitate the delivery of effector proteins into the secretion system . Chaperones remain in the bacterial cytoplasm after their effector protein partners have been secreted. The most important component of the T3SS is the effector proteins, which are the “payload” that is injected into the host cell that disrupts various cellular processes, leading to clinical disease.
|Figure 2: The Type III secretion system of Pseudomonas aeruginosa . Type III secretion system is a specialized contact-dependent or low calcium-induced bacterial virulence system. Transport of exotoxins through needle-like complex affects host cells either by acute cell lysis (ExoU) or host invasion (ExoS)|
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Currently, only four effector proteins of the P. aeruginosa T3SS have ever been identified despite extensive characterization: ExoS, ExoU, ExoT, and ExoY.
ExoS is a 453-amino acid (48 kDa) cytotoxin that exhibits both GTPase-activating protein (GAP) activity and ADP ribosyl transferase (ADPRT) activity . Analysis of the protein sequence suggests that residues 96–233 contain the GAP domain, which targets small GTPases such as Rho, Rac, and cell division cycle 42 (CDC42) and turns them into an inactive form, disrupting host cell actin cytoskeleton organization. Residues 233–453 contain the ADPRT domain, with residues 418–429 containing a binding site for a 14-3-3 protein necessary for the activation of ADPRT activity . The requirement for a 14-3-3 protein – a eukaryotic cofactor – protects the bacteria against self-damage until ExoS is secreted into the host. Once injected, ADPRT activity of ExoS becomes active and disrupts the host's actin cytoskeleton, which then interferes with vesicular trafficking and endocytosis, ultimately leading to cell death with the features of apoptosis or necrosis . The disruption of the host's cytoskeleton can also reduce cell–cell adherence, facilitating P. aeruginosa invasion through epithelial barriers .
In contrast to ExoS, ExoU (74 kDa) is a phospholipase that causes host cell lysis within 1–2 h . Analysis of its protein sequence reveals a patatin-like domain with phospholipase A2 (PLA2) activity between residues 107 and 357 . PLA2 enzymes hydrolyze the ester bond of phospholipids at the SN2 position, resulting in the release of free fatty acids and lysophospholipids ,. To facilitate host cell lysis, ExoU contains a membrane localization domain between residues 550–687 that directs ExoU to the phospholipid plasma membrane of the host cell . To ensure tha this potent weapon is not turned against the bacteria itself, ExoU requires activation by a eukaryotic cofactor: Cu2+, Zn2+-superoxide dismutase 1 ,. Taken altogether, ExoU may be used to kill the host's epithelial cells and immune cells, thereby promoting bacterial invasion and dissemination .
ExoT is a 457-amino acid (40 kDa) cytotoxin that shares 76% homology with ExoS . Similar to ExoS, residues 78–235 of ExoT contain GAP activity toward Rho, Rac, and CDC42, causing reversible disruption of the actin cytoskeleton. This leads to cell rounding, cell detachment, and inhibition of cell migration, phagocytosis, and cytokinesis ,. Further, like ExoS, residues 235–457 of ExoT contain an ADPRT domain that similarly requires binding of the host cell 14-3-3 cofactor for activation. While ExoT ADP ribosylates a different set of host proteins , the net effects of GAP and ADPRT activity in ExoT are similar to ExoS, which is actin cytoskeleton disruption and inhibition of cell adhesion and phagocytosis. This allows P. aeruginosa to disseminate by evading phagocytosis and breaking down epithelial barriers ,.
ExoY is a 378-amino acid (42 kDa) adenylyl cyclase that also requires a host cell cofactor for activation, although the identity of this cofactor is currently unknown . When ExoY was injected into mammalian cells, elevated intracellular cAMP concentrations and differential gene expression were observed, which led to the disruption of the actin cytoskeleton, inhibition of host phagocytosis of bacteria, and increased endothelial permeability ,.
For reasons that are unclear, most strains do not carry all four genes encoding for the four effectors. In fact, while almost all strains of P. aeruginosa carry both exoT and exoY genes, most have only either exoU or exoS, not both . As such, two genotypes of P. aeruginosa with different infection phenotypes can be distinguished by the secretion of either ExoU or ExoS. Strains that are ExoS positive and ExoU negative are known as invasive strains as they can invade into corneal epithelial cells ,,,. On the other hand, strains that are ExoU positive and ExoS negative are known as cytotoxic strains because ExoU, a phospholipase, causes acute host cell lysis ,. The invasive and cytotoxic phenotypes with their respective exoS and exoU genotypes were found to be mutually exclusive in nearly all strains .
| Pseudomonal Type III secretion system and clinical manifestation of microbial keratitis|| |
From our investigation of invasive and cytotoxic strains isolated from MK cases over a 10-year period in Taiwan, the two phenotypes of P. aeruginosa showed significant differences both in clinical manifestation and in visual prognosis. Clinical P. aeruginosa isolates were mostly of cytotoxic strains among contact lens wearer, while invasive strains were significantly related to a history of trauma or previous surgery ,. This was similarly noted among Australian isolates . Cytotoxic strains were also more commonly seen in young females in contrast to invasive strains, which predominantly occurred in older males . Initial presenting visual acuity for cytotoxic strains was also significantly better compared to MK due to invasive strains. This is mainly due to smaller infiltration size and less fulminant disease due to cytotoxic strains . Invasive strains often had a greater infiltration size and depth accompanied by the presence of hypopyon therefore poorer final visual outcome and even higher treatment failure rate (Failure was defined as severe uncontrollable infection requiring therapeutic penetrating keratoplasty, evisceration, or enucleation) .
Antibiotic susceptibility varied according to the regions and between the two phenotypes. A greater proportion of cytotoxic strains from the USA, Australia, and India were more resistant to fluoroquinolones and aminoglycosides, although differences between phenotypes were not significant ,,. This is in contrast to isolates from Taiwan, which showed an increased antibiotic resistance to fluoroquinolones for invasive strains . Cytotoxic strains from CLMK cases were all sensitive to commonly used aminoglycosides and fluoroquinolones . These results suggest that analysis of P. aeruginosa phenotype may be helpful clinically in predicting visual prognosis and also suggesting clinical guidelines for the treatment of pseudomonal keratitis with some regional differences.
| Type III secretion system and host invasion|| |
The effect of T3SS effectors on corneal epithelial cells differ with their genotypes. Strains with the exoS genotype can invade and multiply within corneal epithelial cells both in vitro and in vivo [52,55]. It was found that functional T3SS was required for intracellular survival of P. aeruginosa within corneal epithelial cells . Wild-type strains with functional T3SS can be seen replicating within plasma membrane blebs . In contrast, the T3SS needle-complex pscC mutant could not form membrane blebs and thus had reduced intracellular survival . Thus, these membrane blebs are essentially used as niches by P. aeruginosa for intracellular survival and replication . Visualization of the membrane localization of intracellular P. aeruginosa can be seen with confocal microscopy using GFP-transformed strains . Although preliminary work on how ExoS promotes intracellular survival had been done, the studies of ExoS on disruption of epithelial barrier function were mostly done on mucosal cells of the lung .
The effect of ExoS with a scaffold protein IQ-domain GTPase-activating protein 1 (IQGAP1) on the corneal epithelial barrier was recently published by ShenW et al. . IQGAP1 co-localized with junctional proteins actin and zonular occludin 1 to induce changes in the corneal epithelial cell tight junction . Knockdown of IQGAP1 enhanced tight junction formation with increased transepithelial resistance . Since invasive strain P. aeruginosa invades human corneal epithelial cells by rapidly breaking down tight junctions, enhancement of tight junctions resulting from the knockdown of IQGAP1 can protect against P. aeruginosa invasion, leading to enhanced cell survival . Viability of cells increased by 45% early in the infection . After IQGAP1 knockdown, PAK was also less able to invade and survive within the corneal epithelial cells . These novel findings suggested that T3SS enables invasiveness of P. aeruginosa through breakdown of tight junctions. Invasion of the bacterium into host cells protected the pathogen from host immune defenses and evaded antibiotics control. The poor clinical outcomes due to invasive pseudomonal strains may be partially due to this evasion tactic. Therefore, understanding the mechanism of pseudomonal invasion is essential in the development of new therapeutic targets, especially with rising antibiotic resistance.
| Type III secretion system and contact lenses|| |
The T3SS virulence factors not only influence clinical prognosis and bacterial antibiotic sensitivity, but it has also been shown to affect pseudomonal adherence to contact lenses. Previously, environmental and clinical isolates from lung, urinary tract, or burn wound infections were shown to be mostly invasive ,,. However, the higher prevalence or predisposition of finding cytotoxic genotype among contact lens wearers suggested that T3SS may be involved either directly or indirectly with adhesion to contact lens materials. By using low calcium-inducing conditions to compare the bacterial adhesions between wild-type and pscC-mutant strains, it was demonstrated that pscC mutants were unable to secrete T3SS exotoxins, irrespective of strain. These mutants showed significantly less adhesion to both conventional hydrogel and silicone hydrogel contact lenses compared to wild-type strains . Compared to noninducing conditions, bacteria grown under T3SS-inducing conditions also showed significantly greater bacterial adhesion to contact lenses, indicating that functional and active T3SS is essential for contact lens adhesion . Although functional T3SS affects bacterial lens adhesion, genotype differences were not found. Therefore, other factors must be involved in the predisposition of cytotoxic genotype among CLMK.
Contact lens material had been shown to affect pseudomonal adherence. Regardless of strain, silicone hydrogels with plasma oxidation surface treatment tend to adhere greater bacteria . Generally, galyfilcon silicone hydrogel lenses (lenses without surface treatment) had the least amount of bacterial adhesion compared to surface-treated silicone hydrogel and conventional hydrogels . Thus, surface smoothness was proposed to affect bacterial adhesion. Cosmetic hydrogel lenses that easily dislodge color pigments were shown to adhere significantly more bacteria ,. Scanning electron microscope of pigmented contact lenses showed a significant association of surface smoothness with pigment dislodgement . Therefore, improper contact lens material or surface treatment may increase the propensity for bacterial adhesion onto lens surfaces.
| Type III secretion system and disinfectant selectivity|| |
As previously mentioned, functional T3SS was required for bacterial adherence to contact lenses. However, there were no genotype differences in adhesion demonstrated by us and others ,. Selectivity of cytotoxic strains by disinfectants or multipurpose solutions was thought to be a possible explanation. In 2001, Lakkis and Fleiszig found an increase in resistance to two contact lens chemical disinfectants . This resistance was associated with acute cytotoxic activity to corneal epithelial cells . Recently, we compared the sensitivity of the two genotypes of P. aeruginosa to four commercially available disinfectants (Renu Fresh, PureMoist, Replenish, and AoSept Plus). Cytotoxic strains were significantly more resistant to disinfectants, especially Renu Fresh, even at manufacturer's recommended disinfection time. The best disinfectant was AoSopt Plus, the hydrogen peroxide system, which was able to completely eradicate P. aeruginosa even at 25% of recommended disinfection time. Compared to standard wild-type strains, pscC-mutant strains were all susceptible to disinfectants, indicating that functional T3SS may contribute to bacterial disinfectant resistance. These cumulative findings suggest that the relative higher prevalence of cytotoxic strains with contact lens wearers may be due to the relative selectivity of marketed disinfectants. Careful selection of effective disinfectants should be advocated for proper lens hygiene.
| Conclusion|| |
P. aeruginosa is the most common pathogen causing vision-threating corneal infections, especially in contact lens wearers. The rapid progressive course and poor clinical outcomes due to emerging antibiotic resistance stimulated extensive research in the role of bacterial virulence factor T3SS interactions with contact lenses. As extensive reviewed, recognition of the importance of the various effects of T3SS exotoxins will better enable early prevention measures and novel treatment options to salvage the devastating sight-threatening complication due to P. aeruginosa infections.
Financial support and sponsorship
This article was supported by the funding from Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation (TCRD-TPE-110-20 and TCRD-TPE-110-47) and the Ministry of Science and Technology, Taiwan (MOST105-2314-B-002- 167-MY3 and MOST106-2314-B-303-011MY3).
Conflicts of interest
There are no conflicts of interest.
| References|| |
Stapleton F, Keay LJ, Sanfilippo PG, Katiyar S, Edwards KP, Naduvilath T. Relationship between climate, disease severity, and causative organism for contact lens-associated microbial keratitis in Australia. Am J Ophthalmol 2007;144:690-8.
Ormerod LD, Smith RE. Contact lens-associated microbial keratitis. Arch Ophthalmol 1986;104:79-83.
Cheng KH, Leung SL, Hoekman HW, Beekhuis WH, Mulder PG, Geerards AJ, et al. Incidence of contact-lens-associated microbial keratitis and its related morbidity. Lancet 1999;354:181-5.
Poggio EC, Glynn RJ, Schein OD, Seddon JM, Shannon MJ, Scardino VA, et al. The incidence of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses. N Engl J Med 1989;321:779-83.
Liesegang TJ. Contact lens-related microbial keratitis: Part I. Epidemiol Cornea 1997;16:125-31.
Steinemann TL, Fletcher M, Bonny AE, Harvey RA, Hamlin D, Zloty P, et al. Over-the-counter decorative contact lenses: Cosmetic or medical devices? A case series. Eye Contact Lens 2005;31:194-200.
Sauer A, Bourcier T; French Study Group for Contact Lenses Related Microbial Keratitis. Microbial keratitis as a foreseeable complication of cosmetic contact lenses: A prospective study. Acta Ophthalmol 2011;89:e439-42.
Henriques M, Sousa C, Lira M, Elisabete M, Oliveira R, Oliveira R, et al. Adhesion of Pseudomonas aeruginosa
and Staphylococcus epidermidis
to silicone-hydrogel contact lenses. Optom Vis Sci 2005;82:446-50.
Shen EP, Tsay RY, Chia JS, Wu S, Lee JW, Hu FR. The role of Type III secretion system and lens material on adhesion of Pseudomonas aeruginosa
to contact lenses. Invest Ophthalmol Vis Sci 2012;53:6416-26.
Vijay AK, Zhu H, Ozkan J, Wu D, Masoudi S, Bandara R, et al. Bacterial adhesion to unworn and worn silicone hydrogel lenses. Optom Vis Sci 2012;89:1095-106.
Nilsson SE, Montan PG. The hospitalized cases of contact lens induced keratitis in Sweden and their relation to lens type and wear schedule: Results of a three-year retrospective study. CLAO J 1994;20:97-101.
Fleiszig SM, Efron N, Pier GB. Extended contact lens wear enhances Pseudomonas aeruginosa
adherence to human corneal epithelium. Invest Ophthalmol Vis Sci 1992;33:2908-16.
Fletcher EL, Fleiszig SM, Brennan NA. Lipopolysaccharide in adherence of Pseudomonas aeruginosa
to the cornea and contact lenses. Invest Ophthalmol Vis Sci 1993;34:1930-6.
Fletcher EL, Weissman BA, Efron N, Fleiszig SM, Curcio AJ, Brennan NA. The role of pili in the attachment of Pseudomonas aeruginosa
to unworn hydrogel contact lenses. Curr Eye Res 1993;12:1067-71.
Engel J, Balachandran P. Role of Pseudomonas aeruginosa
Type III effectors in disease. Curr Opin Microbiol 2009;12:61-6.
Yahr TL, Wolfgang MC. Transcriptional regulation of the Pseudomonas aeruginosa
Type III secretion system. Mol Microbiol 2006;62:631-40.
Hauser AR. The Type III secretion system of Pseudomonas aeruginosa
: Infection by injection. Nat Rev Microbiol 2009;7:654-65.
Cruz CS, Cohen EJ, Rapuano CJ, Laibson PR. Microbial keratitis resulting in loss of the eye. Ophthalmic Surg Lasers 1998;29:803-7.
Green M, Apel A, Stapleton F. Risk factors and causative organisms in microbial keratitis. Cornea 2008;27:22-7.
Cavanagh HD, Robertson DM, Petroll WM, Jester JV. Castroviejo lecture 2009: 40 years in search of the perfect contact lens. Cornea 2010;29:1075-85.
Fleiszig SM, Evans DJ. Pathogenesis of contact lens-associated microbial keratitis. Optom Vis Sci 2010;87:225-32.
Willcox MD. Pseudomonas aeruginosa
infection and inflammation during contact lens wear: A review. Optom Vis Sci 2007;84:273-8.
Yanai R, Ko JA, Morishige N, Chikama T, Ichijima H, Nishida T. Disruption of zonula occludens-1 localization in the rabbit corneal epithelium by contact lens-induced hypoxia. Invest Ophthalmol Vis Sci 2009;50:4605-10.
Willcox MD, Holden BA. Contact lens related corneal infections. Biosci Rep 2001;21:445-61.
Holden BA. The Glenn A. Fry Award Lecture 1988: The ocular response to contact lens wear. Optom Vis Sci 1989;66:717-33.
Stapleton F, Keay L, Edwards K, Naduvilath T, Dart JK, Brian G, et al. The incidence of contact lens-related microbial keratitis in Australia. Ophthalmology 2008;115:1655-62.
Fleiszig SM, Wiener-Kronish JP, Miyazaki H, Vallas V, Mostov KE, Kanada D, et al. Pseudomonas aeruginosa
-mediated cytotoxicity and invasion correlate with distinct genotypes at the loci encoding exoenzyme S. Infect Immun 1997;65:579-86.
Twining SS, Kirschner SE, Mahnke LA, Frank DW. Effect of Pseudomonas aeruginosa
elastase, alkaline protease, and exotoxin A on corneal proteinases and proteins. Invest Ophthalmol Vis Sci 1993;34:2699-712.
O'Callaghan RJ, Engel LS, Hobden JA, Callegan MC, Green LC, Hill JM. Pseudomonas keratitis
. The role of an uncharacterized exoprotein, protease IV, in corneal virulence. Invest Ophthalmol Vis Sci 1996;37:534-43.
Kessler E, Blumberg S. Specific inhibitors of Pseudomonas aeruginosa
elastase as potential drugs for the treatment of Pseudomonas keratitis
. Antibiot Chemother (1971) 1987;39:102-12.
Pastor A, Chabert J, Louwagie M, Garin J, Attree I. PscF is a major component of the Pseudomonas aeruginosa
Type III secretion needle. FEMS Microbiol Lett 2005;253:95-101.
Lee VT, Smith RS, Tümmler B, Lory S. Activities of Pseudomonas aeruginosa
effectors secreted by the Type III secretion system in vitro
and during infection. Infect Immun 2005;73:1695-705.
Wolfgang MC, Lee VT, Gilmore ME, Lory S. Coordinate regulation of bacterial virulence genes by a novel adenylate cyclase-dependent signaling pathway. Dev Cell 2003;4:253-63.
McCaw ML, Lykken GL, Singh PK, Yahr TL. ExsD is a negative regulator of the Pseudomonas aeruginosa
Type III secretion regulon. Mol Microbiol 2002;46:1123-33.
Yahr TL, Goranson J, Frank DW. Exoenzyme S of Pseudomonas aeruginosa
is secreted by a Type III pathway. Mol Microbiol 1996;22:991-1003.
Frank DW. The exoenzyme S regulon of Pseudomonas aeruginosa
. Mol Microbiol 1997;26:621-9.
Vallis AJ, Yahr TL, Barbieri JT, Frank DW. Regulation of ExoS production and secretion by Pseudomonas aeruginosa
in response to tissue culture conditions. Infect Immun 1999;67:914-20.
Parsot C, Hamiaux C, Page AL. The various and varying roles of specific chaperones in Type III secretion systems. Curr Opin Microbiol 2003;6:7-14.
Zhang Y, Barbieri JT. A leucine-rich motif targets Pseudomonas aeruginosa
ExoS within mammalian cells. Infect Immun 2005;73:7938-45.
Krall R, Zhang Y, Barbieri JT. Intracellular membrane localization of pseudomonas ExoS and Yersinia YopE in mammalian cells. J Biol Chem 2004;279:2747-53.
Rolsma SL, Frank DW. In vitro
assays to monitor the activity of Pseudomonas aeruginosa
Type III secreted proteins. Methods Mol Biol 2014;1149:171-84.
Rabin SD, Hauser AR. Functional regions of the Pseudomonas aeruginosa
cytotoxin ExoU. Infect Immun 2005;73:573-82.
Sato H, Frank DW, Hillard CJ, Feix JB, Pankhaniya RR, Moriyama K, et al. The mechanism of action of the Pseudomonas aeruginosa
-encoded Type III cytotoxin, ExoU. EMBO J 2003;22:2959-69.
Phillips RM, Six DA, Dennis EA, Ghosh P. In vivo
phospholipase activity of the Pseudomonas aeruginosa
cytotoxin ExoU and protection of mammalian cells with phospholipase A2 inhibitors. J Biol Chem 2003;278:41326-32.
Rabin SD, Veesenmeyer JL, Bieging KT, Hauser AR. A C-terminal domain targets the Pseudomonas aeruginosa
cytotoxin ExoU to the plasma membrane of host cells. Infect Immun 2006;74:2552-61.
Sato H, Feix JB, Frank DW. Identification of superoxide dismutase as a cofactor for the pseudomonas Type III toxin, ExoU. Biochemistry 2006;45:10368-75.
Maresso AW, Baldwin MR, Barbieri JT. Ezrin/radixin/moesin proteins are high affinity targets for ADP-ribosylation by Pseudomonas aeruginosa
ExoS. J Biol Chem 2004;279:38402-8.
Krall R, Schmidt G, Aktories K, Barbieri JT. Pseudomonas aeruginosa
ExoT is a Rho GTPase-activating protein. Infect Immun 2000;68:6066-8.
Garrity-Ryan L, Kazmierczak B, Kowal R, Comolli J, Hauser A, Engel JN. The arginine finger domain of ExoT contributes to actin cytoskeleton disruption and inhibition of internalization of Pseudomonas aeruginosa
by epithelial cells and macrophages. Infect Immun 2000;68:7100-13.
Sun J, Barbieri JT. Pseudomonas aeruginosa
ExoT ADP-ribosylates CT10 regulator of kinase (Crk) proteins. J Biol Chem 2003;278:32794-800.
Yahr TL, Vallis AJ, Hancock MK, Barbieri JT, Frank DW. ExoY, an adenylate cyclase secreted by the Pseudomonas aeruginosa
Type III system. Proc Natl Acad Sci U S A 1998;95:13899-904.
Fleiszig SM, Zaidi TS, Pier GB. Pseudomonas aeruginosa
invasion of and multiplication within corneal epithelial cells in vitro
. Infect Immun 1995;63:4072-7.
Fleiszig SM, Zaidi TS, Preston MJ, Grout M, Evans DJ, Pier GB. Relationship between cytotoxicity and corneal epithelial cell invasion by clinical isolates of Pseudomonas aeruginosa
. Infect Immun 1996;64:2288-94.
Lee EJ, Cowell BA, Evans DJ, Fleiszig SM. Contribution of ExsA-regulated factors to corneal infection by cytotoxic and invasive Pseudomonas aeruginosa
in a murine scarification model. Invest Ophthalmol Vis Sci 2003;44:3892-8.
Fleiszig SM, Zaidi TS, Fletcher EL, Preston MJ, Pier GB. Pseudomonas aeruginosa
invades corneal epithelial cells during experimental infection. Infect Immun 1994;62:3485-93.
Shen EP, Hsieh YT, Chu HS, Chang SC, Hu FR. Correlation of Pseudomonas aeruginosa
genotype with antibiotic susceptibility and clinical features of induced central keratitis. Invest Ophthalmol Vis Sci 2014;56:365-71.
Choy MH, Stapleton F, Willcox MD, Zhu H. Comparison of virulence factors in Pseudomonas aeruginosa
strains isolated from contact lens- and non-contact lens-related keratitis. J Med Microbiol 2008;57:1539-46.
Khan M, Stapleton F, Summers S, Rice SA, Willcox MD. Antibiotic resistance characteristics of Pseudomonas aeruginosa
isolated from keratitis in Australia and India. Antibiotics (Basel) 2020;9:600.
Borkar DS, Acharya NR, Leong C, Lalitha P, Srinivasan M, Oldenburg CE, et al. Cytotoxic clinical isolates of Pseudomonas aeruginosa
identified during the Steroids for Corneal Ulcers Trial show elevated resistance to fluoroquinolones. BMC Ophthalmol 2014;14:54.
Zhu H, Conibear TC, Bandara R, Aliwarga Y, Stapleton F, Willcox MD. Type III secretion system-associated toxins, proteases, serotypes, and antibiotic resistance of Pseudomonas aeruginosa
isolates associated with keratitis. Curr Eye Res 2006;31:297-306.
Angus AA, Lee AA, Augustin DK, Lee EJ, Evans DJ, Fleiszig SM. Pseudomonas aeruginosa
induces membrane blebs in epithelial cells, which are utilized as a niche for intracellular replication and motility. Infect Immun 2008;76:1992-2001.
Tam C, LeDue J, Mun JJ, Herzmark P, Robey EA, Evans DJ, et al. 3D quantitative imaging of unprocessed live tissue reveals epithelial defense against bacterial adhesion and subsequent traversal requires MyD88. PLoS One 2011;6:e24008.
Soong G, Parker D, Magargee M, Prince AS. The Type III toxins of Pseudomonas aeruginosa
disrupt epithelial barrier function. J Bacteriol 2008;190:2814-21.
Shen EP, Chen MR, Chen WL, Chu HS, Chen KL, Hu FR. Knockdown of IQGAP-1 enhances tight junctions and prevents P. aeruginosa
invasion of human corneal epithelial cells. Ocul Immunol Inflamm 2020;28:876-83.
Feltman H, Schulert G, Khan S, Jain M, Peterson L, Hauser AR. Prevalence of Type III secretion genes in clinical and environmental isolates of Pseudomonas aeruginosa
. Microbiology (Reading) 2001;147:2659-69.
Bradbury RS, Roddam LF, Merritt A, Reid DW, Champion AC. Virulence gene distribution in clinical, nosocomial and environmental isolates of Pseudomonas aeruginosa
. J Med Microbiol 2010;59:881-90.
Lomholt JA, Poulsen K, Kilian M. Epidemic population structure of Pseudomonas aeruginosa
: Evidence for a clone that is pathogenic to the eye and that has a distinct combination of virulence factors. Infect Immun 2001;69:6284-95.
Chan KY, Cho P, Boost M. Microbial adherence to cosmetic contact lenses. Cont Lens Anterior Eye 2014;37:267-72.
Shen EP, Chu HS, Hsieh YT, Chen WL, Chang SC, Hu FR. Analysis of P. aeruginosa
disinfectant sensitivity and microbial adhesions to worn cosmetic contact lenses. Cont Lens Anterior Eye 2020;43:338-44.
Watanabe T, Uematsu M, Mohamed YH, Eguchi H, Imai S, Kitaoka T. Corneal erosion with pigments derived from a cosmetic contact lens: A case report. Eye Contact Lens 2018;44(Suppl 1):S322-5.
Choy MH, Stapleton F, Willcox MD, Zhu H. Comparison of virulence factors in Pseudomonas aeruginosa
strains isolated from contact lens- and non-contact lens-related keratitis. J Med Microbiol 2008;57:1539-46.
Lakkis C, Fleiszig SM. Resistance of Pseudomonas aeruginosa
isolates to hydrogel contact lens disinfection correlates with cytotoxic activity. J Clin Microbiol 2001;39:1477-86.
[Figure 1], [Figure 2]