Extracellular proteases of Aspergillus flavus: Fungal keratitis, proteases, and pathogenesis

Capoor

Indian Journal of Medical Microbiology

et al. 2014

This study was undertaken to evaluate the clinico-demographical profile of keratomycosis. (January 2004 to January 2012). The corneal scrapings were processed by direct microscopic methods and standard culture techniques. Of 209 cases of keratitis studied, culture yielded growth in 80 cases (38.3%). Out of these 80 cases of growth, fungi were isolated in 77.5% and bacteria in 22.5%. The spectrum of keratomycosis was Aspergillus flavus (22.5%), Fusarium solani (16.1%), A. fumigatus (11.3%), Candida albicans (6.4%), etc., Routine surveillance of fungal keratitis is necessary to know the existing and emerging pattern of pathogens and to prevent use of un-warranted anti-microbial therapy.

Section: Discussionmentioning

confidence: 99%

Clinico-demographical profile of keratomycosis in Delhi, North India

Capoor

Indian Journal of Medical Microbiology

et al. 2014

“…[217] examined the role of fungal proteases in the pathogenesis of mycotic keratitis. It was observed that the clinical isolate of A. flavus, isolated from a patient with severe keratitis, secrete variety of proteases including serine proteases, cysteine proteases, metalloproteases and concluded that fungal collagenases are the mediator of the severe corneal destruction observed in keratitis.…”

Section: Toxigenicitymentioning

confidence: 99%

Pathogenesis of microbial keratitis

Lakhundi

Siddiqui

Khan

2017

Microbial Pathogenesis

181

121

Microbial keratitis is a sight-threatening ocular infection caused by bacteria, fungi, and protist pathogens. Epithelial defects and injuries are key predisposing factors making the eye susceptible to corneal pathogens. Among bacterial pathogens, the most common agents responsible for keratitis include Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pneumonia and Serratia species. Fungal agents of corneal infections include both filamentous as well as yeast, including Fusarium, Aspergillus, Phaeohyphomycetes, Curvularia, Paecilomyces, Scedosporium and Candida species, while in protists, Acanthamoeba spp. are responsible for causing ocular disease. Clinical features include redness, pain, tearing, blur vision and inflammation but symptoms vary depending on the causative agent. The underlying molecular mechanisms associated with microbial pathogenesis include virulence factors as well as the host factors that aid in the progression of keratitis, resulting in damage to the ocular tissue. The treatment therefore should focus not only on the elimination of the culprit but also on the neutralization of virulence factors to minimize the damage, in addition to repairing the damaged tissue. A complete understanding of the pathogenesis of microbial keratitis will lead to the rational development of therapeutic interventions. This is a timely review of our current understanding of the advances made in this field in a comprehensible manner. Coupled with the recently available genome sequence information and high throughput genomics technology, and the availability of innovative approaches, this will stimulate interest in this field.

“…Other fungi do secrete serine proteinase and/or metalloproteinase activity (Abbas et al, 1989;Ahman et al, 2002;Chou et al, 2002;Jaton-Ogay et al, 1994;Kunert & Kopecek, 2000;Monod et al, 1991Monod et al, , 1993Moutaouakil et al, 1993;van den Hombergh et al, 1994;Zhu et al, 1990). Second, a public B. cinerea EST database contains a number of sequences that presumably encode a non-KEX-like serine proteinase and a carboxypeptidase, respectively.…”

Section: B Cinerea Cultures Exclusively Contain Secreted Ap Activitymentioning

confidence: 99%

An aspartic proteinase gene family in the filamentous fungus Botrytis cinerea contains members with novel features

et al. 2004

Botrytis cinerea, an important fungal plant pathogen, secretes aspartic proteinase (AP) activity in axenic cultures. No cysteine, serine or metalloproteinase activity could be detected. Proteinase activity was higher in culture medium containing BSA or wheat germ extract, as compared to minimal medium. A proportion of the enzyme activity remained in the extracellular glucan sheath. AP was also the only type of proteinase activity in fluid obtained from B. cinerea-infected tissue of apple, pepper, tomato and zucchini. Five B. cinerea genes encoding an AP were cloned and denoted Bcap1–5. Features of the encoded proteins are discussed. BcAP1, especially, has novel characteristics. A phylogenetic analysis was performed comprising sequences originating from different kingdoms. BcAP1 and BcAP5 did not cluster in a bootstrap-supported clade. BcAP2 clusters with vacuolar APs. BcAP3 and BcAP4 cluster with secreted APs in a clade that also contains glycosylphosphatidylinositol-anchored proteinases from Saccharomyces cerevisiae and Candida albicans. All five Bcap genes are expressed in liquid cultures. Transcript levels of Bcap1, Bcap2, Bcap3 and Bcap4 are subject to glucose and peptone repression. Transcripts from all five Bcap genes were detected in infected plant tissue, indicating that at least part of the AP activity in planta originates from the pathogen.