Molecular Diagnosis of Subcutaneous Pythium insidiosum Infection by Use of PCR Screening and DNA Sequencing

Abstract

h Pythium insidiosum is an emerging human pathogen classified among brown algae and diatoms that can cause significant morbidity and mortality in otherwise healthy individuals. Here we describe a pediatric patient with pythiosis acquired in the southern United States, diagnosed by molecular screening and DNA sequencing of internal transcribed spacer region 1. CASE REPORTA n otherwise healthy 14-year-old girl living in urban north Texas presented to an urgent care facility with a 2-week history of a progressively enlarging, erythematous bump on the medial aspect of her left lower leg. She denied recent travel but was noted to have gone swimming in a swimming pool with signs of algal overgrowth. She was treated with incision and drainage and given a course of oral cephalexin. Although initially responding to antibiotics, over 2 weeks she again developed worsening local edema and erythema. The patient was switched to oral clindamycin but did not show improvement, prompting hospital admission about 3 weeks into her illness. She was administered intravenous clindamycin, and an ultrasound of the area revealed soft-tissue swelling with some patchy areas suggestive of fluid accumulation but without clear signs of an abscess. Incision and drainage was performed, and a drain was placed. Wound cultures were sent and returned positive for Staphylococcus intermedius and Pseudomonas aeruginosa. Based on the culture sensitivities of those organisms, antibiotic therapy was tailored to cefepime, tobramycin, and clindamycin. The patient showed clinical improvement and was discharged on oral ciprofloxacin 1 week after admission.After approximately 5 days, erythema and edema around the wound had visibly increased and the patient was readmitted approximately 1 month after onset of her initial symptoms. She was administered intravenous meropenem and amikacin and incision and drainage was repeated, revealing an abscess measuring 10 cm by 15 cm. A drain was again placed, and wound cultures were sent for growth of bacteria, fungi, and acid-fast bacilli. Histologic sections from debridement material demonstrated an acute and chronic inflammatory infiltrate, interrupted by eosinophilic pools comprised of poorly formed granulomas with central necrosis admixed with neutrophils, eosinophils, and mineralized debris (Fig. 1A). Rare hyphal elements on Gomori methenamine silver stain were identified (Fig. 1B and C). Consequently, amikacin was discontinued, and the patient was started on liposomal amphotericin B (250 mg intravenously [i.v.]

Pythium keratitis in South India: Incidence, clinical profile, management, and treatment recommendation

“…This was further confirmed both by PCR-based DNA sequencing targeting internal transcribed spacer (ITS) region and with zoospores formation identifying the organism as P. insidiosum in all the isolates. [192122] Treatment initiated according to clinical and microbiological evaluations. The eyes with positive fungal smears were treated with 5% natamycin suspension on an hourly basis during waking hours.…”

Pythiosis in sheep from Paraná, southern Brazil

“…An important pathogen species in mammals is Pythium insidiosum (Mendoza et al 1996). It causes fast-growing clinical conditions leading to death, and treatment with antimicrobial agents may be contradictory (Salipante et al 2012). Normally, outbreaks occur during summers and in those animals that have closer contact with floodplains (Gaastra et al 2010).…”

Retrospective multifactorial analysis of Pythium keratitis and review of literature

“…Early identification of Pythium keratitis with usage of proper diagnostic algorithm helped us to initiate appropriate antibiotic treatment based on existing literature. [ 1 2 7 8 9 10 11 12 23 ] This might explain the fairer outcome in our study sample.…”