Use of the “FilmArray® blood culture identification 2” panel in a case of endophthalmitis due to Candida parapsilosis

The FilmArray® (BioFire Diagnostics, Salt Lake City, UT, USA) system is a multiplex PCR that integrates sample preparation, amplification, detection and analysis. One of the available panels is the "Blood Culture Identification 2 (BCID2)", which allows for searching for up to 43 different targets associated with bacteraemia, including five antimicrobial resistance genes, directly from positive blood cultures. The objective of this text is to present our experience about the use of this PCR technique to help in the aetiological and therapeutic orientation in a case of endophthalmitis caused by Candida parapsilosis (C. parapsilosis).

We present the case of a 79-year-old man on anticoagulation and antiplatelet therapy with diabetes mellitus and hypertension, who underwent cataract surgery by phacoemulsification and intraocular lens implant without incident. Six months later, the patient has onset of pain, photophobia, and a slight decrease in visual acuity in that same eye. Upon examination, positive Tyndall effect, mild capsular phimosis and fibrosis, and whitish deposits are described. An ocular ultrasound is performed revealing data regarding complete retinal detachment and linear floaters similarly fixed to the optic disc suggestive of membranes residual to endophthalmitis (Fig. 1). A sample of vitreous humor (not diluted) is taken prior to infusion of saline solution, and subsequently a pars plana vitrectomy is performed. Samples are sent to the microbiology laboratory: vitreous and aqueous humor, as well as vitrectomy cassette and intraocular lens capsular bag complex. Intravitreal ceftazidime and vancomycin (1,000 mg and 500 mg diluted in 50 ml, respectively) are administered.

Figure 1.

In the left eyeball, a linear image of V-shaped morphology fixed to the optic disc is visualised, suggestive of complete retinal detachment. In an internal location to the retina, other linear images are visualised, also fixed to the optic disc, suggestive of residual membranes of endophthalmitis.

Upon arrival at the microbiology laboratory, the diluted aqueous and vitreous humor samples are processed by centrifugation (5 min at 3,000 rpm) and all but the last 0.5 ml of the supernatant is transferred to another tube. The sediment is resuspended in this 0.5 ml for Gram staining and culture inoculation. The samples are inoculated on chocolate agar (Becton Dickinson, Franklin Lakes, NJ, USA), Trypticase Soy Agar with 5% Sheep Blood (Becton Dickinson, Franklin Lakes, NJ, USA) and Sabouraud agar with chloramphenicol (Becton Dickinson, Franklin Lakes, NJ, USA), as well as in thioglycolate broth enrichment medium. Yeasts are observed in the Gram stain. At this point, 200 µl of the remaining supernatant is removed from the centrifuged vitreous humor for the performance of the FilmArray®BCID2 Panel, through which C. parapsilosis identified. After this result, the patient is taken to the operating room that same day for intravitreal injection of voriconazole (200 mg diluted in 20 ml). At 24 h, white colonies are observed in cultures of vitreous humor, aqueous humor, vitrectomy cassette and intraocular lens capsular bag complex, later being identified as C. parapsilosis by MALDI-TOF (matrix-assisted laser desorption/ionisation mass spectrometry, Bruker™). The patient is discharged from the hospital with oral fluconazole 100 mg/24 h and corticosteroids 2.5 mg/48 h, as well as tobramycin/corticosteroid 1 mg/mL and voriconazole 10 mg/mL/4 h eye drops.

The FilmArray® BCID2 panel multiplex PCR system has been extensively tested, with numerous studies demonstrating high sensitivity and specificity in positive blood culture samples.^1,2 Its applicability to sterile samples other than blood cultures has also been studied for therapeutic guidance in both the adult and paediatric population.^3–6 Even in the context of septic arthritis or pleural empyema, where the consistency of the sample and the high leukocyte concentration could inhibit this test, this technique could be a helpful complementary diagnostic tool.⁷

It is rare that the FilmArray® multiplex PCR system yields false negatives, but Gonzalez-Donapetry et al. presented a representative example.⁸ Following their recommendations, the melting curves and internal controls must be carefully reviewed because at times there may be alterations, the meaning of which could differ depending on the clinical context.

The FilmArray® BCID2 system has demonstrated some utility in sterile samples other than those indicated by the manufacturer, and it is a tool to consider when it is necessary to establish early antibiotic treatment in patients and complex situations, such as the case of endophthalmitis that we present. Despite this, the limitations of the technique in this type of sample must be taken into account, carrying out a prior validation, and further prospective studies that add more evidence to what has been observed up until now.

Author contributions

• •

  Domingo Fernández Vecilla: drafted the scientific text.

• •

  Iris Sharon Pérez Ramos: helped draft the clinical case.

• •

  Cristina Aspichueta Vivanco: reviewed the case and helped modify it.

• •

  Miren Josebe Unzaga Barañano: reviewed the case and helped modify it.

Funding

This text has not received funding.

Conflicts of interest

The authors declare that they have no conflicts of interest.