Diagnostic value of paediatric blood culture bottle allied to MALDI-TOF mass spectrometry in the aetiological assessment of microbial keratitis.

PURPOSE: Infectious keratitis remains a sight-threatening condition, yet its aetiological diagnosis is often hampered by low culture positivity, largely due to limited corneal scraping material. Identifying alternative, high-yield methods is crucial to optimise treatment protocols. This study evaluates the diagnostic performance of paediatric blood culture bottles (PBCB) compared with the conventional multi-sampled method. MALDI-TOF mass spectrometry (MS) was used as the standardised identification tool for isolates recovered using both approaches.

METHODS

This prospective study included patients with infectious keratitis at a tertiary referral centre (2019-2023). Corneal scrapings were cultured using PBCB and, in parallel, using a conventional multi-sampled approach (thioglycolate broth, brain heart infusion broth with antibiotics, blood agar, chocolate agar, Sabouraud dextrose agar). Pathogens were identified by MALDI-TOF MS. Diagnostic agreement between methods was assessed using Cohen's kappa with 95% confidence intervals.

RESULTS

Among 150 corneal scrapings, the overall culture positivity was 49.3%. PBCB yielded positive cultures in 41.3% (62/150) of cases, comparable to the multi-sampled approach (43.3%; 65/150). Pseudomonas aeruginosa was the most frequently isolated pathogen in both methods (22.9% vs 20.8%). Diagnostic agreement between the two techniques was substantial (kappa = 0.69; 95% CI: 0.57-0.80). Of note, the conventional method detected fungal pathogens in some cases where PBCB were negative.

CONCLUSION

PBCB represents an effective diagnostic alternative for bacterial keratitis, performing comparably to conventional multi-sampling. Although standard techniques remain necessary for fungal detection, PBCB offers practical advantages, particularly in small-volume samples. Its use may reduce the number of corneal scrapings required, contributing to a safer diagnostic approach.