In Brief | Multidrug-resistant keratitis: challenging yet manageable

Published on MedED: 21 June 2023

Corneal opacities are a leading cause of vision loss globally, and the corneal scarring resulting from infection contributes significantly to this disease burden.¹ Microbial keratitis (MK) is one of the infectious conditions that, if inadequately treated, can lead to severe complications, scarring and eventually loss of sight. 

This retrospective study set out to review the instances of multi-drug resistant bacterial keratitis presenting a tertiary eye care institute in the eastern part of India over a period of two years (January 2018- December 2019). The researchers, Sahoo et al., reviewed the risk factors associated with the development of the condition, the size and depth of the infiltrate, the causative organism and subsequent treatment administered, and the outcomes of that treatment. The study sample included cases resistant to three or more antibiotics classes. 

Of the original sample group of 1035 cases of MK, 637 cases were caused by bacterial infection, and MDR was determined in 40 eyes of 40 patients. Four times more males than females were in the MDR cohort (4.7:1), and the mean age was 50.9 years. The most common risk factor was ocular trauma (vegetative), which occurred in at least 30% of the cases, followed by previous corneal transplant in 7 of the patients ( (17.5%) and systemic comorbidities including post-renal complications, vitamin-A deficiency and chemotherapy for renal carcinomas accounting for a further 17.5%. 

The researchers recorded that Gram-negative bacilli (GNB) accounted for 45% (18) of the MDR cases, with Pseudomonas Aeruginosa being the most common GNBs. Gram-positive bacilli  (GPB) were cultured in 15 patients( 37.5%), Corynebacterium Amycolatum being the most common MDR organism (12.5%). Gram-positive cocci occurred in 6 patients, and Gram-negative cocci were found in one patient. 

17 (42.5%) patients were resistant to at least three antimicrobials; one was resistant to all seven antimicrobials. The highest rates of AMR were found in Moxifloxacin (82.5%) and chloramphenicol (85.0%), respectively, while no resistance to tobramycin was observed.

In terms of outcomes:

“Complete resolution of the condition was seen in 15 (37.5%) of the MDR patients on medical management only: eleven (27.5%) patients required TA+BCL application and five (12.5%) patients underwent therapeutic penetrating keratoplasty.”^.1(pg771) 

Of interest, the researchers note, the size of the infiltrate rather than the duration of symptoms at presentation and the pattern of drug resistance correlated with the success or failure of medical management in MDR keratitis. They highlight that their study found a high rate of MDR  in cases of gram-negative bacterial infection, with Corynebacterium as the most commonly occurring MDR organism, in contrast to the findings of similar studies in which methicillin-resistant Staphylococcus was most common. Their results confirm the emerging drug resistance profile of Pseudomonas and the growing resistance to the fluoroquinolones found in other studies. 

They conclude that MK is treatable by medical therapies alone, provided the appropriate treatment is given and commenced early in the disease progression.

1. Mahajan, P., VanBuren, J. M., Tzimenatos, L., Cruz, A. T., Vitale, M., Powell, E. C., Leetch, A. N., Pickett, M. L., Brayer, A., Nigrovic, L. E., Dayan, P. S., Atabaki, S. M., Ruddy, R. M., Rogers, A. J., Greenberg, R., Alpern, E. R., Tunik, M. G., Saunders, M., Muenzer, J., Levine, D. A., … Pediatric Emergency Care Applied Research Network (PECARN) (2022). Serious Bacterial Infections in Young Febrile Infants With Positive Urinalysis Results. Pediatrics, 150(4), e2021055633. https://doi.org/10.1542/peds.2021-055633