Evaluation of Excreta/Secreta of Lucilia sericata Larvae as a New Antibacterial Candidate for Treatment of MRSA Ocular Infection

Staphylococcus aureus is the most serious cause of bacterial keratitis in most populations. Due to the resistance of this bacteria to methicillin (MRSA), the novel antimicrobial component is required for novel treatments for keratitis. Excretions/secretions (ES) from larvae of Lucilia sericata (maggot) have antibacterial activity against a number of bacteria. Around 500 larvae were washed with 1 mL of sterile water every hour for ES development. Bactericidal activity of ES was examined by time killing assay. MRSA strain was injected intrastromal into rabbit corneas. The rabbits have been split into three categories, including artificial tear, gentamicin, and maggot ES. Following, the eyes were clinically examined by a slit lamp. This evaluation included the conjunctiva, iris, and cornea. Lastly, the cornea of rabbits was collected for bacterial colony counts. After statistical analysis by ANOVA, it was found that gentamicin and ES, significantly reduced ocular infections in rabbits. Comparisons of corneal opacity scores with Mann–Whitney U-test showed a decreasing trend of therapeutic effects as shown below: gentamicin˃ES˃control. Gentamicin and ES significantly decrease CFU (number of colony-forming units) compared with the control. The mean bacterial count (log CFU/mL) from corneal culture for ES, gentamicin, and untreated groups were 6.04, 5.0, and 8.9, respectively (P≤0.05). In conclusion, the extraction of maggot larvae is useful in treating keratitis mediated by MRSA.

Bilateral Moraxella Keratitis in a Healthy Person after an Episode of Conjunctivitis: A Case Report

Moraxella species are gram-negative diplobacilli and are rare cause of bacterial keratitis. We report a case of a 55-year-old woman presented with pain, redness and profound decrease in vision in both eyes for 2 weeks. One month back she had been treated as acute follicular conjunctivitis elsewhere. She had been treated with ofloxacin drops. On examination, she had central oval full-thickness infiltrate with thinning of cornea and hypopyon in both eyes. She had pseudomembrane in the tarsal conjunctiva. Corneal culture, done separately, showed isolation of Moraxella species, which was resistant to fluoroquinolones. She responded to fortified amikacin and ulcer healed with best-corrected vision of 6/24 and 6/18 in right and left eye respectively. Moraxella keratitis can cause severe keratitis. Conjunctivitis may be complicated by keratitis. Antibiotic resistance can cause problem. Bilateral keratitis should be referred promptly to higher centers if not responding well to treatment.

Corneal Culture in Infectious Keratitis: Effect of the Inoculation Method and Media on the Corneal Culture Outcome

Background: To compare two different methods of corneal culture in infectious keratitis: multiple sampling for direct inoculation and enrichment (standard method) and a single sample via transport medium for indirect inoculation (indirect inoculation method). Methods: Prospective inclusion of patients fulfilling predefined criteria of infectious keratitis undergoing corneal culture according to both studied methods in a randomized order. Results: The standard method resulted in a significantly higher proportion of positive culture outcomes among the 94 included episodes of infectious keratitis (61%; 57/94) than the indirect inoculation method (44%; 41/94) (p = 0.002) and a significantly higher proportion of microorganisms than the indirect inoculation method, with a Cohen’s kappa of 0.38 (95% CI: 0.28–0.49) for agreement between the methods. Subanalysis of culture results showed that direct inoculation on gonococcal agar only combined with the indirect inoculation method resulted in a similar rate of culture positive patients and proportion of detected microorganisms to the standard method. Conclusion: Indirect inoculation of one corneal sample cannot replace direct inoculation of multiple corneal samples without loss of information. A combination of directly and indirectly inoculated samples can reduce the number of corneal samples by four without statistically significant differences in culture outcome or in the proportion of detected microorganisms.

Does the sampling instrument influence corneal culture outcome in patients with infectious keratitis? A retrospective study comparing cotton tipped applicator with knife blade

ObjectiveThis study aimed to compare the efficacy of a cotton tipped applicator and a knife blade in obtaining corneal samples in patients with infectious keratitis.Methods and analysisThis is a retrospective cohort study of patients with suspected infectious keratitis during 2004–2014. Samples for corneal culture were obtained by a cotton tipped applicator and a knife blade, and directly inoculated on GC agar, blood agar and Sabouraud agar.ResultsIn all, 355 patients were included. Corneal sampling by cotton tipped applicator yielded a significantly higher rate of patients with positive corneal culture, 156/355 (43.9%), compared with knife blade, 111/355 (31.3%) (p<0.001). On a patient level, the culture results obtained by the cotton tipped applicator and the knife blade were identical in 269/355 (76%) of the patients. The overall agreement between the two instruments on microbial level was 0.66 (Cohen’s kappa 95% CI 0.60 to 0.72).ConclusionCorneal sampling by cotton tipped applicator generated a higher rate of positive corneal cultures and a higher proportion of isolated microbes than by knife blade. Future studies with randomised sampling order are needed to establish which instrument, cotton tipped applicator or knife blade, is the most effective in sampling microbes for direct inoculation in patients with infectious keratitis.