Brazilian study links conjunctival bacteria to higher fluoroquinolone resistance

A real-world, longitudinal, prospective study conducted in Brazil found that bacteria typically found on the conjunctiva were more resistant to fluoroquinolones, according to first author Luca Bongiovanni de Miranda Gonçalves, MD. This result suggested the possible selection of resistant bacteria should not be taken for granted in a clinic setting.¹

De Miranda Gonçalves is from the Centro Universitário Faculdade de Medicina Do ABC/FMABC, Santo André, Brazil, and the Universidade Federal de São Paulo/UNIFESP, São Paulo, Brazil.

Knowledge about resistance to antibiotics is becoming increasingly important in light of the burgeoning numbers of intravitreal injections administered in ophthalmology and their associated complications, the authors explained.

The authors commented, “The rampant use of antibiotics in medicine has created the emergence of numerous multidrug resistant infections. The selection of resistant microbiota at an alarming rate worldwide has become an important target for studies that the promote awareness of the medical community to the flagrant use of antibiotics.^2,3 In cultures of endophthalmitis, resistant strains are increasingly found and they are demonstrating more virulence.⁴ It is essential to better understand how to reduce this growth in resistant and more virulent bacteria, so that the treatment of endophthalmitis does not become even more challenging.”

In their study, de Miranda Gonçalves and colleagues analyzed the conjunctival flora obtained from patients treated with intravitreal injections and the topical antibiotics used. The 98 patients included in the study were from a retina outpatient clinic and were using 0.3% ofloxacin eye drops as prophylaxis against infection.

The swabs (n=148) obtained from the patients were cultured and underwent antibiotic sensitivity testing. The results showed that all bacteria except Escherichia coli were sensitive to vancomycin, and they also responded to the third-generation cephalosporin ceftriaxone, which is the same class and generation as ceftazidime, both of which are important for treating endophthalmitis, the authors reported.

“The bacterial species were specifically coagulase-negative Staphylococcus sp., 92% of which was penicillin-resistant and 56.9% was resistant to ciprofloxacin, a second-generation fluoroquinolone. The culture results were similar to that described in the literature and showed the same higher prevalence of coagulase-negative Staphylococcus sp. and S. epidermidis,” they said.

The results also showed that vancomycin, a third-generation cephalosporin, and penicillin had almost identical resistance profiles to those reported previously. Regarding fluoroquinolones, the incidence of resistant coagulase-negative Staphylococcus sp. was lower than the findings worldwide, but the resistance rates found were as follows: S. aureus (26.7%), S. epidermidis (61.3%), and Staphylococcus sp. (coagulase negative, 56.9%), the investigators reported.

They concluded that the conjunctival bacteria typically identified exhibited higher resistance to fluoroquinolones, although, they pointed out that they were not tested specifically to ofloxacin. This suggested a possible selection of resistant bacteria that should not be taken for granted. However, the same bacteria did not exhibit cross-resistance in the analysis of vancomycin and third-generation cephalosporins. “This real-world, longitudinal, prospective study on conjunctival flora analyzed bacterial resistance profiles and contemporary antibiotic use, offering deeper insights into this subject,” they said.

References

1. de Miranda Gonçalves LB, Campos MLLS, Barros GF, et al. Analysis of topical conjunctival microbiotic cultures in patients treated with intravitreal injections using antibiotic prophylaxis with 0.3% ofloxacin eye drops. Int J Retina Vitr. 2024;10; https://doi.org/10.1186/s40942-024-00604-x

2. Ghosh D, Veeraraghavan B, Elangovan R, Vivekanandan P. Antibiotic resistance and epigenetics: more to it than meets the eye. Antimicro Agents Chemother. 2020;64:e02225-e2319.

3. Asbell PA, Sanfilippo CM, Sahm DF, DeCory HH. Trends in antibiotic resistance among ocular microorganisms in the United States from 2009 to 2018. JAMA Ophthalmol. 2020;138:439–50.

4. Hooper DC. Fluoroquinolone resistance among Gram-positive cocci. Lancet Infect Dis. 2002;2:530–8.

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