Antimicrobial Resistance Rising

What do global warming, microplastics, and antimicrobial resistance (AMR) all have in common? They are all growing global challenges, but AMR is positioned to be particularly problematic for ophthalmology.

“AMR occurs when bacteria, viruses, fungi, and parasites no longer respond to antimicrobial medicines,” Alvin L Young MBBCh explained. “As a result of such resistance, antibiotics and antimicrobials will become ineffective, and infections become difficult or impossible to treat, increasing the risk of disease spread, severe illness, disability, and death.

“Why is this happening? Excess consumption of broad-spectrum antibiotics, inappropriate dosages of standard antibiotics, poor patient compliance, external use outside the medical field (such as for veterinary or agricultural purposes), inappropriate disposal, etc., leading to higher antibiotic resistance globally.”

Professor Young said AMR can occur in a number of ways, including through enzymatic inactivation. For example, Escherichia coli can inactivate penicillin and cephalosporins when they produce enzymes to destroy or chemically modify antibiotics.

In target modification, mutations can alter the antimicrobial target site, reducing or preventing drug binding. One example is herpes simplex virus (HSV), which modifies the thymidine kinase so acyclovir is no longer activated or incorporated. There are also efflux pumps, where transport protein pumps antimicrobials out to lower intracellular drug concentration, as is the case with Candida.

“Resistant microbes will grow and become the dominant strain afterwards, and that is why you would end up with resistant bacteria with repeated antibiotics,” Prof Young said. “In ophthalmology, this affects blepharitis and conjunctivitis, as well as keratitis, uveitis, vitritis, retinitis, scleritis, orbital cellulitis, and other conditions.”

AMR risk increases with patient age, Prof Young said, as it is associated with more time spent in hospitals and nursing homes. Ophthalmologists should therefore consider treatment options less likely to encounter AMR, like dropless cataract surgery, although he also stressed caution with this option, as there have been rare reports of endophthalmitis after dropless cataract surgery with moxifloxacin.

Prof Young said the eye’s accessibility to antibiotics poses a unique challenge for ophthalmologists, as topical exposures may be higher than systemic ones. Minimum inhibitory concentrations (MICs), the standard for measuring microbial resistance, may struggle with monitoring this potential exposure as they are measured in the lab and have not been validated for keratitis.

Ultimately, these challenges make prevention the best cure.

“Prophylaxis should be considered as the first antibiotic,” Prof Young said, adding that every course of action with a patient requires good hygiene, too.

He also recommends that ophthalmologists obtain microbial cultures and adjust antimicrobial and bacterial treatment based on sensitivity results.

“We should follow local and international guidelines, observe antibiotic stewardship, and avoid unnecessary prolonged antibiotic prescription. We should also educate patients on adherence to antibiotic regimens,” Prof Young said.

“If we do all that, we can protect the treatment effectiveness of antibiotics, and, with concerted efforts, we can limit the development of AMR. This will reduce the added cost in medical treatment, public safety issues, and patient mortality.”

Prof Young presented at the EuCornea annual congress in Porto, Portugal.

Alvin L Young MBBCh, BAO (NUI), MMedSc (Hons), FRCOphth, FHKAM (Ophth) is Deputy Hospital Chief Executive & Chief of Service at the Prince of Wales Hospital, the Chinese University of Hong Kong. youngla@ha.org.hk