Sydney Eye Podcast | @CabreraMarie

Antimicrobial resistance in corneal infections

February 04, 2021 Dr Maria Cabrera Season 1 Episode 2
Sydney Eye Podcast | @CabreraMarie
Antimicrobial resistance in corneal infections
Show Notes Transcript

Did you know that antimicrobial resistance also occurs in corneal infections as well as in systemic infections?

Dr. Maria Cabrera talks about what antimicrobial resistance is, some causes of antimicrobial resistance, and how to prevent antimicrobial resistance in corneal infections.

The transcript is available in the 'Transcript' tab on this page.
 Closed captioning for this episode can be found on YouTube --> HERE

Don't forget to listen to our previous episode -->
Ep1: Corneal infection and contact lenses

If you have any questions, comments, or suggestions please send them to

Connect with us on Twitter:
Dr. Maria Cabrera: @CabreraMarie,
Prof Stephanie Watson: @profswatson,
Corneal Research Group, Save Sight Institute, University of Sydney: @cornealresearch
using #Sydeyepod

Music provided by: Energized morning by Airae

Maria Cabrera: Have you heard that about 300 people die each year in Australia due to infections resistant to bacteria?

Did you know that resistance to antibiotics occur in ocular infections as well as in systemic infections?

Have you heard that patients with a bacterial corneal infection resistant to antibiotics had been usually treated with other antibiotics in the two weeks prior to presentation to the hospital?

By the end of this podcast, you’ll know…

·         What antimicrobial resistance is;

·         Some causes of antimicrobial resistance; and

·         What to do to prevent antimicrobial resistance in bacterial corneal infections.

First, I will give a brief introduction about antimicrobial resistance, and later we are going to explore some research on antimicrobial resistance in corneal infections in Australia.

I am Maria Cabrera-Aguas. A Researcher at the University of Sydney, Save Sight Institute. Welcome to the Sydney Eye podcast!

I hope you have enjoyed our first episode on corneal infections associated with contact lenses. If you have not yet, I encourage you to listen to it, as the first episode gives you an introduction to corneal infections.

Today, we are going to talk about antimicrobial resistance in corneal infections as it has become such an important issue that the World Health Organisation has a global action plan to combat this resistance. 

But what is antimicrobial resistance? 

We surveyed some people, with no health background, about this question and here are their answers. Let’s listen!

P1: I heard about it in the news. I think it is when the virus or bacteria creates a resistance to drugs that are supposed to kill them. When people self-medicate, it contributes to create resistance to those drugs if people take them too frequently. 

P2: I have never heard the word before. But by looking at the words, I think it is something to do with bacteria, the body develops immune system against certain bacteria, so we won’t get sick or it is something like when you take antibiotics, and it doesn’t work anymore because the body is used to certain types of antibiotics. 

P3: My understanding of antimicrobial resistance is that it is resistance by the body to some form of bacteria or it could be similar to antibiotic resistance as well. So, I have heard of MRSA and other illnesses associated with resistance to something that could be antibiotic or something that is microbial.  

P4: I have not heard of antimicrobial resistance, but I think it refers to resistance of microbes in the eye which I think are sort of organisms that perhaps live in your eye, like microorganisms that probably serve some purpose in the eye but are not really sure the that natural occurring in the eye or some sort of foreign invasion in the eye. But I think it is a measure of resistance to microbes occurring in the eye.

In general, although some people have not heard the term ‘antimicrobial’, they interpreted it well by saying that antimicrobial was an antibiotic. Moreover, one of the participants mentioned that she had heard about MRSA which stands for methicillin-resistant staphylococcus aureus. A MRSA infection is caused by a type of staphylococcus aureus bacteria that becomes resistant to many antibiotics used to treat common infections.

An antimicrobial is a medication used to prevent and treat infections in humans, plants, and animals. An antimicrobial can be an antibiotic, used for bacterial infections; an antiviral, used for viral infections; an antifungal, for fungal infections; or an antiparasitic for parasitic infections. An antimicrobial is something that can treat any microbe.

Antimicrobial resistance happens when bacteria, virus, fungi, or parasites change overtime and then cannot respond to the medications which makes them harder or impossible to treat. Therefore, there is a risk of disease spread, severe disease and even death, and for eye infection cases: loss of sight or even the eye.

So, what causes antimicrobial resistance? 

Antimicrobial resistance occurs naturally over time, usually through genetic changes, but antibiotic use makes it worse. Bacteria can become resistant to antibiotics when they turn on certain internal resistance processes, change to protect themselves from an antibiotic, or receive resistance genes from other bacteria.

Some causes are:

·         Overuse of antibiotics: when we use antibiotics, some bacteria die but resistant bacteria can survive and multiply. The overuse of antibiotics makes resistant bacteria more common. The more we use antibiotics, the more chances bacteria have to become resistant to them.

·         Inappropriate prescribing: studies in the United States have reported that treatment indication, choice of medication or duration of antibiotic therapy was incorrect in 30 to 50% of patients in 2014. Moreover, in Australia in the same year, a study showed that half of general practitioners prescribed antibiotics for upper respiratory tract infections to meet patient’s expectations. That is, patients seeing a general practitioner often expect them to prescribe antibiotics. In fact, a survey showed that one in five patients would ask the doctor to prescribe antibiotics. Incorrectly prescribed antibiotics promote antibiotic resistance by supporting genetic alterations in the bacteria. 

·          Poor hygiene and poor infection prevention and control: this can provide more opportunity for resistant bacteria to spread and make more people sick increasing the need for antibiotics. Hand hygiene is the most important way of preventing the spread of infections. 

Antimicrobial resistance is a health threat worldwide as having a significant potential impact on treatment outcomes. In the United States, resistant infections cause about 23,000 deaths and more than two million illnesses annually with costs of US$35 billion American dollars. Similarly, 25,000 deaths per year related to resistant infections occur in Europe. The Organisation for Economic Co-operation and Development estimated that an average of 290 deaths is caused by eight resistant bacteria each year in Australia, and that the cost to the health systems of Australia, the United States and Canada combined will be of US$74 billion American dollars between 2015 and 2050 from such resistance.

A bacterial corneal infection is an ocular emergency needing an immediate and effective antibiotic treatment as it can progress very rapidly, causing visual impairment and, potentially, blindness. Symptoms of a corneal infection include a red and sore eye, blurring vision, sensitivity to light, tearing, or discharge. You can also see a ulcer, which may look like a white spot on your cornea. There are significant collateral costs of this infection, for example: a reduced quality of life for those affected and an increased health-system burden. Therefore, there is a need to undertake antimicrobial resistance surveillance to determine the suitability of the initial antibiotic therapy for bacterial corneal infections given the challenge of organisms becoming resistant to antibiotics.

Surveillance programs for antimicrobial resistance were recommended by the World Health Organization, Global Action Plan to support disease prevention and control strategies. These strategies include evidence-based antibiotic prescribing guidelines based on local and regional data. In Australia, there were such programs for systemic infections but not for ocular infections. At the Sydney Eye Hospital, we created a surveillance program in collaboration with NSW Health Pathology to monitor the antimicrobial resistance in bacterial corneal infections in this hospital in 2016. 

More on the results of the antimicrobial resistance surveillance program up next…

But first, we have a question for you, the listeners. Have you had a corneal infection before? If so, how was your treatment? Were you treated as an out-patient or admitted in a hospital? What antibiotics were you prescribed?

Email us at or share on Twitter with the hashtag sydeyepod, that’s Hashtag S-Y-D-E-Y-E-P-O-D.

Now, more on the research of antimicrobial resistance and surveillance programs

To find the organism causing a corneal infection, a corneal scraping is performed. This involves scraping the ulcer to get a sample which is sent to the lab for culture, to grow the causing bacteria and to determine what antibiotic is the most appropriate for the infection. The culture results are usually available within 48 hours.  But, as the infection may worsen very rapidly, doctors start intensive antibiotics that are the most likely to work when the scraping is performed. The initial antibiotics can be changed when culture results are available. 

In Australia, the most common bacteria causing corneal infections are Staphylococci and Pseudomonas aeruginosa. Staphylococci are the most common in people with dry eye or blepharitis which is the inflammation of the eye lids, and Pseudomonas aeruginosa, in contact lens wearers.

Our surveillance program reported in 2016 that nine in ten bacterial corneal infections would be covered by the current antibiotic recommendations of ciprofloxacin or ofloxacin alone, or a combination of cefalotin and gentamicin. This remained stable for the years 2017 and 2018, according to our most recent report published in November 2020 in the journal of Communicable Diseases Intelligence published by the Australian Department of Health.

And what to do to prevent resistance to antibiotics?

Between 2012 and 2016, we studied patients admitted at the Sydney Eye Hospital with a bacterial corneal infection resistant to antibiotics. We found that one in two episodes had been treated with other antibiotics within the last 14 days prior to the presentation to the hospital, and the duration of the symptoms was between 3-8 days. These patients were more likely to have poor vision after the resolution of the infection, delay in the healing of the ulcer and perforation of the cornea needing a corneal transplantation. 

It is also important to highlight that the antibiotic called chloramphenicol, commercially known as Chlorsig, has been widely accessible to the public without a prescription since 2010 in Australia. This antibiotic kills a wide range of bacteria but does not have any use for Pseudomonas aeruginosa. Remember that Pseudomonas aeruginosa is the most common cause of corneal infection in contact lens wearers. After this change in 2010, there was a sudden rise in sales of this product to 600,000 additional units in the following year. This suggested that the rise in use of Chlorsig was due to recommendations by pharmacists or optometrists.

Poor outcomes such as loss of the eye and lifelong reduced vision from corneal scarring have been reported due to the inappropriate Chlorsig use which delayed diagnosis and early management.

Therefore, as a patient you can do these three things to avoid having a corneal infection resistant to the antibiotics:

·         One: you must see an eye doctor immediately after the onset of symptoms. The eye doctor will perform a corneal scrape and will start appropriate antibiotics. Do not self-treat with over-the-counter antibiotics such as Chlorsig as it may not work for the bacteria causing the infection. Inappropriate antibiotic therapy may cause serious complications for example need of corneal transplantation or even loss of your eye.

·         Two: finish the entire course of antibiotics so they can be fully effective and not promote antibiotic resistance, and

·         Three: practise good hand washing to prevent infection especially from contact lens wear

In summary, antimicrobial resistance happens when bacteria, virus, fungi, or parasites develop resistance to antibiotics that were commonly used to treat them. 

Some causes of antimicrobial resistance are overuse of antibiotics, incorrect antibiotic prescribing by clinicians, and lack of hygiene and infection control.

The World Health Organisation has recommended surveillance programs to monitor antimicrobial resistance. In Australia, there were surveillance programs for systemic infections, but not for ocular infections. At the Sydney Eye Hospital, we established a surveillance program in 2016 which has reported that most of the patients with bacterial corneal infections are still susceptible to the most common antibiotics. 

In our study, patients with a corneal infection resistant to antibiotics received antibiotics during the last two weeks prior to presentation and presented to the hospital between 3 to 8 days after the symptoms started. 

To prevent a corneal infection resistant to antibiotics please seek an eye doctor as soon as possible to get checked, do not self-treat with over-the-counter antibiotics such as Chlorsig, finish your course of antibiotics and practice good hand washing.

I’m Maria Cabrera-Aguas, thanks for joining me today in the second episode of the Sydney Eye podcast. 

If you have any questions, comments or suggestions please send them to and connect with us on Twitter @CabreraMarie, it’s C-A-B-R-E-R-A-M-A-R-I-E or @cornealresearch using the hashtag S-Y-D-E-Y-E-P-O-D.  Until next time. Bye!