AVR Funded Grant – 2022
Project Title:
The Bacterial Ocular Surveillance System (BOSS)
Chief Investigator:
Professor Stephanie Watson
Co-Investigators:
Prof Monica Lahra, A/Prof Richard Mills, Dr Steve Wiffen, Dr Maria Cabrera- Aguas
Aim
The aim of this study was to report the type of bacteria and antibiotic resistance of bacteria isolated from corneal
scrapings in bacterial keratitis (corneal infections) from 2019 to 2022.
Methods
A retrospective analysis of bacteria isolated from cornea scrapings from 12 centres in Sydney,
Melbourne, Adelaide, and Perth from January 1, 2019 to December 31, 2022 was conducted. Bacteria were
identified by MALDI-TOF mass spectrometry.
Antibiotic susceptibilities were determined using standard methodology.
Key results
There were 1791 organisms isolated. Of these, 1311
(73%) were Gram-positive and 480 (27%) Gram-
negative organisms. Coagulase-negative
staphylococci (CoNS) 32% (569/1791),
Staphylococcus aureus 22% (398/1791), including 26
methicillin-resistant S. aureus (MRSA),
Corynebacterium spp. 5% (83/1791); and
Pseudomonas aeruginosa 14% (252/1791) were the
most common organisms.
Antimicrobial non-susceptibility was found for CoNS
to cefalotin 25%, chloramphenicol 12%,
ciprofloxacin 7% and gentamicin 5%; methicillin-
sensitive S. aureus (MSSA) to ciprofloxacin 6%,
chloramphenicol 5%, gentamicin 1%; MRSA to
ciprofloxacin 42% and gentamicin 8% and
chloramphenicol 6%; Corynebacterium spp. to
cefalotin 29%, ciprofloxacin 12%, chloramphenicol
9%; Pseudomonas aeruginosa to ciprofloxacin 2%,
gentamicin 1.2%, and tobramycin 1%. All Gram-
positive isolates were susceptible to vancomycin.
Implications for Clinical Practice/Science and Future Research
Results from this study will inform
ophthalmologists on treating patients with bacterial
keratitis according to antibiotic susceptibilities in
each region in Australia. It is known that antibiotic
susceptibilities change according to climate and
geographical regions.
Next steps are to continue this surveillance program
nationwide including other sites such Tasmania,
Australian Capital Territory, Queensland, and
Northern Territory. We also aim to include other
infectious conditions such as conjunctivitis and
endophthalmitis.
Conclusion
Coagulase negative Staphylococci were the main
causal organisms of bacterial keratitis. Of these,
one-quarter of these were resistant to cefalotin. An
ongoing antimicrobial resistance surveillance
program in ocular infections across Australia is
needed to provide evidence-base therapy
recommendations according to geographic
locations..
Lay Summary of Outcomes
This study investigated the trends of bacteria and
their antibiotic susceptibility from corneal scrapes
from patients with corneal infection in Australia.
Coagulase negative staphylococci were the main
causal bacteria. Of these, 25% were resistant to
cefalotin and 7% to ciprofloxacin.