In May 2024, the World Health Organisation (WHO) updated the Bacterial Priority Pathogens List (BPPL), an important tool in the global fight against antibiotic resistance, the previous edition of which was dated 2017.
The BPPL plays an essential role as a guide in identifying the priorities towards which scientific research should be directed and in directing the pharmaceutical industry's investments in the fight against microbial resistance.
The BPPL includes 24 pathogens, belonging to 15 families of antibiotic-resistant microorganisms, which are classified into three priority groups: critical, high and medium.
This is the updated list, published in May 2024
Critical priority:
- Acinetobacter baumannii, resistant to carbapenems;
- Enterobacterales, resistant to third-generation cephalosporins;
- Carbapenemase-resistant enterobacteria;
- Mycobacterium tuberculosis, rifampicin-resistant
High priority:
- Salmonella Typhi, resistant to fluoroquinolones
- Â Shigella spp., resistant to fluoroquinolones
- Enterococcus faecium, vancomycin-resistant
- Pseudomonas aeruginosa, carbapenemase-resistant
- Non-typhoid Salmonella, fluoroquinolone-resistant
- Neisseria gonorrhoeae, resistant to third-generation cephalosporins and/or fluoroquinolones
- Methicillin-resistant Staphylococcus aureus
 Medium priority:
- Macrolide-resistant group A streptococci
- Macrolide-resistant Streptococcus pneumoniae
- Haemophilus influenzae, ampicillin-resistant
- Penicillin-resistant group B streptococci
The WHO BPPL is also of utmost importance for mapping resistance on a territorial level and thus emphasising the need for regionally and locally designed strategies to combat resistance effectively.
Multi-resistant eye infections
With regard to ocular infections, numerous studies have highlighted the presence of multi-resistant bacterial strains in infected eye tissue samples in recent years. A study conducted in the United States, by Collier et al, showed that patients diagnosed with bacterial keratitis had resistance to commonly used antibiotics, such as fluoroquinolones, in approximately 40% of cases.
Even Italy is not immune to the challenge posed by antibiotic-resistant eye infections. A study by an Italian surveillance group reported a worrying increase in the prevalence of aminoglycoside- and methicillin-resistant Staphylococcus (MRSA) strains in cases of ocular infections through a retrospective analysis covering the last 30 years in the Turin urban area.
As is well known, there are several factors that contribute to the development and spread of microbial resistance in cases of eye infections, including the inappropriate use of antibiotics (including poor self-medication), incorrect dosage or duration of treatment.
The inappropriate use of antibiotics is sometimes not only attributable to the patient, but also to doctors, who - out of a kind of medico-legal caution - tend to prescribe antibiotics with a broad spectrum of action. Another reason could be the overcrowding of ophthalmology clinics, which induces the specialist to prescribe a 'safe' antibiotic molecule in order to avoid a new admission to the facility by a patient with an infection considered to be 'minor'.
There are also particular risk factors related to comorbidities, such as diabetes or diabetic retinopathy, which expose patients to an increased chance of developing conjunctival and corneal bacterial infections, including acute infectious conjunctivitis and keratitis.
Strategies to combat microbial resistance
Firstly, it is essential to develop a multi-pronged strategy involving doctors, politicians and the public, and new and more advanced surveillance models of ocular antibiotic resistance are needed to guide treatment choices in practice.
Ophthalmologists and family doctors should limit the prescription of antibiotics to what is strictly necessary and, in parallel, information campaigns would be desirable to raise public awareness of the risks of antibiotic abuse and the importance of completing treatment cycles according to the doctor's instructions to prevent the development of resistance.
The importance for the general prevention of all infections of certain primary practices, such as hand hygiene and appropriate disinfection of diagnostic and surgical instruments, must also be emphasised.
The increasing use of contact lenses, also due to the increased prevalence of myopia, has contributed to an increase in the incidence of corneal infections and the spread of saprophytic species of the silicone hydrogel used in contact lens production.
It is essential to invest more, both in terms of financial resources and human capital, in the research and development of new antimicrobial agents, including alternative therapies such as antimicrobial peptides and bacteriophages.
As far as the national monitoring system is concerned, a surveillance system similar to the Centers for Disease Control and Prevention (CDC), which in the United States support the National Healthcare Safety Network (NHSN), could be implemented, providing data to set prevention strategies and guide antimicrobial research programmes.
At the regional and local level, it is crucial to identify the elements that characterise specific territorial patterns of resistance. An Italian study from 2024. Antibiotic Resistance Profiles in Eye Infections: A Local Concern with a Retrospective Focus on a Large Hospital in Northern Italy, collected epidemiological data from a group of hospitals in the Milan area over the last 6 years, with a focus on antibiotic resistance in cases of eye infections. The results indicate the prevalence of infections by Gram-positive bacteria, good bactericidal activity of fluoroquinolones and glycopeptides, and increasing resistance to aminoglycosides and third-generation cephalosporins. Among the Gram-negatives of note is resistance to amoxicillin and enterobacteria.
Chloramphenicol has been found to be an overused therapeutic agent, but not included in antibiograms, so the lack of clinical data limits the ability to verify its efficacy in treating infections. To overcome this gap, chloramphenicol should be routinely included in antibiograms.
Ocular infections also present particular difficulties in collecting adequate samples of infected tissue, which often leads to false negatives, particularly with conventional techniques using swabs. This problem often arises in the case of keratitis, as the limited microbial load and varied aetiology would require more sensitive investigation methods than conventional swabs.
Alternative methods for collecting eye tissue samples, such as corneal scraping or aqueous humour aspiration, could be used. These diagnostic tests could also be supplemented with molecular tests such as polymerase chain reaction (PCR) and Next Generation Sequencing (NGS).
These biomolecular and metagenomic approaches could allow faster and more accurate identification of pathogenic micro-organisms, and this superior sensitivity and specificity would enable targeted antibiotic therapy, leading to optimised management of currently available antimicrobial drugs.
- WHO bacterial priority pathogens list, 2024: Bacterial pathogens of public health importance to guide research, development and strategies to prevent and control antimicrobial resistance https://www.who.int/publications/i/item/9789240093461
- Drago L, Minasi V, Lembo A, Uslenghi A, Benedetti S, Covi M, Nucci P, Deflorio L. Antibiotic Resistance Profiles in Eye Infections: A Local Concern with a Retrospective Focus on a Large Hospital in Northern Italy. 2024 May 14;12(5):984. doi: 10.3390/microorganisms12050984. PMID: 38792813; PMCID: PMC11123888.
- Collier, S.A.; Gronostaj, M.P.; MacGurn, A.K.; et al . Estimated burden of keratitis-United States, 2010. MMWR Morb. Mortal. Wkly. Rep. 2014, 63, 1027-1030.
- Grandi, G.; Bianco, G.; Boattini, M.; et al. Bacterial etiology and antimicrobial resistance trends in ocular infections: A 30-year study, Turin area, Italy. Eur. J. Ophthalmol. 2021, 31, 405-414.
- Sanfilippo, C.M.; Morrissey, I.; Janes, R.; Morris, T.W.. Surveillance of the Activity of Aminoglycosides and Fluoroquinolones against Ophthalmic Pathogens from Europe in 2010-2011. Curr. Eye Res. 2016, 41, 581-589.
- Gentili, V.; Strazzabosco, G.; Spena, R.; et al . Comparison between Moxifloxacin and Chloramphenicol for the Treatment of Bacterial Eye Infections. Curr. Ther. Res. Clin. Exp. 2024, 100, 100740.
- D'Oria, F.; Buonamassa, R.; Rizzo, T.; et al. Bacterial isolates and antimicrobial susceptibility pattern of ocular infection at a tertiary referral hospital in the South of Italy. J. Ophthalmol. 2023, 33, 370-376.
English 
Italian