The increasing use of contact lenses worldwide has led to an increase in cases of Acanthamoeba keratitis, which are often associated with inappropriate cleaning of contact lenses and lens cases. This study aimed to retrospectively review 28 cases of Acanthamoeba keratitis in Porto Alegre (southern Brazil) and identify the risk factors and clinical outcomes of affected patients. Most patients had higher education (66.6%), all were users of contact lenses, mostly women (67.9%). Most patients were soft contact lens wearers (66.7%) and 85.7% used multipurpose cleaning solutions. Sixteen patients (64.0%) used to wear contact lenses while swimming and/or bathing. Pain was the most common symptom (92.6%). For treatment, patients used polyhexamethylene biguanide drops (92.6%), propamidine isethionate drops (81.5%), chlorhexidine drops (55.6%), topical corticosteroids (63.0%), and systemic corticosteroids (37.0%). Herpes simplex keratitis was the most common misdiagnosis (72.7%). The majority of patients (76.0%) underwent a corneal transplant to control the disease.

Several strains of free-living amoebae belonging to the genus Acanthamoeba can cause a painful sight-threatening disease of the cornea known as Acanthamoeba keratitis (AK). The numbers of AK cases keep rising worldwide mainly due to an increase in contact lens wearers and lack of hygiene in the maintenance of contact lenses and their cases. We report a case of AK in a healthy young woman admitted to the Hospital de Clinicas in Porto Alegre, southern Brazil. Corneal scrapings were examined for the presence of Acanthamoeba strains. The initial isolate was characterized by morphological and genotypic properties. The isolate belonged to group III according to Pussard and Pons' cyst morphology. Analysis of its 18S rDNA sequence identified the isolate as genotype T4. The T4 genotype is the most commonly reported among keratitis isolates and the most common in environmental samples.

Free-living amoebae (FLA) are cosmopolitan microorganisms known to be pathogenic to humans who often have a history of contact with contaminated water. Swimming pools and recreational waters are among the environments where the greatest human exposure to FLA occurs. This study aimed to determine the prevalence of FLA in swimming pools and recreational waters, through a systematic review and meta-analysis that included studies published between 1977 and 2022. A total of 106 studies were included and an overall prevalence of FLA in swimming pools and recreational waters of 44.34% (95% CI = 38.57–50.18) was found. Considering the studies published up to 2010 (1977–2010), between 2010 and 2015, and those published after 2010 (> 2010–2022), the prevalence was 53.09% (95% CI = 43.33–62.73) and 37.07% (95% CI = 28.87–45.66) and 45.40% (95% CI = 35.48–55.51), respectively. The highest prevalence was found in the American continent (63.99%), in Mexico (98.35%), and in indoor hot swimming pools (52.27%). The prevalence varied with the variation of FLA detection methods, morphology (57.21%), PCR (25.78%), and simultaneously morphology and PCR (43.16%). The global prevalence by genera was Vahlkampfia spp. (54.20%), Acanthamoeba spp. (33.47%), Naegleria spp. (30.95%), Hartmannella spp./ Vermamoeba spp. (20.73%), Stenamoeba spp . (12.05%), and Vannella spp. (10.75%). There is considerable risk of FLA infection in swimming pools and recreational waters. Recreational water safety needs to be routinely monitored and, in case of risk, locations need to be identified with warning signs and users need to be educated. Swimming pools and artificial recreational water should be properly disinfected. Photolysis of NaOCl or NaCl in water by UV-C radiation is a promising alternative to disinfect swimming pools and artificial recreational waters. Graphical abstract Supplementary information The online version contains supplementary material available at 10.1007/s00436-022-07631-3.

No abstract