Resumen
Streptococcus uberis is one of the most common pathogens associated with bovine mastitis, commonly treated with antimicrobials (AM), favoring the appearance of antimicrobial resistance (AMR). The objective of this work was to determine the proportion of phenotypic AMR among S. uberis isolated worldwide from bovine intramammary infections between the years 1983–2022, and to assess the variables associated by means of a systematic review and metanalysis. Sixty articles were eligible for quantitative review. Ninety-four independent studies were obtained. The antimicrobials evaluated in more S. uberis strains were penicillin (21,987 strains), oxacillin (21,727 strains), erythromycin (20,013 strains), and ampicillin (19,354 strains). Most of the studies included in this meta-analysis were from Europe (44), followed by America (25), Africa (10), Asia (10), and Oceania (5). Among the included articles, 22 were published from 1983 to 2006, 23 from 2007 to 2012, 25 from 2013 to 2015, and the remaining 24 after 2016. Penicillin, erythromycin, and tetracycline were the antimicrobials with >25 studies. Therefore, the following analyses were performed only for these antimicrobials, presenting a high heterogeneity index (I2). The variability observed for penicillin and tetracycline was only explained, partially, by continent of origin. The variability observed for erythromycin was not explained by any of the potential explanatory variables included in this study. The S. uberis proportion of resistance to antimicrobials is highly variable and probably influenced by many factors other than those studied in this metaanalysis, where it was not possible to inform a unique average proportion of resistance.
Métodos
This systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) (Page et al., 2021). The working protocol was performed in five steps: search strategy, study selection, outcome variable, information extraction, and statistical análisis. The search for scientific papers was conducted by key words in five bibliographic databases: PubMed, Scielo, Scopus, Science Direct, and Academic Google. The used search terms were “Streptococci,” OR “Streptococcus,” AND “antimicrobial,” OR “antibiotic,” AND “susceptibility,” OR “resistance,” AND “bovine,” OR “cow,” AND “intramammary infection,” OR “mastitis”. The search strings were: “Streptococcus or Streptococci + antimicrobial or antibiotic + resistance or susceptibility + bovine or cow + intramammary infection or mastitis”. The same string leaving out one term at a time was used, always including at list 3 terms (e.g. “Streptococcus or Streptococci + antimicrobial or antibiotic + resistance or susceptibility,” “Streptococcus or Streptococci + antimicrobial or antibiotic + intramammary infection or mastitis”). Also, all the searching strings were made changing the connector “+” to “and”. The suitability of the articles based on their titles and abstracts was analyzed in agreement with the inclusion/exclusion criteria. The primary questions used for titles and abstracts of searched articles screening were: Is the article based on Streptococcus uberis strains isolated from bovine milk? Does the article study S. uberis strains isolated from intramammary infections? Is the article written in Spanish, English, Portuguese or French? Is the full article available online? Only articles published between 1983 and February 2023 were included due to their availability on the web and because it is a long period of time to evaluate the changes in the antimicrobial resistance. The selection of the scientific articles included in this meta-analysis was based on the following criteria: the articles must have been published in peer-reviewed journals, must be derived from observational studies, and the strains must be isolated from clinical or subclinical bovine mastitis. Only S. uberis isolated from the bovine udder were included. The total number of S. uberis strains examined and the number of resistant/sensitive strains must be informed. If the scientific papers showed results from different sample times, different methodologies, or different countries or regions, each situation was reflected as one independent study in our database. Therefore, one scientific article may include several studies. Reviews, duplicated reports, information from other species milk, AMR reported for Streptococcus spp. instead of only for S. uberis, and articles without a peer review system (such as a thesis or editorial notes) were excluded.