Effect of the use of acetylcysteine on the reduction of the percentage of neutrophil polymorphonuclear cells present in subclinical endometritis of dairy cattle diagnosed with the cytobrush technique

Abstract

The objective of the present study was to evaluate the effect of N-acetylcysteine (NAC) administration as
a pretreatment prior to antibiotic therapy in the control of subclinical endometritis (SE). Endometrial mucosa samples were collected from 14 housed Holstein Friesian cows from the Majes Irrigation Area, Caylloma, Arequipa, Peru. The animals were between their first and fourth lactation, with a body condition score (BCS) of 4. A cervical–uterine cytological brush was used for Papanicolaou sampling. Smears were prepared and submitted to the laboratory, stained using the Diff-Quick technique, and examined under bright-field microscopy for the count and calculation of the percentage of polymorphonuclear neutrophils (%PMN-N). SE was confirmed when %PMN-N was ≥ 5%. The brushes were transported in tubes containing Amies transport medium for subsequent aerobic culture on MacConkey agar, Mueller–Hinton agar, blood agar base, and Chromagar, with bacterial identification from the endometrial mucosa performed through Gram staining and biochemical tests. Antibiograms were carried out according to the bacteria identified. Of the 14 cows sampled, 11 showed %PMN-N values above the 5% threshold and were classified as SE-positive, with those below this value excluded from further analysis. Two groups were formed: T-NAC (n = 5) and nT-NAC (n = 5). The T-NAC group received an intrauterine infusion of 40 cm3 of 2% NAC (Fluimucil® 300 mg/3 mL) for three consecutive days, starting 72 hours after sampling, while the nT-NAC group served as a control (no NAC treatment). Endometrial bacteria were isolated in four cows, identified as Staphylococcus epidermidis, Staphylococcus aureus, and Escherichia coli. Twelve hours after NAC administration, differentiated intrauterine antibiotic treatment was applied to both groups according to the bacterial species identified. Seven days after the first sampling, vaginal cytology was repeated to reassess %PMN-N. Data were analyzed using InfoStat 2020 software. Summary and dispersion measures
were calculated; for the total animals evaluated for PMN-N (n = 14), the median was 9.50 with a standard
error (SE) of 1.21. Paired-sample inference was performed using the Student’s t-test for both treatment
and control groups with a two-tailed contrast, yielding a statistically significant effect for the T-NAC group (p < 0.05) and a non-significant result for the nT-NAC group (p > 0.05). In conclusion, intrauterine administration of N-acetylcysteine in cows with subclinical endometritis significantly reduces %PMN-N.