Identification of Hafnia alvei by MALDI-TOF MS and Their Antimicrobial Resistance Profiles from Milk of Dairy Cows with Subclinical Mastitis

Hafnia alvei, which belongs to the Enterobacteriaceae family, has been occasionally documented in animal infections but is still not well characterized in the context of bovine mastitis. This research examined the prevalence and antimicrobial resistance characteristics of H. alvei in dairy cows suffering from subclinical mastitis in South Africa’s Free State Province. In the Thabo Mofutsanyana District, a total of 174 milk samples were obtained from cows on six different dairy farms. The California Mastitis Test (CMT) was used to screen for subclinical mastitis, and somatic cell count was used to confirm it. Standard culture methods were used for bacterial isolation, and presumptive Enterobacteriaceae isolates were identified through matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Out of the 174 samples, 84 (48.2%) tested positive for CMT, and 68 (39.1%) met the SCC criteria for subclinical mastitis at a cow level, while 96/336 (28.5%) were infected at a quarter level. Of the 100 presumptive Enterobacteriaceae isolates, 33 (33.0%) were identified as H. alvei (p = 0.0034). Antimicrobial susceptibility testing showed that 50% of the isolates were resistant to penicillin, followed by tetracycline and erythromycin with 25% and 10%, respectively. Furthermore, the results showed that 17 (51.5%) isolates exhibited multidrug-resistant profiles. The results suggest that H. alvei could be a contaminant in raw milk associated with bovine subclinical mastitis in this area, necessitating additional epidemiological research that includes healthy matched controls.