Hetacillin, a new approach to mastitis control

Abstract

Potassium hetacillin, a derivative of 6-aminopenicillanic acid, showed in vitro bactericidal activity against both Gram-negative and -positive mastitis pathogens. Intramammary infusion of hetacillin (10 ml, containing the equivalent of 62.5 mg ampicillin activity, in stable groundnut oil gel) resulted in elimination of the pathogen in 81% of 619 cases treated; it was eliminated in 100% of Streptococcus uberis, 94% of Str. agalactiae, 80% of other streptococcal, 61% of Staphylococcus aureus, 86% of other staphyloccal, 63% of Escherichia coli, 78% of Klebsiella and 86% of Proteus cases. It was most effective against subclinical infections (89% elimination) followed by chronic (82%), acute (69%) and 'acute flare-up' (61%). Hetacillin was very effective when used in mastitis control studies involving 4 herds; it also significantly reduced (P < 0.001) CMT scores of 473 cases studied. There was good agreement between in vitro and in vivo results. The potassium salt of hetacillin (International Nonproprietary Name and British Approved Name for 'Hetacin K') was highly effective in acute, chronic and subclinical forms of mastitis caused by all the major mastitis bacterial pathogens, and gave very gratifying results when used on a herd control basis.