Septicaemia and septic arthritis in a neonatal calf caused by Lactococcus lactis

Streptococcus lactis, recently reclassified as Lactococcus lactis lactis, is not recognised as a common veterinary pathogen but has occasionally been reported as a cause of mastitis in cattle (Gallis 1990). It is considered to be a skin commensal, with cattle being its natural host. Although rare, human infection with L lactis was first reported by Ledger and others ( 1974) and, since then, it has been reported as a cause of endocardi- tis (Clark and Burnie 1991), arthritis (Campbell and others 1993) and septicaemia in an immunocompromised patient (Durand and others 1995). In bacteraemic neonatal calves, Escherichia coli and other Gram-negative enteric bacteria are most commonly isolated, while Gram-positive cocci comprise less than 12 per cent of all isolates (Aldridge and others 1993, Fecteau and others 1997). To the authors' knowledge, infec-tion in the bovine neonate due to L lactis has not previously been reported. This short communication describes a case of septicaemia and septic arthritis caused by L lactis in a young dairy heifer which showed a disappointing initial response to therapy..