M. Daly et al., Molecular analysis of Pseudomonas aeruginosa: Epidemiological investigation of mastitis outbreaks in Irish dairy herds, APPL ENVIR, 65(6), 1999, pp. 2723-2729
Pseudomonas aeruginosa is a pathogen in both humans and animals. This bacte
rium, most often associated with respiratory infections in cystic fibrosis
patients, was found to be the causative agent in bovine mastitis outbreaks
among 11 Irish dairy herds. Epidemiological findings suggested that the inf
ection was spread to all herds by teat wipes that had been contaminated wit
h this organism. Two molecular-typing strategies were used in an attempt to
determine the genomic relationship(s), if any, of the P. aeruginosa strain
s isolated from the various herds and to verify whether the same strain was
responsible for each outbreak Thirty-six isolates from the mastitis outbre
aks were tested and compared to fourteen clinical isolates from Cork Univer
sity Hospital. With one exception, all outbreak-linked strains produced ide
ntical patterns when ribotyped with ClaI and PvuII enzymes. Eight of the cl
inical isolates gave the same ClaI ribotype pattern as the mastitis-causing
strains. However, PvuII proved more discriminatory, with only the outbreak
isolates producing identical patterns. Similar results were obtained with
RW3A-primed DNA amplification fingerprinting, with all outbreak isolates ex
cept one displaying the same fingerprint array. The clinical strains produc
ed several fingerprint patterns, all of which were different from those of
the mastitis-causing isolates. Fine-resolution DNA fingerprinting with a fl
uorescence-labelled RW3A primer also identified a number of low-molecular-w
eight polymorphisms that would have remained undetected by conventional met
hods. These data support the view that the same P. aeruginosa strain was re
sponsible for the mastitis outbreaks in all 11 herds.