Blood culture isolates and antimicrobial sensitivities from 427 critically ill neonatal foals.
OBJECTIVE
To assist correct decision-making about antimicrobial treatment of equine neonates with septicaemia.


METHODS
Retrospective study of microbial blood culture results obtained from foals less than 7 days of age.


METHODS
Microbial blood culture results from foals less than 7 days of age admitted to an intensive care unit between July 1999 and December 2004 were reviewed. Antimicrobial sensitivity was assessed by the Kirby Bauer disc diffusion method. Antimicrobials were defined as an effective first-line choice antimicrobial if greater than 70% of isolates were susceptible. Multiple drug resistance (MDR) was defined as resistance to at least three antimicrobials in different chemical classes or with different mechanisms of resistance.


RESULTS
Of the 427 Thoroughbred foals included in the study, a positive blood culture was obtained in 110 foals and 124 microorganisms were isolated. Gram-positive isolates, predominantly Streptococcus/Enterococcus spp, were obtained in 41% of foals. Gram-negative isolates were predominantly of the Enterobacteriaceae family, in particular Escherichia coli. The overall antimicrobial sensitivity of the isolates was low. The Gram-positive organisms had unpredictable sensitivity patterns. MDR was recorded in 32% of isolates. In total, 81% of foals were discharged from hospital and 74.5% of foals with a positive blood culture were discharged.


CONCLUSIONS
With the increasing prevalence of Gram-positive microorganisms and their unpredictable sensitivity patterns, blood cultures remain important in the diagnosis and treatment of equine neonatal septicaemia.
Russell
C M
CM
Scone Veterinary Hospital, 106 Liverpool Street, Scone, NSW 2337. catherinerussell@bigpond.com
Axon
J E
JE
Blishen
A
A
Begg
A P
AP
D000818:Animals; D000831:Animals, Newborn; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D015169:Colony Count, Microbial / Q000662:veterinary; D016638:Critical Illness; D003657:Decision Making; D004305:Dose-Response Relationship, Drug; D024881:Drug Resistance, Bacterial; D005260:Female; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000302:isolation & purification; D006094:Gram-Positive Bacteria / Q000187:drug effects / Q000302:isolation & purification; D006734:Horse Diseases / Q000188:drug therapy / Q000382:microbiology*; D006736:Horses; D008297:Male; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D012189:Retrospective Studies; D018805:Sepsis / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D016896:Treatment Outcome
D000900:Anti-Bacterial Agents