Basic HTML Version
Molecular Microbiology Research (Online) 2012, Vol.2 No.1 1-9
ISSN 1027-5595
http://mmr.sophiapublisher.com
3
treatment failure (Constable and Morin, 2003; Pengov
and Ceru, 2003; Hoe and Ruegg, 2005). The
explanation should therefore be sought in terms of
other factors, which also influence the outcome of
therapy (Pengov and Ceru, 2003).
The bovine mammary gland is an immunologically
inept organ, both because dilution effect of milk on
immune defences and poor phagocytic activity.
Intracellular slow growth rate of
S. aureus
and failure
of antibiotics to penetrate and act effectively within
phagocytic environment leads clinical cure but
bacterial cures being curtailed (Sandholm et al., 1990).
Poor contact of the antimicrobial with micro
organisms at the site of infection is a major cause of
mastitis treatment failure (Serieys et al., 2005).
The successful use of antimicrobial drugs for mastitis
treatment depends on the same basic principles that
apply to all microbial infections: (1) Selecting an
effective antimicrobial agent, (2) Attaining and
maintaining therapeutic concentrations of the drug at
the infection site for long enough, (3) Minimising
local or systemic side effects of therapy, and (4) The
administration of supportive, non-antimicrobial
therapy when indicated (Ziv, 1980).
There are four major groups of factors associated with
bovine mastitis treatment failure:
a Management and iatrogenic factors
b Drug factors
c Mastitis-causing organism factors
d Mammary gland factors
Additionally, herd, cow and quarter level factors, can
also affect results of the bovine mastitis treatment.
a Management and iatrogenic factors: in accurate
diagnosis:
(1) Inadequate supportive treatment
(2) Partial or full insertion of cannula
(3) Re-infection
(4) Delayed initial treatment
(5) Duration of treatment
(6) Super infection
(7) Improper route of administration
b Drug factors:
(1) Improper antimicrobial selection
(2) Short half-life of the drug
(3) Inadequate local tissue concentration
(4) Side effects of the drug
(5) High degree of milk and serum protein binding
(6) Combined use of bactericidal and bacteriostatic
antimicrobials
(7) Other factors that will lead to inactivation of the
antimicrobial invivo or
in vitro
(8) Low bio-availability
(9) Weak passage of drug across the blood-milk
barrier
c Mastitis pathogens related factors:
(1) Tissue invaders or intracellular location
(2) Microbial dormancy and metabolic state
(3) Microbial mechanisms that overcome antimicro-
bial effects in milk
(4) Mastitis causing organisms that are short lived in
mammary gland, such as Coliforms
(5) Drug tolerance and resistance (Ziv, 1980, Erskine
et al.,2003)
d Mammary gland factors
(1) Poorer and uneven distribution and physical obstruction
(2) Trauma
(3) Udder tissue necrosis
(4) Adverse effects of drug
(5) Teat canal infection
(6) Irritation
Despite of appropriate choice of antimicrobial,
treatment of mastitis may be unsuccessful. Current
treatments of mastitis in during lactation are not very
successful and cure rates are poorer, especially in case
of Staphylococcus aureus usually between 25%~50%
(Gruet et al.,2001).
Veterinarians should have an active role in the
education of the farmers in the treatment and
management of bovine mastitis. Management and
iatrogenic factors can be easily influenced. One of the
main objectives must be early treatment initiated as
soon as signs of the disease become apparent. The
length of treatment should be accordingly to the speed
of recovery. Extended therapy protocols are designed
to maintain antimicrobial levels in milk greater than
the minimum inhibitory concentration for a period
that extends beyond the lifespan of neutrophils,
aiming to kill organisms that seek a refuge into the