Basic HTML Version
Molecular Microbiology Research (Online) 2013, Vol.3 No.1 1-8
ISSN 1027-5595
http://mmr.sophiapublisher.com
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barrier and prevent the adsorption of antibodies or
different antibiotics. EPS also bind the antibiotics that
are attempting to reach across the biofilm because
these are negatively charged and act as ion-exchange
resin, (b) bacteria embedded in biofilm results in
decreased growth rate of the bacteria and smaller size
of the cells which make the cells less pervious to
antibiotics, as all antimicrobial drugs are more
operative in destroying the fast growing cells (Thien
and O’ toole, 2001), (c) antibiotic degrading enzymes
are also trapped in the biofilm structure and inactivate
the incoming antibiotic molecules effectively, like in
Pseudomonas aeruginosa
β-lactamase is 32-folds
higher in biofilm producing cells than the same strain
grown planktonically and (d) the cell wall protein
structure of the bacteria in biofilm is transformed up
to 40 % from that of free living bacteria (Potera,
1999).
The membrane of the bacteria in biofilm have greater
tendency to propel out the antibiotics before they
impair or even targets of the antibiotics on cell surface
may disappear (Potera, 1999); most of the antibiotics
are deactivated by the reactive oxidants such as
hypochlorite and H
2
O
2
which are produced by
oxidative burst of phagocytic cells. This mechanism of
deactivation is more in the outer layers of biofilm than
inner ones because the oxidants have poor penetration
across the biofilm layers that might be the reason of
failure of the phagocytic cells to extinguish biofilm
microorganisms (Thien and O’ toole, 2001; De Beer et
al., 1994); biofilms also provide an ideal place for the
interchange of extra-chromosomal DNA which is
accountable for antibiotic resistance, virulence
dynamics and environmental persistence competences
at enhanced rates leading to an ideal environment for
development of drug resistance (Ghigo, 2001).
Ciftci et al. (2009) conducted a study for the
determination of methicillin resistance and slime
production of
S. aureus
in bovine mastitis. A triplex
PCR was targeting 16S rRNA,
nuc
and
mec
A genes
for recognition of staphylococcus species,
Staphy-
lococcus aureus
and MRSA, singly. For determination
of slime production, a PCR test targeting
ica
A and
ica
D genes was performed. In the expermient, a total of
59 strains were confirmed as
Staphylococcus aureus
by both conservative tests and PCR, while 13 of them
were found to be methicillin resistant (MR) and
mec
A
gene was present in only 4 (30.7%) isolates. Even
though out of 59, 22 (37.2%)
S. aureus
isolates were
positive for slime production in CRA while in PCR
study, only 15 were positive for both
ica
A and
ica
D
genes. Sixteen and 38 out of 59 strains were positive
for
ica
A and
ica
D genes, respectively. Only 2 out of
59 strains were positive for MR and mucus (slime)
production, phenotypically, suggesting lack of corre-
lation between MR and slime production in these
isolates. In conclusion, the optimized triplex PCR in
this study was useful for rapid and reliable detection
of methicillin resistant
S. aureus
. It also showed that
only PCR targeting
ica
A and
ica
D may not be
sufficient to detect the slime production and further
studies targeting other
ica
genes should be conducted
for accurate evaluation of slime production characters
of
S. aureus
strains.
Melchoir et al. (2006) reviewed role of biofilm in
recurrent mastitis. They suggested that production of
mammary gland infection where symptoms are trailed
by subclinical disease is relatively parallel to the signs
described for infective maladies in humans. They also
reviewed that phase variation between biofilm
production and planktonic bacteria is caused by
genomic alteration which makes bacteria less hostile
and more resistant to host’s immune response as well
as resistant to effective antimicrobials.
Turkyilmaz and Eskiizmirliler (2006) conducted a trial
to determine the production of slime factor and
antibiotic resistance in staphylococcal isolates
sequestered from different clinical samples of animal
origin. They collected 180 staph spp. (90 positive for
coagulase production and 90 staphylococci negative
for coagulase production). They determined the slime
production by Congo red agar method (CRA),
microplate method (MP) and standard tube (ST)
method. The rate of slime production by all staphy-
lococci scrutinized by CRA, MP and ST methods was
61.1%, 55.5% and 50.5%, correspondingly. The
presence of antibiotic resistance was evaluated by the
agar disk diffusion technique. The proportion of
resistance against penicillin, methicillin, ampicillin
and
gentamycin
in
slime-producing
(SP)