Post on 02-Aug-2020
Antimicrobial Activity of Probiotic Strains by Well Diffusion Agar Method
Antimicrobial Susceptibility Profile
The antimicrobial activity of probiotic strains tested by
broth assay showed inhibition of Listeria monocytogenes
up to 6.60 log10 CFU/ml and probiotic growth of up to 8.66
log10 CFU/ml .
Probiotic strains analyzed in this study were able to
reduce Salmonella, E. coli O157:H7, and Listeria
monocytogenes.
A similar effect was observed when comparing the
antimicrobial effect of overnight cultures to cell-free
suspensions.
Probiotics showed bacteriostatic activity against
Salmonella and E. coli O157:H7, compared to a
bactericidal activity against Listeria monocytogenes.
From the 28 selected strains, 3 were selected for
further study to reduce Listeria monocytogenes in
ready-to-eat meats.
Figure 9: Inhibition
of Listeria
monocytogenes by
probiotic J19 on
timepoint 6 hours
Figure 8: Inhibition of Listeria
monocytogenes by probiotic
J19, J7, J34, J27, J25, J43 on
timepoint 6 hours
Figure 7: Inhibition
of Listeria
monocytogenes by
probiotic L25 on
timepoint 6 hours
Antimicrobial Activity of Probiotic Strains by Broth assay
From the selected panel of 28 probiotic strains, 13 probiotic strains had antimicrobial activity on the agar
well diffusion assay against Salmonella with a maximum inhibition zone of 12 mm; 13 strains for E. coli
O157:H7 with 9mm; and all 28 strains showed antimicrobial activity against L. monocytogenes with up
to 26 mm of inhibition.
Figure 2: Inhibition of pathogens by probiotic strains
Listeria monocytogenes
E.Coli O157:H7
Salmonella
Antimicrobial Activity of Novel Probiotic Strains against Listeria
monocytogenes, Salmonella and E. coli O157:H7Valencia, María Jose1; Ayala, Diana,PhD2; Franco, Jorge2; Brashears, Mindy,PhD2
1 SOWER Scholar, 2 Texas Tech University
13 13
28
In the United States, 9.4 million episodes of foodborne
illness are caused by 31 major pathogens, from which Listeria
monocytogenes, Salmonella and E. coli O157:H7 are among
the most common causes of foodborne infections. Indeed,
over 40,000 and 3,500 laboratory-confirmed Salmonella and
E. coli O157:H7 cases respectively are reported annually to
the Centers for Disease Control and Prevention. On the other
hand, an estimated 1,600 people get listeriosis each year, and
about 260 die. Probiotics are a natural alternative to
counteract foodborne pathogens, they are live
microorganisms that when administered in adequate amounts
confer beneficial health effects to the host. Lactic acid bacteria
are the most commonly used group of bacteria as probiotic
strains, they produce antimicrobial compounds such as
bacteriocins able to reduce and/or inhibit human foodborne
pathogens. This study aimed to characterize potential
probiotic strains to reduce Salmonella, E. coli O157:H7, and
Listeria monocytogenes.
Abstract Results
A natural alternative to counteract foodborne pathogens are
probiotics, live microorganisms that when administered in
adequate amounts confer beneficial health effects to the host.
Probiotics are also an alternative to decrease the use of
antibiotics in animal feed, which could have potential risks
such as the development of antimicrobial resistance and the
spread of antibiotic resistance genes.
Results
Figure 3: Inhibition of Listeria monocytogenes by
probiotic J27 with a zone of inhibition of 21.5 mm, and
probiotic J7 with 25.5 mm.
Introduction
Methods
5.014
9.136 8.778 8.204
4.523 2.921 2.477 2.731
0.000
2.000
4.000
6.000
8.000
10.000
0 hrs 6 hrs 12 hrs 24 hrs
Log
CFU
/cm
2
HoursFigure 4: Probiotic J14
Probiotic Listeria m.
5.286
9.186 8.637 8.067
4.523 3.125 2.564 2.810
0.000
2.000
4.000
6.000
8.000
10.000
0 hrs 6 hrs 12 hrs 24 hrs
Log
CFU
/cm
2
HoursFigure 6: Probiotic J16
Probiotic Listeria m.
5.824
9.176 8.778 8.669
4.5233.308 2.778 2.354
0.000
2.000
4.000
6.000
8.000
10.000
0 hrs 6 hrs 12 hrs 24 hrs
Log
CFU
/cm
2
HoursFigure 5: Probiotic L20-B
Probiotic Listeria m.
10.5 11 11.514
11.5 10.5 1114
9 914
9
18
10.5 9
25.5 25 25
10 9
2623
20.524 24.5 25 25.5
21.5
8 9 6.5
8
7 7 6
8
7
0
0
0
0
77
7 7 7
0 0
0
00
0 0 0 0
078
7
6
6 6 7
8
7
7
6
6
12
0
0 0 0
0 0
0
00
0 0 0 0
0
0
5
10
15
20
25
30
35
L2-A L3-A L4-A L4-B L5-B L22 L23-A L28 L25 L1 L19 L23-B L24-B L8-B L21 J7 J34 J43 L11 L12 J19 L3-A L8-A L20-B J14 J16 J25 J27In
hib
itio
n z
on
e (
mm
)Probiotics
Figure 1: Well Diffusion Agar method
Listeria monocytogenes (mm) E. coli O157:H7 (mm) Salmonella (mm)
200 strains of probiotics isolated from meat and vegetables samples
Well diffusion method
Broth assayAntimicrobial
resistance
28 most effective strains selected
0 2 4 6 8 10 12 14 16 18
Ampicilin
Clindamycin
Daptomycin
Erythromycin
Gentamicin
Levofloxacin
Linezolid
Penicillin
Rifampicin
Synercid
Tetracycline
Tmp/Sxt
Vancomycin
No.IsolatesResistant
No.IsolatesSusceptible
ResultsConclusion
Figure 10: Antimicrobial
resistance