Transcript Document

Survival Potential of Enterococci in Beach Sand
Sumbul Khan, Helena Solo-Gabriele, Matthew Phillips, Yifan Zhang, Amir M. Abdelzaher, Laura Vogel, Amber Enns, Noha Abdel-Mottaleb
MATERIALS & METHODS
ABSTRACT
RESULTS
Inoculation of Sand
Prior work has questioned the meaning of enterococci measurements, the most
commonly used microbe to evaluate sewage impacts to marine waters. Reports
indicate that enterococci are capable of growing on beach sand, which defies one
of the standards of indicator bacteria of not growing in natural surroundings. This
research evaluated the conditions which enhance the growth of enterococci in wet
sand. To conduct this study, wet sand samples were collected from a non-point
source pollution beach in Florida. The sand was inoculated with enterococci and
the indicator’s growth was monitored under varying conditions including varying
growth periods, temperature (41.5°C and 19°C) and the nature of the sand on
which the indicator was grown, which included sterile and natural beach sand.
Results suggest that enterococci might not be an appropriate indicator organism
since its growth varies under different conditions and as a result it may not indicate
sewage impacts.
Time vs. CFU/g
 Preparation of enterococci working stock
120
 Number of enterococci in stock calculated (~39 CFU/g)
 Intertidal wet sand samples collected for inoculation from Hobie Cat
Beach, FL
 Isolates prepared from both sterile and natural sand consisting of 100 g
sand and 50 mL thoroughly mixed enterococci stock
80
CFU/g
 Half of the sand autoclaved for sterile sand inoculation and remaining
half set aside for natural sand inoculation
100
Autoclaved sand at
incubator temperature
60
40
Autoclaved sand at incubator temperature
Autoclaved sand at
room temperature
20
Autoclaved sand at room temperature
0
0
2
4
6
8
10
12
14
16
18
20
22
24
26
Time (hours)
incubator temp.
39 CFU/g ±1
43 CFU/g ±1
98 CFU/g ±3
Initial:
2 hours:
24 hours:
OBJECTIVES
room temp.
39 CFU/g ±1
45 CFU/g ±1
98 CFU/g ±2
Time vs. CFU/g
 Explain abundances of enterococci in beach sand
45
 Asses enterococci survival in sand under varying conditions:
40
35
 Temperature (41.5 °C and 19 °C)
30
CFU/g
 Growth period
 Nature of sand (sterile and natural)
Nautral sand at incubator
temperature
25
Natural sand at incubator temperature
20
Natural sand at room
temperature
15
10
5
0
0
STUDY SITE
1
2
3
4
5
6
Time (days)
Sand Analysis
 Membrane filtration performed on the inoculated sand samples
Initial:
3 days:
4 days:
5 days
incubator temp.
39 CFU/g ±1
0.5 CFU/g ±0.01
0 CFU/g
0 CFU/g
room temp.
39 CFU/g ±1
10 CFU/g ±1
5 CFU/g ±1
4 CFU/g ± 1
DISCUSSION & CONCLUSIONS
 Increase in time period lead to an increase in growth in sterile
sand

 Increase in time period lead to a decrease in concentration
compared to initial count in natural sand
Hobiie Cat BeachMiami-Dade
County, Florida, USA.
Natural sand at room temperature
RECOMMENDATIONS
 The need for additional sampling in deeper water
 Studies be conducted 10m offshore to test improved risk
assessment
 No growth in natural systems due to predation and competition
 Growth in sterile systems due to protection and moisture
 Decrease in survival at high temperature due to predation and
competition in natural sand
 Enterococci survives better in sand compared to water since
sand provides moisture, nutrients, and UV protection in biofilms
 Enterococci is not an appropriate indicator organism since its
growth varies under different conditions and complicates
interpretation of levels detected
ACKNOWLEDGEMENTS
Helena Solo-Gabriele, Environmental Engineering Labs
mEI Agar