Prevalence, characterization and antibiotic resistance of Salmonella spp. isolated from raw vegetables
Growing consumption of fresh vegetables has led to an increase in the number of outbreaks of food-borne disease linked to fresh produce including salmonellosis. In Malaysia, some vegetables are eaten raw, known as ulam or salad in other countries. Therefore, this research was conducted to study t...
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| Format: | Thesis |
| Language: | English |
| Published: |
2016
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/69434/1/FSTM%202016%2012%20-%20IR.pdf |
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| Summary: | Growing consumption of fresh vegetables has led to an increase in the number
of outbreaks of food-borne disease linked to fresh produce including
salmonellosis. In Malaysia, some vegetables are eaten raw, known as ulam or
salad in other countries. Therefore, this research was conducted to study the
prevalence and antibiotic resistance of Salmonella spp., Salmonella Enteritidis (S.
Enteritidis) and Salmonella Typhimurium (S. Typhimurium) in ulam. This study
also aimed to determine the relation among different isolates of same serovar
of Salmonella spp. by employing random amplification of polymorphic DNApolymerase
chain reaction (RAPD-PCR) method and the risk acquiring
salmonellosis through consumption of ulam.
A total of 96 samples of ulam were purchased from wet markets and
hypermarkets in limited geographical locations of Selangor. Most probable
number (MPN) method was combined with multiplex polymerase chain
reaction (PCR) and plating method for detection of Salmonella spp. Prevalence
of Salmonella spp., S. Enteritidis and S. Typhimurium was higher in samples
from hypermarkets than wet markets which were 100%, 64.6% and 87.5%
respectively at hypermarkets and 95.8%, 43.8% and 75% respectively at wet
markets. The density of Salmonella spp., S. Enteritidis and S. Typhimurium
ranged from <3 to >2400 MPN/g. MPN-multipex PCR detected more
Salmonella spp., S. Enteritidis and S. Typhimurium which were 97.9%, 54.2%
and 81.3% respectively, as compared to MPN-plating which were 7.3%, 6.3%
and 10.4% respectively.
Six isolates of S. Enteritidis and 10 isolates of S. Typhimurium were recovered
from ulam. Both Salmonella spp. serovars showed high resistance to
amoxicillin/clavunic acid, cephalothin, streptomycin and ciprofloxacin with
100% resistant to ampicillin and erythromycin. All isolates showed resistance
to at least three antibiotics tested. S. Typhimurium was more resistant
compared to S. Enteritidis with multiple antibiotic resistances (MAR) index
ranging from 0.27 to 0.82 and 0.27 to 0.55 respectively.
RAPD-PCR dendograms showed that most isolates of S. Enteritidis and S.
Typhimurium tend to type together based on same sample type which 3 RAPD
types (RAPD type 3 of S. Enteritidis and RAPD type 1 and 6 of S.
Typhimurium) were typed together respectively on same sample type and
same sampling locations. The other 3 RAPD types (RAPD type 1 of S.
Enteritidis, RAPD type 2 and 4 of S. Typhimurium) were typed based on the
same sample type but different sampling locations. RAPD type 3 of S.
Typhimurium was typed on different sample types but same sampling location
was observed.
The quantitative microbiological risk assessment (QMRA) simulations by
single-hit concept showed that overall risk of acquiring salmonellosis due to
consumption of ulam was higher for S. Typhimurium than S. Enteritidis. The
mean risk of illness per serving per year for S. Typhimurium was 1 while for S.
Enteritidis, the risk was ~1 in the exposed population.
All in all, the prevalence of Salmonella spp. in ulam is alarming and should be
monitored from time to time seems prevention is better than cure. |
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