First detection of Shiga toxin producing Escherichia coli O157:H7 (HlyA gene) and enumeration of most probable number (MPN) of fecal coliforms and Escherichia coli in cage cultured oysters (Crassostrea iredalei) and water from southern Malaysia

Tee Ka Hong; George Bobby; Nurshafiqah Norizan; Nurshuhada Ariff; Siti Nor Khadijah Addis; Najiah Musa; Sandra Catherine Zainathan

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First detection of Shiga toxin producing Escherichia coli O157:H7 (HlyA gene) and enumeration of most probable number (MPN) of fecal coliforms and Escherichia coli in cage cultured oysters (Crassostrea iredalei) and water from southern Malaysia

Author: Tee Ka Hong ^{1
,

2} ; George Bobby ^{1
,

2} ; Nurshafiqah Norizan ^{1
,

2} ; Nurshuhada Ariff ^{1
,

2} ; Siti Nor Khadijah Addis ^{2
,

3} ; Najiah Musa ^{1
,

4} ; Sandra Catherine Zainathan ^{1
,

2}
Author Information

1. Faculty of Fisheries and Food Sciences, Universiti Malaysia Terengganu, 21030, Kuala Nerus, Terengganu, Malaysia. &
2. Institute of Marine Biotechnology, Universiti Malaysia Terengganu, 21030, Kuala Nerus, Terengganu, Malaysia.
3. Faculty of Marine and Environmental Science, Universiti Malaysia Terengganu, 21030, Kuala Nerus, Terengganu, Malaysia. &
4. Institute of Tropical Aquaculture and Fisheries, Universiti Malaysia Terengganu, 21030, Kuala Nerus, Terengganu, Malaysia.
Publication Type:Journal Article
Keywords: Escherichia coli O157:H7; HlyA gene; Fecal coliforms; Crassostrea iredalei; Malaysia
MeSH: Escherichia coli O157; Crassostrea
From:Malaysian Journal of Microbiology 2021;17(4):390-402
CountryMalaysia
Language:English
Abstract: Aims:Escherichia coli O157:H7 is known to be transmitted via fecal-oral route, where water plays a role in the transmission process. Oysters as bivalves, bio accumulate pathogens from the water through filter feeding and are suspected to play a role as disease transmission vector. In Malaysia, the data on oyster’s microbiological quality are limited. Hence, it was vital to conduct oyster related studies in Malaysia. The main objectives of this study include the enumeration of most probable number (MPN) of fecal coliforms and E. coli and isolation of E. coli from oyster (Crassostrea iredalei) and water sample for the detection of 16S rRNA and HlyA (Hemolysin A) genes of E. coli O157:H7.
Methodology and results:A total of 120 oysters and water samples (n=6) were collected from a fisherman village located in southern Malaysia. Total fecal coliforms and E. coli were determined using the MPN procedure. Colonies of E. coli were identified based on Gram staining, biochemical test, and PCR detection for the presence of 16S rRNA and HlyA gene of E. coli O157:H7. The enumeration results showed that the MPN of the fecal coliforms and E. coli found in the collected oyster samples do not meet the standard to be directed for human consumption (0.72 ± 0.19 × 104 MPN/100 g and 0.13 ± 0.03 × 10 4 MPN/100 g, respectively). The PCR assays showed that 16 out of the 104 (15.38%) of E. coli isolated from water and oysters showed the presence of HlyA gene. The phylogenetic tree analysis showed there were genetic relationships between the HlyA gene of the E. coli isolated in this study with the ones isolated from calf and human faeces.
Conclusion, significance and impact of study:The detection of Shiga toxin producing E. coli O157:H7 (HlyA gene) in cage cultured oysters (C. iredalei) and water from southern Malaysia was first time reported here. In the future, more study can be conducted to study the expression of the HlyA gene and confirm of its identity as E. coli O157:H7 using different target genes such as eaeA (encodes a 94 kD outer membrane protein called intimin) and Stx1 (Shiga toxin, Shigella dysenteriae type 1).
Full text:20.2021my0042.pdf