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Published on: March 11, 2015
Metschnikowia bicuspidata and Enterococcus faecium co-infection in the giant freshwater prawn Macrobrachium
Shih-Chu Chen1, Tung-Hung Chen, Pei-Chi Wang
1Department of Veterinary Medicine, National Pingtung University of Science and Technology, Pingtung 912, Taiwan, ROC. scchen@mail.npust.edu.tw
Abstract:
In May 2001, an epizootic yeast and bacterial co-infection in the giant freshwater prawn Macrobrachium rosenbergii occurred in Taiwan causing a cumulative mortality of 25%. The diseased prawns had a yellowish-brown body color, milky hemolymph, opaque, whitish muscles, and were approximately 7 mo old with total lengths ranging from 8 to 10 cm. Histopathological examination showed marked edema, yeast infiltration, and necrotic lesions with inflammation in the muscles, hepatopancreas and other internal organs. We isolated 2 pathogens from the diseased prawns, one was a yeast (AOD081MB) and the other a gram-positive coccus (AOD081EF). The gram-positive coccus was identified as Enterococcus faecium by the API 20 Strepsystem, conventional biochemical tests, and it had 99% 16S rDNA sequence identity (GenBank Accession Number AJ276355) to E. faecium (GenBank Accession Number AF529204). The sequence of a PCR product from the D1/D2 domain of 26S rDNA (GenBank Accession Number AF529297) from the yeast gave 99% sequence identity to Metschnikowia bicuspidata (GenBank Accession Number U44822). Experimental infections with these isolates produced gross signs and histopathological changes similar to those observed in the naturally infected prawns. The lethal doses (LD50) for isolate E. faecium AOD081EF, M. bicuspidata AOD081MB and the co-infection were 4.7 x 10(4), 2.6 x 10(2), and 2.4 x 10(2) colony-forming units prawn(-1), respectively. This is the first report of a confirmed co-infection of M. bicuspidata and E. faecium in prawn aquaculture.
Insights
A yeast and bacterial co-infection caused significant mortality in giant freshwater prawns. This study identified Metschnikowia bicuspidata and Enterococcus faecium as the causative agents in aquaculture.
Area of Science:
- Aquatic animal health
- Microbiology
- Pathology
Background:
- Giant freshwater prawn (Macrobrachium rosenbergii) aquaculture is economically important.
- Disease outbreaks can cause significant economic losses in aquaculture.
- Yeast and bacterial co-infections pose a complex challenge in disease management.
Purpose of the Study:
- To identify the causative agents of a yeast and bacterial co-infection in Macrobrachium rosenbergii.
- To characterize the pathogens and their role in disease.
- To report the first confirmed co-infection of Metschnikowia bicuspidata and Enterococcus faecium in prawn aquaculture.
Main Methods:
- Isolation and identification of yeast and bacterial pathogens from diseased prawns.
- Biochemical tests and 16S and 26S rDNA sequencing for pathogen identification.
- Experimental infections to confirm pathogenicity and determine lethal doses (LD50).
Main Results:
- A yeast (Metschnikowia bicuspidata) and a gram-positive coccus (Enterococcus faecium) were isolated from diseased prawns.
- Experimental infections with both pathogens reproduced the clinical signs and histopathological findings.
- Lethal doses (LD50) were determined for each isolate and the co-infection.
Conclusions:
- Metschnikowia bicuspidata and Enterococcus faecium were confirmed as causative agents of co-infection in Macrobrachium rosenbergii.
- This co-infection led to significant mortality and characteristic pathological changes.
- Understanding these co-infections is crucial for developing effective disease control strategies in prawn aquaculture.
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