﻿Quantitative estimation of the bacterial load of the brown mussels cultured at Vizhinjam has been shown as 10*. The occurrence 	 

of Coliforms, Escherichia coli, faecal streptococci and coagulate positive staphylococci is reported. Pseudomonas, Vibrio and 	 

Micrococcus are seen as normal flora

Pillai, C Thankappan

CMFRI Digital Repository

X MICROBIAL FLORA OF MUSSELS IN THE NATURAL BEDS AND FARMS C. THANKAPPAN PILLAl Quantitative estimation of the bacterial load of the brown mussels cultured at Vizhinjam has been shown as 10*. The occurrence of Coliforms, Escherichia coli, faecal streptococci and coagulate positive staphylococci is reported. Pseudomonas, Vibrio and Micrococcus are seen as normal flora. INTRODUCTION In India quite encouraging results have been achieved, in culture of the economically important species of brown mussel (Perna indica) and green mussel (P. viridis). However, adequate care has to be taken against diseases, that can occur to these animals, as they can deplete the stock as a result of mass mortality. Moreover, infestation can result in poor growth, thin meat, change of normal colour and failure of byssal development (Sindermann, 1970 in Principle diseases of Marine Fish, and Shell-fish, Acad., Press, 369 pp^). Paralytic shelfish poisoning is another problem (Mason, 1971, Underwater Journal, 3 : 52-59 )^. Hence, studies on the life history of the aetiological agents of various diseases, treatment of diseases and necessary prophylac-tic measures against diseases are significant areas for CMFRI BULLETIN 29 41 investigations for the success and development of mussel culture. MATERIAL AND METHODS In view of the above, a preUminary study of microbial flora of suspended cultured mussels (P. indica) in Vizhinjam, Trivandrum and surface sea water in that environment was made. Similar investigations were carried out in the mussels of the natural beds also at Kovalam, Trivandrum for comparison. The mussels were aseptically collected in sterile containers. Surface sea water samples were collected aseptically in sterile glass bottles both from the culture site and from the environment of the natural mussel beds. The collected samples were immediately trans-ported to the laboratory for further investigation. In the laboratory, the mussels were aseptically opened and the mussel meat along with fluid was separated and suitably diluted in sterile sea water. Similarly, water samples were also diluted. The diluted samples were inoculated into sea water agar. The samples were further plated in selective media for coliforms, Escherichia coli, faecal streptococci and coagulase positive staphylococci. The inoculated petri dishes were incubated at room temperature for 2-3 days and readings taken. The selected colonies, from the sea water agar, were transferred into see water agar slants for further observation. The isolates, were tested for their purity, and identi-fied using the system of classification of Buchanan and Gibbons (1974, Bergey's Mannual of Determinate Bacteriology, 8th ed. Williams «fe Wilkins Co., Baltimore; 1246 pp».) RESULTS The results of the quantitative and qualitative studies are presented in Table 1 and 2 respectively. TABLE 1. Quantitative Aspects of the Bacterial Flora in Mussels and in Sea-water Organisms Meat emulsion Meat emulsion of the cultivated of the mussels Sea water from Sea water from the culture site the natural mussels from the natural mussel bed area bed Average counts per millilitre Total bacterial counts: Coliforms : Escherichia coli: Faecal streptococci: Coagulase positive staphylococci; Oct. 1977 May 1979 Oct. 1977 May 1979 Oct. 1977 May 1979 Oct. 1977 May 1979 Oct. 1977 May 1979 2.5 X 10« 3.4 X 10» 1.0 X 10« 2.2 X 10* 3.0 X 10» 7.0 X 10» Nil 1.0 X 10» 6.1 X 10» Nil 2.2 X 10° TNC 1.6 X 10' TNC 1.0 X 10» TNC Nil TNC 1.5 X 10« TNC 1.7 X 10» 1.2 X 10« 3.5 X 10« 6.3 X 10« 1.4 X 10» 1.9 X 10» Nil 2.7 X 10" 2.8 X 10» Nil 2.0 X 10^  TNC 2.8 X 10* TNC 7.0 X 10» TNC Nil TNC 1.2 X 10' TNC Nil — No growth. TNC — Test not made TABLE 2. Qualitative Aspects of the Bacterial Flora in Mussels and in Sea water (In percentage) Material Pseudomonas Spp. Vibrio Spp. Micrococcus Spp. Meat emulsion of the cultivated mussels : Meat emulsion of the mussels from the natural bed Sea water from the culture site : Sea water from the natural bed : Oct. 1977 .. May 1979 .. Oct. 1977 .. Oct. 1977 .. May 1979 .. Oct. 1977 .. 50 60 50 50 50 37.5 34 40 25 25 33 37.5 16 25 25 17 25 42 MUSSEL FARMING Quantitatively, the bacterial load'of the '^suspended culture'of mussels was relatively higher t^han^ t^hat of the mussels in the natural^bed. It was l(fi and 10* reapec-tivdy. Similar situation was also noticed in the <m6--of sea water. The occurrence of coMim^, Escherichia celi, faecal streptococci and coagulase positive staphy-lococci were almost steady both in mussels and sea water. Faecal streptococci was not noticed in October 1977 but noted in May 1979. Coagulase positive staphylococci which was present in October 1977 was absent in May 1979. As the normal flora in mussels and in sea water, species of Pseudomonas, Vibrio and Micrococcus were present. Species of Pseudomonas predominated both in the mussel and sea water. All the isolates of Vibrio were luminescent. The results of this investigation are almost in agreement with those of Colwell and Liston (1962, / . Insect. Pathol, 4 : 23-33*) and Karthiayani and Iyer (1975, / . mar. biol. Ass. India, 17(1): 96-100'>). DISCUSSION In the present investigation, species of Pseudomonas, Vibrio and Micrococcus are found as the normal flora of the mussels. Aquatic bacteria such s^ Pseudomonas, Aeromonas and Vibrio are potential pathogens and can cause diseases to the aquatic animals especially when the animals are under stress (Bullock, 1964, Dev. Indust. Microbiol, 5 : 101-108«). In the present study, Escherichia coli, an indicator organism of faecal pollution, was present in the nliissels and sea water both at Kovalam and Vizhinjam. This reveals the possibiUties of outbreaks of epidemics like gastro-enteritis if the polluted mussels are con-sumed without proper washing and cooHhg. If these mussels are to be marketed alive, they tnay first be depurated as discussed by Wood (1969, LS. Uitflet, 20 (N.S.), Lowestaft Fisheries Lab., 15 pp'.) and Mason (1971 and 1976, in Marine mussels : their ecology and physiology, Camb. Univ. Press: 585-410') by Storing the mussels in sterile sea water for 2 &ys. The depurated mussels should be well washed and cooked for human consumption. Diroase causing bacteria, fungi, viruses, protistans and other parasites have been better studied in the case of oysters and clams than in mussels. Apart from the large-scale mortality of mussels caused by the parasitic attack of Mytiltcola intestinalis in American and European waters, pathogens like Labyrinthomyxa marina, Monilia sp., Ostracobiabe iit^lexa and Sirol-pi^rni zoophthonm are known to cause mortality among sheM^ies. It is quite possible that under certain conditions mussels in the farm might also be affected by the above organisms. A haplosporidian, Chytridiopsis mytilorum is known to destroy mussel eggs in North Atlantic waters. Similarly Haplosporidium tumefacientis invades the digestive glands of mussels causing niild mortality. The gregarine Nematopsis schneideri causes mortality of mussels destroying the gill region. In Baltic waters, Hypocomides mytili and Kidderia mytili have been identified to cause mortality of mussels. Ancistrocoma pelseneeri, a ciliate, also causes consider-able damage to the digestive system of mus^ls resulting in mortality. Species of Aeromonas and Vibrio are particularly dangerous to the hatchery produced molluscan larvae. The aboye instances only go to show the potential dangers to be foreseen from different sources.. Fortu-nately cases of diseases and mortality among mussels in India have not been so far reported. It is possible that this is not because of the absence of the diseases but due to inadequacy of attention to this aspect. Future investigations might throw light on this aspect. Taking steps to prevent the outbreak of diseases is very important. In this context, the following points appear to warrant our attention. (1) Selection of farm site free of bi(fl<^cal and chemical contamination after studymg tiie extent of contamination. (2) SelM^on of disease reastant seed for culture. (3) Avoiding overcrowded stocking in order to minimise the ill effects of epizootics. (4) Care in handlmg the cultured stock to avoid contamination. (5) Periodical investigation of the level of patho-genic organisms in the culture system to assess the status of the stock population. (6) Eliminating other source of disease transmission by selective removal of reservoir host of pathc^tes. (7) Routine disinfection of materials used in culture (materials like buckets, rope etc.) and (8) Timely harvesting of stock reducing the vulnerability of older stock to diseases. d ^ S u t l i t t M 29 4 •43 

Microbial flora of mussels in the natural beds and farms

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Microbial flora of mussels in the natural beds and farms

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