A report on the shrimp of commercial importance and the marine fish industry of Pakistan is followed by a review of literature on various aspects of bacteriology of fish and shrimp.
Experiments are described which enumerate the bacteriological status of shrimp at different levels of handling i.e in trawler, harbour and local retail markets. Both spoilage flora and the organisms of public health significance are discussed. Shrimp Jaira (penaeus merquiensis and Kalri Metapenaeus monoceros) before landing from trawler, from fish harbour and local retail markets, in general reveal no quantitative difference during a period of twelve months. 'Total number of bacteria are found to be remarkably equal both at 20° and, 37°C. A noticeable difference is observed in percentage composition and type of organisms present at both the incubation temperatures. Market and harbour samples give higher count than the trawler samples indicating unhygienic handling at harbour and markets. Strains of psychrotrophic organisms of Flavobacterium, Pseudomonas, Moraxella and Alteromonas are isolated from harbour and trawler samples but do not encounter in market samples. Market samples appear to be more polluted than those from harbour. Harbour samples are also excessively polluted if compare with those of trawler samples.
Vibrio parahaemolyticus and V.alqinolyticus are commonly present in the waters around the Karachi coast. These organisms are frequently isolated from trawler, harbour and market samples. Highest positive isolations are observed in market samples followed by harbour and trawler in descending order. Experiments are also described which show the sources', of bacterial contamination during the commercial handling offish and shrimp. ' All the surfaces examined are found to be heavily contaminated with bacteria especially those of faecal origin. Methods to prevent such contamination are discussed.
An indepth study is reported on the bacterial flora of two important commercial shrimp varieties of Karachi coastal waters. Total number of bacteria are found to be remarkably equal at 37° 30° and 25°PC. Aerobic plate count of Penaeus merquiensis at 37°C ranges from 1.2x105 to 6.0x107CFU/g (Median 1 .8x106 CFU/g), and are predominantly Vibrio, Micrococcus Pseudomonas, Staphylococcus, Bacillus and Flavobacterium. The corresponding count at 30°C ranges from 3.2x105to 4.7x107CFU/g (Median 2.6x10 6 CFU/g).The bacterial flora in order of predominance are Vibrio, Micrococcus, Pseudomonas, Moraxella, Flavobacterium, Bacillus, Alteromonas and Acinetobacter. The 25°C counts ranges from 5.3x10s to 8.5x107 CFU/g, (Median 3.1x106 CFU/g), the flora is composed of Vibrio, Moraxella, Mirococcus, Pseudomonas, Flavobacterium, Bacillus,Alteromonas, and Acinetobacter in order of predominance. The aerobic plate count of Metapenaeus monoceros at 30° C ranges from 8.4x105 to 3.8x107 CFU/g (Median 2.9x106 CFU/g). The bacterial flora in order of predominance are Vibrio,Micrococcus Moraxella, Pseudomonas, Alteromonas, Flavobacterium, and Staphylococcus. No significant qualitative or quantitative difference is observed between the two shrimp species. The presence of Staphylococcus at 37° C is attributed to favourable incubation temperature as well as to excessive unsanitary handling. While the absence of Moraxella and Alteromonas putrefaciens at this temperature is considered due to the psychrotrophic nature of these organisms.
Experiments are described which show the changes occurring total bacterial populations and in generic composition of bacterial flora of two shrimp species, (Penaeus merquiensis and Metapenaeus monoceros) during ice storage. No significant quantitative or. qualitative bacterial differences are observed between the two species of the shrimp during storage. The total bacterial population increases from 106to 109 CFU/g after 20 days. Irrespective of the initial flora, the flora that emerges at the end of the storage is remarkably similar. In both species of shrimp Vibrio, Micrococcus, Pseudomonas or Moraxella genera are initially dominated. During storage Vibrio spp. Disappears and Alteromonas increases steadily to become the dominant genus. At the end of storage period Alteromonas putrefaciens, Pseudomonas Group II and III, Moraxella and Micrococcus constitute the bulk of the flora of the stored shrimp species.
The influence of freezing on the bacteriological quality of shrimp is studied in a survey of two shrimp processing plants located at Karachi fish harbour. Frozen shrimp samples (100) collected from plant A have the following bacterial profile: average (geometric) total aerobic plate count 9.4x106 CFU/g; MPN coliforms 94/g, and MPN faecal coliforms 41/g. The bacterial profile of 114 frozen shrimp samples from plant Bare 8.3x106 CFU/g, 180/g and 133/g for total plate count, MPN coliforms and MPN faecal coliforms, respectively. Samples (126) of raw and laboratory processed (simulating commercial processing) shrimp are also examined. The composition of microbial flora is nearly the same for both species of shrimps from both plants. Pseudomonas are the predominant microflora followed by Micrococcus spp. When shrimp are handled expeditiously under good sanitary conditions in the laboratory, the bacterial counts are significantly lower than on shrimp from the plants. Laboratory processed shrimp have an average (geometric) total aerobic plate count of 8.1x105 CFU/g and average (geometric) coliform and faecal coliform MPNs are(3/g.
Experiments are also described which show the spoilage potential of representative pure cultures of organisms isolated from spoiling shrimp and inoculated both in cooked and raw sterile shrimp muscles. After 14 days storage at ~C Alteromonas putrefaciens strains produce putrid odours, slimy appearance increase in pH, TMA, TVB and significant changes in electrophoretic protein pattern. Similarly, Pseudomonas Group II also appear to have spoilage potential. Pseudomonas Group III, Moraxella and Micrococcus do produce changes but not to the extent of Alteromonas and Pseudomonas Group II. No such changes are obtained inthe controls. Possible implications concerning spoilage of shrimp are discussed.