Biochemical and molecular investigations on Salmonella serovars from seafood

The present investigation was envisaged to determine the prevalence and identify the different Salmonella serovar in seafood from Cochin area. Though, the distribution of Salmonella serovars in different seafood samples of Cochin has been well documented, the present attempt was made to identify the different Salmonella serovars and determine its prevalence in various seafoods. First pan of this investigation involved the isolation and identification of Salmonella strains with the help of different conventional culture methods. The identified isolates were used for the further investigation i.e. serotyping, this provides the information about the prevalent serovars in seafood. The prevalent Salmonella strains have been further characterized based on the utilization of different sugars and amino acids, to identify the different biovar of a serovar.A major research gap was observed in molecular characterization of Salmonella in seafood. Though, previous investigations reported the large number of Salmonella serovars from food sources in India, yet, very few work has been reported regarding genetic characterization of Salmonella serovars associated with food. Second part of this thesis deals with different molecular fingerprint profiles of the Salmonella serovars from seafood. Various molecular typing methods such as plasmid profiling, characterization of virulence genes, PFGE, PCR- ribotyping, and ERIC—PCR have been used for the genetic characterization of Salmonella serovars.The conventional culture methods are mainly used for the identification of Salmonella in seafood and most of the investigations from India and abroad showed the usage of culture method for detection of Salmonella in seafood. Hence, development of indigenous, rapid molecular method is most desirable for screening of Salmonella in large number of seafood samples at a shorter time period. Final part of this study attempted to develop alternative, rapid molecular detection method for the detection of Salmonella in seafood. Rapid eight—hour PCR assay has been developed for detection of Salmonella in seafood. The performance of three different methods viz., culture, ELISA and PCR assays were evaluated for detection of Salmonella in seafood and the results were statistically analyzed. Presence of Salmonella cells in food and enviromnental has been reported low in number, hence, more sensitive method for enumeration of Salmonella in food sample need to be developed. A quantitative realtime PCR has been developed for detection of Salmonella in seafood. This method would be useful for quantitative detection of Salmonella in seafood.

Physicochemical and molecular characterization of bacteriophages ΦSP-1 and ΦSP-3, specific for pathogenic Salmonella and evaluation of their potential as biocontrol agent

This thesis entitled Physicochemical and molecular characterization of bacteriophages ΦSP-1and ΦSP-3, specific for pathogenic Salmonella and evaluation of their potential as biocontrol agent . Salmonella were screened using standard methodologies from various environmental samples including chicken caecum. Salmonella strains, which were previously isolated and stocked in the lab, were also included in this study as host, for screening Salmonella specific lytic phages. The Salmonella strain in this study designated as S49 which helped in phage propagation by acting as host bacteria was identified as Salmonella enterica subsp. enterica by 16S rRNA gene analysis and serotyping . A total of three Salmonella specific phage named as ΦSP-1, ΦSP-2 and ΦSP-3 were isolated from chicken intestine samples via an enrichment protocol employing the double agar overlay method. ΦSP-1 and ΦSP-3 showing consistent lytic nature were selected for further study and were purified by repeated plating after picking of single isolated plaques from the lawns of Salmonella S49 plates. Both the phages produced small, clear plaques indicating their lytic nature. ΦSP-1 and ΦSP-3 were concentrated employing PEG-NaCl precipitation method before further characterization. The focus of present study was to isolate, characterize and verify the efficacy of lytic bacteriophages against the robust pathogen Salmonella, capable of surviving under various hostile conditions. Two phages, ΦSP-1 and ΦSP-3, belonging to two families, Podovoridae and Siphoviridae were isolated.

Studies on The Ecophysiology Of Some Heterotrophic and Indicator Bacteria In The Marine Environments of Kerala

The thesis entitled "Studies on the eco-physiology of heterotrophic and indicator bacteria in the marine environments of Kerala" embodies the results of an investigation carried out by the candidate at the Central Marine Fisheries Research Institute, Cochin. It is presentedd under 4 chapters in two parts (Parts A & B) and includes 6 sections. The material for the study was collected in the Cochin backwater during April 1972 to February. 1973, March 1974 to February 1975, July 1975 to June 1976 and in the ishore area during January to October, 1978 and an account of the heterotropic and indicator bacteria are given with intensity charts and tables. Samples from all the stations contained significant quantities of heterotrophs (Part A, Section I) and faecal pollution indicators (Section II). Maximum number of heterotrophic bacteria was observed during the postmonsoon period. The total counts betwen one station and the other did not vary as much as the counts between months did. The distribution was characterised by overdispersion. During 1972-73 in all the stations except the fourth the minimum heterotrophs (Total counts) were recorded during the monsoon period. Minimum counts were observed during the premonsoon period, with an increasing trend from the premonsoon to postmonsoon seasons. Maximum counts were recorded during monsoon months during 1974-75. No significant difference was noted in the total plate count between stations, months and regions. Seasonal variations in sea water was meagre during 1975-76, whereas in sediments variations were prominent during monsoon in Station I - near the mouth of the sewage effluent of Cochin City and in postmonsoon at Station II in the Mattancherry Channel and Station III near barmouth

Prevalence of Salmonella in fish and crustaceans from markets in Coimbatore, South India

Seven hundred and thirty fishes and 276 crustaceans collected from various fish markets of Coimbatore, South India, over a period of 2 years (September 1990 to August 1992) were analysed for the prevalence of Salmonella. Fishes (14·25%) and 17·39% of crustaceans were found to be contaminated with Salmonella. Of the different fishes analysed, the highest incidence of Salmonella was seen in Scopelidae (28%) followed by Trachnidae (26·9%). Among crustaceans Portunus pelagicus (33·33%) showed the highest incidence followed by Scylla serrata (28·57%). A well-marked seasonal variation in the incidence pattern was observed in both fishes and crustaceans with a higher incidence during monsoon season followed by post-monsoon and pre-monsoon. The region of the body that showed frequent isolation was the alimentary canal in fishes (41·33%) and gills (35·06%) in crustaceans. Serotyping of the isolates revealed prevalence of Salmonella weltevreden, Salmonella typhi, Salmonella paratyphi B, Salmonella mgulani and Salmonella typhimurium in both fishes and crustaceans. Salmonella senftenberg was isolated only from crustaceans

Antibiotic Resistance of Escherichia coli Serotypes from Cochin Estuary

This study aimed at detecting the prevalence of antibiotic-resistant serotypes of Escherichia coli in Cochin estuary, India. E. coli strains were isolated during the period January 2010–December 2011 from five different stations set at Cochin estuary. Water samples from five different stations in Cochin estuary were collected on a monthly basis for a period of two years. Isolates were serotyped, antibiogram-phenotyped for twelve antimicrobial agents, and genotyped by polymerase chain reaction for uid gene that codes for β-D-glucuronidase. These E. coli strains from Cochin estuary were tested against twelve antibiotics to determine the prevalence of multiple antibiotic resistance among them. The results revealed that more than 53.33% of the isolates were multiple antibiotic resistant. Thirteen isolates showed resistance to sulphonamides and two of them contained the sul 1 gene. Class 1 integrons were detected in two E. coli strains which were resistant to more than seven antibiotics. In the present study, O serotyping, antibiotic sensitivity, and polymerase chain reaction were employed with the purpose of establishing the present distribution of multiple antibiotic-resistant serotypes, associated with E. coli isolated from different parts of Cochin estuary.

Prevalence and antimicrobial resistance of Salmonella enteritidis and other salmonellas in the eggs and egg-storing trays from retails markets of Coimbatore, South India

A study was conducted to determine the incidence of Salmonella enterica serovar Enteritidis and other Salmonella serovars on eggshell, egg contents and on egg-storing trays. A total of 492 eggs and 82 egg-storing trays were examined over a period of 1 year from different retail outlets of a residential area of Coimbatore city, South India. Salmonella contamination was recorded in 38 of 492 (7.7%) eggs out of which 29 was in eggshell (5.9%) and 9 in egg contents (1.8%). Around 7.5% of the egg-storing trays were also found to be contaminated with Salmonella. Serotyping of the Salmonella strains showed that 89.7% of the strains from eggshell, 100% of the strains from egg contents and 71.4% of the strains from egg-storing trays were Salmonella Enteritidis. Other serovarvars encountered were S. Cerro, S. Molade and S. Mbandaka from eggshell and S. Cerro from egg-storing trays. Seasonal variations in the prevalence pattern were identified with, a higher prevalence during monsoon months followed by post-monsoon and premonsoon. Further examination of the Salmonella strains was carried out by testing their antimicrobial sensitivity against 10 commonly used antimicrobials. Results revealed high prevalence of multiple antimicrobial resistance among these strains suggesting possible prior selection by use of antimicrobials in egg production

Salmonella cross contamination in retail chicken outlets and the efficacy of spice extracts on salmonella enteritidis growth inhibhition on various surfaces

The source of samonella cross contamination in 15 retail chicken outlets in aresidual area in coimbatore city ,sourthern India was studied. Chopping boards and the butchers hands were predominant followed by knives and the weighing balance tray. Serotyping of the salmonella strains revealed that all strains were salmonella enteritis, except one which was found to be salmonella cerro.The anti bacterial activity of commonly used spices were evaluated.

Microbial quality of shrimp products of export trade produced from aquacultured shrimp

Bacteriological quality of individually quick frozen (IQF) shrimp products produced from aquacultured tiger shrimp (Penaeus monodon) has been analysed in terms of aerobic plate count (APC), coliforms, Escherichia coli, coagulase-positive staphylococci, Salmonella, and Listeria monocytogenes. Eight hundred forty-six samples of raw, peeled, and deveined tail-on (RPTO), 928 samples of cooked, peeled, and deveined tail-on (CPTO), 295 samples of headless, undeveined shell-on (HLSO), and 141 samples of raw, peeled, and deveined tail-off (RPND) shrimps were analysed for the above bacteriological parameters. Salmonella was isolated in only one sample of raw, peeled tail-on. Serotyping of the strain revealed that it was S. typhimurium. While none of the cooked, peeled tail-on shrimp samples exceeded the aerobic plate count (APC) of 105 colony forming units per gram (cfu/g), 2.5% of raw, peeled, tail-on, 6.4% of raw, peeled tail-off, and 7.5% of headless shell-on shrimp samples exceeded that level. Coliforms were detected in all the products, though at a low level. Prevalence of coliforms was higher in headless shell-on (26%) shrimps followed by raw, peeled, and deveined tail-off (19%), raw, peeled tail-on (10%), and cooked, peeled tail-on (3.8%) shrimps. While none of the cooked, peeled tail-on shrimp samples were positive for coagulase-positive staphylococci and E. coli, 0.6–1.3% of the raw, peeled tail-on were positive for staphylococci and E. coli, respectively. Prevalence of staphylococci was highest in raw, peeled tail-off (5%) shrimps and the highest prevalence of E. coli (4.8%) was noticed in headless shell-on shrimps. L. monocytogenes was not detected in any of the cooked, peeled tail-on shrimps. Overall results revealed that the plant under investigation had exerted good process control in order to maintain superior bacteriological quality of their products

Prevalence and antimicrobial resistance of Salmonella enteritidis and other salmonellas in the eggs and egg-storing trays from retails markets of Coimbatore, South India

A study was conducted to determine the incidence of Salmonella enterica serovar Enteritidis and other Salmonella serovars on eggshell, egg contents and on egg-storing trays. A total of 492 eggs and 82 egg-storing trays were examined over a period of 1 year from different retail outlets of a residential area of Coimbatore city, South India. Salmonella contamination was recorded in 38 of 492 (7.7%) eggs out of which 29 was in eggshell (5.9%) and 9 in egg contents (1.8%). Around 7.5% of the egg-storing trays were also found to be contaminated with Salmonella. Serotyping of the Salmonella strains showed that 89.7% of the strains from eggshell, 100% of the strains from egg contents and 71.4% of the strains from egg-storing trays were Salmonella Enteritidis. Other serovarvars encountered were S. Cerro, S. Molade and S. Mbandaka from eggshell and S. Cerro from egg-storing trays. Seasonal variations in the prevalence pattern were identified with, a higher prevalence during monsoon months followed by post-monsoon and premonsoon. Further examination of the Salmonella strains was carried out by testing their antimicrobial sensitivity against 10 commonly used antimicrobials. Results revealed high prevalence of multiple antimicrobial resistance among these strains suggesting possible prior selection by use of antimicrobials in egg production