Occurrence of Staphylococcus aureus and evaluation of anti-staphylococcal activity of Lactococcus lactis subsp. lactis in ready-to-eat poultry meat

Dietary supplementation of methionine, lysine, and tryptophan as possible modulators of growth, immune response, and disease resistance in striped catfish (Pangasius hypophthalmus)

The present study investigated the potential role of different essential amino acids (AA) in striped catfish (Pangasius hypophthalmus). Fish (initial weight = 17.91±0.27 g, n = 260) were fed with eight isonitrogenous (30%), and isolipidic diets (6%) formulated to include different combinations of tryptophan (Trp), methionine (Met), and lysine (Lys) (T0: Zero AA, T1: Trp, T2: Lys, T3: Met, T4: Trp+Met, T5: Lys+Trp, T6: Met+Lys, T7: Lys+Trp+Met) for eight weeks. The dose of amino acid supplementation, whether individually or in combination, was 5g of each amino acid per kg of diet. The trial comprised eight treatments, with each treatment consisted of three replicates (n = 10/replicate). At the end of the growth experiment, the highest total body weight, crude protein, digestive enzymatic activity, immune response, and amino acids level were observed in treatments supplemented with amino acids compared to T0. After the growth experiment, fish in all treatments were exposed to Staphylococcus aureus (5×105 CFU/ml). For bacterial challenge trial, the T0 treatment was designated as positive (+ve T0) and negative control (-ve T0). Following the S. aureus challenge, fish fed with amino acids showed a better response to reactive oxygen species and lipid peroxidation, as indicated by the increased levels of catalase and superoxide dismutase. Conversely, the concentration of malondialdehyde gradually decreased in all treatments compared to the +ve T0 treatment. It is concluded that supplementation of amino acids improved the growth, protein content, and immunocompetency against S. aureus in striped catfish. The most favorable outcomes in striped catfish were shown by fish supplemented with T7 diet. These essential amino acids hold potential as efficient supplements for use in the intensive aquaculture for striped catfish.

Effects of Bacillus subtilis as a single strain probiotic on growth, disease resistance and immune response of striped catfish (Pangasius hypophthalmus)

The present study investigated the potential role of Bacillus subtilis as probiotic in striped catfish (Pangasius hypophthalmus). Fish (initial weight = 150.00±2.63g n = 180) were stocked in circular tanks. Four isonitrogenous (30%) and isolipidic (3.29%) diets were formulated having supplementation of B. subtilis at four different levels (P0; 0, P1: 1×106, P2: 1×108 and P3: 1×1010 CFU/g). Each treatment had three replicates, while each replicate had fifteen fish. The trial started on second week of July and continued for eight weeks. Growth, feed conversion ratio, crude protein content, the concentration of amylase and protease, the profile of both dispensable and non-dispensable amino acids in all four dietary groups increased with a gradual increase of B. subtilis in the diet. At the end of growth experiment, fish in all four groups were exposed to Staphylococcus aureus (5×105 CFU/ml). After S. aureus challenge, fish fed with B. subtilis responded better to damage caused by reactive oxygen species and lipid peroxidation and better survival rate. The catalase and superoxide dismutase level also increased in response to bacterial challenge in B. subtilis fed groups. On the other hand, the concentration of malondialdehyde gradually decreased in these groups (+ve P0 >P1>P2>P3). It is concluded that supplementation of B. subtilis as a probiotic improved the growth, protein content, antioxidant response and immunocompetency against S. aureus in striped catfish. The optimum dosage of B. subtilis, at a concentration of 1×1010 CFU/g, resulted in the most favorable outcomes in striped catfish. This single bacterial strain can be used as an effective probiotic in large scale production of aquafeed for striped catfish. Future studies can investigate this probiotic's impact in the intensive culture of the same species.

Antimicrobial Activities and Biopreservation Potential of Lactic Acid Bacteria (LAB) from Raw Buffalo (Bubalus bubalis) Milk

The aim of this study was to investigate the antimicrobial and biopreservation potential of lactic acid bacteria. The potential probiotic culture inhibited the growth of gram-positive and gram-negative foodborne pathogens in agar spot assay with inhibition zones ranging from 10 to 21 mm in diameter. The strains showed coaggregation capabilities ranging from 7 to 71% with tested food pathogens including Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Salmonella enterica subsp. enterica serovar Typhimurium. The effect of cell-free supernatants on the release of 260 nm absorbing material, especially nucleic acids, was evaluated and indicated the antagonistic activity on foodborne pathogens, the highest being Lactobacillus paraplantarum against E. coli (3.77) and S. aureus (3.86) after 60 min. The effect of cell-free supernatant (CFS) on the growth of pathogens showed that Lactobacillus paraplantarum 11 and L. pentosus 93 had the highest inhibitory activity against tested strains. The biopreservation assay indicated that the potential probiotic strains Lactobacillus paraplantarum 11 (BT), Lactiplantibacillus plantarum 19, Lactobacillus pentosus 42, Limosilactobacillus fermentum 60, Lactobacillus pentosus 93, and Limosilactobacillus reuteri 112 were effective in reducing the Listeria monocytogenes population in raw buffalo milk. Complete Listeria monocytogenes inhibition was observed after 6-8 days. This study showed that probiotic LAB from buffalo milk have antimicrobial and biopreservation potential; these strains have the potential to be utilized as biopreservative agents in food products.

Enterotoxigenic methicillin resistant Staphylococcus aureus contamination in salted fish from Gwadar Balochistan

Staphylococcus aureus is an important foodborne pathogen associated to food intoxication and other multiple infections in human being. Its presence in salted food is a serious issue due to its salt tolerance potential. A study was conducted to analyze the presence of enterotoxins producing drug resistance S. aureus in salted sea fish from Gwadar. Freshly persevered samples (n=50) of salted fish were subjected to analyze the presence of S. aureus using 16S rRNA and Nuc genes primers. The isolates were then evaluated for drug resistance and enterotoxins producing potential using specific primers for MecA (methicillin resistance gene), (SEA) staphylococcal enterotoxin A and (SEB) staphylococcal enterotoxin B genes. Total 13/50 (26%) of the samples were found positive for the presence of S. aureus, preliminary confirmed with biochemical profiling and finally with the help of target genes presence. The isolates were found showing 100% resistant to methicillin, which were molecularly confirmed by the presence of MecA gene present in genome. The isolates 5/13 (38%) were positive for SEA and 3/13 (23%) for SEB genes, whereas 2/13 (15%) were confirmed having both SEA and SEB genes in its genome. It was also confirmed that all the isolates were capable to form biofilm over the glass surfaces. It was concluded that the study confirmed the presence of enterotoxigenic methicillin resistance Staphylococcus aurous (MRSA) in salted fish product, that poses gross food safety concern. Preventive and control measures are necessary to handle this serious food safety concern.

Virulent and multidrug-resistant Klebsiella pneumoniae from clinical samples in Balochistan

Klebsiella pneumoniae is an important pathogen causing hospital-acquired infections in human beings. Samples from suspected patients of K pneumoniae associated with respiratory and urinary tract infections were collected at Bolan Medical Complex, Quetta, Balochistan. Clinical samples (n = 107) of urine and sputum were collected and processed for K pneumoniae isolation using selective culture media. Initially, 30 of 107 isolates resembling Klebsiella spp. were processed for biochemical profiling and molecular detection using gyrase A (gyrA) gene for conformation. The K pneumoniae isolates were analysed for the presence of drug resistance and virulence genes in their genomes. The 21 of 107 (19.6%) isolates were finally confirmed as K pneumoniae pathogens. An antibiogram study conducted against 17 different antibiotics showed that a majority of the isolates are multidrug resistant. All the isolates (100%) were resistant to amoxicillin, cefixime, amoxicillin-clavulanic acid, cefotaxime, and ceftriaxone followed by tetracycline (95.2%), ciprofloxacin and gentamicin (76.2%), sulphamethoxazol (66.7%), nalidixic acid (61.9%), norfloxacine (42.9%), piperacillin-tazobactam (23.8%), cefoperazone-sulbactam (19%), and cefotaxime-clavulanic acid (33.3%), whereas all the isolates showed sensitivity to amikacin, chloramphenicol, and imipenem. The presence of tetracycline, sulphamethoxazol-resistant genes, and extended-spectrum beta-lactamase was reconfirmed using different specific genes. The presence of virulence genes fimH1 and EntB responsible for adherence and enterobactin production was confirmed in the isolates. The high virulence and drug resistance potential of these Klebsiella isolates are of high public health concern. Multidrug resistance and virulence potential in K. pneumoniae are converting these nosocomial pathogens into superbugs and making its management harder.

Probiotic Potential of Lactobacillus Strains with Antifungal Activity Isolated from Animal Manure

The aim of the study was to isolate and characterize the lactic acid bacteria (LAB) from animal manure. Among the thirty LAB strains, four strains, namely, KCC-25, KCC-26, KCC-27, and KCC-28, showed good cell growth and antifungal activity and were selected for further characterization. Biochemical and physiology properties of strains confirmed that the strains are related to the Lactobacillus sp.; further, the 16S rRNA sequencing confirmed 99.99% sequence similarity towards Lactobacillus plantarum. The strains exhibited susceptibility against commonly used antibiotics with negative hemolytic property. Strains KCC-25, KCC-26, KCC-27, and KCC-28 showed strong antifungal activity against Aspergillus fumigatus, Penicillium chrysogenum, Penicillium roqueforti, Botrytis elliptica, and Fusarium oxysporum, respectively. Fermentation studies noted that the strains were able to produce significant amount of lactic, acetic, and succinic acids. Further, the production of extracellular proteolytic and glycolytic enzymes, survival under low pH, bile salts, and gastric juice together with positive bile salt hydrolase (Bsh) activity, cholesterol lowering, cell surface hydrophobicity, and aggregation properties were the strains advantages. Thus, KCC-25, KCC-26, KCC-27, and KCC-28 could have the survival ability in the harsh condition of the digestive system in the gastrointestinal tract. In conclusion, novel L. plantarum KCC-25, KCC-26, KCC-27, and KCC-28 could be considered as potential antimicrobial probiotic strains.

Isolation of Salmonella from ready-to-eat poultry meat and evaluation of its survival at low temperature, microwaving and simulated gastric fluids

A study was conducted to evaluate the risk of Salmonella contamination and its survival at different stages in chill ready-to-eat poultry meat products chain. Samples (n = 181) were collected and examined for the presence of Salmonella species. The bacteria were initially identified against polyvalent antisera "O" and "H", followed by confirmation with 16 s rDNA. The single Salmonella, isolate from the tested food samples showed 99.8 % phylogenetic similarity with Salmonella enterica. It was further evaluated for antibiotic sensitivity pattern and found resistant to four antibiotics including ampicillin, chloramphenicol, tetracycline and nalidixic acid. Salmonella associated with ready-to-eat poultry meat products were found active at storage temperature ≥4 °C in a challenge study. It was revealed that shape and weight of the meat pieces have direct influence on the reduction of pathogens during microwave heating. The 30 and 60 s microwaving (with radiation power fixed at 900 W) was found ineffective for the elimination of target bacteria (10(6)-10(7) CFU/g) in meat pieces with weight ≥90 g. Salmonella enterica was able to survive in simulated gastric fluid. The storage temperature and microwaving were found critical point for the transfer of pathogens through ready-to-eat poultry meat products to consumer in chill ready-to-eat poultry meat chain.