One hundred strains of Gram-negative bacteria were isolated from a brackish water Lagoon, Küçükçekmece in Istanbul-Turkey. Identification studies showed that 31% of the isolated bacteria were Escherichia coli, 28% were Citrobacter, and 12% were Enterobacter. Antibiotic and heavy metal resistances exhibited by these bacteria were evaluated. In antibiotic susceptibility tests, 68% of the isolates appeared to be resistant to vancomycin, while 38% was resistant to erythromycin, 23% to penicilin G, 19% to ampicillin, 13% to nalidixic acid and streptomycin, 7% to chloramphenicol, 5% to amikacin, 2% to gentamycin, and 1% to kanamycin. Most of the isolates tolerated various concentrations of heavy metals, and the minimum inhibitory concentrations (MIC) ranged from 20 μg/ml to >5000 μg/ml. In terms of heavy metal sensitivity, 98% of the isolates were resistant to Fe, 95% to Cd, 85% to Co, 83% to Cu and Zn, and 74% to Ni. When antibioticheavy metals multiresistance index was examined, it was determined that the multiple heavy metal resistance (MHMR) index was remarkably high for the bacteria, while the multiple antibiotic resistance (MAR) index was low according to heavy metal resistance. It was demonstrated that the bacteria isolated from Küçükçekmece Lagoon were highly resistant to antibiotics and heavy metals. It was concluded that if the wastewater discharge to the Lagoon is not regulated, resistance gene transfers into the bacteria hosted normally in human microbiota could create significant health issues.

Nine Legionella pneumophila strains isolated from cooling towers and a standard strain (L. pneumophila serogroup 1, ATCC 33152, Philadelphia 1) were analyzed and compared in terms of motility, flagella structure, ability to form biofilms, enzymatic activities (hemolysin, nucleases, protease, phospholipase A, phospholipase C, acid phosphatase, alkaline phosphatase and lipase), hemagglutination capabilities, and pathogenicity in various host cells (Acanthamoeba castellanii ATCC 30234, mouse peritoneal macrophages and human peripheral monocytes). All the isolates of bacteria appeared to be motile and polar-flagellated and possessed the type-IV fimbria. Upon the evaluation of virulence factors, isolate 4 was found to be the most pathogenic strain, while 6 out of the 9 isolates (the isolates 1, 2, 3, 4, 5, and 7) were more virulent than the ATCC 33152 strain. The different bacterial strains exhibited differences in properties such as adhesion, penetration and reproduction in the hosts, and preferred host type. To our knowledge, this is the first study to compare the virulence of environmental L. pneumophila strains isolated in Turkey, and it provides important information relevant for understanding the epidemiology of L. pneumophila.

Listeria monocytogenes that the most common human listeriosis agent is one of 21 species of the Listeria genera. In fact, the mortality rate of listeriosis is higher than that of the more common foodborne pathogens such as Vibrio species or Salmonella Enteritidis. This study was aimed to determine the L. monocytogenes contamination in different minced meat samples. In this study, 100 minced meat samples purchased from different butchers in 11 districts of Istanbul between December 2018 and November 2019 were examined for the presence of L. monocytogenes. Isolates were molecularly confirmed for the presence of the iap and hlyA gene regions. It was determined that 21 biochemically defined isolates were susceptible to tetracycline and ampicillin, while resistant to amoxicillin/clavulanic acid, penicillin, cefaclor, and vancomycin. In addition, it was determined that only 16 of these 21 isolates were L. monocytogenes in terms of iap and hlyA gene regions. L. monocytogenes incidence in minced meat sold in Istanbul is low (17%), we believe that these contamination rates indicate a significant risk to public health due to cross-contamination and raw consumption of minced meat.

Since minced meat provides a large contact surface, it is a food in which the total bacterial load and the enzymatic profiles of the species that make up this load should be addressed, even in cases where it does not contain pathogens. Therefore, this study aimed to investigate the effect of freezing, one of the most commonly used storage methods for minced meat, on total and proteolytic bacterial loads. To simulate the actual storage process, individuals belonging mainly to the genera Bacillus, Serratia, Pseudomonas, Citrobacter, Acinetobacter, and Escherichia were isolated from the samples examined directly and after 15 days of freezing, without any process that would cause a change in the microbial load. 71.11% of these isolates exhibited valine and cystine aminopeptidase activity, while 37.77 and 33.33% exhibited trypsin and α-chymotrypsin activity, respectively. In addition, the results show that cryopreservation allows psychrophilic proteolytic bacteria to increase their numbers in meat.

Skates and rays, which are widely encountered in the by-catch of fisheries activities from the Sea of Marmara and banned for sale by regulation, are species that are discarded if caught. For this reason, in our study, we aimed to determine the bioactive potentials of these species, considered fishing waste, by investigating the skin secretions and microbial flora. In our study, both the skin flora and mucus contents of the discarded species Dasyatis pastinaca (Linnaeus,1758), Myliobatis aquila (Linnaeus, 1758), and Raja clavata (Linnaeus, 1758) caught in the Sea of Marmara were investigated to determine their potential antimicrobial activities. A total of 164 bacteria were isolated from the epidermal mucus of the three batoid species. Antibacterial activity was observed from three isolated bacteria against Escherichia coli, Vancomycin-resistant Enterococcus faecium, E. faecalis, and Bacillus subtilis. Additionally, the highest antibacterial activity was observed for skin mucus of R. clavata. Mouse fibroblast cell viability was challenged with mucus secretions. M. aquila and R. clavata mucus secretions exhibited no observable change after 24 and 48 hours. The assays indicated that both the isolates and the skin mucus have potential antimicrobial activity against opportunistic pathogens.