**4. Conclusion**

84 Salmonella – A Dangerous Foodborne Pathogen

TESTS *Salmonella* spp. *Salmonella* spp.

APPA - - ADO - - PyrA - - IARL - dCEL - - BGAL - - H2S + + BNAG - - AGLTp - dGLU + + GGT - - OFF + + BGLU - dMAL - dMAN + + dMNE + + BXYL - - BAlap - - ProA - - LIP + + PLE - - TyrA - - URE - dSOR - - SAC - dTAG + + dTRE + + CIT - - MNT - - 5KG - - ILATk - - AGLU - - SUCT - - NAGA - - AGAL - + PHOS + + GlyA - - ODC + + LDC + + IHISa - - CMT - - BGUR - - O129R - +

The frequency of *Salmonella* spp. according to their exposure to environmental factors in the areas from which they were isolated were different. For instance, higher indicator bacteria and *Salmonella* spp. abundance was found in the coastal stations compared to the offshore areas. The *Salmonella* spp. prevalence in a total of 832 samples of seawater (495), shellfish (243), and fish (94) which were collected from six sites between 1998 and 2010 exhibited diversity according to geographical areas. The coastal areas which were under the influence of biological pollution with respect to heavy inland population displayed higher levels of *Salmonella* spp. than the offshore areas.

Enteric bacteria of sewage origin undergo a sudden osmotic shock when they enter seawater and may adapt their metabolism to the new medium by means of their osmoregulation systems. This ability of enteric bacteria aids them in gaining resistance to salt in sea environments and increases their probability of survival (Munro et al., 1989). The presence of a negative relationship between salinity concentration and the number of enteric bacteria in sea medium has been determined (Carlucci et al., 1960, APHA 1998, Bitton 2005)

In this study, the influence of salinity on the presence of *Salmonella* spp. associated with water samples was also investigated. In the Sea of Marmara it was possible to isolate *Salmonella* spp. from the under and upper stratification of various localities which possessed salinity values between 24.0 psu and 39.2 psu during the study. The bacteria levels determined in water samples taken from under the halocline layer in the Sea of Marmara were sometimes found to be higher in comparison to sea water samples taken from 0-30 cm. The higher bacteria levels found in the undercurrent were considered to be a result of deep discharge systems carrying domestic waste products. Hydrographic changeable parameters

The Occurrence of Salmonella in Various Marine Environments in Turkey 87

of notable significance with respect to public health due to the potential risk of acquiring infections as a result of the consumption of contaminated aquatic products or ingestion of

The author wishes to thank Dr. Mine Cardak, PhD students Sevan Gürün and Pelin S. Çiftçi for their support. The author also thanks the crew of the research vessel Yunus-S for their

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contaminated seawater.

**5. Acknowledgment** 

help in sampling.

**6. References** 

such as seawater temperature, pH, salinity and dissolved oxygen are significant factors associated with the presence of *Salmonella* spp. In this study, seawater temperature was the only variable showing a linear positive effect on the presence of *Salmonella* in the sea, while the other parameters showed more complex nonlinear effects in the studied areas.

There are many factors such as temperature, salinity, sunlight, grazing by heterotrophic microorganisms affecting the survival of enteric bacteria in marine areas (*Sinton et al 2007:*  Harm, 1980, Gameson & Gould 1985, Jagger 1985, Rozen and Belkin 2001, Sinton 2005)

Temperature also seemed to affect efficiently the abundance of indicator bacteria and *Salmonella* spp. in the study areas. *Salmonella* spp. positive samples were mostly recorded in the summer seasons and the indicator bacteria level was also higher during these periods compared to the other sampling seasons in 1998-2010. This situation is directly related to the increase of human activity, especially in coastal areas in summer seasons. However it also shows that despite the salinity stress, occurrences of indicator bacteria and *Salmonella* spp. were possible under these conditions in the seawater.

*C. gallina* and *D. trunculus* are two most common and abundant species in Turkish clam resources. Especially *C. gallina* is very important and valuable species, due to its great export potential, *C. gallina*, which has begun to be gathered since 1986 via mechanical dredge in Turkey, has great importance in terms of economy (Altuğ et. al., 2008).

The mean values of bacterial contamination found in the 75 *R. venosa* samples under bacteriological analysis were between 15x10 and 24x103 and above. It is concluded that the area is under the influence of the waste products of dwellings and naval transportation (Altuğ and Güler 2002).

Beta-lactam antibiotics are widely used for treatment of infections in the world. Domestic waste waters might be an important source of antibiotic-resistant *Enterobacteriaceae*. Resistances to clinically relevant antibiotics are widespread in aquatic bacteria, including potential human pathogens. Because antibiotic resistance related to domestic waste waters is important for the ecosystem and also for human health, the resistance frequency of *Salmonella* spp. isolates to some beta-lactam antibiotics was investigated in this study. The antibiotic derivates which were found to be resistant to bacteria were different in different regions. This situation shows that pollution input and the usage rate of antibiotics have differences related to geographic regions. Further research will help towards setting limits on the prevalence of antibiotic-resistant bacteria and supporting the effectiveness of antimicrobial agents.

It was reported that *Salmonella* spp. presence in marine waters is adequately predicted by total coliforms or fecal coliforms (Efstratiou et al. 2009). In this study, positive correlations were found between the presence of coliform bacteria (especially >103 cfu/100 ml) and occurrences of *Salmonella* spp. positive isolates. Efstratiou et al.( 2009) reported that the *E. coli* limits set by the EU Directive for defining "good" coastal bathing water quality (500 CFU100 ml−1) are much higher than the fecal coliform concentration which would best predict the absence of *Salmonella* spp.

The percentage distribution of the ratio values of Fecal Coliform to Fecal Streptococci in the surface water of the Aegean Sea and the relation of this ratio with the occurrence of *Salmonella* spp. was also investigated (Altuğ et al., 2007). The percentages of *Salmonella* spp. among total enteric bacteria were between 25% and 37%. Positive correlations were observed between the level of indicator bacteria and the presence of *Salmonella,* implying that *Salmonella* spp. occurrence is a part of anthropological pollution input in the investigated areas. The presence of isolates of *Salmonella* spp. in the marine environment is of notable significance with respect to public health due to the potential risk of acquiring infections as a result of the consumption of contaminated aquatic products or ingestion of contaminated seawater.
