This study was undertaken to determine the prevalence of coagulase positive staphylococci (CPS) by examining a total of 71 raw milk cheeses. Additionally, enterotoxigenicity, antimicrobial susceptibility and the presence of mecA and mecC genes in the staphylococcal isolates were investigated. The isolation and enumeration procedure of CPS followed the International Organization for Standardization (ISO) standard. The presumptive staphylococci were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) using the VITEK MS system. VIDAS® Staph enterotoxin II assay was used for the detection of classical enterotoxins. Antimicrobial susceptibility testing (AST) was accomplished performing the disk diffusion method. All suspected methicillin resistant staphylococci were investigated for the presence of mecA and mecC genes by PCR assay. A high prevalence (87.32%) of CPS was detected in the cheeses at contamination levels up to 5.58 log CFU g. Among 47 staphylococcal isolates screened for enterotoxin production, only one isolate, identified as S. hyicus, was confirmed as being enterotoxigenic. Resistance to penicillin (63.70%) was the most common resistance among the tested Staphylococcus aureus isolates. The dominant phenotypic resistance patterns in coagulase negative staphylococci (CNS) were resistance to ofloxacin and fusidic acid. All CNS isolates were susceptible to the clinically important antibiotics clindamycin, chloramphenicol, gentamicin, linezolid, rifampicin and trimethoprim-sulfamethoxazole. The mecA and mecC genes were not detected. To the best of our knowledge, this is the first study concerning evaluation of the presence of methicillin resistant staphylococci (MRS) in dairy products in Serbia.

For many consumers egg yolk color is a very important characteristic of egg quality. Since hens are not able to synthesize coloring pigments, the intensity of the yolk color depends directly on the content and profile of pigmenting carotenoids present in their feed. The aim of this study was to assess the combined pigmenting effect of paprika and carrot and their ability to achieve egg yolks in the desired color range. Biological tests lasted for 30 days and were conducted on 180 Lohmann Brown layers. The laying hens were divided in six groups. Every group was assigned to one of six possible treatments, control 1 (C1) treatment without any pigments added, control 2 (C2) treatment with synthetic pigments added and four experimental diets (D1, D2, D3, D4) with the addition of natural color sources (paprika and carrot). After experimental period collected eggs were analyzed regarding physical characteristics of eggs, content of β-carotene and yolk color of eggs. Obtained results has shown that dried carrot and milled paprika can successfully replace synthetic pigments, with no negative effects on physical characteristics of produced eggs, egg yolk color, acceptability or β-carotene content.

[Projekat Ministarstva nauke Republike Srbije, br. 31087]

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For the purpose of precise antibiotic susceptibility testing it is necessary to clearly distinguish Pseudomonas and Stenotrophomonas genera, considering acquired resistance of Pseudomonas species, as well as the intrinsic resistance of Stenotrophomonas species. This is why in the identifi cation of the 51 isolates originated from fi sh, the following methods were used: standard PCR, 16S rRNA gene sequencing, and MALDI-TOF.The results of the standard PCR test, 16S rRNA gene sequencing and MALDI-TOF analysis confi rmed 35 strains to belong to the Pseudomonas genus. Standard PCR test and VITEK MS device confi rmed that 10 strains belong to Stenotrophomonas maltophilia species.Three strains were positive in both standard PCR tests for Pseudomonas and Stenotrpohomonas. 16S rRNA gene sequencing identifi ed these 3 strains to be 99% Pseudomonas sp. and 99% Stenotrophomonas sp. VITEK MS fi rst identifi ed these three strains as 99% Stenotrophomonas, and in the repeated identifi cation it identifi ed them as 99% Pseudomonas. MALDI TOF/TOF 4800 Plus device identifi ed these strains as Stenotrophomonas.Three strains were negative in both standard PCR tests for Pseudomonas and Stenotrpohomonas. 16S rRNA gene sequencing identifi ed these 3 strains to be 99% Pseudomonas sp. and 99% Stenotrophomonas sp. VITEK MS fi rst identifi ed these three strains as 99% Stenotrophomonas, and in the repeated identifi cation it identifi ed them as 99% Pseudomonas. MALDI TOF/TOF 4800 Plus device identifi ed these strains as Stenotrophomonas.Although modern test methods that have very high specifi city (PCR, 16S rRNA gene sequencing, MALDI TOF) were used in this study, precise differentiation between Unauthenticated Download Date | 5/11/18 8:55 PM Aksentijević et al.: Differentiation between Pseudomonas and Stenotrophomonas species isolated from fi sh using molecular and MALDI-TOF method 305Pseudomonas and Stenotrophomonas species for 6 isolates could not be reached using the above mentioned methods.

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Water stability of eight samples of extruded salmon feeds was first determined by applying two gravimetric methods developed by the authors: gravimetric static and wet sieving method. Then, the conductometric method, primarily developed for investigation of nutrient leaching of feed into the water by the authors, was used for each sample. The aim of this study was to evaluate the potential of the conductometric measurement as a technique for determining water stability of extruded fish feed. In order to find any correlation between the results of two gravimetric tests and conductometric method, correlation analysis was employed. The results of static and wet sieving method were expressed as water stability index, which was expressed as the percent of remained dry matter of sample after being disintegrated in the water. The results of conductometric method were shown as conductivity curves for each sample, giving the insight in rate of nutrient leaching during the time. The obtained values of water conductivity showed no significant (p < 0.05) correlation with the results of static water method, while there was a negative significant (p < 0.05) correlation with the results of wet sieving method during first four hours of pellets soaking in water. The highest correlation coefficients were obtained within the first hour of conductivity measurement, demonstrating that proposed conductometric method had a potential to be applied as a rapid and simple method for determination and relative comparison of salmon feed water stability.