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Reports of methicillin-resistant Staphylococcus aureus (MRSA) in food have become more frequent in recent years. The aim of this study was to estimate the presence of MRSA in raw milk, pasteurized milk and ice cream in Tabriz by culture and polymerase chain reaction (PCR) techniques, as well as the determination of their antimicrobial susceptibility. For this purpose, 300 samples of raw milk, pasteurized milk and ice cream were collected from different sellers in Tabriz. They were first evaluated for contamination by coagulase positive S. aureus through culturing method, and then the isolates were subjected to PCR method according to nuc gene in order to confirm S. aureus and methicillin resistance gene (mecA). Finally the antimicrobial resistance trend of the isolates was investigated by disc diffusion agar method. The cultured samples indicated that 50 (50%) of raw milk samples, 2 (2%) of pasteurized milk samples and 26 (26%) of ice cream samples were contaminated by S.aureus. Forty five, 1 and 23 of these isolates, respectively were confirmed to be S.aureus based on PCR using nuc gene primer. From the total of 69 isolates containing nuc gene, 20 isolates had the resistant mecA gene. Of the 69 isolates, 17 isolates showed simultaneous resistance against 4 antibiotics, 18 against 5 antibiotics, 8 against 6 antibiotics, 8 against 7 antibiotics, 7 against 8 antibiotics, 6 against 9 antibiotics, 2 against 10 antibiotics and 3 isolates against 11 antibiotics. In other words 100% of the isolates showed simultaneous resistance to more than 3 antibiotics. The results provide evidence that the presence of antimicrobial resistant strains of S. aureus has become remarkably widespread in food samples. This calls for better control of the sources of food contamination and as well as the spread of antimicrobial-resistance organisms.

Evidence suggests that the expected increase in frequency and magnitude of extreme weather events during climate change will alter plant productivity. Therefore, extreme weather events might also be capable of changing C sequestration and allocation. Here, experimental grassland communities of two species compositions, differing in their diversity, were exposed either to a simulated single drought or to a heavy-rainfall event. The magnitude of these manipulations imitated the local 100-year weather extreme according to extreme-value statistics. Effects on Net Ecosystem CO 2 Exchange (NEE in lmol m -2 s -1 ) as well as aboveground biomass production and leaf-area index (LAI) were recorded from prior to the manipulations until two months after the manipulations ended. Initial light utilization efficiency and maximum NEE increased after the drought. No change in the respiration was detected and maximum uptake capacity (GPP max ) was 15% higher for the drought-manipulated plots compared to controls, which indicates an enhanced CO 2 uptake into the systems. The level of diversity was also found to alter the lightresponse curves, increasing respiration and maximum NEE to a higher degree than drought in the more diverse compared to the less diverse community. This resulted in an increase of GPP max by 55%. No significant interactions between species composition and weather manipulations were detected. Interestingly, aboveground biomass production was not significantly affected by weather manipulations, even though LAI increased due to drought. This increase was caused by a decrease in the ratio between reproductive and vegetative growth. The heavyrainfall manipulation resulted in no significant effects. Our data suggest that C sequestration can be enhanced by a single weather event. However the importance, long-term duration, and thresholds or turning points of such effects need to be investigated further as intensification of weather extremes is currently emerging as one of the most important facets of climate change.

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