ABSTRACT
Aflatoxins are secondary toxic metabolites produced by some Aspergillus spp. particularly, Aspergillus flavus and A. parasiticus that contaminate food and feed. The objective of this study was to evaluate the contamination of feedstuffs with Aspergillus spp. And detect genes involved in the aflatoxin biosynthesis pathway of A. flavus and A. parasiticus isolates. A total of 110 cow feed samples [comprised of silage, concentrate, hay and total mixed ration] from 30 industrial and semi-industrial dairy farms of Khorasan Razavi province, northeastern Iran, were examined using cultural and PCR methods. 68 [61.82%] Aspergillus spp. were isolated from 110 samples of feedstuff. The predominant Aspergillus isolates were A. fumigates [21.81%], followed by A. flavus [17.27%], A. niger [10%], A. parasiticus [8.18%], and A. oryzae [4.54%]. Fungal contamination levels of industrial and semi-industrial dairy farm samples were not significantly different [P>0.05]. Using four sets of primers, a quadruplex PCR was developed to detect genes [nor1, ver1, omtA and aflR] at different loci coding enzymes in the aflatoxin biosynthesis pathway of A. flavus and A. parasiticus strains. Out of 28 strains of A. flavus and A. parasiticus, 10 isolates [35.71%] showed a quadruplet pattern indicating the important genes involved in the aflatoxin biosynthesis pathway, encoded for functional products. These isolates were confirmed to be aflatoxigenic by Thin Layer Chromatography. 18 isolates [64.29%] had three, two and single molecular patterns. The results obtained by this study show that rapid and specific detection of aflatoxigenic molds is important to ensure the microbiological safety of feedstuffs
ABSTRACT
The objective of this study was to determine the occurrence of antimicrobial resistance among Staphylococcus aureus and to estimate the presence of methicillin-resistance in S. aureus [MRSA] isolates obtained by culture and polymerase chain reaction [PCR] methods. For this purposes, 100 Iranian white and feta cheese samples collected from different suppliers were initially evaluated for the occurrence of S. aureus by culturing methods. The obtained isolates were subjected to disc diffusion antimicrobial susceptibility tests and a PCR method to detect the mecA gene. Out of the 100 cheese samples examined, 25 [25%] samples were contaminated with S. aureus with a mean of 5.74 +/- 5.67 log cfu/g. Out of the 25 isolates, 23 [92%] were found to be resistant to at least one antibiotic or more, tested by a disk diffusion method. The highest rate of antibiotic resistance was observed to penicillin G [92%] followed by ampicillin [73%] and cloxacillin [68%]. None of the isolates was resistant to gentamycin and vancomycin. Eight [34.78%] of the 23 S. aureus isolates were genotypically confirmed as MRSA. The results indicate that the presence of antimicrobial resistant strains of S. aureus in Iranian cheese samples constitute a potential risk for human health. This calls for better control of the spread of antimicrobial resistant strains as well as cheese contamination sources
ABSTRACT
The extensive consumption of milk and dairy products makes these foodstuffs targets for potential adulteration with financial gains for unscrupulous producers. The aim of this study was using PCR assay to detect cow milk in labeled sheep milk, sheep yoghurt, and Lighvan cheese [a traditional ripened cheese produced from sheep's milk]. The assay utilized primers targeting the mitochondrial 12s and 16s rRNA gene. In this study, 35 samples of sheep milk, 35 samples of sheep yoghurt, and 35 samples of Lighvan cheese were purchased from different supermarkets in Mashhad city with different batch numbers. The results showed only 21 out of 105 [20%] samples contained pure sheep milk. Undeclared presence of cow and goat milk was detected in 33[31.5%] and 68[65%] of the 105 samples, respectively. It seems the PCR based analytical method is an applicable technique to monitor adulteration in dairy products