title: Evaluation of Antibiotic Residues in Pasteurized and Raw Milk Distributed in the South of Khorasan-e Razavi Province, Iran.
abstract: BACKGROUND
  The presence of antibiotic residues in milk and other products livestock is a health problem which can endanger public health. Antibiotics are used widely in animal husbandry to treat diseases related to bacterial infections. Antimicrobial drugs have been in use for decades in industry. They are commonly used in livestock facilities to treat mastitis.
  
  
  OBJECTIVE
  This study aimed to investigate antibiotic residues in pasteurized milk distributed in schools, in milk collection centers, and in milk production factories in Gonabad city.
  
  
  METHODS
  This cross-sectional study was conducted on 251 samples of commercial pasteurized milk packet distributed in schools (code A), raw milk collection centers in Gonabad city (code B), and pasteurized milk production factories (code C) in Gonabad city. The Copan test kit of Denmark Christian Hansen Company was used to monitor antibiotic residues in milk. The data were analysed employing Chi-square test and one-way analysis of variance (ANOVA) to determine significant differences using SPSS software version 20. The significant level was considered at p<0.05.
  
  
  RESULTS
  In total, 251 milk samples were collected out of which 143 (57%) were code A, 84 (33.5%) code B and 24 (9.6%) code C. Total number of 189 samples (75.2%) were negative and 62 (24.8%) were positive. From the three types of milk samples, 41 samples (28.7%) of the code A, 18 samples (21.4%) of the code B and 3 samples (12.5%) of the code C were positive. In general, from the milk samples most contaminated with antibiotics, 17 samples were positive in January and regarding code A, 13 samples were positive in the same month. There was not a significant difference among the three types of milk (p>0.05). The highest number of milk samples (n=7) contaminated with antibiotics were related to code B (38.5%). Most positive cases were related to code A in winter. Also, there was no significant difference among the three types of contaminated milk regarding the year and month (p=0.164 and p=0.917, respectively).
  
  
  CONCLUSIONS
  Pasteurized milk supplied in the studied city has high level of contamination due to high use of antibiotics. A standard limit needs to be set for the right level of residue of antibiotics in milk to avoid the harmful effects.
authors.affiliation: PhD. Student, Deputy of Food and Drugs, Gonabad University of Medical Sciences , Gonabad, I.R, Iran .
authors.forename: Mortez Mohammadzadeh
authors.initials: MM
authors.lastname: Moghadam
authors.affiliation: Assistant Professor in TEFL, Department of Basic Sciences, Faculty of Medicine, Gonabad University of Medical Sciences , Gonabad, Iran .
authors.forename: Mostafa
authors.initials: M
authors.lastname: Amiri
authors.affiliation: Faculty of Health, Department of Public Health, Gonabad University of Medical Sciences , Gonabad, I.R, Iran .
authors.forename: Hamed Ramezani Awal
authors.initials: HR
authors.lastname: Riabi
authors.affiliation: Student, Department of Basic Sciences, Gonabad University of Medical Sciences , Gonabad, I.R, Iran .
authors.forename: Hamid Ramezani Awal
authors.initials: HR
authors.lastname: Riabi
keywords: Antibiotic residue; Copan test; Food safety; Milk quality