Iranian Journal of

Background and Objectives: widely use of antibiotics as therapy and uncontrolled discharge of them to receiving waters increased the percentages of antibiotic resistant bacteria in various environments which may cause problems in therapy. The aim of this study was to investigate the antibiotic resistance of E. coli, K. pneumoniae and P. aeruginosa bacteria isolated from urban and hospital wastewaters. Nine antibiotics namely Chloramphenicol, Ciprofloxacin, Trimethoprim Sulfamethoxazol, Gentamycin, Ceftizoxime, Nalidixic Acid, Ceftazidime, Ceftriaxon and Cefalexin were investigated in this study.
Materials and Methods: through a cross-sectional descriptive study the isolation of bacteria from hospital and urban wastewater samples was performed by microbiological identification techniques. The resistance to nine antibiotics was tested by application of the standard disc diffusion technique and zone-size interpretation chart of Kirby-Baeur. Non-parametric Mann-Whitney test was used to assessing two environments differences.
Results: The resistance percentage of E. coli to studied antibiotics was significantly less (ranged from 1.81 to 51.02%) than the resistance percentage of P. aeroginosa (ranged from 3.57 to 61.76) and K. pneumoniae (ranged from 6.45 to 91.83%). the highest resistance to antibiotics studied was for K. pneumonia in comparison with others. E. coli, K. pneumonia and P. aeroginosa bacteria showed the highest resistance to CAZ, SXT and CN, respectively. The study showed the resistance rate in hospital wastewater is more than urban wastewater.
Conclusion: Easy access and uncontrolled usage of antibiotics cause discharge of antibiotics to wastewaters and consequently diminish the drugs' effectiveness. High concentration of antibiotic and diversity in wastewater of hospital in comparison with urban wastewater causes to transfer resistant agents between bacteria and increased the multiple resistances.

Background and Objectives: Milk is a full meal that can provide an appropriate growing environment for different bacteria. Hence, it can be hazardous to human health in unpasteurized conditions. The present study was conducted in order to assess the prevalence and antimicrobial resistance of Staphylococcus aureus in raw and pasteurized milks of Sari City in the summer of 2014.

Materials and Methods: This cross-sectional study was conducted in the summer of 2014 in the city of Sari. Totally, 160 samples- each 200 mL of raw milk were collected from collection and distribution centers (80 samples) of raw milk, and pasteurized milk from food stores (80 samples). Under aseptic conditions, confirmatory tests were carried out in Chapman and Blood agar media. Antibiogram test was performed for positive samples. Results were analyzed using SPSS (Ver. 19) software through the t-test descriptive statistical analysis.

Results: The results showed that 38.75% of 80 samples of raw milk collected were contaminated by Staphylococcus aureus, while no contamination was observed in pasteurized milk samples. The average number of colony formation of raw milk was estimated to be within 3×10⁴ to 7×10⁴ Cfu/mL. Maximum sensitivity was found against vancomycin, gentamicin, and Co-trimoxazole antibiotics and the maximum resistance was observed  against ampicillin, methicillin and cephalotin antibiotics with of 87.5, 25, and 12.5%, respectively.

Conclusion: The raw milk showed the prevalence of Staphylococcus aureus. Therefore, compliance with and control of sanitation at different steps of preparation, supplying and consumption of milk can prevent the human infection with this type of contamination.