نشریه تازه ها در میکروب شناسی دامپزشکی
سال هفتم شماره 2 (پاییز و زمستان 1403)

Staphylococcus aureus produces a wide range of exotoxins that makes diseases in the host. Pyrogenic superantigens are a group of exotoxins produced by Staphylococcus aureus. This group includes toxic shock syndrome toxin, exfoliative and all enterotoxins of this bacterium. Identifying these factors is essential in understanding the pathogenic process of bacteria. The aim of this study was to investigate the presence of toxic shock syndrome (TSST-1), exfoliative A/B and enterotoxins A, B, C, D, E genes in methicillin-resistant and sensitive Staphylococcus aureus isolated from mosquito larvae in Sistan region by PCR method. This research was conducted on 57 isolates of Staphylococcus bacteria. Methicillin-resistant and sensitive isolates were identified using agar diffusion method and oxacillin-containing DNA plates. Bacteria were extracted by boiling method. Using PCR method and specific primers, genes encoding toxic shock syndrome (tst), exfoliative (eta, etb) and enterotoxin (sea, seb, sec, sed, see) were investigated in this bacterium. Out of a total of 57 Staphylococcus aureus isolates, 32 resistant isolates and 25 methicillin sensitive isolates were identified. The frequency of enterotoxin, exfoliative and toxic shock syndrome genes in resistant isolates was 50%, 21.87%, 3.12% respectively and in sensitive isolates 44,08%, 23,75% and 0% respectively. The results showed that the prevalence of methicillin-resistant isolates and isolates capable of carrying enterotoxin and exfoliative genes was high in Sistan region.

Listeria monocytogenes, as Gram-positive bacteria, is the cause of a opportunistic fatal infection in humans, which can be transmitted via a wide range of food products, including dairy, meat, and vegetables. Local white cheese in Iran is not produced under good manufacturing practices, however a comprehensive study about the prevalence of different serotypes of Listeria monocytogenes in this product has not been done yet. Babol, Qaem-shahr, Amol, Urmia, Hamedan, Tehran and Garmsar cities were selected as areas with high consumption of local white cheese, and 343 samples were collected from the dairy shops and delivered to the Food Safety and Hygiene Laboratory. Isolation and identification of Listeria monocytogenes, from cheese samples were carried out by pre-enrichment and cultivation in the selective media, the isolates were confirmed by biochemical methods, and then the serotype of each species was determined. Finally, the positive samples was enumerated using the five-tubes most probable number method. 9 cases of 343 samples were contaminated for Listeria monocytogenes. Most positive cases were isolated from Urmia city (3 cases). Considering the possibility of the survival of this organism during the processing of local white cheese, it seems that the monitoring of the manufacturing, storage and supply should be increased for this product and as much as possible, the production should be done in plants under the supervision of regulatory organizations.

Salmonella and Pseudomonas are among the most important food-borne pathogens around the world that cause risks for consumers; Therefore, it is necessary to monitor them in food. In this regard, the purpose of this study is to investigate the prevalence and pattern of antibiotic resistance of Salmonella, Pseudomonas and coliform in slaughtered turkey meat and tools in Najaf Abad slaughterhouse, Isfahan. 100 samples of turkey breast meat were randomly sampled from the slaughterhouse and transferred to the laboratory under sterile conditions. Sampling was also done using the swap method from the tools in the slaughterhouse. The prevalence of Salmonella and Pseudomonas infection was determined using ANOVA statistical test. The results showed that out of a total of 100 samples, 24 samples were contaminated with Pseudomonas and 11 samples were contaminated with Salmonella. Statistical analyzes showed that there is no significant relationship between the prevalence of Salmonella and Pseudomonas in turkey meat sold in Najaf Abad city (p<05/00). The highest antibiotic resistance was related to ciprofloxacin and kanamycin in salmonella and Amicasin in pseudomonas. Due to the high pollution, it is recommended to clean the tools in the slaughterhouse with disinfectants in different stages of poultry slaughtering to prevent the accumulation of pathogenic microorganisms and biofilm pollution. In this way, human health is not endangered.

Contamination of food by microorganisms is a serious public health concern that can cause foodborne diseases. The purpose of this study was to investigate the contamination with Staphylococcus aureus, Escherichia coli, Listeria and Yersinia in sausages and sausages offered in Karaj city. In this study, 191 sausage samples and 192 sausage samples were randomly sampled from the supply centers of this product in Karaj city and transferred to the laboratory under sterile conditions. The samples were tested according to the standard method for contamination evaluation. SPSS software and chi-square method for statistical analysis of data and (p<0.05) was considered as the significance level. The results showed that the most contamination in sausages was related to Staphylococcus aureus. Out of a total of 384 samples, the average contamination in sausages and sausages sold in Karaj county was Escherichia coli 77.6%, Salmonella 7.29%, Staphylococcus aureus 40.36% and Yersinia enterocolitica 0.78%. The results showed that there is no significant relationship between the contamination of sausages and sausages (p>0.05). Considering the high level of contamination among the samples, it is necessary and necessary for the authorities to monitor the quality of food as much as possible in order to prevent the occurrence of infections and food poisoning that endanger human health.

Camels, as a valuable source of protein and labor in arid and semi-arid regions, hold significant importance. Considering their key role in the economy and livelihood of local communities, examining the health of these animals is crucial. In this study, aimed at investigating the diversity and prevalence of fungal species causing ocular infections in camels in the Zabol region, samples were randomly collected from 50 camels. The collected samples were cultured on specialized media, and the fungal species present were identified. The results showed that 88% of camels (n=44) harbored at least one fungal species, with Aspergillus fumigatus as the most prevalent, found in 11 cases (22%), followed by Penicillium in 9 cases (18%), Aspergillus flavus in 8 cases (16%), Mucor in 6 cases (12%), Aspergillus niger and Rhizopus in 3 cases each (6%), Cladosporium in 2 cases (4%), and Absidia and Trichophyton in 1 case each (2%). According to the study results, infection rates were higher in camels over 2 years of age (68.18%). Statistical analysis showed no significant relationship between age or gender and the prevalence rate of isolated fungi (p>0.5). Additionally, while male camels exhibited a higher rate of fungal isolates than females, this difference was not statistically significant (P=0.11). The findings suggest that the unique climatic conditions of the region may contribute to the prevalence of ocular fungal infections, especially in desert-dwelling animals.

Alpha toxin, sometimes referred to as phospholipase C (PLC), is a significant toxin generated by C. perfringens that possesses both deadly and dermonecrotic properties. All strains (A, B, C, D, E) of C. perfringens generate varying quantities of this toxin, which is recognized as a key various  factor in the development of clostridial myonecrosis.Alpha-toxin is known to significantly influence several human and animal disorders, exhibiting deleterious impacts, specifically on the intestinal system. The primary objective of this research was to conduct a comparative analysis of two distinct purification techniques in order to extract alpha-toxin from C. perfringens type A. The first approach involved the alpha-toxin purification through a series of techniques, including ammonium sulfate precipitation, ion-exchange chromatography using DEAE Sephadex at pH values of 7 and 9, and gel filtration chromatography using Sephadex G-100, while the second approach was implemented using the affinity chromatography. The degree of purity of alpha-toxin was assessed at each stage of the purification process by the utilization of SDS-PAGE.The protein content and hemolysis activity were also quantified at each purification step. Based on the obtained findings, examining these two approaches revealed that the first method yielded a percentage of 88, while the second method yielded percentage of 91.7. The specific activity values obtained from the calculations for the first and second methods were 69170 U/mg and 105.71 U/mg, respectively. Our research shows that affinity chromatography can produce a highly pure alpha toxin with a specific activity of 108700 (HU/mg), produced by Clostridium perfringens type A.

This study was conducted to investigate the effect of dietary supplementation of selenium nanoparticles (SeNP) and selenium yeast (SY) on ruminal protozoan population and ammonia nitrogen of Baluchi male lambs. Thirty Baluchi lambs with an average initial body weight of 21.56±0.33 kg were used in a completely randomized design with 5 treatments and 6 repetitions for 70 days (14 days of adaptation and 56 days of data collection). The experimental groups were 1) control (without selenium supplement), 2), 3) and 4) were feeding with 0.4, 0.8 and 1.2 mg Se/kg of diet as SY respectively, and 5) feeding with 0.4 mg Se/kg of diet as SeNP. The results showed that the number of protozoa in the ruminal fluid of lambs receiving 0.8 and 1.2 mg of Se/kg of diet as SY and 0.4 mg of Se/kg of diet as SeNP was higher than that of the control group (P<0.05). In addition, both SY and SeNP sources significantly increased the number of Ophryoscolex species, while 0.4 mg of Se as SeNP resulted in a significant increase in Dasytricha species (P<0.05). Furthermore, dietary supplementation of 0.8 mg of Se as SY and 0.4 mg of Se as SeNP increased the number of Diplodinium species (P<0.05). However, the populations of Entodinium and Isotricha species were not affected by the experimental treatments. Feeding with 0.8 and 1.2 mg of Se as SY/kg of diet and 0.4 mg of Se as SeNP/kg of diet led to decreased ruminal ammonia nitrogen quantity (P<0.05). The results of this research indicated that dietary selenium supplementation as Nano selenium and selenium yeast, can increase the protozoa population and decrease the concentration of ammonia nitrogen in the ruminal fluid of Baluchi fattening lambs.

Macrorhabdosis, also known as Megabacteriosis, is a wasting disease in birds caused by the fungus Macrorhabdus ornithogaster. This study aimed to detect the fungus using PCR from the feces of birds showing clinical signs of infection, and to perform a phylogenetic analysis of the collected isolates. In this study, 54 positive samples were detected among the 300 suspicious birds referred to the wet smear method. Subsequently, the polymerase chain reaction (PCR) technique was employed for the final diagnosis. Positive samples were then subjected to PCR analysis using panfungal primers. For phylogenetic evaluation, 15 samples were sequenced, and the resulting sequences were compared with entries in the World GeneBank to assess their similarity and overlap. A total of 300 stool samples were subjected to analysis using the wet smear technique, of which 54 were found to be positive. Furthermore, 33 samples were identified as positive using the PCR method. Sequencing revealed the presence of M. ornithogaster in only two samples from lovebirds. Phylogenetic analysis showed an 86.76%-100% similarity between the isolates from budgerigars and finches and sequences recorded in the NCBI database. These findings highlight that PCR is an effective diagnostic tool for M. ornithogaster due to its speed, accuracy, and sensitivity.

Group A rotaviruses are the main cause of diarrhea in most livestock species, and the death of calves under one month due to rotavirus diarrhea is common in many countries and causes huge economic losses every year. Serological and molecular methods can be used for quick diagnosis of the disease, but isolation and identification of the virus causes the disease in terms of the specific biological and structural characteristics of this virus is very difficult in usual methods, and needs to special methods of cell culture and suitable cell line. The effort to prepare a vaccine from the native strains isolated in each country helps to control, combating and possibly eradicate it and prevents the economic losses caused by this disease to a great extent. In general, rotavirus small amount reproduces only in a limited number of cell lines and they do not have the infectivity necessary to isolate the virus. But the presence of trypsin, under certain conditions, increases the proliferation and titer of the virus in cell cultures. On the other hand, too much trypsin in cell culture is toxic and causes cell death. This article describes the function of trypsin in the infectivity of rotaviruses, and standard and practical method in its non-toxic concentration for the appropriate cell line to isolate rotaviruses.

To combat the shortage of new antimicrobial compounds and the increase in antibiotic resistance, plants could be a potential solution. The aim of the present study is to investigate the antimicrobial properties of fennel and green cumin essential oils against strains of Enterococcus faecalis and Acinetobacter baumannii under laboratory conditions. In this method, the essential oil solution was added at a specific concentration to sterile discs and transferred to a microbial culture medium. To examine growth inhibition, the disc diffusion method was used with a bacterial suspension on a plate containing Mueller-Hinton agar, and the MIC and MBC of the essential oil were also examined at dilutions of 101 and 1010, and finally, the optical density was measured at a wavelength of 540 nm. The results of the growth inhibition by the disc diffusion method showed that both bacteria, Acinetobacter baumannii and Enterococcus faecalis, created a 1.2 mm diameter. The results of MIC and MBC of green cumin essential oil on Acinetobacter baumannii at a dilution of 103 (MIC) showed an inhibitory effect at 0.078 in a concentration of 2000 ppm, and at MBC in a dilution of 102, it had a lethal effect at 0.135 in this bacterium. In Enterococcus faecalis, at a dilution of 101, both MIC and MBC had an inhibitory and lethal effect at 0.311 in a concentration of 2000 ppm. Given the spread of drug resistance in pathogenic strains, medicinal plants with antimicrobial effects are a suitable option with fewer side effects.

Methicillin-resistant Staphylococcus aureus is the most important threats to human health due to its ability to cause a wide range of food poisoning, and its monitoring in food is important. The purpose of this study was to investigate the frequency of enterotoxin coding genes and the antibiotic resistance pattern of methicillin-resistant Staphylococcus aureus isolates isolated from food samples supplied in Shahrekord city. 450 food samplesincluding traditional dairy products, salad and nuggets were randomly collected from supply centers in Shahrekord city and transferred to the laboratory. The standard method was used to isolate staphylococcus and the diffusion disk method was used to evaluate antibiotic resistance .The results showed that the highest contamination with Staphylococcus aureus was related to dairy products (14%), salad (10.66%) and nuggets (2.2%). The prevalence of methicillin-resistant Staphylococcus aureus in dairy samples was 71%, salads 64.58% and nuggets 30%. The highest and lowest prevalence of genes were respectively related to SEA (39.24%), SEB (17.18%), SEC (14.49%), SED (2.27%) and SEE (5.88%). The results of antibiotic resistance showed that the highest resistance was related to gentamicin, sulfamethoxazole, and the lowest resistance was related to ampicillin and amikacin. Due to the abundance of methicillin-resistant Staphylococcus aureus and the simultaneous presence of several coding genes in dairy products, salad and nuggets, the need for health supervision on the production and supply of food storage increases, as well as the use of Antibiotics should be limited in cases of poisoning caused by Staphylococcus aureus.

The challenge of today's medicine is to find alternatives in treatment of infections caused by antibiotic-resistant bacteria. Many types of molecules with antimicrobial potential are produced through the secondary metabolism of plants. This study was aimed to investigate the antimicrobial and anti-biofilm properties of ursolic acid against broad-spectrum beta-lactamase producing E. coli isolated from poultry meat. The inhibitory effect of ursolic acid against the test isolates was investigated using disk diffusion methods. MIC determination and its anti-biofilm effect were investigated using broth microdilution and microtiter plate methods respectively. Additionally, the effect of ursolic acid on the survival of E. coli has been checked by Time Kill assay and its effect on the expression level of fimH and csgA biofilm genes was analyzed by Real time-PCR. In this study, ursolic acid showed an inhibitory effect on the growth of all isolates, with MIC values ranging between 0.4 and 1.6 mg/ml.  The percentage of biofilm inhibition in the conditions treated with the concentration of 1/2 MIC of ursulic acid in the 6 studied isolates varied between 51.2 and 67.3%. Furthermore, in the present study, treatment with sub-MIC concentrations of ursolic acid significantly decreased the expression of the fimH and csgA genes. The results of this study indicate the inhibitory effect of ersolic acid on the growth of beta-lactamase-producing E. coli isolates and the reduction of its biofilm formation ability. In vivo studies are required to further clarify its potential clinical application in controlling infections caused by drug-resistant isolates.