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Revista da Sociedade Brasileira de Medicina Tropical

versão impressa ISSN 0037-8682versão On-line ISSN 1678-9849

Rev. Soc. Bras. Med. Trop. vol.52  Uberaba  2019  Epub 14-Nov-2019

http://dx.doi.org/10.1590/0037-8682-0290-2019 

Major Article

Phage Therapy as an Approach to Control Salmonella enterica serotype Enteritidis Infection in Mice

Mohammad Mehdi Soltan Dallal1  2 

Farhad Nikkhahi3  4 
http://orcid.org/0000-0003-0369-8179

Mahmoud Alimohammadi5 

Masoumeh Douraghi2  3 

Zahra Rajabi2 

Abbas Rahimi Foroushani6 

Akram Azimi3  4 

Fatemeh Fardsanei3 

1Division of Food Microbiology, Department of Pathobiology, School of Public Health (TUMS), Tehran, Iran.

2Food Microbiology Research Center, Tehran University of Medical Sciences (TUMS), Tehran, Iran.

3Division of Medical Bacteriology, Department of Pathobiology, School of Public Health (TUMS), Tehran, Iran.

4Medical Microbiology Research Center, Qazvin University of Medical Science, Qazvin, Iran.

5Environmental Health Engineering Department, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.

6Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.


Abstract

INTRODUCTION:

Salmonella enterica serotype Enteritidis (S. Enteritidis) is a cause of food-borne human illness. Given the prevalence of antibiotic resistance of Salmonella Enteritidis and the lack of antibiotic efficacy in future years, its replacement with other agents is necessary. One of the most useful agents is bacteriophages.

METHODS

S. Enteritidis was identified using a multiplex polymerase chain reaction assay. The effective bacteriophages were isolated from hospital wastewater samples. The effects of the bacteriophages were evaluated both in vitro and in vivo.

RESULTS

The phage SE20 belonged to the Podoviridae family, and the genome size was 40 kb. The evaluation of phage SE20 at variable pH ranges showed its susceptibility to pH < 3 and pH > 12. The animal model showed that mice infected with S. Enteritidis developed hepatomegaly and splenomegaly, but did not experience gastrointestinal complications after receiving the bacteriophages.

CONCLUSIONS

The results of this study suggest that phage SE20 is a promising candidate for controlling salmonellosis caused by Salmonella Enteritidis.

Keywords: Salmonella enterica serotype Enteritidis; Phage SE20; Pulsed-field gel electrophoresis; Mice; Sewage

INTRODUCTION

Foodborne diseases are one of the most important economic and health problems in industrialized and developing countries. In recent years, Salmonella has been one of the most common causes of foodborne diseases1. Salmonellosis is an infectious disease that is often transmitted through contaminated food, especially food products derived from meat, chicken, eggs, animal feed, milk, and sometimes vegetables2,3. However, estimating the prevalence of salmonellosis is challenging in developing countries, as no comprehensive research has been conducted in this area4-8. In addition, non-typhoidal salmonellosis is a disease caused by Salmonella serotypes other than Typhi, Paratyphi A, Paratyphi B, and Paratyphi C. Numerous studies have been carried out globally on the prevalence of Salmonella serotypes in different regions9-11. Salmonella enterica subsp. enterica serovar Enteritidis and Typhimurium are two common serotypes that have been identified in Iran and other countries12-15.

Over the past two decades, the prevalence of antibiotic-resistant Salmonella has become a serious global challenge. Moreover, the extensive use of antibiotics, for instance, as a standard component of domestic animal feed, has led to antibiotic resistance16. In recent years, multidrug-resistant (MDR) strains have become major global concerns, and many studies in Iran and other countries have reported the high resistance of Salmonella strains to several antibiotics9,22. Antibiotics are among the most commonly used drugs in human medicine and are used unnecessarily for up to 50% of patients17,18. These agents are also used in animal feed to prevent, control, and treat diseases and improve animal growth17,18.

In contrast, phages are viruses that can infect bacteria. The most important characteristic of lytic phages is their specific host range. In other words, they only kill strains of a specific bacterium; therefore, they are recognized as strong antimicrobial agents. Unlike broad-spectrum antibiotics and regardless of the target specificity, phage therapy has some other advantages, such as its minimum side effects, phage multiplication, site-specificity (concentration of phages at the infection site), and singular prescription19,20.

Therefore, this study aimed to isolate an effective titer of phages against Salmonella Enteritidis and determine the phage characteristics. In addition, the use of a proper dose for the treatment of infection was investigated in an animal model.

METHODS

S. Enteritidis was isolated from 46 salmonellosis outbreak samples. After the primary diagnosis via biochemical tests, bacterial cells were cultured on Hektoen enteric agar (HE) medium and incubated at 37°C. After 18 hours, several colonies were inoculated in tryptic soy broth (TSB) medium (Difco Laboratories, Detroit, MI, USA ). After three hours of incubation, the colonies were then stored at −20°C in the presence of 30% glycerol.

A multiplex-PCR assay was used to determine Salmonella serotypes. The reference primer used has been described elsewhere21. The amplification reaction tests were performed using a PEQLAB thermocycler (Germany) at a final volume of 25 μL, containing 1X PCR buffer (50 mmol/L KCl, 10 mmol/L Tris, pH 9), 2.5 mmol/L of MgCl2, 0.2 mmol/L of each primer, 1 U of Taq DNA polymerase, and 2 μL of sample DNA. The PCR conditions for amplification were as follows: five minutes of initial denaturation at 95°C, followed by 30 cycles of denaturation at 94°C for 30 seconds, annealing at 56°C for 30 seconds, an extension at 72°C for 60 seconds, and a final extension at 72°C for two minutes. S. Enteritidis ATCC 13076 was used as the positive control22,23.

Twenty samples from municipal wastewater and two samples from hospital wastewater were collected and sent to the laboratory immediately. The samples were stored at 4°C for 24 hours to precipitate their suspended solids. Then, 15 mL of the samples were centrifuged at 5000 g for 10 minutes to remove the bacterial cells. Next, the supernatant was passed through a 0.22 μm membrane filter (Millipore, USA). In order to enrich the bacteriophage, the supernatant was added to an equal volume of brain-heart infusion (BHI) broth, containing 106 CFU/mL of S. Enteritidis (Salmonella isolated from outbreaks), and incubated at 37°C for 24 hours. The broth culture was centrifuged at 5000 g for 10 minutes. Next, the supernatant was again passed through a 0.22 μm filter. The double-layer agar (DLA) method was used to confirm the presence of lytic phage in the supernatant23. Briefly, 50 μL of the filtered liquid was added to 450 μL of log-phase S. Enteritidis, incubated at 37°C for 15 minutes, and shaken at 120 rpm. After pouring the solution into 4.5 mL of 0.7% BHI agar, it was vortexed rapidly, added to 1.5% BHI agar, stored at room temperature (22°C ) for 30 minutes, and finally incubated at 37°C for 20 hours.

To purify the phages SE20, the agar containing the phage plaque was cut using a sterile scalpel. The plaque was then removed using a Pasteur glass pipette, added to the S. Enteritidis broth suspension (1×106 CFU/mL), and incubated at 37°C for 24 hours. Afterward, the suspension was centrifuged at 4500 g for 10 minutes and passed through a 0.22 μm filter. The DLA method was performed three times until pure plaques were obtained. The bacteriophage was then purified by adding 5 mL of SM buffer (For 1 liter: 50 mL, 1 M Tris-HCl [pH 7.5]; 5.8 g, NaCl; 2 g, MgSO4.7H2O; 5 mL, 2% gelatin) to the plate. Next, the bacteriophage was incubated and shaken at room temperature ( 22°C ) for four hours. Finally, the buffer containing the bacteriophages was removed from the plate, centrifuged at 4500 g for 10 minutes, and passed through a 0.22 μm filter.

To determine the size and morphology of the phages, the isolated phage SE20 was tested via transmission electron microscopy (TEM; Zeiss-Em10c-80k). For this purpose, copper-coated carbon was used, and 50 μL of freshly purified phage pellets suspended in SM buffer, was added. The phages were stained with 2% uranyl acetate and detected by TEM at an acceleration voltage of 80 kV.

Some phage infections create lysogens and do not result in a lytic infection. Because only lytic phages can be used in the treatment process, lysogens were removed by spreading phage-infected cultures of the host bacteria (100 ml) onto Luria-Bertani Miller (LB) agar plates containing kanamycin (50 μg ml-1)35. The bacteriophage host range was determined using the SPOT test24. Different bacteria were selected to determine the bacteriophage SE20 specificity, including Yersinia enterocolitica (ATCC9610), Escherichia coli (ATCC25922), Pseudomonas aeruginosa (ATCC27853), Staphylococcus aureus (ATCC2392), Enterococcus faecalis (ATCC29212), Shigella flexneri (ATCC12022), Listeria monocytogenes (ATCC19114), Cronobacter sakazakii (ATCC29544), and Salmonella species. The bacteria were cultured overnight in LB broth (10 g of tryptone, 5 g of yeast extract, 5 g of NaCl, and 1 mL of 2 N NaOH per liter). Next, 100 μL of culture and 4 mL of 0.7% BHI were vortexed and covered with 1.5% BHI agar. Then, 10 μL of the bacteriophage suspension was added to the surface of the agar, which was then incubated at 37°C overnight. In addition, sensitivity to bacteriophages was determined by measuring the clear zone. All experiments were performed in triplicate.

To determine phage sensitivity to temperature, the aliquots of phage SE20 suspensions were incubated in titers of 1×108 PFU/mL at 4°C, 25°C, 37°C, 50°C, 60°C, and 70°C (pH 7), respectively, for 60 minutes. Then, the phage titer was tested using the DLA method.

To determine phage sensitivity to pH, the aliquots of phage SE20 suspensions were incubated in titers of 1×108 PFU/mL at 4°C (pH 3-12) for 60 minutes. Then, the phage titer was tested according to the DLA method.

To conduct the one-step growth test, a modified version of the Ellis and Delbruck method25 was used. Briefly, phage SE20 was added to the liquid culture medium containing S. Enteritidis with a multiplicity of infection (MOI) of 0.1. It was then incubated at 37°C for 15 minutes to induce phage adsorption by bacteria. Then, it was centrifuged at 12000 g for 10 minutes to remove the unbound phage particles. In the next stage, the supernatant was removed, and the pellet was added to LB broth. It was resuspended in 100 mL of LB medium and incubated at 37°C with shaking. The aliquots were removed at 10-minute intervals for 100 minutes, and the phage titer was determined using the DLA method. All experiments were repeated in triplicate.

To determine the effect of isolated phage on Salmonella Enteritidis in vitro, the aliquots of S. Enteritidis were added to fresh LB broth and incubated at 37°C while shaking for six hours at 150 rpm. Then, the bacteria were poured into four tubes (2×109 CFU/mL). The phage SE20 (2×108, 2×109, and 2×1010 PFU/mL) was also added to the four tubes. In addition, phosphate-buffered saline (PBS) was added to the fourth tube as the control. Bacterial growth was monitored by measuring the OD600 at 30-minute intervals.

PFGE was used to determine the size of genomes, according to the Erika Linghor method26. Briefly, the phage SE20 suspension was dialyzed, and the cassette plug was assembled. To prepare the plug agarose, 0.5 mL of the phage suspension was used. After it was placed in a 54°C water bath, 400 μL of the purified phage were transferred to microcentrifugal tubes, which were then heated to 50°C in a temperature-controlled bath. Next, 400 μL of molten agarose plaque was added to a heated microtube containing the phage and mixed thoroughly via pipetting. The mixture (250 μL) was immediately added to the wells of the appropriate plug-in cassette. The plug was stored at 4°C for 15 minutes until rigidity. The plug was transferred into a tube containing 5 mL of phage lysis buffer (50 mM Tris, 50 mM EDTA, and 1% SDS w/v) and 25 μL of Proteinase K (20 mg/mL) and placed in a hot-water bath at 54°C for two hours with shaking. Then, the buffer was aspirated and added to the tube containing the plug and 5 mL of sterilized 1X TE buffer (10 mM Tris and 1 mM EDTA, pH= 8.0), followed by incubation at 54°C for 15 minutes. The plug was stored at 4°C and analyzed using a PFGE system (CHEF DRIII Chiller, BioRad, USA) at 6 v/cm for 20 hours with an incremental pulse of 2.2-54.2 s at 14°C. The gel was stained with 1X ethidium bromide solution and analyzed after washing with deionized water under UV light.

To evaluate the effect of phage SE20 on Salmonellosis, all the procedures involving animals were approved by the Animal Ethics Committee of Tehran University of Medical Sciences (Ethics Approval Code: IR.TUMS.REC.1394.2090). Five-week-old female BALB/c mice (mean weight, 20 g) were purchased from the Faculty of Pharmacology, Tehran University of Medical Science, and then weighed. The animal tests were carried out in accordance with the recommendations of the Ethics Committee of Tehran University of Medical Sciences. Salmonellosis model: Twenty-four mice were divided into three groups; the control group A, 200 μL of PBS was gavaged; group B, 200 μL of S. Enteritidis (1.5×107 CFU/mL) was gavaged; group C, 200 μL (1.5×107 CFU/mL) of S. Enteritidis was gavaged on the first day, and a single dose of phage SE20 was gavaged (2×108 PFU/mL) after 24 hours. To prevent damage to the phages in the digestive tract of the animal, anti-acid was gavaged.

Histopathology of the liver and spleen: After six days of infection, four mice from each group were anesthetized. Next, the spleen and liver were removed and fixed in 10% formalin for 24 hours at the refrigerated temperature (6°C). The samples were then sent to the Pathology Department of the Parsian Hospital in Tehran for hematoxylin and eosin (H&E) staining.

Data were analyzed in SPSS version 22 and GraphPad Prism version 6. For analyzing the results, the sphericity assumption test, Greenhouse-Geisser test, Levene’s test, Mauchly’s test, and posthoc tests were performed.

RESULTS

The Multiplex-PCR assay was used to confirm the serotypes of S. Enteritidis. The serotypes were isolated from five samples. One of the samples was randomly selected for the subsequent stages.

A lytic phage against S. Enteritidis was isolated from the hospital wastewater and purified. The size of the plaque was 2-3 mm. The TEM images showed that the phage had a head (about 64±3 nanometers) and a very small tail, which was hardly visible. The morphology showed that this phage belonged to the Podoviridae family (Figure 1).

FIGURE 1: (A) A bacteriophage plaque and (B) electron micrograph of the isolated phage. 

The size of the bacteriophage genome was determined based on the PFGE method. The ladder used in this study was S. enterica subsp. enterica serovar Braenderup (ATCC BAA-664TM). Based on the results of this ladder, the genome size was 40 kb.

The SPOT test was used to determine the specificity of the bacteriophage. The results showed that the phage could infect S. Enteritidis and S. Typhimurium, which were sensitive to the phage. However, no lytic effect was observed in other bacteria. It was concluded that S. Enteritidis and S. Typhimurium have a common receptor for this phage, and the receptor was not present in the other tested bacteria.

Evaluation of the phage and its activity in vitro showed that pH plays an important role in its function. The results in a pH range of 3-12 showed that the phage was susceptible to pH < 3 and pH > 12 and was stable at a pH of 3-11. The optimal pH for this phage was 6-8. The results of the phage test at various temperatures (pH 7) showed that the phage was stable up to 60°C. However, the highest level of stability was reported at 4°C. On the other hand, the phage lost its stability at 70°C (Figure 2). The single-stage growth curve showed that the phage had a latent period of 30 minutes; after that, the number of phage particles in the medium increased rapidly, indicating that the bacteria were lysed, and viruses were released into the environment.

FIGURE 2: The stability of the specific bacteriophages under different (A) pH and (B) temperature conditions. 

To determine the phage capacity to lyse the host bacteria in vitro, the bacteriophage titers (2×108, 2×109, and 2×1010 PFU/mL) were added to four tubes to evaluate the host bacterial growth in the presence of the phage. The isolated bacteriophage showed a latent period of about 30 minutes. The burst time occurred between the 30th and 80th minutes. The differences between the groups gradually became insignificant after six hours of incubation. The optical density of the phage-inoculated groups was much lower than that of the control group (Figure 3).

FIGURE 3: (A) The one-step growth curve of the S. Enteritidis bacteriophage. The isolated bacteriophage showed a latent period of about 30 minutes. The burst time occurred between the 30th and 80th minutes. (B) The function of the isolated lytic phage in vitro. S. Enteritidis (2×109 PFU/mL) was infected with different phage MOIs. The optical density was also measured for each sample.  

In this study, a total of 24 mice were examined. The mice were infected with 1.5×107 CFU/mL of S. Enteritidis via oral gavage. The mice grew well in the control group (group A), whereas group B showed symptoms after the infection, including a significant weight loss within 14 days (p-value < 0.005). In this group, the appearance of the mouse hair also changed. The bacterial count was determined from stool and liver samples. The average number of S. Enteritidis was 1.63×108 CFU/mL in the stool sample (1 g) and 2.1×107 CFU/mL in the liver sample (1 g). The mice in group B as a result of infection with bacteria died at the end of the study period. Hepatomegaly and splenomegaly were observed after the clinical evaluation of the liver and spleen. Abscesses were also observed in the pathology of liver tissues (Figure 4). The size of the spleen was approximately three times larger in group B than in group A. Twenty-four hours after infecting the animals in group C, the specific bacteriophage with an MOI of 10 was gavaged. In this group, the animals grew well and showed normal activity similar to the mice in group A. The appearance of their hair was completely normal, and no cases of death were reported. Moreover, a bacterial count of the liver was performed on the 7th and 10th days, and S. Enteritidis was not isolated. After autopsy, the clinical findings of the spleen and liver did not show any pathological changes under normal and pathological conditions.

FIGURE 4: (A) The status of the liver, spleen, and intestine of mice treated with the phage (group C). (B) Comparison of the size (control: 18 mm, bacteria: 25 mm, and bacteria + phage: 17 mm) and appearance of the liver. In the phage-treated group, the liver status was similar to that of the control group. (C) The gastrointestinal condition in the mice with salmonellosis due to S. Enteritidis without administration of the bacteriophage; hepatomegaly and splenomegaly were observed in group B. (D) Histopathology of the spleen tissues of mice treated with the bacteriophage. The white pulp (blue arrow) and red pulp (black arrow) are in a completely normal state. (E) Histopathology of the spleen tissue in mice with salmonellosis. Parts of the spleen showed signs of structural abnormalities and the depletion of certain lymphoids (100x). 

DISCUSSION

There are over 2300 known serotypes of S. enterica with remarkable differences in their pathogenicity27,28. Considering the high prevalence of antibiotic resistance in S. enterica isolates, third-generation fluoroquinolones and cephalosporins are used as antibiotics to treat severe forms of S. enterica infection29. Therefore, it is necessary to replace antibiotics with other antimicrobials. Bacteriophages are a suitable alternative to antibiotics. In a report published by the National Institute of Allergy and Infectious Diseases in 2014, phage therapy was recognized as one of the seven methods integrated in a coordinated approach to address the threats of antibacterial resistance; this highlights the importance of phage therapy as an effective tool for combating resistant bacteria30,31.

In this study, we detected a bacteriophage that could adequately control the growth of S. Enteritidis, showed intermediate resistance to ciprofloxacin in vitro, and prevented complications caused by Salmonella infection in an animal model. In this study, the isolated bacteriophage was evaluated to determine the proper hosts and their sensitivity to the phage among different bacteria, including Salmonella genera (S. Typhimurium, S. Enteritidis, and S. Infantis) and non-Salmonella genera (Y. enterocolitica, E. coli, P. aeruginosa, and S. aureus). It was shown that S. Typhimurium and S. Enteritidis were susceptible to this bacteriophage, while other bacteria did not show any sensitivity. In another study, after determining Salmonella as the host for bacteriophage iEPS5, no growth zone was observed around the colonies of some S. Typhimurium strains. Moreover, in some strains, the lack of growth was observed with more opacity. Some strains of S. Enteritidis were susceptible to this phage; S. paratyphoid A was also susceptible to this phage. However, other species and genera, such as S. Typhi, S. Paratyphi B, S. Paratyphi C, S. Dublin, E. coli, Shigella boydii, Vibrio fischeri, P. aeruginosa, C. sakazakii, E. faecalis, S. aureus, S. epidermidis, Bacillus subtilis, B. cereus, and L. monocytogenes, were not reported; this indicates the specificity of this bacteriophage in some serotypes of Salmonella24.

One of the objectives of this study was to evaluate the phage function at different temperatures. Therefore, the function of the isolated bacteriophage was evaluated at 4°C, 25°C, 37°C, 50°C, 60°C, 70°C, and 80°C. A temperature of 4°C was considered optimal for the survival of this bacteriophage, which is lower than the ambient temperature. The bacteriophage also survived at 37°C and in a temperature range of 50-70°C, although its count decreased significantly, and it was killed at 80-90°C. In another study, an isolated bacteriophage was evaluated for its sensitivity to different temperatures in the range of 50-90°C. The bacteriophage survived at 50-70°C, and its count decreased gradually with temperature; in other words, no bacteriophage was detected at 80-90°C32.

The first step of phage infection is the attachment of phage receptors to the surface of a susceptible bacterial cell. In this study, an MOI of 0.1 was used to study the growth curve for 100 minutes.

A phage count was performed every 10 minutes. The growth curve showed that the number of bacteriophages exponentially expanded from the 20th minute. Therefore, the virus was absorbed by the bacteria in the first 20 minutes. From the 70th to 100th minutes, the phage count reached almost a constant level. In another study, to determine the absorption of phages by bacterial cells, the cells were cultured in a nutrient broth to reach the exponential phase. Then, these cells were contaminated with SAL-PG phage and placed at room temperature ) 25°C). The samples were centrifuged every five minutes for 40 minutes. The supernatant was evaluated for titration of the absorbed phages. According to this study, after five minutes, more than 50% of the phage was absorbed by the bacterial cells, and 95% was absorbed within 15 minutes33.

In another previous study, the effect of a bacteriophage was evaluated on the control of S. Enteritidis. The results showed that the isolated phage controlled the pathogenicity of bacteria, and S. Enteritidis was not isolated from the animal stool after phage administration23. In addition, Coombes et al. infected mice with S. Typhimurium at doses of 106 to 108 CFU/mL. After being infected, the mice showed decreased activity and weight. In the pathological study, meningitis and thrombosis were diagnosed; inflammation was also observed in the subarachnoid space of the brain34. In the present study, mice in group B that were infected with S. Enteritidis had softer feces on the third day and experienced slight diarrhea. A substantial decrease was observed in the animals’ activity, as they remained immobile in the cage for a long time and lost weight. Finally, seven mice died on the 12th day. In this group, the observed signs included hepatomegaly, splenomegaly, signs of meningitis, turgidity, and intestinal dilatation. In addition, liver necrosis and abscess were observed.

In conclusion, the results of this study suggest that oral phage administration is effective in the treatment of salmonellosis and other infections caused by S. Enteritidis. The safety of the phage and its activity against biofilm formation need to be evaluated in future studies.

ACKNOWLEDGMENTS

We kindly thank the Division of Medical Bacteriology, Department of Pathobiology, School of Public Health, for their cooperation and suggestions for improving both the study and manuscript. We also thank Dr. Davoud Afshar from Zanjan University of Medical Sciences for his valuable feedback on this manuscript.

REFERENCES

1. Busani L1, Scavia G, Luzzi I, Caprioli A. Laboratory surveillance for prevention and control of foodborne zoonoses. Ann Ist Super Sanita. 2006;42(4):401-4. [ Links ]

2. Bouchrif B1, Paglietti B, Murgia M, Piana A, Cohen N, Ennaji MM, et al. Prevalence and antibiotic-resistance of Salmonella isolated from food in Morocco. J Infect Dev Ctries. 2009;3(1):35-40. [ Links ]

3. Eblen DR1, Barlow KE, Naugle AL. U.S. Food safety and Inspection Service testing for Salmonella in selected raw meat and poultry products in the United States, 1998 through 2003: an establishment-level analysis. J Food Prot. 2006;69(11):2600-6. [ Links ]

4. Douris A1, Fedorka-Cray PJ, Jackson CR. Characterization of Salmonella enterica serovar Agona slaughter isolates from the animal arm of the National Antimicrobial Resistance Monitoring System-Enteric Bacteria (NARMS): 1997 through 2003. Microb Drug Resist. 2008;14(1):55-63. [ Links ]

5. Layton AN1, Galyov EE. Salmonella-induced enteritis: molecular pathogenesis and therapeutic implications. Expert Rev Mol Med. 2007;9(18):1-17. [ Links ]

6. Solghan SM1, Dumas NB, Root TP, Quinlan TM, Armstrong LR, Spina NL, et al. Multidrug-resistant nontyphoidal Salmonella in New York state's foodborne diseases active surveillance network counties. Foodborne Pathog Dis. 2010;7(2):167-73. [ Links ]

7. Travers K1, Barza M. Morbidity of infections caused by antimicrobial-resistant bacteria. Clin Infect Dis. 2002;34(Suppl 3):S131-4. [ Links ]

8. Voetsch AC1, Van Gilder TJ, Angulo FJ, Farley MM, Shallow S, Marcus R, et al. FoodNet estimate of the burden of illness caused by nontyphoidal Salmonella infections in the United States. Clin Infect Dis . 2004;38(Suppl 3):S127-34. [ Links ]

9. Carramiñana JJ1, Rota C, Agustín I, Herrera A. High prevalence of multiple resistance to antibiotics in Salmonella serovars isolated from a poultry slaughterhouse in Spain. Vet Microbiol. 2004;104(1-2):133-9. [ Links ]

10. Nzouankeu A1, Ngandjio A, Ejenguele G, Njine T, Ndayo Wouafo M. Multiple contaminations of chickens with Campylobacter, Escherichia coli and Salmonella in Yaounde (Cameroon). J Infect Dev Ctries . 2010;4(9):583-686. [ Links ]

11. Enayat K, Mansour A, Nasrin B, Mohammad T, Mohammad H, Hanar N. Antibiotic resistance pattern in bacterial isolates obtained from frozen food samples of animal origin in Sanandaj and Ahvaz. J Bacteriol. 2012;4(3):38-41. [ Links ]

12. Bonyadian M, Ale Agha S. Isolation and identification of Salmonellae from chicken carcasses in processing plants in Yazd province, central Iran. Iran J Vet Res. 2007;8(3):275-8. [ Links ]

13. Mehdi SDM, Mahnaz T, Latif G, Shabnam M, Maryam S, Rounak B, et al. Characterization of antibiotic resistant patterns of Salmonella serotypes isolated from beef and chicken samples in Tehran. Jundishapur J Microbiol. 2009;2009(4, Autumn):124-31. [ Links ]

14. Shahpouri R, Eghbalzade M. The Prevalence of Salmonella serotypes from Chicken and egg samples and determination theirs antibiotical sensitive in Zanjan. Biol Sci J Zanjan Azad Uni. 2009;6(2):63-71. [ Links ]

15. White PL1, Naugle AL, Jackson CR, Fedorka-Cray PJ, Rose BE, Pritchard KM, et al. Salmonella Enteritidis in meat, poultry, and pasteurized egg products regulated by the U.S. Food Safety and Inspection Service, 1998 through 2003. J Food Prot . 2007;70(3):582-91. [ Links ]

16. Kikuvi GM1, Ombui JN, Mitema ES. Serotypes and antimicrobial resistance profiles of Salmonella isolates from pigs at slaughter in Kenya. J Infect Dev Ctries . 2010 1;4(4):243-8. [ Links ]

17. Koskella B1, Meaden S. Understanding bacteriophage specificity in natural microbial communities. Viruses. 2013 11;5(3):806-23. [ Links ]

18. Van TT1, Moutafis G, Istivan T, Tran LT, Coloe PJ. Detection of Salmonella spp. in retail raw food samples from Vietnam and characterization of their antibiotic resistance. Appl Environ Microbiol. 2007;73(21):6885-90. [ Links ]

19. Dallal MMS, Imeni SM, Nikkhahi F, Rajabi Z, Salas SP. Isolation of E. Coli Bacteriophage from Raw Sewage and Comparing Its Antibacterial Effect with Ceftriaxone Antibiotic. Int J Adv Biotechnol Res. 2016;7(3):385-391. [ Links ]

20. Stevenson JE1, Gay K, Barrett TJ, Medalla F, Chiller TM, Angulo FJ. Increase in nalidixic acid resistance among non-Typhi Salmonella enterica isolates in the United States from 1996 to 2003. Antimicrob Agents Chemother. 2007;51(1):195-7. [ Links ]

21. Firoozeh F1, Shahcheraghi F, Zahraei Salehi T, Karimi V, Aslani MM. Antimicrobial resistance profile and presence of class I integrongs among Salmonella enterica serovars isolated from human clinical specimens in Tehran, Iran. Iran J Microbiol. 2011;3(3):112-7. [ Links ]

22. Fardsanei F, Soltan Dallal MM, Douraghi M, Zahraei Salehi T, Mahmoodi M, Memariani H, et al. Genetic diversity and virulence genes of Salmonella enterica subspecies enterica serotype Enteritidis isolated from meats and eggs. Microb Pathog. 2017;107:451-6. [ Links ]

23. Nikkhahi F, Soltan Dallal MM, Alimohammadi M, Rahimi Foroushani A, Rajabi Z, Fardsanei F, Imeni SM, et al. Phage therapy: assessment of the efficacy of a bacteriophage isolated in the treatment of salmonellosis induced by Salmonella Enteritidis in mice. Gastroenterol Hepatol Bed Bench. 2017;10(2):131-6. [ Links ]

24. Choi Y1, Shin H, Lee JH, Ryu S. Identification and characterization of a novel flagellum-dependent Salmonella-infecting bacteriophage, iEPS5. Appl Environ Microbiol . 2013;79(16):4829-37. [ Links ]

25. Ellis EL, Delbrück M. The growth of bacteriophage. J Gen Physiol. 1939;22(3):365-84. [ Links ]

26. Lingohr E, Frost S, Johnson RP. Determination of bacteriophage genome size by pulsed-field gel electrophoresis. Methods Mol Biol. 2009;502:19-25. [ Links ]

27. Phillips I, Casewell M, Cox T, De Groot B, Friis C, Jones R, et al. Does the use of antibiotics in food animals pose a risk to human health? A critical review of published data. J Antimicrob Chemother. 2004;53(1):28-52. [ Links ]

28. Turner J, Dritz S, Minton J. Alternatives to conventional antimicrobials in swine diets. The Professional Animal Scientist. 2001;17(4):217-26. [ Links ]

29. Bruun T, Sørensen G, Forshell LP, Jensen T, Nygard K, Kapperud G, et al. An outbreak of Salmonella Typhimurium infections in Denmark, Norway and Sweden, 2008. Euro Surveill. 2009 12;14(10). pii: 19147. [ Links ]

30. Nobrega FL, Costa AR, Kluskens LD, Azeredo J. Revisiting phage therapy: new applications for old resources. Trends Microbiol. 2015;23(4):185-91. [ Links ]

31. Viertel TM, Ritter K, Horz HP. Viruses versus bacteria-novel approaches to phage therapy as a tool against multidrug-resistant pathogens. J Antimicrob Chemother . 2014;69(9):2326-36. [ Links ]

32. Rattanachaikunsopon P, Phumkhachorn P. Bacteriophage PPST1 Isolated from Hospital Wastewater, A Potential Therapeutic Agent Against Drug Resistant Salmonella enterica subsp. enterica serovar Typhi. Salmonella-Distribution, Adaptation, Control Measures and Molecular Technologies: IntechOpen; 2012. [ Links ]

33. Rahaman M, Rahman M, Rahman M, Khan M, Hossen M, Parvej M, et al. Poultry Salmonella specific bacteriophage isolation and characterization. Bangladesh Journal of Veterinary Medicine. 2014;12(2):107-14. [ Links ]

34. Wickham ME, Brown NF, Provias J, Finlay BB, Coombes BK. Oral infection of mice with Salmonella enterica serovar Typhimurium causes meningitis and infection of the brain. BMC Infect Dis. 2007;7:65. [ Links ]

35. James CE, Stanley KN, Allison HE, Flint HJ, Stewart CS, Sharp RJ, et al. Lytic and Lysogenic Infection of DiverseEscherichia coliandShigellaStrains with a Verocytotoxigenic Bacteriophage. Appl Environ Microbiol . 2001;67(9):4335-7. [ Links ]

Financial Support: This study was supported by a grant (No. 27670) from the Research Deputy of Tehran University of Medical Sciences (Tehran, Iran).

Recebido: 08 de Junho de 2019; Aceito: 04 de Outubro de 2019

Corresponding author: Dr. Farhad Nikkhahi. e-mail:farhadnikkhahi@gmail.com

Conflict of Interest: The authors declare that there is no conflict of interest.

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