Evaluation of safety and therapeutic potential of environmental waste water lytic bacteriophage against multidrug resistant staphylococcus aureus (MDRSA) in BALB/c mice
Oduor, Joseph Michael O.
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Methicillin resistant Staphylococcus aureus (MRSA) pose a great threat to the global public health. Control of these bacteria has become difficult due to acquisition of resistance against even some of the best antibiotics. Thus, phage therapy could be the better alternative as they are easy to isolate and produce in mass within a short time. However, phage therapy has been a subject of debate over the years but recently there has been a renewed interest due to their proved therapeutic potential and have, therefore, found commercial application in some countries. Thus, this study was specifically designed to evaluate the efficacy of phages against MRSA both in vitro and in vivo. A litre of environmental waste water and sewage samples were collected around the county of Nairobi. The MRSA isolates were obtained from environmental waste water and sewage samples from Nairobi and its environs and evaluated for drug resistance using antibiogram test. In addition, lytic phages were isolated from these samples too. Thereafter, the in vitro efficacy of the phages against MRSA was done by spot assay and tube culture tests. Only the most virulent phage isolate was used for in vivo efficacy study which involved six groups of mice of n=5 per group (BALB/c mice; both sex). The first three groups acted as controls (group 1=only physiological saline, group 2=MRSA bacteria only and group 3=phage only) while the remaining groups were used for efficacy studies using a dosage of 108 CFU/ml for MRSA bacteria, 108 PFU/ml for phage and clindamycin at 8mg/kg. The efficacy study groups (groups 4-6) were first infected by MRSA and observed for 3 days before treatment with either antibiotic (group 4), or phage (group 5) or phage + antibiotic (cocktail therapy group 6). The mice were then observed for an additional 7 days. During the entire 10 days of observation blood samples were collected daily for bacteremia level determination before being euthanized. Different organs including the liver, brain, kidney and lungs were harvested for histopathological studies. All studies were done in accordance with the IPR Institutional Ethical Committee approved protocols. Antibiogram test indicated that MRSA isolated was a multidrug resistant strain (Figure 1). While the in vitro test showed the virulence of the phage isolates after 24 hrs culture at 370C. Toxicity test showed that phages were safe. There was no significant difference in survival rates between phage infected group and non-infected control group (p>0.05). Bacteremia was significantly lower in phage treated group as compared to other treatment groups and bacteria non-treated group (p<0.001) (Figure 2). In addition, pathological results show that phage prevented organ damage by the bacteria (Figure 3). Thus, a single dose of phage was more effective than other therapeutic agents used in the study. Results of this study show that phage therapy is safe and its application should be considered for the treatment of multidrug resistant bacterial infections.