Isolation and Characterization of Bacteriophages Active against Pseudomonas aeruginosa Strains Isolated from Diabetic Foot Infections

Diabetic foot infection has become one of the most important public health concerns and is a growing problem. Pseudomonas aeruginosa is an important opportunistic multidrug-resistant bacterium in diabetic foot infections. In the absence of antibiotics active against MDR strains of P. aeruginosa, phage therapy becomes a key way to deal with P. aeruginosa infections. Out of ۱۸۵ samples collected from diabetic foot ulcers, ۵۰ (۲۷.۰۲%) isolates were identified as P. aeruginosa. The incidence increases with older ages, and males (n=۳۴, ۶۸%) predominated in all age groups. The tested isolates showed maximum susceptibility towards colistin (۸۰%), imipenem (۷۲%), amikacin (۶۶%), and piperacillin/tazobactam (۶۲%), while these isolates showed moderate susceptibility towards ceftazidime (۵۸%), cefepime (۵۲%) and gentamicin (۴۶%). However, it showed complete resistance (۱۰۰%) to ampicillin, cefaclor, and sulphamethoxazole/trimethoprim and highly resistance to clindamycin (۹۰%) and amoxicillin/clavulanic acid (۸۴%). Two bacteriophages (ϕPAE۱ and ϕPAE۲) isolated from sewage samples showed a broad host range against P. aeruginosaa clinical strains. ϕPAE۲ infected ۷۴% (۳۷/۵۰) and ϕPAE۲ ۵۸% (۲۹/۵۰). Furthermore, both phages were host-specific, infecting only P. aeruginosa strains and could not infect other bacterial species in the cross-infectivity studies. Both phages were found to be relatively heat stable as over a period of ۱ h, after exposure to a temperature range of ۳۷–۵۰°C, no significant loss in phage activity was observed. On the other hand, the lowest activity was observed at ۷۰°C (۳۹.۱۵%) for ϕPAE۱ whereas it was inactivated at ۷۵°C while the lowest activity was observed at ۷۵°C (۳۸.۰۱%) for ϕPAE۲ whereas it was inactivated at ۸۰°C. Isolated phages were able to survive and lyse host bacteria over a wide pH range. The optimum pH range for infection was from ۶ to ۸. Furthermore, ϕPAE۱ lost its ability to lyses at pH ۲, ۳, ۱۱ and ۱۲, whereas; ϕPAE۲ lost its infectivity at pH ۲, ۳ and ۱۲. Chloroform was the most effective solvent that reduced the infectivity of ϕPAE۱ and ϕPAE۲ to ۶۳.۲۷% and ۷۷.۸۸%, respectively. On the other hand, petroleum ether showed the lowest effect on the infectivity of ϕPAE۱ and ϕPAE۲; it was reduced to ۹۶.۴% and ۹۷.۴۸%, respectively, followed by acetone and ethyl alcohol. The ability of P. aeruginosa phages to form plaques after different storage temperatures (۴°C, ۳۰°C, ۳۷°C and ۴۴°C) for a month was slightly affected. The storage of ϕPAE۱ and ϕPAE۲ at ۴ºC showed the least effect on its infectivity, and the storage at ۴۴ºC showed the highest reduction in its infectivity. Moreover, Phage counts were slightly decreased by increasing storage period and temperature.

کلیدواژه ها:

Bacteriophages ، Phage treatment ، Pseudomonas aeruginosa ، Diabetic foot ، Antibiotic resistance