Journal of Pure and Applied MicrobiologyVol. 6 No. 4

Antibiogram Characteristics and Associated Resistance Genes of Commensal Pseudomonas species Isolated from Soil and Plant Rhizosphere in the Eastern Cape Province, South Africa

Isoken H. Igbinosa, Mvuyo Tom and Anthony I. Okoh*

Applied and Environmental Microbiology Research Group (AEMREG), Department of Biochemistry and Microbiology, University of Fort Hare Private Bag X1314, Alice 5700, South Africa.

Received on 18 June 2012 and accepted on 02 August 2012



The prevalence, antibiogram characteristics and associated antibiotic resistance genes of commensal Pseudomonas species isolated from soil and plant rhizosphere in the Eastern Cape province of South Africa were investigated. Polymerase chain reaction (PCR) based procedure was used to identify the isolates and screened for antibiotic resistant genes. Seasonal distributions of isolates were as follows: summer (70.59%), winter (20.59%), autumn (6.86 %) and spring (1.96%). During summer, most of the Pseudomonas isolates were recovered from plant rhizosphere (95.8%), followed by plant root (2.8%) and cultivated soil (1.4%). Pseudomonas putida was the most prevalent Pseudomonas species and distributed in the following order: plant rhizosphere (95%); plant root (41.2%); and cultivated soil (20%). Antibiogram of the isolates revealed 100% resistance to clinamycins, trimethoprim, vancomycin and oxacillin. About 92.9% of the isolates from plant roots; 85% from plant rhizosphere; and 75% from cultivated soils were susceptible to gentamicin. Ofloxacin showed activity against the isolates from plant root (78.6%), cultivated soil (75%) and plant rhizosphere (55%). Ciprofloxacin was also active against isolates from cultivated soil (75%), plant root (64.3%) and plant rhizosphere (63.8%). Integron gene was detected in all the Ps. aeruginosa isolates, and in about 30% of Ps. putida, and 6.3% of the unspeciated Pseudomonas species. The presence of integron gene in some of the Pseudomonas strains is of environmental and public health concern as it suggests the Pseudomonas isolates to be potential reservoirs of antibiotic resistance determinants in the environment.

Keywords : Pseudomonas species, Resistance determinants, Plant rhizosphere, Integron gene, Public health.