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The Sensitivity to Aminoglycosides and Heavy Metals of Isolates of Pseudomonas Aeruginosa Strains from Lagos, Nigeria
Abstract
Eighty-two clinical isolates of Pseudomonas aeruginosa strains were tested for their sensitivity to aminoglycosides by an agar diffusion method and to heavy metals by a dilution technique on tri –buffered mineral salt agar containing 10 – 100mg/L CdCl2.H20, CoCl2.6H20, ZnCl2, AgNO3 and HgCl2.
All the strains tested were sensitive to amikacin and tobramycin but showed resistance to gentamicin (4.9%), kanamycin (43.9%) and streptomycin (97.6%). At 40mg/L, the increasing order of resistance to heavy metals displayed by the strains was observed as follows: Co2+ (50%), Cd2+ (54.9%), Hg+ (56.1%), Ag+ (64.6%), Zn (72.0%). Further sensitivity profiling revealed a total of 22 distinct antibiotic-heavy metal resistance patterns with KanStrCdCoZn and StrZnAgHg occurring mostly. All the strains tested resisted not less than two heavy metals and strains that showed resistance to gentamicin also resisted at least three heavy metals including zinc. MIC50 and MIC90 of the heavy metals against the isolates were found in the range of 35 – 40mg/L and 60 – 70mg/L respectively. The data obtained from this study indicated broad-spectrum resistance of streptomycin and kanamycin resistant Pseudomonas aeruginosa strains to heavy metals including silver, mercury and zinc. While tobramycin and amikacin with the exception of gentamicin were clinically favoured for empirical treatment of Pseudomonas infections in Lagos, Nigeria, the clinical benefits inherent in the use of coated catheters are also discussed.
KEY WORDS: Aminoglycosides, heavy metal resistance, Pseudomonas aeruginosa.
Nig. Jnl Health & Biomed. Sciences Vol.3(1) 2004: 28-32
All the strains tested were sensitive to amikacin and tobramycin but showed resistance to gentamicin (4.9%), kanamycin (43.9%) and streptomycin (97.6%). At 40mg/L, the increasing order of resistance to heavy metals displayed by the strains was observed as follows: Co2+ (50%), Cd2+ (54.9%), Hg+ (56.1%), Ag+ (64.6%), Zn (72.0%). Further sensitivity profiling revealed a total of 22 distinct antibiotic-heavy metal resistance patterns with KanStrCdCoZn and StrZnAgHg occurring mostly. All the strains tested resisted not less than two heavy metals and strains that showed resistance to gentamicin also resisted at least three heavy metals including zinc. MIC50 and MIC90 of the heavy metals against the isolates were found in the range of 35 – 40mg/L and 60 – 70mg/L respectively. The data obtained from this study indicated broad-spectrum resistance of streptomycin and kanamycin resistant Pseudomonas aeruginosa strains to heavy metals including silver, mercury and zinc. While tobramycin and amikacin with the exception of gentamicin were clinically favoured for empirical treatment of Pseudomonas infections in Lagos, Nigeria, the clinical benefits inherent in the use of coated catheters are also discussed.
KEY WORDS: Aminoglycosides, heavy metal resistance, Pseudomonas aeruginosa.
Nig. Jnl Health & Biomed. Sciences Vol.3(1) 2004: 28-32
