Ismaeel N A
Department of Microbiology, College of Medicine and Allied Sciences, King Abdulaziz University, Jeddah, Saudi Arabia.
Microbios. 1991;66(268-269):197-204.
In recent years, a number of clinical microbiology laboratories have isolated Pseudomonas aeruginosa with the unusual aminoglycoside disk diffusion result of resistance to both amikacin and gentamicin but susceptibility to tobramycin (ArGrTs). A total of 27 isolates of P. aeruginosa reported to have this resistance pattern was retested by the standard National Committee for Clinical Laboratory Standards disk diffusion procedure; twenty strains (74%) were confirmed to be ArGrTs. These twenty isolates were further examined for susceptibility to those aminoglycosides by agar dilution and both micro- and macrodilution methods. Only 25, 25 and 24% of the isolates appeared to be ArGrTs by agar, broth microdilution, and broth macrodilution testing respectively. Most of the remaining isolates were resistant to all three aminoglycosides when tested by broth dilution and resistant only to gentamicin when tested by agar dilution. The percentages of strains resistant to any particular aminoglycoside by agar dilution, broth microdilution and broth macrodilution, respectively were 44, 79 and 69 for amikacin, 95, 91 and 100 for gentamicin, 100, 100 and 100 for netilmicin, 28, 85 and 91 for sisomicin, and 11, 54 and 46 for tobramycin. These results indicate that strains showing the unusual aminoglycoside antibiogram are less susceptible to aminoglycosides in general and should probably be considered borderline resistant to all aminoglycosides. The efficacy of aminoglycosides in the treatment of infections produced by these strains is unknown.
近年来，一些临床微生物学实验室分离出了具有不寻常氨基糖苷类纸片扩散结果的铜绿假单胞菌，即对阿米卡星和庆大霉素均耐药，但对妥布霉素敏感（ArGrTs）。对总共27株报告有这种耐药模式的铜绿假单胞菌分离株，按照美国国家临床实验室标准委员会的标准纸片扩散程序重新进行检测；20株（74%）被确认为ArGrTs。通过琼脂稀释法以及微量和常量稀释法，对这20株分离株进一步检测其对那些氨基糖苷类药物的敏感性。通过琼脂稀释法、肉汤微量稀释法和肉汤常量稀释法检测时，分别只有25%、25%和24%的分离株表现为ArGrTs。其余大多数分离株通过肉汤稀释法检测时对所有三种氨基糖苷类药物均耐药，而通过琼脂稀释法检测时仅对庆大霉素耐药。通过琼脂稀释法、肉汤微量稀释法和肉汤常量稀释法检测时，对任何一种特定氨基糖苷类药物耐药的菌株百分比，阿米卡星分别为44%、79%和69%，庆大霉素分别为95%、91%和100%，奈替米星分别为100%、100%和100%，西索米星分别为28%、85%和91%，妥布霉素分别为11%、54%和46%。这些结果表明，表现出不寻常氨基糖苷类抗菌谱的菌株总体上对氨基糖苷类药物的敏感性较低，可能应被视为对所有氨基糖苷类药物的临界耐药。氨基糖苷类药物对这些菌株所致感染的治疗效果尚不清楚。
