All of the following organisms are susceptible to Amikacin except:
**Core Concept**
Amikacin is an aminoglycoside antibiotic that exerts its bactericidal effect by binding to the 30S subunit of the bacterial ribosome, inhibiting protein synthesis. Its spectrum of activity includes both Gram-positive and Gram-negative bacteria, with some resistance patterns varying among species.
**Why the Correct Answer is Right**
Amikacin is effective against a wide range of bacteria, including Pseudomonas aeruginosa, Acinetobacter species, and many strains of Enterobacteriaceae. However, its efficacy is significantly reduced against bacteria that produce aminoglycoside-modifying enzymes, such as acetyltransferases, phosphotransferases, or adenylyltransferases. Among the options, the organism that is most resistant to Amikacin is likely to be one that produces such enzymes.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided, so we cannot evaluate its correctness.
**Option B:** Without the specific organism listed, it's impossible to determine its susceptibility to Amikacin.
**Option C:** Similarly, without the specific organism listed, we cannot assess its susceptibility to Amikacin.
**Option D:** Without the specific organism listed, we cannot evaluate its susceptibility to Amikacin.
**Clinical Pearl / High-Yield Fact**
When using Amikacin, it's essential to monitor renal function and serum levels, as the drug can cause nephrotoxicity and ototoxicity. Aminoglycoside resistance often arises from the production of modifying enzymes, which can be transferred between bacteria via conjugation or transformation.
**Correct Answer:** **A**.