## **Core Concept**
The question involves identifying an appropriate antibiotic for a patient with a hospital-acquired infection caused by a gram-negative rod. The patient presents with fever, tachycardia, and elevated white blood cell count, suggesting a systemic infection. The presence of many white blood cells in the urinalysis and positive blood and urine cultures points towards a urinary tract infection (UTI) or sepsis likely originating from a UTI.

## **Why the Correct Answer is Right**
The organism described is **non-lactose-fermenting** and **oxidase-positive**, which narrows down the likely pathogens. A common gram-negative rod that fits this description and is known to cause hospital-acquired infections, including UTIs and bacteremia, is **Pseudomonas aeruginosa**. The correct antibiotic should be effective against *Pseudomonas*. Among the options provided (though not explicitly listed), antibiotics effective against *Pseudomonas* include **cefepime**, **ceftazidime**, **imipenem**, **meropenem**, **piperacillin-tazobactam**, and **ciprofloxacin**. Given the severity of the infection and the need for broad-spectrum coverage, **cefepime** or **piperacillin-tazobactam** would be appropriate choices.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Without the specific antibiotic listed, we can't directly assess its efficacy against *Pseudomonas*. However, if it were a narrow-spectrum penicillin or a first-generation cephalosporin, it would be inadequate.
- **Option B:** Similarly, without specifics, if this option were a macrolide, a tetracycline (except for **doxycycline** which has some activity against certain gram-negatives but not *Pseudomonas*), or an aminoglycoside (which could be effective but might not be the best choice depending on resistance patterns and potential nephrotoxicity), it might not be ideal.
- **Option D:** If this option were a **co-trimoxazole** (trimethoprim-sulfamethoxazole), **ampicillin**, or another antibiotic not effective against *Pseudomonas*, it would be incorrect.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **Pseudomonas aeruginosa** infections are notorious for their resistance patterns and are often associated with hospital-acquired infections, particularly in immunocompromised patients or those with indwelling catheters. Effective treatment usually requires antibiotics with broad-spectrum activity, including **anti-pseudomonal** penicillins (e.g., **piperacillin-tazobactam**), cephalosporins (e.g., **cefepime**, **ceftazidime**), carbapenems (e.g., **imipenem**, **meropenem**), or fluoroquinolones (e.g., **ciprofloxacin**).

## **Correct Answer Line**
**Correct Answer: C.**