Question

A 48-year-old man undergoing chemotherapy for acute myeloid leukemia presents with high-grade fever, chills, and hypotension. Laboratory tests show an absolute neutrophil count (ANC) of 300 cells/$mm^3$. Blood cultures are pending. Which of the following organisms is most commonly responsible for sepsis in patients with febrile neutropenia?

• A. Escherichia coli
• B. Streptococcus pneumoniae
• C. Pseudomonas aeruginosa
• D. Enterococcus

Hint:

While it is true that Gram-positives cause the highest overall number of bacteremias in neutropenia today (due to central lines), Gram-negatives (specifically Pseudomonas) are undeniably the most lethal and cause the most rapid, terrifying clinical deterioration.
Always ensure broad antipseudomonal coverage is started immediately without delay!

Answer 1

The Correct Option is C

Concept:
A vulnerable chemotherapy patient presenting with profound, severe neutropenia (defined as an ANC $< 500$) presents acutely in a state of septic shock, characterized by high fever, chills, and dangerous hypotension.
The core question asks the examinee to precisely identify the classical bacterial organism most notoriously and historically responsible for causing rapidly progressive, highly lethal sepsis in this specific, severely immunocompromised population.
Step-by-step Explanation:

• Febrile neutropenia is universally considered an absolute medical emergency precisely because these patients completely lack the vital white blood cells necessary to mount a localized inflammatory response, which allows even minor mucosal infections to rapidly and silently disseminate into fulminant, life-threatening sepsis.

• Historically, and deeply ingrained within classical infectious disease teaching and board examinations, Gram-negative bacilli originating from the patient's gastrointestinal tract and the surrounding hospital environment were recognized as the predominant and most rapidly lethal pathogens in this highly vulnerable setting.

• Among all these dangerous bacteria, Pseudomonas aeruginosa (Option C) is unequivocally the most feared and classically tested organism responsible for causing devastating, fulminant Gram-negative sepsis and rapid mortality in profoundly neutropenic patients.

• This specific organism causes severe, direct endothelial damage, often manifesting pathologically as ecthyma gangrenosum skin lesions, and rapidly induces profound, refractory hypotension.

• While modern epidemiology clearly shows that Gram-positive organisms (like Coagulase-negative Staphylococci and S. aureus) are now technically the most common overall cause of infections or bacteremias in this population (primarily due to the widespread, ubiquitous use of indwelling central venous catheters), Gram-negative organisms, with Pseudomonas at the forefront, remain by far the most common and critical causes of rapidly fulminant sepsis and fatal septic shock.

• Therefore, all standardized empirical antibiotic treatment regimens for febrile neutropenia are specifically and intentionally designed around providing immediate, robust antipseudomonal coverage.

• Escherichia coli (Option A) is certainly also a very common and dangerous Gram-negative pathogen in this setting, but Pseudomonas remains the definitive, hallmark answer for severe, rapid neutropenic sepsis in all classical exam contexts.

• Streptococcus pneumoniae (Option B) is a very common cause of standard community-acquired pneumonia, but it is not primarily associated with rapid neutropenic sepsis.
Final Answer:
Pseudomonas aeruginosa is historically the most classic and most virulent organism responsible for rapid, life-threatening sepsis in patients presenting with profound febrile neutropenia.