What is the appropriate empirical intravenous (IV) antibiotic for a patient with leukocytosis (elevated white blood cell count), neutrophilia (elevated neutrophil count), significant bacteriuria (presence of bacteria in urine), and urinary tract infection (UTI) symptoms, who is allergic to Penicillin (a type of beta-lactam antibiotic)?

From the Guidelines

For a patient with suspected urinary tract infection (UTI) based on the laboratory findings and leukocytosis, I would recommend empiric IV ceftriaxone 1-2 grams once daily. This third-generation cephalosporin provides excellent coverage against common urinary pathogens including E. coli and other gram-negative organisms, as recommended by the European Association of Urology guidelines on urological infections 1. Despite the patient's penicillin allergy, ceftriaxone is generally safe to use unless the patient has a history of anaphylaxis or severe reaction to cephalosporins specifically. Some key points to consider in the management of this patient include:

• The patient's laboratory findings, including elevated urine WBCs, RBCs, many bacteria, positive leukocyte esterase, and proteinuria, are consistent with a UTI.
• The patient's leukocytosis, with an elevated WBC count and neutrophilia, also supports the diagnosis of a UTI.
• The European Association of Urology guidelines recommend prompt differentiation between uncomplicated and potentially obstructive pyelonephritis, as the latter can swiftly progress to urosepsis 1.
• The guidelines also recommend fluoroquinolones and cephalosporins as the only antimicrobial agents that can be recommended for oral empiric treatment of uncomplicated pyelonephritis, with IV fluoroquinolones or extended-spectrum cephalosporins recommended for patients requiring hospitalization 1. Alternative options include IV fluoroquinolones like ciprofloxacin 400mg every 12 hours or levofloxacin 750mg daily, or IV gentamicin 5mg/kg daily with appropriate renal dosing and level monitoring. The choice should be adjusted based on local resistance patterns, patient's renal function, and severity of infection. Once urine culture results return with susceptibilities, therapy should be narrowed accordingly. The duration of treatment typically ranges from 7-14 days depending on clinical response and the specific diagnosis (uncomplicated UTI vs. pyelonephritis).

From the FDA Drug Label

DOSAGE AND ADMINISTRATION Dosage in Adult Patients AZACTAM may be administered intravenously or by intramuscular injection. Dosage and route of administration should be determined by susceptibility of the causative organisms, severity and site of infection, and the condition of the patient Table 2: Azactam Dosage Guidelines for Adults* Type of Infection Dose Frequency (hours)

• Maximum recommended dose is 8 g per day Urinary tract infections 500 mg or 1 g 8 or 12

The patient has a urinary tract infection with many bacteria, and is allergic to penicillin. Aztreonam (IV) can be considered as an empirical antibiotic treatment.

• The recommended dose for urinary tract infections is 500 mg or 1 g every 8 or 12 hours 2.
• Since the patient's renal function is not explicitly stated as impaired, the standard dosing guidelines can be followed.
• However, it is essential to monitor the patient's renal function and adjust the dosage accordingly, as aztreonam is eliminated by the kidneys.
• The patient's condition and response to treatment should be closely monitored, and the dosage adjusted as necessary.

From the Research

Patient Assessment

• The patient has a high white blood cell count (WBC) of 14.8, indicating a potential infection.
• The mean corpuscular volume (MCV) is 98.5, which is within the normal range.
• The segmented neutrophil absolute count is 10.7, which is elevated, suggesting a bacterial infection.
• The comprehensive metabolic panel (CMP) is unremarkable, indicating no significant electrolyte or metabolic imbalances.
• The urinalysis shows a high WBC count (21-50), RBC count (21-30), and the presence of bacteria, blood, and protein in the urine, indicating a urinary tract infection (UTI).

Treatment Options

• The patient is allergic to penicillin, so alternative antibiotics must be considered.
• According to the study 3, parenteral treatment options for UTIs due to ESBL-producing Enterobacteriales include piperacillin-tazobactam, carbapenems (such as meropenem/vaborbactam), and ceftazidime-avibactam.
• The study 4 suggests that meropenem/vaborbactam (MV) is a first-choice treatment for carbapenem-resistant cUTI, but it also has a higher risk of adverse events.
• The study 5 mentions cefepime/taniborbactam as a potential treatment option for complicated UTIs, but its effectiveness against carbapenem-resistant infections needs further investigation.

Empiric IV Antibiotic Therapy

• Based on the patient's allergy to penicillin and the presence of a UTI, an empiric IV antibiotic therapy could be: + Meropenem/vaborbactam (MV) 3, 4 + Ceftazidime-avibactam 3 + Piperacillin-tazobactam (for ESBL-E coli only) 3
• It is essential to note that the choice of antibiotic should be guided by local susceptibility patterns and the patient's specific condition.