Table 2.

Clinical and microbiological descriptions of cases associated with treatment failure.

Age (sex)	Underlying diseases	Type of initial infection	Concomitant bacteremia	Susceptibility of the isolated Pseudomonas aeruginosaa	Treatment regimen (duration in days)	Ceftolozane-tazobactam doseb	Outcome (at 14 d)	Cause of treatment failure	30-d death
73 (M)	DM, HTN, bowel perforation with complicated abdominal surgeries	Intra-abdominal abscesses	No	Ceftazidime = R Ciprofloxacin = R Amikacin = S Gentamicin = I	Ceftolozane-tazobactam10 PLUS Amikacin6	1.5 g every 8 hours	Fever stopped, remained in ICU for circulatory support, repeated cultures remained positive	Lack of source control	YES
69 (M)	DM, HTN, CAD, CKD, rectal cancer	VAP	No	Ceftazidime = I Ciprofloxacin = S Amikacin = R Gentamicin = S	Ceftolozane-tazobactam14 PLUS Aztreonam14	1.5 g every 8 hours	Clinically improved with persistent positive respiratory culture	Pneumonia on chronic tracheostomy	NO
61 (M)	HTN, non-small-cell lung cancer with long-term mechanical ventilation	VAP	No	Ceftazidime = I Ciprofloxacin = I Amikacin = S Gentamicin = S	Ceftolozane-tazobactam10 PLUS Colistin14	3 g every 8 hours	Clinically improved with persistent positive respiratory culture	Recurrent pneumonia due to lung collapse and emphysematous changes	NO
57 (M)	HIV/AIDS, nasopharyngeal lymphoma	Complicated perianal abscesses	Yes	Ceftazidime = I Ciprofloxacin = R Amikacin = R Gentamicin = R	Ceftolozane-tazobactam7 PLUS Colistin13	1.5 g every 8 hours	Clinically deteriorated with persistent positive blood cultures	Patient died while on antibiotics	YES
45 (F)	DM, HTN, polymyalgia rheumatica, postcardiac arrest	HAP	No	Ceftazidime = R Ciprofloxacin = R Amikacin = S Gentamicin = S	Piperacillin-tazobactam7 PLUS Colistin7 switched after cultures to ceftolozane-tazobactam7	1.5 g every 8 hours	Clinically improved with respiratory positive culture after treatment	Colonized with MDR Pseudomonas aeruginosa (did not require therapy)	NO

Abbreviations: AIDS, acquired immunodeficiency syndrome; CAD, coronary artery disease; CKD, chronic kidney disease; DM, diabetes mellitus; F, female; HAP, hospital-acquired pneumonia; HIV, human immunodeficiency virus; HTN, hypertensionI, intermediate; ICU, intensive care unit; M, male; MDR, multidrug resistant; R, resistant; S, susceptible; VAP, ventilator-associated pneumonia.

^aMinimum inhibitory concentrations (MICs) were determined using reference broth microdilution methods and interpreted according to the Clinical Laboratory Standards Institute (CLSI) criteria.¹⁶

^bBefore adjustment for renal impairment.