Fluoroquinolone antibiotics are widely used in our communities and healthcare facilities. This review focuses upon the relationship between fluoroquinolone use and the rising prevalence in neutropenic cancer patients of multidrug resistant pathogens including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci, Clostridium difficile, and aerobic Gram-negative bacilli. Fluoroquinolones such as ciprofloxacin or levofloxacin are efficacious for the prevention and treatment of neutropenic fever syndromes, including infections due to aerobic Gram-negative bacilli. Recent clinical practice guidelines recommend their prophylactic use in acute leukaemia patients receiving intensive remission-induction, postremission consolidation, or salvage induction therapy, and haematopoietic stem cell transplant recipients during pre-engraftment when the duration of profound neutropenia (absolute neutrophil count <0.1 × 10(9)/l) is at least 7 days. These same agents combined with amoxicillin/clavulanate are recommended for oral outpatient empirical antibacterial treatment of febrile neutropenic patients at low risk for medical complications. Fluoroquinolone-resistant Enterobacteriaceae is linked to community fluoroquinolone consumption. Prophylaxis efficacy is reduced when the prevalence of fluoroquinolone Gram-negative bacillary resistance exceeds 20%. Widespread use encourages the transmissibility of multiclass antimicrobial resistance genes among Gram-negative bacilli. Fluoroquinolone-driven colonization with MRSA enhances the risk of subsequent infection, the use of vancomycin, and risk of colonization by vancomycin-resistant Enterococcus spp. The relative roles of widespread fluoroquinolone use and ineffective infection prevention and control practices in encouraging the spread of virulent C. difficile-associated diarrhoea in healthcare facilities remain controversial. Widespread use of antibacterial agents of one class can encourage multiclass drug resistance, which reduces prophylaxis and treatment efficacy in neutropenic cancer patients.

Candidemia and invasive candidiasis (C/IC) are life‐threatening opportunistic infections that add excess morbidity, mortality and cost to the management of patients with a range of potentially curable underlying conditions. The Association of Medical Microbiology and Infectious Disease Canada developed evidence‐based guidelines for the approach to the diagnosis and management of these infections in the ever‐increasing population of at‐risk adult patients in the health care system. Over the past few years, a new and broader understanding of the epidemiology and pathogenesis of C/IC has emerged and has been coupled with the availability of new antifungal agents and defined strategies for targeting groups at risk including, but not limited to, acute leukemia patients, hematopoietic stem cell transplants and solid organ transplants, and critical care unit patients. Accordingly, these guidelines have focused on patients at risk for C/IC, and on approaches of prevention, early therapy for suspected but unproven infection, and targeted therapy for probable and proven infection.

Antifungal prophylaxis is a promising strategy for reducing invasive fungal infections (IFIs) in allogeneic hematopoietic cell transplant (alloHCT) recipients, but the optimum prophylactic agent is unknown. We used mixed treatment comparison (MTC) meta-analysis to compare clinical trials examining the use of oral antifungals for prophylaxis in alloHCT recipients, with the goal of informing medical decision-making. Randomized controlled trials (RCTs) of fluconazole, itraconazole, posaconazole, and voriconazole for primary antifungal prophylaxis were identified through a systematic literature review. Outcomes of interest (incidence of IFI/invasive aspergillosis/invasive candidiasis, all-cause mortality, and use of other antifungals) were extracted from eligible RCTs and incorporated into a Bayesian hierarchical random-effects MTC. Five eligible RCTs, randomizing 2147 patients in total, were included. Relative to fluconazole, prophylaxis with itraconazole (odds ratio [OR]: 0.52; interquartile range [IQR]: 0.35–0.76), posaconazole (OR: 0.56; IQR: 0.32–0.99), and voriconazole (OR: 0.46; IQR: 0.28–0.73) reduced incidence of overall proven/probable IFI. Posaconazole (OR: 0.31; IQR: 0.17–0.58) and voriconazole (OR: 0.33; IQR: 0.17–0.58) prophylaxis reduced proven/probable invasive aspergillosis more than itraconazole (OR: 0.68; IQR: 0.42–1.12). All-cause mortality was similar across all mould-active agents. As expected, mould-active azoles prevented IFIs, particularly invasive aspergillosis, more effectively than fluconazole in alloHCT recipients. The paucity of comparative efficacy data suggests that other factors such as long-term tolerability, availability of intravenous formulations, local IFI epidemiology, and drug costs may need to form the basis for selection among the mould-active azoles.

The success of modern anticancer treatment is a composite function of enhanced efficacy of surgical, radiation and systemic treatment strategies and of our collective clinical abilities in supporting patients through the perils of their cancer journeys. Despite the widespread availability of antibacterial therapies, the threat of community- or healthcare facility-acquired bacterial infection remains a constant risk to patients during this journey. The rising prevalence of colonization by multidrug-resistant (MDR) bacteria in the population, acquired through exposure from endemic environments, antimicrobial stewardship and infection prevention and control strategies notwithstanding, increases the likelihood that such organisms may be the cause of cancer treatment-related infection and the likelihood of antibacterial treatment failure. The high mortality associated with invasive MDR bacterial infection increases the likelihood that many patients may not survive long enough to reap the benefits of enhanced anticancer treatments, thus threatening the societal investment in the cancer journey. Since cancer care providers arguably no longer have, and are unlikely to have in the foreseeable future, the antibacterial tools to reliably rescue patients from harm's way, the difficult ethical debate over the risks and benefits of anticancer treatments must now be reopened.