It is extremely difficult for patients with cancer and associated immunodeficiency to be treated to balance the need to administer a wide range of antimicrobial agents (AMPs) to prevent or treat infections and the risk of emergence and selection of strains of antibiotic resistant microorganisms which are extremely difficult to treat with further treatment.

In a study by a group of oncologists in the United States, microbial isolates from 622 blood samples from cancer patients with bacteremia were studied. Of all the episodes of bacteremia, 345 occurred in the context of ongoing antibiotic therapy (ABT) and 277 occurred in patients who did not receive AMP. In both groups, approximately 10% of the cases revealed a polymicrobial etiology of bacteremia.

The bacteremia occurring in the context of ABT was significantly more often associated with the isolation of multi-resistant strains of Escherichia coli (p = 0.002), Pseudomonas aeruginosa ( p = 0.02) and resistant to vancomycin enterococci (p = 0.01). The risk factors for the occurrence of bacteremia in the presence of ABT were the presence of hematological diseases (odds ratio OR = 9.9) and neutropenia (OS = 3.0).

Monotherapy with fluoroquinolones (PF) compared to all other ABT regimens (including combination therapy with PF) was significantly associated with the isolation of multidrug-resistant strains P. aeruginosa (p = 0 , 05), E. coli (p less than 0.001) or Methicillin-resistant Staphylococcus aureus (MRSA) (p = 0.04). Multivariate analysis has shown that the use of FP is associated with the highest probability of bacteremia on the background of ABT compared to all other treatment regimens (OS = 22.0; p less than 0.001). Treatment with vancomycin resulted in a significant increase in the risk of isolation of vancomycin-resistant enterococci (p less than 0.001). The researchers also noted that the use of AMP combinations increases the risk of isolation of multi-drug resistant E. coli, P. aeruginosa and enterococci resistant to vancomycin compared to the absence of ABT.

Thus, ABT and antibiotic prophylaxis in cancer patients lead to the development of antibiotic resistance, with the most harmful environmental consequences associated with the use of fluoroquinolones in this category of patients.