Cancer patients due to their immune-compromised nature are more prone to infections among which respiratory tract infections (RTIs) are frequently reported to account for 3 to 5% of deaths. In recent years, antibiotic resistance among respiratory pathogens is increasing emergently. The present study was conducted retrospectively at the microbiology division of a tertiary care hospital over 4 years (Jan 2016 – Dec 2019) aimed to find out the bacterial etiology of RTIs in cancer patients. Patients of all age groups, suspected of RTI recorded in microbiology registers were included in the study. During the study period, out of 2918 specimens (Jan 2016- Dec 2019) received in the microbiology lab, 2,065 (70%) specimens showed meaningful growth, whereas 269 (9%) specimens showed contaminated growth, 584 (20%) specimens showed no growth. From the 2,065 specimens, 1420 bacterial isolates were recovered. Out of the total 1420 isolates identified, 912 (64%) were gram-negative bacilli (GNB) and 508 (35.7%) were gram-positive organisms. About 19.6 % of patients were in the age group of fewer than 20 years, 54.4% in 21–60 years and 26% were of more than 60 years of age. The male-to-female ratio was 60.1:39.9. Trends of antimicrobial resistance among the leading pathogens causing RTI were studied in two phases, i.e., from 2016–2017 (phase I) and 2018–2019 (phase II). Phase I and II showed an increasing trend in resistance to cephalosporins and a declining trend in resistance to aminoglycosides (resistance to gentamicin was relatively high when compared with amikacin). In Phase I (2016 and 2017) resistance to Beta Lactams ranged from 66 to 97% and it is relatively high in phase II (2018 and 2019). But in contrast to other gram-negative isolates, Acinetobacter spp were more resistant to most groups of antibiotics during both Phases I (85–97%)  and II (95–97%). Multidrug resistance (resistance to three or more than three drugs) was observed in most of the total isolates during the study period. The increasing trend of resistance in gram-negative organisms is alarming. Judicious use of older and newer antimicrobial agents is essential to prevent the emergence of multidrug-resistant bacteria. The development of newer therapeutic alternatives to address the problem of MDR GNBs is needed.

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