Prevalence and 30-day all-cause mortality of carbapenem-and colistin-resistant bacteraemia caused by Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae: Description of a decade-long trend

Background: Bacteraemia due to carbapenem-resistant gram-negative bacteria is challenging. This study examined the burden of carbapenem and colistin resistance in Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii bacteraemia in Oman. Methods: Adult patients admitted to Sultan Qaboos University Hospital between January 1, 2007 and December 31, 2016 with positive blood cultures for P. aeruginosa, A. baumannii, or K. pneumoniae were identified. Rates of carbapenem resistance, trends in prevalence, and 30-day all-cause mortality were examined. Results: Two hundred and twenty-seven (29.8%) of 761 bacteraemia cases due to these three isolates were carbapenem-resistant, with 87.2% being healthcare-associated. A. baumannii caused 52% of all carbapenem-resistant bacteraemia, K. pneumoniae caused 30%, and P. aeruginosa caused 18%. Rates of carbapenem resistance in P. aeruginosa, A. baumannii, and K. pneumoniae bacteraemia increased from 20%, 67%, and 0%, respectively, in 2007 to 25%, 86%, and 35%, respectively, in 2016. Seventeen (7.9%) carbapenem-resistant bacteraemia cases were also colistin-resistant. Thirty-day all-cause mortality was 62% in patients with carbapenem-resistant bacteraemia and 22% in patients with carbapenem-sensitive bacteraemia. Conclusions: The prevalence of carbapenem-resistant K. pneumoniae, A. baumannii, and P. aeruginosa bacteraemia is increasing alarmingly in Oman, with a large proportion of K. pneumoniae and P. aeruginosa demonstrating additional resistance to colistin. Patients with carbapenem-resistant bacteraemia had higher 30-day all-cause mortality.