Detection of carbapenemases blaOXA48-blaKPC-blaNDM-blaVIM and extended-spectrum-β-lactamase blaOXA1-blaSHV-blaTEM genes in Gram-negative bacterial isolates from ICU burns patients

Background and objectives Burn patients are highly susceptible to invasion by multidrug-resistant Gram-negative bacteria (MDR-GNB) through post-burn damage. The prevalence of MDR-GNB isolated from burns patients has increased dramatically in the last decade, representing a serious risk to patients admitted to burns units worldwide. The challenges of managing infected burns patients are exacerbated in poor resource settings. This study was designed to develop a pathway for the rapid diagnosis of multidrug-resistant (MDR) Gram-negative infections and identify the bacterial genes including bla(OXA1), bla(TEM), and bla(SHV) encoding ESBLs and bla(OXA48), bla(KPC), bla(NDM), and bla(VIM) encoding carbapenemases from the patient of post burns infection. Methods Clinical isolates were collected (August 2017 to August 2018) from Intensive care unit (ICU) of Burn Centre. Antibiotic susceptibility testing and phenotypic detection of ESBLs and carbapenemases was performed by disk diffusion, double disk synergy test (DDST), combination disk test (CDT), and Imipenem + EDTA combined disk test (IMP + EDTA CDT). Polymerase chain reaction (PCR) detection was performed for ESBLs bla(OXA1)-bla(SHV)-bla(TEM) and carbapenemases genes bla(OXA48)-bla(KPC)-bla(NDM)-bla(VIM) Results In total, of 170 Gram-negative isolates, 104 (61.2%) were confirmed as multidrug-resistant (MDR); Pseudomonas aeruginosa was found to be the most prevalent 43/104 (41.4%), followed by Klebsiella pneumoniae 17/104 (16.4%), Acinetobacter baumannii12/104 (11.5%), and 6/104 Proteus mirabilis (5.8%). All isolates (100%) were resistant to cefotaxime and ceftazidime, while the meropenem resistance was 58.7%. ESBL and carbapenemase genotypes were found to be associated with higher MAR index (0.65-0.88) and MIC (> 32 mu g/ml) values P. aeruginosa was the major ESBL and carbapenemase producer as determined by phenotypic testing and PCR. bla(TEM) positive isolates among ESBLs producers were predominant 81.8% (27/33), followed by 27.3% bla(OXA1) and bla(SHV), respectively. bla(VIM) positive isolates among carbapenemase producers were predominant 47.7% (21/44), followed by 27.3% bla(KPC), 20.5% bla(OXA48), and 11.4% bla(NDM) positive isolates. Conclusions The predominant organism causing burn infections was ESBL and carbapenemase-producing Pseudomonas aeruginosa. There are only limited effective antibiotics against such strains. bla(VIM) and bla(TEM) individually and in co-existence with bla(KPC), bla(OXA48), bla(SHV), and bla(OXA1) confer antimicrobial resistance in burns patients. Rapid detection of ESBL and carbapenemase genes will inform treatment strategies improving the outcome for post-burn patients in ICU.

Automated summary

This study aimed to investigate the drug resistance of pathogens and develop a rapid diagnosis method for multidrug-resistant Gram-negative bacterial infections. The results showed that Pseudomonas aeruginosa is the main pathogen causing burn infections, and there are limited effective antibiotics available to combat such pathogens.