Emergence of blaNDM-1 and blaVIM producing Gram-negative bacilli in ventilator-associated pneumonia at AMR Surveillance Regional Reference Laboratory in India

Abstract

Introduction: Ventilator-associated pneumonia (VAP) may be a life threatening nosocomial infection encountered in intensive care units. Currently the emergence of carbapenem-resistant Gram-negative pathogens has become worrisome threat worldwide.

Material and methods: Endotracheal aspirates samples were collected from patients who were under mechanical ventilation for > 48 h. The bacterial isolates were identified by MALDI-TOF-MS and antibiotic susceptibility testing performed. All carbapenem resistant isolates were tested by Modified Hodge test (MHT), modified carbapenem inactivation method (mCIM), and EDTA-CIM (eCIM) and PCR were performed to detect blaIMP, blaVIM and blaNDM producing MBL genes.

Results: VAP occurred in 172/353(48.7%), 23.3% had early-onset VAP and 76.7% had late-onset VAP. Males (69.2%) were found to suffer more from VAP. Prior antibiotic therapy, CPI>6, prior surgery and tracheostomy were associated with VAP. The mortality in VAP (58.1%) contrasted with non-VAP (40%). 99/169 (58.6%) Gram-negative isolates were resistant to carbapenems. Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae were common pathogens found in late onset VAP, whereas K. pneumoniae, A. baumannii and Staphylococcus aureus were common in early onset VAP. The PCR results detected blaNDM in 37/172(21.5%) and blaVIM in 30/172(17.4%); 15/172(8.7%) isolates carried both genes.

Conclusion: The blaNDM-1 and blaVIM genes are the main antibiotic-resistance genes that induce resistance patterns to carbapenems in VAP, highlighting CRE strains of potential public health concern and therapeutic challenge. Diagnostic laboratories in India must get on high caution for early MBL detection as it may limit the wide dispersal of MBL genes.

Fig 1

A: Isolate positive for mCIM/eCIM test (isolate with bla_NDM gene). B: Isolate showing clover-leaf shaped pattern in Modified-Hodge test.

Fig 2

A: Agarose gel electrophoresis of products obtained by PCR of amplified DNA. Lane 1: 100 bp DNA ladder; Lane 2- Negative control; Lane 9-Positive control bla_VIM (390bp); Lane 10: Isolates positive for bla_VIM gene (390bp). B: Agarose gel electrophoresis of products obtained by PCR of amplified DNA. Lane 1: 100 bp DNA ladder; Lane 2: Negative control; Lane 4: Positive control for bla_NDM gene (984bp); Lane 5, 6, 7, 11,13 and 14: Isolates positive for bla_NDM gene (984bp).