Abstract
Emerging worldwide in the past decade, there has been a significant increase in multidrug-resistant bacteria from serious nosocomial infections, especially carbapenemase-producing Gram-negative bacilli that have emerged worldwide. The objective of this study is to investigate carbapenem resistance in Gram-negative bacilli bacteria using phenotypic detection, antimicrobial resistance profiles and genotypic characterisation methods. 200 Gram-negative bacilli isolates were collected from different clinical specimens. All clinical samples were exposed to isolation and identification of significant pathogens applying bacteriological examination and an automated Vitek-2 system. The isolates were subjected to susceptibility tests by the Vitek-2 automated system and those isolates that were resistant to beta-lactam drugs, including carbapenems, third-generation cephalosporines or cefoxitin, were selected for phenotyping using Carba plus disc system assay for detection of carbapenemase-producing isolates. These isolates were further confirmed by molecular detection. PCR was used for the detection carbapenem-resistant genes (OXA-48, IMP, NDM, VIM, and KPC). 110 (55%) of 200 Gram-negative bacilli were identified as beta-lactam-resistant isolates. The frequency of carbapenem-resistant isolates was calculated to be 30.9% (n = 34/110). A collection totalling 65/110 (59%) isolates were identified as carbapenemase producers by phenotypic method. Moreover, among the 65 carbapenemase-producing Gram-negative isolates with a positive phenotype-based result, 30 (46%), 20 (30%) and 18 (27%) isolates were positive for OXA-48, KPC and MBL enzymes, respectively, as well as the production of 27% of AmpC with porin loss. Tigecycline was the most effective antibiotic that affected 70% of MDR isolates, but high rates of resistance were detected to other tested antimicrobials. Of interest, a high incidence of MDR, XDR and PDR profiles were observed among all carbapenemase-producing isolates. 36% (24/65) of the tested isolates were MDR to 3 to 5 antimicrobial classes. 29% (17/65) of the recovered isolates were XDR to 6 to 7 antimicrobial classes. Alarmingly, 24% (16/65) of isolates displayed PDR to all the tested 8 antimicrobial classes. Genotype assay, including 53 phenotypically confirmed carbapenemase-producing isolates of Gram-negative bacilli, found 51(96%) isolates were harbouring one or more genes. The most common carbapenemase gene was bla NDM 83% (44/53) followed by bla OXA-48 75% (40/53), bla VIM 49% (26/53) and bla IMP 43% (23/53), while the gene bla KPC was least frequent 7% (4/53). 92% (46/51) of isolates were involved in the production of more than one carbapenemase gene. This study demonstrated the emergence of carbapenemase-producing Gram-negative pathogens implicated in healthcare-related infections. Accurate identification of carbapenem-resistant bacterial pathogens is essential for patient treatment, as well as the development of appropriate contamination control measures to limit the rapid spread of pathogens. Tigecycline exhibited potent antimicrobial activity against MDR, XDR and PDR-producing strains that establish a threatening alert which indicates the complex therapy of infections caused by these pathogens.
Highlights
Multidrug resistance has increased globally and is considered a public health threat
Carbapenem resistance has been labelled in Enterobacteriaceae, mostly in Klebsiella pneumoniae compared to Escherichia coli or other Enterobacterial species, and in non-fermentative Gram-negative bacilli such as Pseudomonas aeruginosa and Acinetobacter baumannii [4]
Statistical analysis showed that there was a significant difference in the prevalence of different bacterial pathogens and carbapenemase-resistant isolates recovered from different types of specimens (p < 0.05)
Summary
Multidrug resistance has increased globally and is considered a public health threat. Carbapenems (i.e. meropenem, imipenem, ertapenem and doripenem) are a safe and highly effective class of antibiotics and considered last line drugs for controlling multidrug-resistant Gram-negative pathogens including extended-spectrum betalactamases-producing Enterobacteriaceae [6]. Owing to their broad-spectrum activity, carbapenems are frequently used in the treatment of life-threatening infections. Carbapenem resistance has been labelled in Enterobacteriaceae, mostly in Klebsiella pneumoniae compared to Escherichia coli or other Enterobacterial species, and in non-fermentative Gram-negative bacilli such as Pseudomonas aeruginosa and Acinetobacter baumannii [4] These Gram-negative bacteria are the main nosocomial pathogens and the most prevalent bacteria responsible for a range of hospital-acquired and community-acquired difficult to treat infections such as meningitis, pneumonia, peritonitis, septicaemia and urinary tract infections.
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