Carbapenemase-producing Gram-negative bacterial (GNB) infection is increasing worldwide including India where it is a cause for major concern (Meletis, 2015). Carbapenems are currently the medicine of choice for treating serious hospital-acquired infections, however carbapenem-resistance has been reported very high in India and the Indian subcontinent in recent decades. The accurate identification of carbapenemase-producing microbes is interesting, and it necessitates phenotypic and genotypic studies to identify all genes linked to carbapenemase-production.
This study was carried out in 1060 bedded super-specialty tertiary care hospital in Bihar, India. The majority of patients were referred after using antimicrobials. In addition, 47% of the isolates in the study were from the intensive care unit, where patients are more prone to undergo invasive procedures. These factors and prolonged hospital stay may have contributed for the high prevalence of carbapenem-resistant in admitted patients. Carbapenemase activity has been known in β-lactamases classes namely A, B, and D (Walsh, 2010; (Fonseca et al., 2012). The prevalence of CR-GNB in the current study was 16.8% as compared to the 31.77% in Western Maharashtra (Pawar et al., 2018). Similarly, Wattal et al found a prevalence rate of 13 to 51 percent in a tertiary care hospital in Delhi (Wattal et al., 2010). Nair et al found it to be around 12.26 percent in a study in Mumbai (Nair et al., 2013), while Gupta et al found it to be between 17 and 22 percent in a study in northern India (Gupta et al., 2016). This is consistent to our data.
The most frequently detected β-lactams carbapenem-resistance types of gene was blaCTX−M (37.93%) followed by blaSHV (28.74%), blaTEM (16.09%), blaOXA (6.90%) and blaNDM (4.65%) in GNB isolates in this study. This is consistent with finding from other parts of India. For example, study conducted on 130 clinical samples in E. coli and K. pneumoniae taken from Aligarh, Varanasi (Uttar Pradesh; North India) and Hubli (Karnataka; South India) have shown the prevalence of blaCTX−M−15 gene (Nair et al., 2021). In another study, 300 isolates of E. coli tested and found that blaCTX−M−15 was the most dominant gene (Rohit et al., 2019). Likewise, the study conducted on carbapenem-resistance genes in urinary isolates of K. pneumoniae (from Southern India) showed high prevalence of blaCTX−M−15 gene (Muzaheed et al., 2008), where’s analysis of 1275 strains from E. coli and K. pneumoniae showed the increasing prevalence of blaCTX−M−15 gene in the patients from the rural community of North India (Devi et al., 2020).
Similar trends for blaCTX-M-15 genes were observed in neighbor countries including Nepal (Manandhar et al., 2020), Bangladesh (Khan et al., 2018), Brazil (Rocha et al., 2015), China (Xia et al., 2014), Pakistan (Abrar et al., 2019), Ethiopia (Zeynudin et al., 2018), Switzerland (Yuki et al., 2021, ) (Marie-Frédérique et al., 2007), Argentina (M. et al., 2003), Netherlands (N. et al., 2006), Japan (Zhao & Hu, 2013) and United States in GNB isolates. For example, the study conducted in Ethiopia showed the prevalence of blaCTX-M-15 type extended-spectrum β-lactamases in E. coli (92.3%) and K. pneumoniae (96.7%) among clinical isolates of GNB (Zeynudin et al., 2018). In another study, ESBL-producing E. coli contained higher prevalence of blaCTX-M-15 (58.4%) gene in patients admitted at hospital, Kathmandu, Nepal (Pokhrel et al., 2014). The abundance of blaCTX-M-15 gene was also observed in E. coli clinical isolates from community and hospital-based infection in China (Xia et al., 2014). High prevalence of ESBL-encoding blaCTXM-15 gene was observed in 2372 clinical samples of GNB including E. coli, K. pneumoniae, P. aeruginosa, Enterobacter spp. and A. baumannii obtained from the hospitals and diagnostic research center of Lahore, Pakistan (Nair et al., 2021). The carbapenemase activity for blaCTX-M-15 has been reported earlier (Laurent et al., 2021)(Walsh, 2010).
The abundance of blaCTX-M genes in different species suggests horizontal gene transfer is occurring now or in the past. For example, E. coli from healthy food animals can be key repositories of bla genes and may contribute to the spread and transmission of these β-lactamase genes, and lateral transfer of resistance genes between animals and humans. In contrast, blaNDM and blaOXA was observed to be highly prevalent in GNB isolates in Tamil nadu (Nachimuthu et al., 2016) as well as Mumbai (Kazi et al., 2015). Likewise, blaVIM (Okoche et al., 2015), and blaIMP (Mushi et al., 2014) was observed to be the most common gene in CR-GNB isolates. We found 3 types of carbapenemase gene namely blaNDM (4.65%), blaOXA (6.90%) and blaDIM (1.15%) in our study. Though these carbapenemase gene are not common, yet it is concerning because it can be resistant to even more number of antibiotics. Carbapenem-resistant isolates may exhibit multidrug-resistance as they possessed blaNDM-1 or blaNDM-5, along with other antimicrobial-resistance factors. Among, subclass B1 metallo-beta-lactamase (blaNDM), higher prevalence of blaNDM-5 was detected in GNB isolates which may confers higher resistance against carbapenems than blaNDM-1 as reported earlier (Hornsey et al., 2011). Varying geographic locations, different levels of healthcare institutions engaged, different levels of exposure to healthcare environments, antibiotic use, and antibiotic stewardship procedures may all contribute to these disparities.
In our research, multiple co-existence genes within the same isolate were observed, where β-lactams co-resistance genes with blaNDM was found in 70.6% of carbapenemase-producing isolates. Carbapenem co-resistance retain genes that make them resistant to other antibiotics, making them multi-drug resistant and it threatens global antibiotic chemotherapy, patients’ recovery, and the economy (Kopotsa et al., 2020); (Mmatli et al., 2020). Resistance to carbapenem can be caused by the presence of blaNDM, blaCTX-M, blaTEM, blaSHV, and blaOXA gene family as well as impermeability (Rawat & Nair, 2010). This is particularly problematic in India, where β-lactams carbapenemase prevalence is quite high. This suggests that the detection of carbapenemase-encoding genes is an important index for phenotype in CR-GNB isolates. In our study, more than half of the isolates tested positive for multidrug resistance (MDR) to the most commonly used antibiotics. The acquisition and horizontal transfer of resistant genes from a variety of sources, including pathogenic bacteria, the environment, and animals, could be the main causes of resistance's uncontrolled expansion (Fair & Tor, 2014). Poor infection management in the country might be another reason for the high incidence of MDR and the acquisition of resistance genotypes, necessitating immediate action to combat the burgeoning AMR.