Extensively Drug-Resistant Klebsiella pneumoniae Counteracts Fitness and Virulence Costs That Accompanied Ceftazidime-Avibactam Resistance Acquisition.

The ability of extensively drug-resistant (XDR) Klebsiella pneumoniae to rapidly acquire resistance to novel antibiotics is a global concern. Moreover, Klebsiella clonal lineages that successfully combine resistance and hypervirulence have increasingly occurred during the last years. However, the underlying mechanisms of counteracting fitness costs that accompany antibiotic resistance acquisition remain largely unexplored. Here, we investigated whether and how an XDR sequence type (ST)307 K. pneumoniae strain developed resistance against the novel drug combination ceftazidime-avibactam (CAZ-AVI) using experimental evolution. In addition, we performed in vitro and in vivo assays, molecular modeling, and bioinformatics to identify resistance-conferring processes and explore the resulting decrease in fitness and virulence. The subsequent amelioration of the initial costs was also addressed. We demonstrate that distinct mutations of the major nonselective porin OmpK36 caused CAZ-AVI resistance that persists even upon following a second experimental evolution without antibiotic selection pressure and that the Klebsiella strain compensates the resulting fitness and virulence costs. Furthermore, the genomic and transcriptomic analyses suggest the envelope stress response regulator rpoE and associated RpoE-regulated genes as drivers of this compensation. This study verifies the crucial role of OmpK36 in CAZ-AVI resistance and shows the rapid adaptation of a bacterial pathogen to compensate fitness- and virulence-associated resistance costs, which possibly contributes to the emergence of successful clonal lineages. IMPORTANCE Extensively drug-resistant Klebsiella pneumoniae causing major outbreaks and severe infections has become a significant challenge for health care systems worldwide. Rapid resistance development against last-resort therapeutics like ceftazidime-avibactam is a significant driver for the accelerated emergence of such pathogens. Therefore, it is crucial to understand what exactly mediates rapid resistance acquisition and how bacterial pathogens counteract accompanying fitness and virulence costs. By combining bioinformatics with in vitro and in vivo phenotypic approaches, this study revealed the critical role of mutations in a particular porin channel in ceftazidime-avibactam resistance development and a major metabolic regulator for ameliorating fitness and virulence costs. These results highlight underlying mechanisms and contribute to the understanding of factors important for the emergence of successful bacterial pathogens.

Assessment of the risk for human health of Enterovirus and Hepatitis A virus in clinical and water sources from three metropolitan cities of Pakistan.

INTRODUCTION: Molecular studies have confirmed the silent circulation of enterovirus (EntV) and hepatitis A virus in the environment, even in the absence of clinical manifestation. Viral pathogens are among the major causes of disease outbreaks, particularly in the bigger cities and both in the developed and underdeveloped nations. MATERIAL AND METHODS: Between June 2016 - June 2017, 97 samples of drinking water, river water polluted with sewage and blood were selected and obtained from high risk communities in Pakistan. Negatively charged membrane filters were used to concentrate the virus, followed by the use of specific PCR primers set for quick identification of the waterborne viruses. RESULTS: Enteroviruses were recovered from 40%, 28.57% and 33.33% of river water polluted with sewage samples in Lahore, Islamabad and Rawalpindi, respectively, while the presence of 13.13% and 11.76% of viral load was also confirmed in the drinking water of Lahore and Rawalpindi, respectively. A high prevalence of HAV (12.5% and 21.05%) was also verified in the clinical samples. Phylogenetic analysis indicated close resemblance of HAV isolates with the Indian strains. This study is the first ever comparative analysis of the EntV and HAV isolated from environmental samples and clinical specimen on a molecular level. CONCLUSIONS: The parallel surveillance of EntV and HAV in the river water polluted with sewage, and clinical samples is quite helpful for controlling and reducing the disease burden of the waterborne illnesses.