Gram-negative pathogens such as Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa are the leading cause of nosocomial infections throughout the world. One commonality shared among these pathogens is their ubiquitous presence, robust host-colonization and most importantly, resistance to antibiotics. A significant number of two-component systems (TCSs) exist in these pathogens, which are involved in regulation of gene expression in response to environmental signals such as antibiotic exposure. While the development of antimicrobial resistance is a complex phenomenon, it has been shown that TCSs are involved in sensing antibiotics and regulating genes associated with antibiotic resistance. In this review, we aim to interpret current knowledge about the signaling mechanisms of TCSs in these three pathogenic bacteria. We further attempt to answer questions about the role of TCSs in antimicrobial resistance. We will also briefly discuss how specific two-component systems present in K. pneumoniae, A. baumannii, and P. aeruginosa may serve as potential therapeutic targets.

Access to safe drinking water is now recognized as a human right by the United Nations. In developed countries like Canada, access to clean water is generally not a matter of concern. However, one in every five First Nations reserves is under a drinking water advisory, often due to unacceptable microbiological quality. In this study, we analyzed source and potable water from a First Nations community for the presence of coliform bacteria as well as various antibiotic resistance genes. Samples, including those from drinking water sources, were found to be positive for various antibiotic resistance genes, namely, ampC, tet(A), mecA, ␤-lactamase genes (SHV-type, TEM-type, CTX-M-type, OXA-1, and CMY-2-type), and carbapenemase genes (KPC, IMP, VIM, NDM, GES, and OXA-48 genes). Not surprisingly, substantial numbers of total coliforms, including Escherichia coli, were recovered from these samples, and this result was also confirmed using Illumina sequencing of the 16S rRNA gene. These findings deserve further attention, as the presence of coliforms and antibiotic resistance genes potentially puts the health of the community members at risk. IMPORTANCEIn this study, we highlight the poor microbiological quality of drinking water in a First Nations community in Canada. We examined the coliform load as well as the presence of antibiotic resistance genes in these samples. This study examined the presence of antibiotic-resistant genes in drinking water samples from a First Nations Community in Canada. We believe that our findings are of considerable significance, since the issue of poor water quality in First Nations communities in Canada is often ignored, and our findings will help shed some light on this important issue.A ntibiotic resistance in bacteria has been recognized as one of the greatest threats to human health by the World Health Organization (1). Overuse and misuse of antibiotics contribute to the buildup of selective pressure aiding the proliferation of antibiotic-resistant bacteria (2, 3). While hospital environments are notorious for selecting for antibiotic-resistant bacteria, it is now becoming increasingly evident that overuse and misuse of antibiotics are also creating a selective pressure outside hospital settings. Studies over the last few years have shown the presence of antibiotics and of antibiotic-resistant bacteria in the broader environment, including water supplies and soil samples (4). This is indeed alarming as the high number of antibiotic-resistant bacteria in communities makes the treatment of community-acquired infections increasingly challenging (5, 6).Not surprisingly, water samples from communities that lack access to clean water contain high numbers of bacteria (7-9). While a high bacterial count in the water supply itself poses an increased health risk (10), the presence of antibiotic-resistant bacteria makes this risk even more serious. Lack of access to clean and safe water is a problem that is generally associated with developing countries; however, this is a reality as wel...

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Acinetobacter baumannii, a Gram-negative opportunistic pathogen, is known to cause multidrug resistant infections. This organism has primarily been isolated from clinical environments and its environmental reservoirs remain largely unknown. In the present study, we recovered seven isolates of A. baumannii growing under conditions selective for Campylobacter spp. (microaerophilic at 42°C and in the presence of antibiotics) from dairy cattle manure storage tank or surface water impacted by livestock effluents. Antibiotic susceptibility tests revealed that all of these isolates were less susceptible to at least two different clinically relevant antibiotics, compared to the type strain A. baumannii ATCC17978. Expression of resistance-nodulation-division efflux pumps, an important mechanism of intrinsic resistance in these organisms, was analyzed, and adeB was found to be overexpressed in one and adeJ was overexpressed in three isolates. Comparison of these isolates using genomic DNA Macro-Restriction Fragment Pattern Analysis (MRFPA) revealed relatively low relatedness among themselves or with some of the clinical isolates from previous studies. This study suggests that A. baumannii isolates are capable of growing under selective conditions for Campylobacter spp. and that this organism can be present in manure and water.

This study analyzed the microbiological quality of drinking and source water from three First Nations communities in Manitoba, Canada that vary with respect to the source, storage and distribution of drinking water. Community A relies on an aquifer and Community B on a lake as source water to their water treatment plants. Community C does not have a water treatment plant and uses well water. Quantification of free residual chlorine and fecal bacterial (E. coli and coliforms), as well as detection of antibiotic resistance genes (sul, ampC, tet(A), mecA, vanA, blaSHV, blaTEM, blaCTX-M, blaOXA-1, blaCYM-2, blaKPC, blaOXA-48, blaNDM, blaVIM, blaGES and blaIMP) was carried out. While water treatment plants were found to be working properly, as post-treatment water did not contain E. coli or coliforms, once water entered the distribution system, a decline in the chlorine concentration with a concomitant increase in bacterial counts was observed. In particular, water samples from cisterns not only contained high number of E. coli and coliforms, but were also found to contain antibiotic resistance genes. This work shows that proper maintenance of the distribution and storage systems in First Nations communities is essential in order to provide access to clean and safe drinking water.

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