Phylogenetic relationships, virulence and antimicrobial resistance properties of Klebsiella sp. isolated from pet turtles in Korea

Chromium Toxicity in Plants: Signaling, Mitigation, and Future Perspectives

Plants are very often confronted by different heavy metal (HM) stressors that adversely impair their growth and productivity. Among HMs, chromium (Cr) is one of the most prevalent toxic trace metals found in agricultural soils because of anthropogenic activities, lack of efficient treatment, and unregulated disposal. It has a huge detrimental impact on the physiological, biochemical, and molecular traits of crops, in addition to being carcinogenic to humans. In soil, Cr exists in different forms, including Cr (III) "trivalent" and Cr (VI) "hexavalent", but the most pervasive and severely hazardous form to the biota is Cr (VI). Despite extensive research on the effects of Cr stress, the exact molecular mechanisms of Cr sensing, uptake, translocation, phytotoxicity, transcript processing, translation, post-translational protein modifications, as well as plant defensive responses are still largely unknown. Even though plants lack a Cr transporter system, it is efficiently accumulated and transported by other essential ion transporters, hence posing a serious challenge to the development of Cr-tolerant cultivars. In this review, we discuss Cr toxicity in plants, signaling perception, and transduction. Further, we highlight various mitigation processes for Cr toxicity in plants, such as microbial, chemical, and nano-based priming. We also discuss the biotechnological advancements in mitigating Cr toxicity in plants using plant and microbiome engineering approaches. Additionally, we also highlight the role of molecular breeding in mitigating Cr toxicity in sustainable agriculture. Finally, some conclusions are drawn along with potential directions for future research in order to better comprehend Cr signaling pathways and its mitigation in sustainable agriculture.

Phenotypic and molecular characterization of β-lactamase and plasmid-mediated quinolone resistance genes in Klebsiella oxytoca isolated from slaughtered pigs in Thailand

Background and Aim:

Over recent years, antimicrobial-resistant Klebsiella species in humans, animals, food animals, food products, and agricultural environments have been the center of attention due to its role in the evolution of antimicrobial resistance. The emergence of resistance to fluoroquinolones and cephalosporins of third and higher generations in Klebsiella oxytoca has not received much attention in animal husbandry compared to that in Klebsiella pneumoniae. Reports on K. oxytoca are limited in the study area. Therefore, we investigated the antimicrobial susceptibility and resistance genes in K. oxytoca isolated from slaughtered pigs in Thailand.

Materials and Methods:

Microbiological examination was conducted on 384 Klebsiella spp. isolates recovered from slaughtered pigs in ten provinces of Thailand. Seventy-two K. oxytoca isolates (18.75%) were examined for antimicrobial-resistant genes (β-lactamase [bla_TEM, bla_CTX-M, and bla_SHV]) and fluoroquinolone-resistant genes (qnrA, qnrB, qnrC, qnrD, qnrS, oqxAB, aac(6’)-Ib-cr, and qepA).

Results:

The most common genotype was bla_CTX-M (58/72, 80.55%), followed by bla_TEM with bla_CTX-M (7/72, 9.72%) and bla_TEM (6/72, 8.33%). The most common bla_CTX-M group was bla_CTX-M-1 (19/58, 32.76%), followed by bla_CTX-M-9 (1/58, 1.72%). Plasmid-mediated quinolone resistance genes were identified in 13 (18.05%) isolates: qnrS (16.70%) and qnrB (1.4%). All 13 isolates had qnrS transferable to an Escherichia coli recipient, whereas qnrB was not detected in any transconjugants. Either bla_CTX-M or bla_TEM harbored by one K. oxytoca strain was transferable to an E. coli recipient. Analysis of antimicrobial susceptibility revealed that more than 90% of the bla_CTX-M-carrying K. oxytoca isolates were susceptible to chloramphenicol, trimethoprim, ceftazidime, cefepime, cefotaxime, amoxicillin-clavulanic acid, piperacillin–tazobactam, and fosfomycin. All K. oxytoca isolates (13) harboring qnr were susceptible to carbapenem and ceftriaxone; however, 43 (74.13%) of the K. oxytoca isolates harboring bla_CTX-M exhibited extended-spectrum β-lactamase activity. Most of the K. oxytoca isolates from pigs were highly resistant to ampicillin, azithromycin, and gentamicin.

Conclusion:

To prevent further transmission of Klebsiella spp. Between food animals and humans, strict control of antibiotic use in clinical and livestock settings is necessary along with routine disinfection of the livestock environment and efforts to increase awareness of antimicrobial resistance transmission.

Klebsiella oxytoca Complex: Update on Taxonomy, Antimicrobial Resistance, and Virulence

Klebsiella oxytoca is actually a complex of nine species-Klebsiella grimontii, Klebsiella huaxiensis, Klebsiella michiganensis, K. oxytoca, Klebsiella pasteurii, Klebsiella spallanzanii, and three unnamed novel species. Phenotypic tests can assign isolates to the complex, but precise species identification requires genome-based analysis. The K. oxytoca complex is a human commensal but also an opportunistic pathogen causing various infections, such as antibiotic-associated hemorrhagic colitis (AAHC), urinary tract infection, and bacteremia, and has caused outbreaks. Production of the cytotoxins tilivalline and tilimycin lead to AAHC, while many virulence factors seen in Klebsiella pneumoniae, such as capsular polysaccharides and fimbriae, have been found in the complex; however, their association with pathogenicity remains unclear. Among the 5,724 K. oxytoca clinical isolates in the SENTRY surveillance system, the rates of nonsusceptibility to carbapenems, ceftriaxone, ciprofloxacin, colistin, and tigecycline were 1.8%, 12.5%, 7.1%, 0.8%, and 0.1%, respectively. Resistance to carbapenems is increasing alarmingly. In addition to the intrinsic bla_OXY, many genes encoding β-lactamases with varying spectra of hydrolysis, including extended-spectrum β-lactamases, such as a few CTX-M variants and several TEM and SHV variants, have been found. bla_KPC-2 is the most common carbapenemase gene found in the complex and is mainly seen on IncN or IncF plasmids. Due to the ability to acquire antimicrobial resistance and the carriage of multiple virulence genes, the K. oxytoca complex has the potential to become a major threat to human health.

Pet-turtles: a potential source of human pathogenic bacteria

Human infections caused by the bacterial pathogens transmitted from pet-turtles are becoming very common and getting more importance as the turtles are considered unsafe pet animals, mainly for children and immunocompromised people. Pet-turtles are known as the reservoir of different bacterial species as their intestinal microflora. Extrinsic stressors, such as crowding, unhygienic handling, poor water quality, polluted feeding and inadequate nutrition, can predispose pet-turtles to bacterial infections. The presence of different virulence genes leads to the virulent potential of bacteria. The virulent bacteria can cause infections in turtles and humans, if the turtle owners or shopkeepers don't practice proper sanitation while handling turtles. The aim of this review paper was to provide an overview of different bacterial species isolated from pet-turtles for awareness-raising about potential health risks related to raise pet-turtles.

Colonization dynamics of Klebsiella pneumoniae in the pet animals and human owners in a single household

Klebsiella pneumoniae resides in the gastrointestinal (GI) microbiota of humans and animals. To characterize the population dynamics of GI-colonizing K. pneumoniae, we examined the clonality of K. pneumoniae isolates, which were longitudinally collected from the fecal samplings of a healthy married couple and their pet animals during Sep. 2015 to Oct. 2016. As revealed by XbaI-PFGE analysis, the K. pneumoniae populations detected in the male owner and in one of the dogs, consisted of clonally diverse K. pneumoniae isolates; whereas, a dominant clone persisted in the GI tract of the female owner who was prone to chronic diarrhea. Whole-genome sequencing analysis of a representative strain of this pathobiont clone revealed a sequence type (ST) 29 lineage with the carriage of KL54 cps locus and a 192,603 bp IncHIB-type virulence plasmid. After probiotics intervention, the pathobiont K. pneumoniae diminished. The vacant niche was transiently occupied by other clones of K. pneumoniae, one of which was also present in the male owner. Besides the dog, the fecal carriage of K. pneumoniae was also detected in a pet turtle. This turtle isolate was resistant to multiple antimicrobials, including carbapenems. Possible transmission of drug-resistant K. pneumoniae through human-pet bonds warrants our attention.