Dissemination of ST274 Klebsiella pneumoniae epidemic clone in newborn and adult hospital settings harbouring SHV-2A or CTX-M-15 type extended spectrum β-lactamases-producing known plasmids

Transmissible silver resistance readily evolves in high-risk clone isolates of Klebsiella pneumoniae

Silver is used extensively in both hospitals and outpatient clinics as a disinfectant coating agent on various devices. Resistance to silver was recently reported as an emerging problem in Enterobacteriaceae. Multidrug-resistant high-risk clones of Klebsiella pneumoniae are common causes of serious healthcare-associated infections worldwide posing a serious threat to patients. In this study, we investigated the capacity of both high-risk (CG14/15 and CG258) and minor clone strains of K. pneumoniae to develop resistance to silver. Resistance was induced in vitro in silver-susceptible but otherwise multidrug-resistant clinical isolates. Genetic alterations in the silver-resistant derivative strains with regard to the silver-susceptible isolates were investigated by whole-genome sequencing. The transferability of high-level resistance to silver was also tested. We demonstrated that the high-level resistance to silver can quickly evolve as a consequence of a single-point mutation either in the cusS gene of the chromosomally encoded CusCFBARS efflux system and/or in the silS gene of the plasmid-encoded Copper Homeostasis and Silver Resistance Island (CHASRI) coding also for a metallic efflux. The minimal inhibitory concentrations (MICs) of the strains increased from 4 mg/L (23.5 μM) AgNO₃ to >8,500 mg/L (>50,000 μM) AgNO₃ during induction. Harboring the CHASRI proved an important selective asset for K. pneumoniae when exposed to silver. Successful conjugation experiments using Escherichia coli K12 J5-3^Rif as recipient showed that high-level silver resistance can transmit between strains of high-risk clones of K. pneumoniae (ST15 and ST11) and isolates from additional species of Enterobacteriaceae. The lack of fitness cost associated with the carriage of the CHASRI in a silver-free environment and the presence of the RelEB toxin-antitoxin system on the conjugative plasmids could advance the dissemination of silver resistance. Our results show that multidrug-resistant high-risk clones of K. pneumoniae are capable of evolving and transmitting high-level resistance to silver. This observation should warrant a more judicious use of silver coated-devices to prevent the extensive dissemination of silver resistance.

The Antimicrobial Susceptibility of Klebsiella pneumoniae from Community Settings in Taiwan, a Trend Analysis

Drug-resistant Klebsiella pneumoniae, especially extended-spectrum β-lactamase (ESBL)- and/or AmpC β-lactamase-producing strains, is an emerging problem worldwide. However, few data focusing on drug susceptibility of K. pneumoniae from community is available. In this study, we analyzed 1016 K. pneumoniae isolates from outpatients or those visiting emergency rooms collected during 2002–2012 from Taiwan Surveillance of Antimicrobial Resistance program. Significantly decreased susceptibilities to 3^rd generation cephalosporins and ciprofloxacin were found during the study period. By 2012, susceptibility to cefotaxime and ciprofloxacin was 83.6% and 81.6%, respectively. The prevalence of ESBL-producers increased from 4.8% in 2002 to 11.9% in 2012 (P = 0.012), while that of AmpC β-lactamase-producers increased from 0% to 9.5% in the same period (P < 0.001). Phylogenic analysis of the ESBL and AmpC-β-lactamase-producers by pulsed-field gel electrophoresis and multi-locus sequence typing revealed wide genetic diversity even among the most common sequence type 11 isolates (33.0%). By multivariate analysis, later study year, elderly, and urine isolates were associated with carriage of ESBL genes, while only urine isolates were associated with carriage of AmpC β-lactamase genes. Further studies are needed to determine which antibiotics are reasonable empirical therapy options for patients presenting with severe sepsis that might be caused by K. pneumoniae.

The changing epidemiology of hospital outbreaks due to ESBL-producing Klebsiella pneumoniae: the CTX-M-15 type consolidation

ABSTRACT 

Klebsiella pneumoniae is responsible for a large number of hospital outbreaks. In the 1990s, there were clonal epidemics, affecting mostly intensive care patients, which carried SHV and TEM enzyme types. With the advent of CTX-M-15 enzymes in the 2000, plasmids encoding multiple extended-spectrum β-lactamase (ESBL) types were described and, frequently, nosocomial outbreaks reported polyclonal dissemination and involved multiple Enterobacteriaceae. Worryingly, the interface between community and hospital is becoming blurred, and there is increasing evidence for the presence of ESBL-producing K. pneumoniae in the community. Furthermore, carbapenem resistance is increasingly reported in ESBL-producing K. pneumoniae strains. Infection control measures and stewardship programs are vital weapons in controlling the pandemic evolution of multidrug-resistant K. pneumoniae.