Hospital Outbreak of a Colistin-Resistant, NDM-1- and OXA-48-Producing Klebsiella pneumoniae: High Mortality from Pandrug Resistance

Molecular Characterization of a Multidrug-Resistant Klebsiella pneumoniae Strain R46 Isolated from a Rabbit

To investigate the mechanisms of multiple resistance and the horizontal transfer of resistance genes in animal pathogens, we characterized the molecular structures of the resistance gene-related sequences in a multidrug-resistant Klebsiella pneumoniae strain R46 isolated from a rabbit. Molecular cloning was performed to clone the resistance genes, and minimum inhibitory concentrations (MICs) were measured to determine the resistance characteristics of the cloned genes and related strains. A conjugation experiment was conducted to assess the transferability of the resistance plasmids. Sequencing and comparative genomic methods were used to analyze the structures of the resistance gene-related sequences. The K. pneumoniae R46 genome consisted of a chromosome and three resistance plasmids named pR46-27, pR46-42, and pR46-270, respectively. The whole genome encoded 34 antibiotic resistance genes including a newly identified chromosome-encoded florfenicol resistance gene named mdfA2. pR46-270, besides encoding 26 antibiotic resistance genes, carried four clusters of heavy metal resistance genes and several virulence-related genes or gene clusters. The plasmid-encoded resistance genes were mostly associated with mobile genetic elements. The plasmid with the most similarity to the floR gene-harboring plasmid pR46-27 was pCTXM-2271, a plasmid from Escherichia coli. The results of this work demonstrated that the plasmids with multidrug resistance genes were present in animal-derived bacteria and more florfenicol resistance genes such as mdfA2 could be present in bacterial populations. The resistance genes encoded on the plasmids may spread between the bacteria of different species or genera and cause the resistance dissemination.

Emergent Polymyxin Resistance: End of an Era?

Until recently, the polymyxin antibiotics were used sparingly due to dose limiting toxicities. However, the lack of therapeutic alternatives for infections caused by highly resistant Gram-negative bacteria has led to the increased use of the polymyxins. Unfortunately, the world has witnessed increased rates of polymyxin resistance in the last decade, which is likely in part due to its irrational use in human and veterinary medicine. The spread of polymyxin resistance has been aided by the dissemination of the transferable polymyxin-resistance gene, mcr, in humans and the environment. The mortality of colistin-resistant bacteria (CoRB) infections varies in different reports. However, poor clinical outcome was associated with prior colistin treatment, illness severity, complications, and multidrug resistance. Detection of polymyxin resistance in the clinic is possible through multiple robust and practical tests, including broth microdilution susceptibility testing, chromogenic agar testing, and molecular biology assays. There are multiple risk factors that increase a person’s risk for infection with a polymyxin-resistant bacteria, including age, prior colistin treatment, hospitalization, and ventilator support. For patients that are determined to be infected by polymyxin-resistant bacteria, various antibiotic treatment options currently exist. The rising trend of polymyxin resistance threatens patient care and warrants effective control.

Treatment Options for Colistin Resistant Klebsiella pneumoniae: Present and Future

Multidrug-resistant (MDR) Klebsiella pneumoniae represents an increasing threat to human health, causing difficult-to-treat infections with a high mortality rate. Since colistin is one of the few treatment options for carbapenem-resistant K. pneumoniae infections, colistin resistance represents a challenge due to the limited range of potentially available effective antimicrobials, including tigecycline, gentamicin, fosfomycin and ceftazidime/avibactam. Moreover, the choice of these antimicrobials depends on their pharmacokinetics/pharmacodynamics properties, the site of infection and the susceptibility profile of the isolated strain, and is sometimes hampered by side effects. This review describes the features of colistin resistance in K. pneumoniae and the characteristics of the currently available antimicrobials for colistin-resistant MDR K. pneumoniae, as well as the characteristics of novel antimicrobial options, such as the soon-to-be commercially available plazomicin and cefiderocol. Finally, we consider the future use of innovative therapeutic strategies in development, including bacteriophages therapy and monoclonal antibodies.

NDM Metallo-β-Lactamases and Their Bacterial Producers in Health Care Settings

New Delhi metallo-β-lactamase (NDM) is a metallo-β-lactamase able to hydrolyze almost all β-lactams. Twenty-four NDM variants have been identified in >60 species of 11 bacterial families, and several variants have enhanced carbapenemase activity. Klebsiella pneumoniae and Escherichia coli are the predominant carriers of bla _NDM, with certain sequence types (STs) (for K. pneumoniae, ST11, ST14, ST15, or ST147; for E. coli, ST167, ST410, or ST617) being the most prevalent. NDM-positive strains have been identified worldwide, with the highest prevalence in the Indian subcontinent, the Middle East, and the Balkans. Most bla _NDM-carrying plasmids belong to limited replicon types (IncX3, IncFII, or IncC). Commonly used phenotypic tests cannot specifically identify NDM. Lateral flow immunoassays specifically detect NDM, and molecular approaches remain the reference methods for detecting bla _NDM Polymyxins combined with other agents remain the mainstream options of antimicrobial treatment. Compounds able to inhibit NDM have been found, but none have been approved for clinical use. Outbreaks caused by NDM-positive strains have been reported worldwide, attributable to sources such as contaminated devices. Evidence-based guidelines on prevention and control of carbapenem-resistant Gram-negative bacteria are available, although none are specific for NDM-positive strains. NDM will remain a severe challenge in health care settings, and more studies on appropriate countermeasures are required.

Successful control of the first OXA-48 and/or NDM carbapenemase-producing Klebsiella pneumoniae outbreak in Slovenia 2014-2016

BACKGROUND

Carbapenemase-producing Enterobacteriaceae (CPE) occur only sporadically in Slovenia.

AIM

To describe the first Slovenian carbapenemase-producing (CP) Klebsiella pneumoniae and Escherichia coli outbreak which occurred at the tertiary teaching hospital University Medical Centre Ljubljana from October 2014 to April 2015.

METHODS

A CPE-positive case was defined as any patient infected or colonized with CPE. A strict definition of a contact patient was adopted. Measures to prevent cross-transmission included cohorting of all CPE carriers with strict contact precautions and assignment of dedicated healthcare workers, cohorting of all contact patients until obtaining the result of screening cultures, systematic rectal screening of contact patients, and tagging of all CPE-positive cases and their contacts. Educational campaigns on CPEs were implemented. Clinical specimens were processed using standard procedures. Pulsed-field gel electrophoresis (PFGE) was used to determine relatedness. Multi-locus sequence typing was performed on CP K. pneumoniae isolates that belonged to different pulsotypes.

FINDINGS

Before the outbreak was brought under control, 40 patients were colonized or infected with OXA-48 and/or New Delhi metallo-β-lactamase (NDM)-producing CPE; in 38 patients OXA-48 and/or NDM-producing K. pneumoniae was detected, in seven OXA-48 and/or NDM-producing E. coli was found together with K. pneumoniae, and in two patients only CP E. coli was isolated. The outbreak was oligoclonal with two major CP K. pneumoniae clusters belonging to ST437 and ST147 in epidemiologically linked patients.

CONCLUSION

Initial standard control measures failed to prevent the outbreak. Once the problem had been recognized, strict infection control measures and the education of healthcare workers contributed to the successful control of the outbreak.

Wastewater drains: epidemiology and interventions in 23 carbapenem-resistant organism outbreaks

For many years, patient-area wastewater drains (ie, sink and shower drains) have been considered a potential source of bacterial pathogens that can be transmitted to patients. Recently, evolving genomic epidemiology tools combined with new insights into the ecology of wastewater drain (WWD) biofilm have provided new perspectives on the clinical relevance and hospital-associated infection (HAI) transmission risks related to these fixtures. To further clarify the clinical relevance of WWD-associated pathogen transmission, reports of outbreaks attributed to WWDs were selected for review that (1) investigated the outbreak epidemiology of WWD-associated transmission of bacterial pathogens, (2) utilized advanced microbiologic methods to establish clonality of outbreak pathogens and/or resistance genes, or (3) described interventions implemented to mitigate transmission of the outbreak pathogens from WWDs. These reports were collated, compared, and analyzed, and the results are presented here.

Resistome of carbapenem- and colistin-resistant Klebsiella pneumoniae clinical isolates

The emergence and dissemination of carbapenemases, bacterial enzymes able to inactivate most β-lactam antibiotics, in Enterobacteriaceae is of increasing concern. The concurrent spread of resistance against colistin, an antibiotic of last resort, further compounds this challenge further. Whole-genome sequencing (WGS) can play a significant role in the rapid and accurate detection/characterization of existing and emergent resistance determinants, an essential aspect of public health surveillance and response activities to combat the spread of antimicrobial resistant bacteria. In the current study, WGS data was used to characterize the genomic content of antimicrobial resistance genes, including those encoding carbapenemases, in 10 multidrug-resistant Klebsiella pneumoniae isolates from Pakistan. These clinical isolates represented five sequence types: ST11 (n = 3 isolates), ST14 (n = 3), ST15 (n = 1), ST101 (n = 2), and ST307 (n = 1). Resistance profiles against 25 clinically-relevant antimicrobials were determined by broth microdilution; resistant phenotypes were observed for at least 15 of the 25 antibiotics tested in all isolates except one. Specifically, 8/10 isolates were carbapenem-resistant and 7/10 isolates were colistin-resistant. The bla_NDM-1 and bla_OXA-48 carbapenemase genes were present in 7/10 and 5/10 isolates, respectively; including 2 isolates carrying both genes. No plasmid-mediated determinants for colistin resistance (e.g. mcr) were detected, but disruptions and mutations in chromosomal loci (i.e. mgrB and pmrB) previously reported to confer colistin resistance were observed. A bla_OXA-48-carrying IncL/M-type plasmid was found in all bla_OXA-48-positive isolates. The application of WGS to molecular epidemiology and surveillance studies, as exemplified here, will provide both a more complete understanding of the global distribution of MDR isolates and a robust surveillance tool useful for detecting emerging threats to public health.