In vitro activity of meropenem-vaborbactam plus aztreonam against metallo-ß-lactamase-producing Klebsiella pneumoniae.

We evaluated the in vitro activity of meropenem-vaborbactam plus aztreonam (MEV-ATM) against 140 metallo-ß-lactamase (MBL)-producing Klebsiella pneumoniae isolates. Among them, 25 isolates (17.9%) displayed minimum inhibitory concentrations (MIC) ≥ 8 µg/mL, while 112 (80.0%) had MIC ≤ 2 µg/mL. Genomic analysis and subsequent gene cloning experiments revealed OmpK36 134-135GD-insertion and increased carbapenemase gene (blaNDM-1 and blaOXA-48-like) copy numbers are the main factors responsible for MEV-ATM non-susceptibility. Notably, MEV-ATM is actively against aztreonam-avibactam-resistant mutants due to CMY-16 mutations.

Multicenter Genomic Analysis of Carbapenem-Resistant Klebsiella pneumoniae from Bacteremia in China.

Klebsiella pneumoniae is one of the most common Gram-negative bacilli isolated from bloodstream infections worldwide, and recently an increased rate of carbapenem resistance has been reported in this pathogen. This study aims to describe the genomic characteristics of carbapenem-resistant K. pneumoniae (CRKP) isolated from patients with bacteremia in China. We analyzed 147 isolates from patients with bacteremia attended in 12 referral hospitals in China between April 2015 and November 2018. We conducted a phenotypic susceptibility evaluation and whole genome sequence analysis to characterize antimicrobial resistance profile, virulence genes, and dominant clones among CRKP. ST11 accounted for most infections (n = 98, 66.6%), followed by ST45 (n = 12, 8.2%), ST15 and ST290 (n = 8, 5.4% each). KPC (n = 98, 66.7%) and NDM (n = 27, 18.4%) are the main carbapenemases detected in the CRKP isolates. We detected yersiniabactin (n = 123, 83.7%) and aerobactin (49.9%) siderophores, and both rmpA and aerobactin genes in 21 ST11 isolates (21.43%), which are considered characteristic biomarkers of hypervirulent strains. Isolates showed high resistance rates to the ß-lactams (>90%) and other antibiotics classes such as fluoroquinolones, aminoglycosides and tetracyclines (50%), but were susceptible to ceftazidime-avibactam (74.8%). In addition, we detected intra-hospital transmission of ST11 and ST45 strains in single and multiple wards in several hospitals, whereas inter-hospital transmission was relatively uncommon. In summary, we observed significantly genomic diversity of CRKP bacteremia isolates in China, although KPC-2 producing ST11 strains were found to be the most common clonal types. Reducing intra-hospital transmission remains to be the key to control CRKP caused bloodstream infections in China. IMPORTANCE K. pneumoniae is one of the most frequent Gram-negative bacilli isolated from bloodstream infections worldwide and recent studies have shown an increased rate of carbapenem resistance in China. Among carbapenem-resistant K. pneumoniae (CRKP) diverse clones have been reported, especially the high-risk clone ST11, which also exhibited a multidrug resistant phenotype. In addition to the antimicrobial resistance, previous studies have detected strains co-harboring virulent traits, highlighting the potential of transmission of both antimicrobial resistant and virulent strains. Here we studied the antimicrobial resistance profile, virulence genes and hospital transmission of CRKP from bacteremic patients in China. This study showed a high clonal diversity among CRKP, with the predominance of ST11 lineages. We detected virulence markers among multidrug resistant strains, and a high number of genetically similar isolates, suggesting intra-hospital transmission within single and multiple wards. Reducing intra-hospital transmission remains to be the key to control CRKP caused bacteremia in China.

Epidemiology of Rickettsial Infection in the Municipality of Uramita, Colombia.

This study aimed to analyze epidemiological indicators related to seroprevalent and seroincident cases of spotted fever group rickettsiae (SFGR) and to identify housing conditions related to tick infestation. A prospective study (2016-2018) was conducted to examine rickettsial seropositivity in humans, domestic animals, and wild mammals in the municipality of Uramita, Antioquia, Colombia, where a previous Rickettsia rickettsii outbreak was reported from 2014 to 2015. The seroprevalence and its associated factors were estimated at baseline, and the seroincidence and its risk factors for humans were estimated 20 months later. A cross-sectional analysis was performed to evaluate the housing conditions linked to tick infestation. The SFGR seroprevalence was 26.70% (95% confidence interval [CI], 20.79-31.37), and the factors associated with SFGR seropositivity were male sex (adjusted prevalence ratio [PRa], 1.67; 95% CI, 1.19-2.32), age (evaluated in 5-year increments) (PRa, 1.05; 95% CI, 1.01-1.09), and household proximity (PRascattered vs. very near=3.87; 95% CI, 1.12-8.66). The overall seroincidence was 7.40% (95% CI, 4.71-11.06), and the factors associated with SFGR seroincident cases were the presence of wild animals (adjusted relative risk [RRa], 2.46; 95% CI, 1.06-4.72) and the presence of trees in the peri-domiciliary area (RRa, 0.47; 95% CI, 0.23-0.94). The prevalence of house tick infestation was 27.81% (95% CI, 21.93-34.80), and the factors associated with infestation were dirt floors (PRa, 5.88; 95% CI, 2.28-10.31), fiber cement roofs (PRa, 1.76; 95% CI, 1.07-2.83), and the presence of canines in peri-domiciliary or intra-domiciliary areas (PRa, 5.05; 95% CI, 3.31-7.19). Seropositivity rates for canines and opossums were 35.62% (26/73) and 100% (6/6), respectively. Identification of these factors will help to implement efficient surveillance programs in Colombia.

Molecular Evolution and Adaptation of Livestock-Associated Methicillin-Resistant Staphylococcus aureus (LA-MRSA) Sequence Type 9.

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) sequence type 9 (ST9) has emerged and disseminated in Asia. It is associated with colonization or infection in both humans and animal hosts; however, the genetic factors underpinning its adaptation to animal and human population remain to be determined. Here, we conducted a genomic analysis of 191 ST9 S. aureus genomes collected from 12 different countries, including 174 genomes retrieved from public databases and 17 sequenced in this study. In silico spa typing, staphylococcal cassette chromosome mec (SCCmec) typing, and antimicrobial resistance and virulence gene mining were conducted, and the temporal phylogenetic signal was assessed by Bayesian inference. Our results point toward a human methicillin-susceptible S. aureus (MSSA) origin of ST9 that evolved approximately 2 centuries ago. Three major genetic events occurred during ST9 host shift from human to animals: the loss of the immune evasion cluster genes (scn, chp, and sak), which were reported to contribute to virulence in human infections, the acquisition of the SaPIbov4-like element-encoding vwb gene, which is an animal-specific virulence factor responsible for the clotting of animal plasma, and the acquisition of antibiotic resistance genes, including SCCmec, quinolone resistance-determining region (QRDR) mutations, and a multidrug resistance genetic element (MDRST9). Evidence of direct transmission of animal-adapted strains to human hosts also suggest that transmission could potentially reshape the resistance and virulence genetic pool in these isolates. The rapid clonal expansion of MDR ST9 strains in mainland China and Taiwan highlights the increasing need for effective surveillance of antibiotic consumption in animal husbandry to control antimicrobial resistance spread. IMPORTANCE Staphylococcus aureus sequence type 9 (ST9) is the main LA-MRSA clone spreading in the Asian continent. It can colonize and cause mild to severe infections both in animal and humans. Previous work described its genotypic characteristics; however, the molecular history of global spread of ST9 strains remains largely unclear. We conducted a detailed analysis of genomic evolution of global ST9 strains and identified key genetic changes associated with its adaptation to specific hosts. Our results suggest that the ST9 clone originated from human-adapted strains, which lost genes related to the evasion of the immune system. The introduction of ST9 strains in animal populations was aligned with the acquisition of animal-specific virulent factors and mobile elements harboring multiple antimicrobial resistance genes, especially in isolates from mainland China and Taiwan.

Housing Conditions Linked to Tick (Ixodida: Ixodidae) Infestation in Rural Areas of Colombia: A Potential Risk for Rickettsial Transmission.

This cross-sectional study explores the different conditions related to the infestation of ticks in households and the potential risks for rickettsial transmission in Urabá, Colombia. The main outcome of interest was villagers' perception of tick infestation. The data were analyzed using a clog-log mixed regression model. Ticks were collected from infested humans to diagnose infection by spotted fever group rickettsiae (SFGR). In addition, a thematic analysis of qualitative data from key informants concerning knowledge about ticks was conducted. The prevalence of infestation of ticks in households was estimated at 60.99% (95% CI: 51.58-93.51). The multivariate model suggested that households with palm leaf roofs (PR = 1.95; 95% CI: 1.19-2.95), canines (PR = 1.76; 95% CI: 1.21-2.46), rats (PR = 2.19; 95% CI: 1.45-3.08), and with the presence of opossums in areas surrounding the households (PR = 1.51; 95% CI: 1.05-2.10) had a higher prevalence of tick infestation. Two samples of the tick species Amblyomma patinoi were found infected with Rickettsia amblyommatis and Candidatus Rickettsia colombianensi. A thematic analysis provided the names that local community members give to ticks, areas where ticks are common, and the individuals at risk of infestation. The presence of domestic, synanthropic, and wild animals suggests a high risk of the dissemination of ticks inside dwellings and close to them in these rural areas.

Risk factors and survival of patients infected with carbapenem-resistant Klebsiella pneumoniae in a KPC endemic setting: a case-control and cohort study.

BACKGROUND: Many gaps in the burden of resistant pathogens exist in endemic areas of low- and middle-income economies, especially those endemic for carbapenem resistance. The aim of this study is to evaluate risk factors for carbapenem-resistance, to estimate the association between carbapenem-resistance and all-cause 30-day mortality and to examine whether mortality is mediated by inappropriate therapy. METHODS: A case-control and a cohort study were conducted in one tertiary-care hospital in Medellín, Colombia from 2014 to 2015. Phenotypic and genotypic characterization of isolates was performed. In the case-control study, cases were defined as patients infected with carbapenem-resistant K. pneumoniae (CRKP) and controls as patients infected with carbapenem-susceptible K. pneumoniae (CSKP). A risk factor analysis was conducted using logistic regression models. In the cohort study, the exposed group was defined as patients infected with CRKP and the non-exposed group as patients infected with CSKP. A survival analysis using an accelerated failure time model with a lognormal distribution was performed to estimate the association between carbapenem resistance and all-cause 30-day-mortality and to examine whether mortality is mediated by inappropriate therapy. RESULTS: A total of 338 patients were enrolled; 49 were infected with CRKP and 289 with CSKP. Among CRKP isolates CG258 (n = 29), ST25 (n = 5) and ST307 (n = 4) were detected. Of importance, every day of meropenem (OR 1.18, 95%CI 1.10-1.28) and cefepime (OR 1.22, 95%CI 1.03-1.49) use increase the risk of carbapenem resistance. Additional risk factors were previous use of ciprofloxacin (OR 2.37, 95%CI 1.00-5.35) and urinary catheter (OR 2.60, 95%CI 1.25-5.37). Furthermore, a significant lower survival time was estimated for patients infected with CRKP compared to CSKP (Relative Times 0.44, 95%CI 0.24-0.82). The strength of association was reduced when appropriate therapy was included in the model (RT = 0.81 95%CI 0.48-1.37). CONCLUSION: Short antibiotic courses had the potential to reduce the selection and transmission of CRKP. A high burden in mortality occurred in patients infected with CRKP in a KPC endemic setting and CRKP leads to increased mortality via inappropriate antibiotic treatment. Furthermore, dissemination of recognized hypervirulent clones could add to the list of challenges for antibiotic resistance control.

Genomic Characterization of VIM Metallo-ß-Lactamase-Producing Alcaligenes faecalis from Gaza, Palestine.

Carbapenemase-producing Gram-negative bacteria (CP-GNB) have increasingly spread worldwide, and different families of carbapenemases have been identified in various bacterial species. Here, we report the identification of five VIM metallo-ß-lactamase-producing Alcaligenes faecalis isolates associated with a small outbreak in a large hospital in Gaza, Palestine. Next-generation sequencing analysis showed blaVIM-2 is harbored by a chromosomal genomic island among three strains, while blaVIM-4 is carried by a novel plasmid in two strains.

Colistin Resistance in Carbapenem-Resistant Klebsiella pneumoniae Mediated by Chromosomal Integration of Plasmid DNA.

Here we describe the spread of colistin resistance in clinical isolates of carbapenem-resistant Klebsiella pneumoniae in Medellín, Colombia. Among 32 isolates collected between 2012 and 2014, 24 showed genetic alterations in mgrB Nineteen isolates belonged to sequence type 512 (ST512) (or its single locus variant [SLV]) and harbored an 8.1-kb hsdMSR insertion corresponding to ISKpn25, indicating a clonal expansion of the resistant strain. The insertion region showed 100% identity to several plasmids, suggesting that the colistin resistance is mediated by chromosomal integration of plasmid DNA.