Distinct Resistance Profiles Research Articles

Surveillance of multi-drug resistance phenotypes in Staphylococcus aureus in Japan and correlation with whole-genome sequence findings

Antimicrobial resistance in Staphylococcus aureus imposes a high disease burden. Both phenotypic and genotypic monitoring are key to understanding and containing emerging resistant strains. Phenotypic monitoring of emerging resistance in S.aureus and correlation of priority strain phenotypes with whole-genome sequencing (WGS) findings. Antimicrobial susceptibility test results of >40,000 isolates from 213 participating hospitals from 2011 to 2019 were exported from the national Japan Nosocomial Infections Surveillance (JANIS) database. Longitudinal and geographic distribution and prevalence of distinct multi-drug resistance phenotypes ('resistance profiles') of S.aureus were examined among hospitals and prefectures. We further conducted a genome sequence analysis of strains with specific resistance profiles of concern. The overall prevalence of meticillin-resistant S.aureus (MRSA) decreased from 40.3% to 35.1% from 2011 to 2019. However, among dozens of S.aureus resistance profiles, only one profile of a type of MRSA, exhibited a statistically significant increase in inpatient frequency, exceeding 10% during the nine years. This MRSA profile showed resistance to oxacillin, erythromycin and levofloxacin. Analysis of WGS results of S.aureus isolates with this phenotype revealed that most belonged to clonal complex 8, and all carried SCCmec IV, typical of community-acquired MRSA. Tracking distinct resistance profiles deepened our understanding of the overall decrease in MRSA and led to recognition of the emergence of a new resistance phenotype. This study provides a model for future epidemiological research on antimicrobial resistance correlating multi-drug resistance phenotypes with selective genome sequencing, which can be applied to other bacterial species.

The Regulation of ManLAM-Related Gene Expression in Mycobacterium tuberculosis with Different Drug Resistance Profiles Following Isoniazid Treatment.

IntroductionTuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) remains a global health concern because of the development of drug resistance. The adaptability of MTB in response to a variety of environmental stresses is a crucial strategy that supports their survival and evades host defense mechanisms. Stress regulates gene expression, particularly virulence genes, leading to the development of drug tolerance. Mannose-capped lipoarabinomannan (ManLAM) is a critical component of the cell wall, functions as a virulence factor and influences host defense mechanisms.PurposeThis study focuses on the effect of isoniazid (INH) stress on the regulation of ManLAM-related genes, to improve our understanding of virulence and drug resistance development in MTB.Materials and MethodsMTB with distinct drug resistance profiles were used for gene expression analysis. Multiplex-real time PCR assay was performed to monitor stress-related genes (hspX, tgs1, and sigE). The expression levels of ManLAM-related genes (pimB, mptA, mptC, dprE1, dprE2, and embC) were quantified by qRT-PCR. Sequence analysis of drug resistance-associated genes (inhA, katG, and rpoB) and ManLAM-related genes were performed to establish a correlation between genetic variation and gene expression.ResultsINH treatment activates the stress response mechanism in MTB, resulting in a distinct gene expression pattern between drug resistance and drug-sensitive TB. In response to INH, hspX was up-regulated in RIF-R and MDR. tgs1 was strongly up-regulated in MDR, whereas sigE was dramatically up-regulated in the drug-sensitive TB. Interestingly, ManLAM-related genes were most up-regulated in drug resistance, notably MDR (pimB, mptA, dprE1, and embC), implying a role for drug resistance and adaptability of MTB via ManLAM modulation.ConclusionThis study establishes a relationship between the antibiotic stress response mechanism and the expression of ManLAM-related genes in MTB samples with diverse drug resistance profiles. The novel gene expression pattern in this work is valuable knowledge that can be applied for TB monitoring and treatment in the future.

Distribution of virulence determinants in Streptococcus agalactiae recovered from different clinical sources

Streptococcus agalactiae (group B Streptococcus, GBS) is a pathobiont, a member of human microbiota that can change from commensal to pathogen, causing a large spectrum of diseases. This study assessed virulence determinants of 32 GBS isolates recovered from different clinical sources associated with asymptomatic and symptomatic clinical outcomes that present distinct capsular types and antimicrobial resistance profiles. The ability of a unique strain to colonize and cause infection in different subjects was also evaluated. By PFGE analysis, it was observed that a given strain could be associated with both asymptomatic and symptomatic outcomes. Cell wall anchor proteins β and alpha C encoding genes (bac and bca, respectively) were detected in all capsular type Ib isolates. bca was more frequent among asymptomatic outcome-related isolates, as well as high expression of β-hemolysin/cytolysin (β-H/C). Symptomatic outcome-related isolates produced strong biofilm more frequently. All bacterial isolates recovered from urine were strong biofilm producers. In growth experiments, asymptomatic outcome-related isolates grew faster after 2 h until the end of the log phase. Taken together, these findings show virulence genotypic and phenotypic features of GBS from distinct sources, which may be helpful to understand their pathogenic potential and predict different clinical outcomes.

Histone-like nucleoid-structuring protein (H-NS) regulatory role in antibiotic resistance in Acinetobacter baumannii

In the multidrug resistant (MDR) pathogen Acinetobacter baumannii the global repressor H-NS was shown to modulate the expression of genes involved in pathogenesis and stress response. In addition, H-NS inactivation results in an increased resistance to colistin, and in a hypermotile phenotype an altered stress response. To further contribute to the knowledge of this key transcriptional regulator in A. baumannii behavior, we studied the role of H-NS in antimicrobial resistance. Using two well characterized A. baumannii model strains with distinctive resistance profile and pathogenicity traits (AB5075 and A118), complementary transcriptomic and phenotypic approaches were used to study the role of H-NS in antimicrobial resistance, biofilm and quorum sensing gene expression. An increased expression of genes associated with β-lactam resistance, aminoglycosides, quinolones, chloramphenicol, trimethoprim and sulfonamides resistance in the Δhns mutant background was observed. Genes codifying for efflux pumps were also up-regulated, with the exception of adeFGH. The wild-type transcriptional level was restored in the complemented strain. In addition, the expression of biofilm related genes and biofilm production was lowered when the transcriptional repressor was absent. The quorum network genes aidA, abaI, kar and fadD were up-regulated in Δhns mutant strains. Overall, our results showed the complexity and scope of the regulatory network control by H-NS (genes involved in antibiotic resistance and persistence). These observations brings us one step closer to understanding the regulatory role of hns to combat A. baumannii infections.

Discovery of Novel Dihydrothiopyrano[4,3-d]pyrimidine Derivatives as Potent HIV-1 NNRTIs with Significantly Reduced hERG Inhibitory Activity and Improved Resistance Profiles.

Enlightened by the available structural biology information, a novel series of dihydrothiopyrano[4,3-d]pyrimidine derivatives were rationally designed via scaffold hopping and molecular hybridization strategies. Notably, compound 20a yielded exceptionally potent antiviral activities (EC50 = 4.44-54.5 nM) against various HIV-1 strains and improved resistance profiles (RF = 0.5-5.6) compared to etravirine and rilpivirine. Meanwhile, 20a exhibited reduced cytotoxicity (CC50 = 284 μM) and higher SI values (SI = 5210-63992). Molecular dynamics simulations were performed to rationalize the distinct resistance profiles. Besides, 20a displayed better solubility (sol. = 12.8 μg/mL) and no significant inhibition of the main CYP enzymes. Furthermore, 20a was characterized for prominent metabolic stability and in vivo safety properties. Most importantly, the hERG inhibition profile of 20a (IC50 = 19.84 μM) was a remarkable improvement. Overall, 20a possesses huge potential to serve as a promising drug candidate due to its excellent potency, low toxicity, and favorable drug-like properties.

Genomic molecular signatures determined characterization of Mycolicibacterium gossypii sp. nov., a fast-growing mycobacterial species isolated from cotton field soil.

A Gram-positive, acid-fast and rapidly growing rod, designated S2-37T, that could form yellowish colonies was isolated from one soil sample collected from cotton cropping field located in the Xinjiang region of China. Genomic analyses indicated that strain S2-37T harbored T7SS secretion system and was very likely able to produce mycolic acid, which were typical features of pathogenetic mycobacterial species. 16S rRNA-directed phylogenetic analysis referred that strain S2-37T was closely related to bacterial species belonging to the genus Mycolicibacterium, which was further confirmed by pan-genome phylogenetic analysis. Digital DNA-DNA hybridization and the average nucleotide identity presented that strain S2-37T displayed the highest values of 39.1% (35.7-42.6%) and 81.28% with M. litorale CGMCC 4.5724T, respectively. And characterization of conserved molecular signatures further supported the taxonomic position of strain S2-37T belonging to the genus Mycolicibacterium. The main fatty acids were identified as C16:0, C18:0, C20:3ω3 and C22:6ω3. In addition, polar lipids profile was mainly composed of diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol. Phylogenetic analyses, distinct fatty aids and antimicrobial resistance profiles indicated that strain S2-37T represented genetically and phenotypically distinct from its closest phylogenetic neighbour, M. litorale CGMCC 4.5724T. Here, we propose a novel species of the genus Mycolicibacterium: Mycolicibacterium gossypii sp. nov. with the type strain S2-37T (= JCM 34327T = CGMCC 1.18817T).

Exploring of paritaprevir and glecaprevir resistance due to A156T mutation of HCV NS3/4A protease: molecular dynamics simulation study

Hepatitis C virus (HCV) NS3/4A serine protease is a promising drug target for the discovery of anti-HCV drugs. However, its amino acid mutations, particularly A156T, commonly lead to rapid emergence of drug resistance. Paritaprevir and glecaprevir, the newly FDA-approved HCV drugs, exhibit distinct resistance profiles against the A156T mutation of HCV NS3/4A serine protease. To illustrate their different molecular resistance mechanisms, molecular dynamics simulations and binding free energy calculations were carried out on the two compounds complexed with both wild-type (WT) and A156T variants of HCV NS3/4A protease. QM/MM-GBSA-based binding free energy calculations revealed that the binding affinities of paritaprevir and glecaprevir towards A156T NS3/4A were significantly reduced by ∼4 kcal/mol with respect to their WT complexes, which were in line with the experimental resistance folds. Moreover, the relatively weak intermolecular interactions with amino acids such as H57, R155, and T156 of NS3 protein, the steric effect and the destabilized protein binding surface, which is caused by the loss of salt bridge between R123 and D168, are the main contributions for the higher fold-loss in potency of glecaprevir due to A156T mutation. An insight into the difference of molecular mechanism of drug resistance against the A156T substitution among the two classes of serine protease inhibitors could be useful for further optimization of new generation HCV NS3/4A inhibitors with enhanced inhibitory potency. Communicated by Ramaswamy H. Sarma

The problem of global development of antibiotic resistant nosocomial pathogens

The problem of global expansion of multidrug-resistant nosocomial infections pathogens is under special attention at the moment. Antibiotic resistance increasing give us the limited treatment options. This problem is particularly acute for transplant clinics, because of patients need lifelong immunosuppressive therapy. From the one hand this ensures stable allograft functioning, but from the other increases the risk of severe infectious complications in the postoperative period. The purpose of this article is analysis carbapenem resistance dynamics of Klebsiella spp., Acinetobacter spp., Pseudomonas spp. and Staphylococcus spp. isolated from the blood of recipients of donor organs from 2009 to 2019 in the Shumakov National Medical Research Center of Transplantology and Artificial Organs. A significant annual decrease of carbapenem-sensitive strains of Klebsiella spp. and Acinetobacter spp. are shown. The study of a distinctive pathogen resistance profile specific to each institution can help one in selecting an adequate antimicrobial strategy and is an effective predictive tool for controlling the growth of multidrug-resistant microorganisms.

3 Oral - USP1 inhibitors show robust combination activity and a distinct resistance profile from PARP inhibitors

3 Oral - USP1 inhibitors show robust combination activity and a distinct resistance profile from PARP inhibitors

Review of Doravirine Resistance Patterns Identified in Participants During Clinical Development.

Background:Doravirine (DOR) is a novel non-nucleoside reverse transcriptase inhibitor (NNRTI) approved for the treatment of HIV-1 infection in patients with no known DOR resistance-associated mutations. DOR was rationally designed to address limitations associated with other approved NNRTIs, particularly resistance from common NNRTI resistance-associated mutants containing K103N, Y181C, or G190A reverse transcriptase substitutions.Setting:Data to date from both in vitro studies and clinical trials have been compiled to summarize the resistance profile of DOR.Methods:We analyzed data from in vitro studies and phase 2 and 3 trials to assess the emergence of resistance-associated mutations and their impact on efficacy among participants treated with DOR.Results:DOR exhibited a distinct resistance profile compared with efavirenz and rilpivirine in vitro and in vivo; mutant viruses that were resistant to DOR showed limited cross-resistance to efavirenz and rilpivirine. In clinical trials, the development of DOR resistance-associated substitutions in reverse transcriptase was uncommon.Conclusion:Overall, minimal cross-resistance across NNRTIs was observed for DOR and limited development of DOR-related resistance. These data should assist clinicians in further understanding the resistance profile of DOR, so appropriate treatment decisions can be made for their patients.

Occurrence and Diversity of Intra- and Interhospital Drug-Resistant and Biofilm-Forming Acinetobacter baumannii and Pseudomonas aeruginosa.

Acinetobacter baumannii and Pseudomonas aeruginosa are the most relevant Gram-negative bacteria associated with hospital and opportunistic infections. This study aimed to evaluate the dynamics of drug-resistant A. baumannii and P. aeruginosa and biofilm formers from two public hospitals in northeastern Brazil. One hundred isolates (35 from A. baumannii and 65 from P. aeruginosa) were identified using the automated Vitek®2 Compact method (bioMérieux) and confirmed using the MALDI-TOF (MS) mass spectrometry technique. Molecular experiments were performed by polymerase chain reaction (PCR) to detect the frequency of blaKPC, blaIMP, blaVIM, and blaSHV genes. The biofilm formation potential was evaluated using crystal violet in Luria Bertani Miller and trypticase soy broth culture media under the following conditions: at standard concentration, one quarter (25%) of the standard concentration and supplemented with 1% glucose. In addition, the genetic diversity of the isolates was verified by the ERIC-PCR technique. Isolates presented distinct resistance profiles with a high level of beta-lactam resistance. The highest index of genes detected was blaKPC (60%), followed by blaSHV (39%), blaVIM (8%), and blaIMP (1%). All the isolates were sensitive to the polymyxins tested and formed biofilms at different intensities. Twelve clones of A. baumannii and eight of P. aeruginosa were identified, of which few were indicative of intra- and interhospital dissemination. This study reveals the dispersion dynamics of these isolates in the hospital environment. The results demonstrate the importance of monitoring programs to combat the spread of these pathogens.

An Outbreak of Carbapenem-Resistant and Hypervirulent Klebsiella pneumoniae in an Intensive Care Unit of a Major Teaching Hospital in Wenzhou, China.

Carbapenem-resistant, hypervirulent Klebsiella pneumoniae (CR-hvKP) has recently emerged as a significant threat to public health. In this study, 29 K. pneumoniae isolates were isolated from eight patients admitted to the intensive care unit (ICU) of a comprehensive teaching hospital located in China from March 2017 to January 2018. Clinical information of patients was the basis for the further analyses of the isolates including antimicrobial susceptibility tests, identification of antibiotic resistance and virulence gene determinants, multilocus sequence typing (MLST), XbaI-macrorestriction by pulsed-field gel electrophoresis (PFGE). Selected isolates representing distinct resistance profiles and virulence phenotypes were screened for hypervirulence in a Galleria mellonella larvae infection model. In the course of the outbreak, the overall mortality rate of patients was 100% (n = 8) attributed to complications arising from CR-hvKP infections. All isolates except one (28/29, 96.6%) were resistant to multiple antimicrobial agents, and harbored diverse resistance determinants that included the globally prevalent carbapenemase blaKPC−2. Most isolates had hypervirulent genotypes being positive for 19 virulence-associated genes, including iutA (25/29, 86.2%), rmpA (27/29, 93.1%), ybtA (27/29, 93.1%), entB (29/29, 100%), fimH (29/29, 100%), and mrkD (29/29, 100%). MLST revealed ST11 for the majority of isolates (26/29, 89,7%). Infection assays demonstrated high mortality in the Galleria mellonella model with the highest LD50 values for three isolates (<105 CFU/mL) demonstrating the degree of hypervirulence of these CR-hvKP isolates, and is discussed relative to previous outbreaks of CR-hvKP.

ATP-Competitive Inhibitors Midostaurin and Avapritinib Have Distinct Resistance Profiles in Exon 17-Mutant KIT.

KIT is a type-3 receptor tyrosine kinase that is frequently mutated at exon 11 or 17 in a variety of cancers. First-generation KIT tyrosine kinase inhibitors (TKI) are ineffective against KIT exon 17 mutations, which favor an active conformation that prevents these TKIs from binding. The ATP-competitive inhibitors, midostaurin and avapritinib, which target the active kinase conformation, were developed to inhibit exon 17-mutant KIT. Because secondary kinase domain mutations are a common mechanism of TKI resistance and guide ensuing TKI design, we sought to define problematic KIT kinase domain mutations for these emerging therapeutics. Midostaurin and avapritinib displayed different vulnerabilities to secondary kinase domain substitutions, with the T670I gatekeeper mutation being selectively problematic for avapritinib. Although gatekeeper mutations often directly disrupt inhibitor binding, we provide evidence that T670I confers avapritinib resistance indirectly by inducing distant conformational changes in the phosphate-binding loop. These findings suggest combining midostaurin and avapritinib may forestall acquired resistance mediated by secondary kinase domain mutations. SIGNIFICANCE: This study identifies potential problematic kinase domain mutations for next-generation KIT inhibitors midostaurin and avapritinib.

Phylogeny, sequence-typing and virulence profile of uropathogenic Escherichia coli (UPEC) strains from Pakistan

BackgroundEscherichia coli lineage ST131 predominates across various spectra of extra-intestinal infections, including urinary tract infection (UTI). The distinctive resistance profile, diverse armamentarium of virulence factors and rapid global dissemination of ST131 E. coli makes it an intriguing pathogen. However, not much is known about the prevalence and genetic attributes of ST131 lineage in Pakistan.MethodsWe estimated prevalence and genetic attributes of E. coli ST131 isolates causing UTI among 155 randomly selected samples. Samples were analyzed for phylogenetic grouping, O-typing and fumC/fimH typing. Isolates were further tested for the ESBL and virulence factors using PCR.ResultsOverall, 59% of the UPEC isolates belonged to the phylogenetic group B2, followed by D = 28%, B1 = 8% and A = 5%. Among 18 different Sequence-types, ST131 was the dominant lineage (n = 71; 46%) out of which 72% of the isolates were assigned to the phylogenetic group B2, while 61% adhered to the serogroup O25b. FumC/fimH typing confirmed 49% of the ST131 as H30 sub-types. In this study, significant numbers of the identified ST131 isolates were MDR and 42% showed ESBL phenotypes, out of which 37% carried bla-CTX-M-15. Moreover, different virulence factors were detected in following percentages: fimH,155(100%), iutA 86 (55%), feoB 76 (49%), papC 75 (48%), papGII 70 (45%), kpsMTII 40 (26%), papEF 37 (24%), fyuA 37 (24%), usp 22 (14%), papA 20 (13%), sfa/foc20 (13%), hlyA 18 (12%), afa 15 (10%), cdtB 11 (7%), papGI 6 (4%), papGIII 6 (4%), kpsMTIII 4 (3%) and bmaE2 (1%).ConclusionConclusively, this study provides important insight into the genetic and virulence attributes of pandemic MDR ST131 strains involved in UTIs. It also highlights higher prevalence of ST131-O25b-H30 UPEC isolates in patients, which was previously unreported from this part of globe.

Antimicrobial agent susceptibilities of Legionella pneumophila MLVA-8 genotypes

Legionella pneumophila causes human lung infections resulting in severe pneumonia. High-resolution genotyping of L. pneumophila isolates can be achieved by multiple-locus variable-number tandem-repeat analysis (MLVA-8). Legionella infections in humans occur as a result of inhalation of bacteria-containing aerosols, thus, our aim was to study the antimicrobial susceptibilities of different MLVA-8 genotypes to ten commonly used antimicrobial agents in legionellosis therapy. Epidemiological cut-off values were determined for all antibiotics. Significant differences were found between the antimicrobial agents’ susceptibilities of the three studied environmental genotypes (Gt4, Gt6, and Gt15). Each genotype exhibited a significantly different susceptibility profile, with Gt4 strains (Sequence Type 1) significantly more resistant towards most studied antimicrobial agents. In contrast, Gt6 strains (also Sequence Type 1) were more susceptible to six of the ten studied antimicrobial agents compared to the other genotypes. Our findings show that environmental strains isolated from adjacent points of the same water system, exhibit distinct antimicrobial resistance profiles. These differences highlight the importance of susceptibility testing of Legionella strains. In Israel, the most extensively used macrolide for pneumonia is azithromycin. Our results point at the fact that clarithromycin (another macrolide) and trimethoprim with sulfamethoxazole (SXT) were the most effective antimicrobial agents towards L. pneumophila strains. Moreover, legionellosis can be caused by multiple L. pneumophila genotypes, thus, the treatment approach should be the use of combined antibiotic therapy. Further studies are needed to evaluate specific antimicrobial combinations for legionellosis therapy.

Antimicrobial Resistance Profiles of Nosocomial Pathogens in Regional China: A Brief Report from Two Tertiary Hospitals in China.

BackgroundAntimicrobial resistance of nosocomial pathogens has become a worldwide problem that leads to major healthcare and economic burdens. Regional antimicrobial resistance profiles are needed to inform selection of proper antimicrobial agents.Material/MethodsIn collaboration with the Hospital Infection Control Office at our hospitals, we analyzed the constitution of nosocomial pathogens and the corresponding drug-resistance profiles. We paid particular attention to characteristics of pathogens that were derived from the bloodstream, and summarized the drug-resistance tendency of 2 specific bacteria within the most recent decade to reflect the development of resistance in regional China.ResultsThe most common types of nosocomial pathogens were Escherichia coli (859 isolates, 14.3%), Staphylococcus aureus (763 isolates, 12.7%), Acinetobacter baumannii (681 isolates, 11.3%), Klebsiella pneumonia (660 isolates, 11.0%), and Pseudomonas aeruginosa (654 isolates, 10.9%). The most common types of bloodstream-derived pathogens were K. pneumoniae (125 isolates, 16.3%), E. coli (118 isolates, 15.3%), A. baumanii (81 isolates, 10.5%), Candida albians (57 isolates, 7.4%), S. aureus (45 isolates, 5.9%), P. aeruginosa (44 isolates, 5.7%), and Enterobacterium spp. (42 isolates, 5.5%). Distinct antimicrobial resistance profiles were observed between different pathogens as well as between bloodstream-derived and other sources of pathogens. The resistant rates of A. baumanii and P. aeruginosa to antimicrobial agents have been increasing during the most recent 10 years at our hospital.ConclusionsOur data demonstrated the characteristics of nosocomial infections and antibiotic resistance in regional China. The distinct resistance profile of each pathogen can help to tailor individual antimicrobial strategy. The emerging resistant rates to antimicrobials require reinforced actions for infection prevention and control.

Acquired Resistance to a MET Antibody In Vivo Can Be Overcome by the MET Antibody Mixture Sym015.

Failure of clinical trials due to development of resistance to MET-targeting therapeutic agents is an emerging problem. Mechanisms of acquired resistance to MET tyrosine kinase inhibitors are well described, whereas characterization of mechanisms of resistance toward MET-targeting antibodies is limited. This study investigated mechanisms underlying in vivo resistance to two antibody therapeutics currently in clinical development: an analogue of the MET-targeting antibody emibetuzumab and Sym015, a mixture of two antibodies targeting nonoverlapping epitopes of MET. Upon long-term in vivo treatment of a MET-amplified gastric cancer xenograft model (SNU-5), emibetuzumab-resistant, but not Sym015-resistant, tumors emerged. Resistant tumors were isolated and used to establish resistant cell lines. Characterization of both tumors and cell lines using extensive protein and signaling pathway activation mapping along with next-generation sequencing revealed two distinct resistance profiles, one involving PTEN loss and the other involving activation of the PI3K pathway, likely via MYC and ERBB3 copy number gains. PTEN loss left one model unaffected by PI3K/AKT targeting but sensitive to mTOR targeting, while the PI3K pathway-activated model was partly sensitive to targeting of multiple PI3K pathway proteins. Importantly, both resistant models were sensitive to treatment with Sym015 in vivo due to antibody-dependent cellular cytotoxicity-mediated tumor growth inhibition, MET degradation, and signaling inhibition. Taken together, our data provide key insights into potential mechanisms of resistance to a single MET-targeting antibody, demonstrate superiority of Sym015 in preventing acquired resistance, and confirm Sym015 antitumor activity in tumors resistant to a single MET antibody. Mol Cancer Ther; 17(6); 1259-70. ©2018 AACR.

Diversity of Staphylococcus pseudintermedius in carriage sites and skin lesions of dogs with superficial bacterial folliculitis: potential implications for diagnostic testing and therapy.

Staphylococcus pseudintermedius is genotypically diverse within the canine population and multiple strains may colonize individual dogs at any given time. If multiple strains with distinct antimicrobial resistance profiles are present in superficial bacterial folliculitis (SBF), sampling a single skin lesion for culture and antimicrobial susceptibility testing (AST) might be inadequate to select effective therapy. To investigate S. pseudintermedius diversity in carriage sites and lesions of dogs with SBF. Fourteen dogs with SBF. Staphylococcus pseudintermedius isolates obtained from perineum, gingiva and four to six skin lesions per dog were subjected to pulsed-field gel electrophoresis (PFGE) and AST to assess diversity between lesions. For two dogs, 14-16 isolates per lesion were included in the analysis to assess diversity within lesions. Analysis of one isolate per lesion revealed one to four strains displaying unique PFGE profiles, and up to three unique antimicrobial resistance (AMR) profiles for each dog. Multiple pustules from the same dog always harboured the same strain, whereas papules, crusts and collarettes did not. Up to four strains with distinct AMR profiles were isolated from the same lesion in two dogs. In 12 dogs, at least one carriage site strain also was represented in lesions. Lesions of SBF may harbour multiple S. pseudintermedius strains with distinct antimicrobial resistance profiles. Pustules are the best target for bacterial culture. It remains unclear whether isolation of different strains from other lesion types is a consequence of contamination or co-infection by multiple strains.

Spread of Plasmid-Encoded NDM-1 and GES-5 Carbapenemases among Extensively Drug-Resistant and Pandrug-Resistant Clinical Enterobacteriaceae in Durban, South Africa.

Whole-genome sequence analyses revealed the presence of blaNDM-1 (n = 31), blaGES-5 (n = 8), blaOXA-232 (n = 1), or blaNDM-5 (n = 1) in extensively drug-resistant and pandrug-resistant Enterobacteriaceae organisms isolated from in-patients in 10 private hospitals (2012 to 2013) in Durban, South Africa. Two novel NDM-1-encoding plasmids from Klebsiella pneumoniae were circularized by PacBio sequencing. In p19-10_01 [IncFIB(K); 223.434 bp], blaNDM-1 was part of a Tn1548-like structure (16.276 bp) delineated by IS26 The multireplicon plasmid p18-43_01 [IncR_1/IncFIB(pB171)/IncFII(Yp); 212.326 bp] shared an 80-kb region with p19-10_01, not including the blaNDM-1-containing region. The two plasmids were used as references for tracing NDM-1-encoding plasmids in the other genome assemblies. The p19-10_01 sequence was detected in K. pneumoniae (n = 7) only, whereas p18-43_01 was tracked to K. pneumoniae (n = 4), Klebsiella michiganensis (n = 1), Serratia marcescens (n = 11), Enterobacter spp. (n = 7), and Citrobacter freundii (n = 1), revealing horizontal spread of this blaNDM-1-bearing plasmid structure. Global phylogeny showed clustering of the K. pneumoniae (18/20) isolates together with closely related carbapenemase-negative ST101 isolates from other geographical origins. The South African isolates were divided into three phylogenetic subbranches, where each group had distinct resistance and replicon profiles, carrying either p19-10_01, p18-10_01, or pCHE-A1 (8,201 bp). The latter plasmid carried blaGES-5 and aacA4 within an integron mobilization unit. Our findings imply independent plasmid acquisition followed by local dissemination. Additionally, we detected blaOXA-232 carried by pPKPN4 in K. pneumoniae (ST14) and blaNDM-5 contained by a pNDM-MGR194-like genetic structure in Escherichia coli (ST167), adding even more complexity to the multilayer molecular mechanisms behind nosocomial spread of carbapenem-resistant Enterobacteriaceae in Durban, South Africa.

Two different R gene loci co-evolved with Avr2 of Phytophthora infestans and confer distinct resistance specificities in potato.

Late blight, caused by the oomycete pathogen Phytophthora infestans, is the most devastating disease in potato. For sustainable management of this economically important disease, resistance breeding relies on the availability of resistance (R) genes. Such R genes against P. infestans have evolved in wild tuber-bearing Solanum species from North, Central and South America, upon co-evolution with cognate avirulence (Avr) genes. Here, we report how effectoromics screens with Avr2 of P. infestans revealed defense responses in diverse Solanum species that are native to Mexico and Peru. We found that the response to AVR2 in the Mexican Solanum species is mediated by R genes of the R2 family that resides on a major late blight locus on chromosome IV. In contrast, the response to AVR2 in Peruvian Solanum species is mediated by Rpi-mcq1, which resides on chromosome IX and does not belong to the R2 family. The data indicate that AVR2 recognition has evolved independently on two genetic loci in Mexican and Peruvian Solanum species, respectively. Detached leaf tests on potato cultivar ‘Désirée’ transformed with R genes from either the R2 or the Rpi-mcq1 locus revealed an overlapping, but distinct resistance profile to a panel of 18 diverse P. infestans isolates. The achieved insights in the molecular R – Avr gene interaction can lead to more educated exploitation of R genes and maximize the potential of generating more broad-spectrum, and potentially more durable control of the late blight disease in potato.