Antimicrobial Heteroresistance: an Emerging Field in Need of Clarity

“Heteroresistance” describes a phenomenon where subpopulations of seemingly isogenic bacteria exhibit a range of susceptibilities to a particular antibiotic. Unfortunately, a lack of standard methods to determine heteroresistance has led to inappropriate use of this term. Heteroresistance has been recognized since at least 1947 and occurs in Gram-positive and Gram-negative bacteria. Its clinical relevance may be considerable, since more resistant subpopulations may be selected during antimicrobial therapy. However, the use of nonstandard methods to define heteroresistance, which are costly and involve considerable labor and resources, precludes evaluating the clinical magnitude and severity of this phenomenon. We review the available literature on antibiotic heteroresistance and propose recommendations for definitions and determination criteria for heteroresistant bacteria. This will help in assessing the global clinical impact of heteroresistance and developing uniform guidelines for improved therapeutic outcomes

Experience of 170 cases of ductal carcinoma in ' (DCIS)

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Antibiotic capture by bacterial lipocalins uncovers an extracellular mechanism of intrinsic antibiotic resistance

15 p.-6 fig.The potential for microbes to overcome antibiotics of different classes before they reach bacterial cells is largely unexplored. Here we show that a soluble bacterial lipocalin produced by Burkholderia cenocepacia upon exposure to sublethal antibiotic concentrations increases resistance to diverse antibiotics in vitro and in vivo. These phenotypes were recapitulated by heterologous expression in B. cenocepacia of lipocalin genes from Pseudomonas aeruginosa, Mycobacterium tuberculosis,and methicillin-resistant Staphylococcus aureus. Purified lipocalin bound different classes of bactericidal antibiotics and contributed to bacterial survival in vivo. Experimental and X-ray crystal structure-guided computational studies revealed that lipocalins counteract antibiotic action by capturing antibiotics in the extracellular space. We also demonstrated that fat-soluble vitamins prevent antibiotic capture by binding bacterial lipocalin with higher affinity than antibiotics. Therefore, bacterial lipocalins contribute to antimicrobial resistance by capturing diverse antibiotics in the extracellular space at the site of infection, which can be counteracted by known vitamins.This work was funded by grants from Cystic Fibrosis Canada, the European Commission,a Marie Curie Career Integration grant (projects 618095, NONANTIRES), and the Infection and Immunity Translational Research Group, Northern Ireland HSC to M.A.V.;the Spanish Ministry for Economy and Competitiveness (MINECO CTQ2011-22724 and CTQ2014-57141-R), European Commission Marie Curie grants GLYCOPHARM FP7-PITNGA-2012-317297 and TOLLerant H2020-MSC-ETN-642157 to S.M.S.; and Canadian Institutes of Health research grant MOP-49597 and a grant from Cystic Fibrosis Canada to M.E.P.M.Peer reviewe

Identification of na\uefve HCV-1 patients with chronic hepatitis who may benefit from dual therapy with peg-interferon and ribavirin

Background & Aims The pool of HCV genotype 1 patients likely to be cured by peg-interferon and ribavirin remains to be quantified. Methods In 1045 patients treated with peg-interferon and ribavirin, two therapeutic strategies were confronted: the first one evaluated only baseline variables associated with sustained virological response (SVR), and the second one included the rapid virologic response (RVR) in addition to baseline predictors. An 80% SVR rate was the threshold to retain a strategy as clinically relevant. Results Overall, 414 patients (39.6%) attained SVR. In the first strategy, the hierarchy of features independently associated with SVR was IL28B CC genotype (OR 5.082; CI 3.637-7.101), low (80% SVR threshold. Only 26.6% of no-RVR patients attained SVR. Among the 255 RVR patients, the likelihood of SVR was 61.8% in those with unfavorable predictors, 80% in the presence of a single predictor, and 100% when both predictors were present. By using this model, 200 patients (19.1%) were predicted to have an 80% chance of being cured with dual therapy. Conclusions A consistent subset of na\uefve HCV-1 patients, identified by some baseline characteristics and RVR, may benefit from dual treatment with peg-interferon and ribavirin. \ua9 2013 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved

Transcriptional responses of Burkholderia cenocepacia to polymyxin B in isogenic strains with diverse polymyxin B resistance phenotypes

<p>Abstract</p> <p>Background</p> <p><it>Burkholderia cenocepacia </it>is a Gram-negative opportunistic pathogen displaying high resistance to antimicrobial peptides and polymyxins. We identified mechanisms of resistance by analyzing transcriptional changes to polymyxin B treatment in three isogenic <it>B. cenocepacia </it>strains with diverse polymyxin B resistance phenotypes: the polymyxin B-resistant parental strain K56-2, a polymyxin B-sensitive K56-2 mutant strain with heptoseless lipopolysaccharide (LPS) (RSF34), and a derivative of RSF34 (RSF34 4000B) isolated through multiple rounds of selection in polymyxin B that despite having a heptoseless LPS is highly polymyxin B-resistant.</p> <p>Results</p> <p>A heptoseless LPS mutant of <it>B. cenocepacia </it>was passaged through multiple rounds of selection to regain high levels of polymyxin B-resistance. This process resulted in various phenotypic changes in the isolate that could contribute to polymyxin B resistance and are consistent with LPS-independent changes in the outer membrane. The transcriptional response of three <it>B. cenocepacia </it>strains to subinhibitory concentrations of polymyxin B was analyzed using microarray analysis and validated by quantitative Real Time-PCR. There were numerous baseline changes in expression between the three strains in the absence of polymyxin B. In both K56-2 and RSF34, similar transcriptional changes upon treatment with polymyxin B were found and included upregulation of various genes that may be involved in polymyxin B resistance and downregulation of genes required for the synthesis and operation of flagella. This last result was validated phenotypically as both swimming and swarming motility were impaired in the presence of polymyxin B. RSF34 4000B had altered the expression in a larger number of genes upon treatment with polymyxin B than either K56-2 or RSF34, but the relative fold-changes in expression were lower.</p> <p>Conclusions</p> <p>It is possible to generate polymyxin B-resistant isolates from polymyxin B-sensitive mutant strains of <it>B. cenocepacia</it>, likely due to the multifactorial nature of polymyxin B resistance of this bacterium. Microarray analysis showed that <it>B. cenocepacia </it>mounts multiple transcriptional responses following exposure to polymyxin B. Polymyxin B-regulated genes identified in this study may be required for polymyxin B resistance, which must be tested experimentally. Exposure to polymyxin B also decreases expression of flagellar genes resulting in reduced swimming and swarming motility.</p

A half-site multimeric enzyme achieves its cooperativity without conformational changes

Cooperativity is a feature many multimeric proteins use to control activity. Here we show that the bacterial heptose isomerase GmhA displays homotropic positive and negative cooperativity among its four protomers. Most similar proteins achieve this through conformational changes: GmhA instead employs a delicate network of hydrogen bonds, and couples pairs of active sites controlled by a unique water channel. This network apparently raises the Lewis acidity of the catalytic zinc, thus increasing the activity at one active site at the cost of preventing substrate from adopting a reactive conformation at the paired negatively cooperative site – a “half-site” behavior. Our study establishes the principle that multimeric enzymes can exploit this cooperativity without conformational changes to maximize their catalytic power and control. More broadly, this subtlety by which enzymes regulate functions could be used to explore new inhibitor design strategies

Metabolic disorders across hepatocellular carcinoma in Italy

BACKGROUND: Metabolic disorders are well-known risk factors for HCC. Conversely, their impact on the natural history of HCC is not established. This study aimed at evaluating the impact of metabolic disorders on clinical features, treatment and survival of HCC patients regardless of its aetiology. METHODS: We analysed the ITA.LI.CA database regarding 839 HCC patients prospectively collected. The following metabolic features were analysed: BMI, diabetes, arterial hypertension, hypercholesterolaemia and hypertriglyceridaemia. According to these features, patients were divided into 3 groups: 0-1, 2 and 3-5 metabolic features. RESULTS: As compared with patients with 0-1 metabolic features, patients with 3-5 features showed lower percentage of HCC diagnosis on surveillance (P = .021), larger tumours (P = .038), better liver function (higher percentage of Child-Pugh class A [P = .007] and MELD &lt; 10 [P = .003]), higher percentage of metastasis (P = .024) and lower percentage of portal vein thrombosis (P = .010). The BCLC stage and treatment options were similar among the 3 groups, with the exception of a less frequent access to loco-regional therapies for BCLC stage B patients with 3-5 features (P = .012). Overall survival and survival according to BCLC stage and/or treatment did not significantly differ among the 3 groups. Only using a probabilistic sensitivity analysis, diabetic patients showed a lower survival (P = .046). MELD score, HCC morphology, nodule size, BCLC stage, portal vein thrombosis and metastasis were independent predictors of lead-time adjusted survival. CONCLUSIONS: Our "real world" study suggests that metabolic disorders shape the clinical presentation of HCC but do not seem to play a major role in setting patient survival.Background: Metabolic disorders are well-known risk factors for HCC. Conversely, their impact on the natural history of HCC is not established. This study aimed at evaluating the impact of metabolic disorders on clinical features, treatment and survival of HCC patients regardless of its aetiology. Methods: We analysed the ITA.LI.CA database regarding 839 HCC patients prospectively collected. The following metabolic features were analysed: BMI, diabetes, arterial hypertension, hypercholesterolaemia and hypertriglyceridaemia. According to these features, patients were divided into 3 groups: 0-1, 2 and 3-5 metabolic features. Results: As compared with patients with 0-1 metabolic features, patients with 3-5 features showed lower percentage of HCC diagnosis on surveillance (P&nbsp;=.021), larger tumours (P&nbsp;=.038), better liver function (higher percentage of Child-Pugh class A [P&nbsp;=.007] and MELD&nbsp;&lt;&nbsp;10 [P&nbsp;=.003]), higher percentage of metastasis (P&nbsp;=.024) and lower percentage of portal vein thrombosis (P&nbsp;=.010). The BCLC stage and treatment options were similar among the 3 groups, with the exception of a less frequent access to loco-regional therapies for BCLC stage B patients with 3-5 features (P&nbsp;=.012). Overall survival and survival according to BCLC stage and/or treatment did not significantly differ among the 3 groups. Only using a probabilistic sensitivity analysis, diabetic patients showed a lower survival (P&nbsp;=.046). MELD score, HCC morphology, nodule size, BCLC stage, portal vein thrombosis and metastasis were independent predictors of lead-time adjusted survival. Conclusions: Our \u201creal world\u201d study suggests that metabolic disorders shape the clinical presentation of HCC but do not seem to play a major role in setting patient survival