Antimicrob Agents Chemother Research Articles

Corrigendum.

[This corrects the article DOI: 10.1177/2049936117690501.].

Activation of Stimulator of Interferon Genes in Hepatocytes Suppresses the Replication of Hepatitis B Virus.

Induction of interferon and proinflammatory cytokines is a hallmark of the infection of many different viruses. However, hepatitis B virus (HBV) does not elicit a detectable cytokine response in infected hepatocytes. In order to investigate the molecular mechanism underlying the innate immune evasion, a functional cyclic GMP-AMP (cGAMP) synthase (cGAS)-stimulator of interferon genes (STING) pathway was reconstituted in a human hepatoma cell line supporting tetracycline-inducible HBV replication. It was demonstrated that induction of HBV replication neither activated nor inhibited this cytosolic DNA sensing pathway. However, human hepatoma cells, as well as immortalized mouse hepatocytes, express low levels of STING, which upon activation by cGAMP, the natural ligand of STING, led to induction of a proinflammatory cytokine response. Treatment of immortalized mouse hepatocytes supporting HBV replication with either cGAMP or a small molecule pharmacologic STING agonist significantly reduced viral DNA in a STING- and Janus kinase 1-dependent manner. Moreover, cGAMP treatment was able to induce inflammatory cytokine gene expression and inhibit the transcription of covalently closed circular DNA in HBV-infected human hepatoma cells expressing sodium taurocholate cotransporting polypeptide, an essential receptor for HBV infection of hepatocytes. The studies reported here and previously (F. Guo et al., Antimicrob Agents Chemother 59:1273-1281, 2015, https://doi.org/10.1128/AAC.04321-14) thus support the notion that pharmacological activation of STING in macrophages and hepatocytes induces host innate responses that can efficiently control HBV replication. Hence, despite not playing a significant role in host innate immune response to HBV infection of hepatocytes, STING is potentially a valuable target for immunotherapy of chronic hepatitis B.

Pharmacodynamics of Cefepime Combined with Tazobactam against Clinically Relevant Enterobacteriaceae in a Neutropenic Mouse Thigh Model.

The lack of new antibiotics has prompted investigation of the combination of two existing agents-cefepime, a broad-spectrum cephalosporin, and tazobactam-to broaden their efficacy against extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae We determined the pharmacokinetic (PK) and pharmacodynamic (PD) properties of the combination in a murine neutropenic thigh model in order to establish its exposure-response relationships (ERRs). The PK of cefepime were determined for five doses; that of tazobactam was determined in earlier studies (Melchers et al., Antimicrob Agents Chemother 59:3373-3376, 2015, https://doi.org/10.1128/AAC.04402-14). The PK were linear for both compounds. The estimated mean (standard deviation [SD]) half-life of cefepime was 0.33 (0.12) h, and that of tazobactam was 0.176 (0.026) h; the volumes of distribution (V) were 0.73 liters/kg and 1.14 liters/kg, respectively. PD studies of cefepime administered every 2 h (q2h) with or without tazobactam, including dose fractionation studies of tazobactam, were performed against six ESBL-producing isolates. A sigmoidal maximum-effect (Emax) model was fitted to the data. In the dose fractionation study, the q2h regimen was more efficacious than the q4h and q6h regimens, indicating time-dependent activity of tazobactam. The threshold concentration (CT ) best correlating with tazobactam efficacy was 0.25 mg/liter, as evidenced by the best fit of the percentage of time above the threshold concentration (%fT>CT ) and response. A mean %fT>CT of 24.6% (range, 11.4 to 36.3%) for a CT of 0.25 mg/liter was required to obtain a bacteriostatic effect. We conclude that tazobactam enhanced the effect of cefepime in otherwise resistant isolates of Enterobacteriaceae and that the %fT>CT of 0.25 mg/liter best correlated with efficacy. These studies provide the basis for the development of human dosing regimens for this combination.

Both MisR (CpxR) and MisS (CpxA) Are Required for Neisseria gonorrhoeae Infection in a Murine Model of Lower Genital Tract Infection.

During infection, Neisseria gonorrhoeae senses and responds to stress; such responses may be modulated by MisRS (NGO0177 and NGO0176), a two-component system that is a homolog of CpxRA. In Escherichia coli, CpxRA senses and responds to envelope stress; CpxA is a sensor kinase/phosphatase for CpxR, a response regulator. When a cpxA mutant is grown in medium containing glucose, CpxR is phosphorylated by acetyl phosphate but cannot be dephosphorylated, resulting in constitutive activation. Kandler and coworkers (J. L. Kandler, C. L. Holley, J. L. Reimche, V. Dhulipala, J. T. Balthazar, A. Muszyński, R. W. Carlson, and W. M. Shafer, Antimicrob Agents Chemother 60:4690-4700, 2016, https://doi.org/10.1128/AAC.00823-16) showed that MisR (CpxR) is required for the maintenance of membrane integrity and resistance to antimicrobial peptides, suggesting a role in gonococcal survival in vivo Here, we evaluated the contributions of MisR and MisS (CpxA) to gonococcal infection in a murine model of cervicovaginal colonization and identified MisR-regulated genes using RNA sequencing (RNA-Seq). The deletion of misR or misS severely reduced the capacity of N. gonorrhoeae to colonize mice or maintain infection over a 7-day period and reduced microbial fitness after exposure to heat shock. Compared to the wild type (WT), the inactivation of misR identified 157 differentially regulated genes, most of which encoded putative envelope proteins. The inactivation of misS identified 17 differentially regulated genes compared to the WT and 139 differentially regulated genes compared to the misR mutant, 111 of which overlapped those differentially expressed in the comparison of the WT versus the misR mutant. These data indicate that an intact MisRS system is required for gonococcal infection of mice. Provided the MisR is constitutively phosphorylated in the misS mutant, the data suggest that controlled but not constitutive activation is required for gonococcal infection in mice.

In Vivo Efficacy of Liposomal Amphotericin B against Wild-Type and Azole-Resistant Aspergillus fumigatus Isolates in Two Different Immunosuppression Models of Invasive Aspergillosis.

Using an immunocompetent murine model of invasive aspergillosis (IA), we previously reported that the efficacy of liposomal amphotericin B (L-AmB) (Ambisome) is not hampered by the presence of azole resistance mutations in Aspergillus fumigatus (S. Seyedmousavi, W. J. G. Melchers, J. W. Mouton, and P. E. Verweij, Antimicrob Agents Chemother 57:1866-1871, 2013, https://doi.org/10.1128/AAC.02226-12). We here investigated the role of immune suppression, i.e., neutropenia and steroid treatment, in L-AmB efficacy in mice infected with wild-type (WT) A. fumigatus and with azole-resistant A. fumigatus harboring a TR34/L98H mutation in the cyp-51A gene. Survival of treated animals at day 14 in both immunosuppressed models was significantly better than that of nontreated controls. A dose-response relationship was observed that was independent of the azole-resistant mechanism and the immunosuppression method used. In the neutropenic model, 100% survival was reached at an L-AmB dose of 16 mg/kg of body weight for the WT strain and the TR34/L98H isolate. In the steroid-treated group, 90.9% survival and 100% survival were achieved for the WT isolate and the TR34/L98H isolate with an L-AmB dose of 16 mg/kg, respectively. The 50% effective dose (ED50) was 1.40 mg/kg (95% confidence interval [CI], 0.66 to 3.00 mg/kg) for the WT isolate and 1.92 mg/kg (95% CI, 0.60 to 6.17 mg/kg) for the TR34/L98H isolate in the neutropenic model and was 2.40 mg/kg (95% CI, 1.93 to 2.97 mg/kg) for the WT isolate and 2.56 mg/kg (95% CI, 1.43 to 4.56 mg/kg) for the TR34/L98H isolate in the steroid-treated group. Overall, there were no significant differences between the two different immunosuppressed conditions in the efficacy of L-AmB against the wild-type and azole-resistant isolates (P > 0.9). However, the required L-AmB exposure was significantly higher than that seen in the immunocompetent model.

Carbapenemase-Producing Enterobacteriaceae in Swine Production in the United States: Impact and Opportunities.

The discovery of carbapenemase-producing Enterobacteriaceae in U.S. swine production is troubling and underscores a tumultuous period where the outlook on the battle against superbugs is bleak. However, all is not lost. This commentary highlights both the good and the bad that can come from such findings, including those of a recent study published by Mollenkopf et al. (Antimicrob Agents Chemother 61:e012198-16, 2017, https://doi.org/doi:10.1128/AAC.01298-16).

P53 Mediates Colistin-Induced Autophagy and Apoptosis in PC-12 Cells.

The mechanism of colistin-induced neurotoxicity is still unknown. Our recent study (L. Zhang, Y. H. Zhao, W. J. Ding, G. Z. Jiang, Z. Y. Lu, L. Li, J. L. Wang, J. Li, and J. C. Li, Antimicrob Agents Chemother 59:2189-2197, 2015, http://dx.doi.org/10.1128/AAC.04092-14; H. Jiang, J. C. Li, T. Zhou, C. H. Wang, H. Zhang, and H. Wang, Int J Mol Med 33:1298-1304, 2014, http://dx.doi.org/10.3892/ijmm.2014.1684) indicates that colistin induces autophagy and apoptosis in rat adrenal medulla PC-12 cells, and there is interplay between both cellular events. As an important cellular stress sensor, phosphoprotein p53 can trigger cell cycle arrest and apoptosis and regulate autophagy. The aim of the present study was to investigate the involvement of the p53 pathway in colistin-induced neurotoxicity in PC-12 cells. Specifically, cells were treated with colistin (125 μg/ml) in the absence and presence of a p53 inhibitor, pifithrin-α (PFT-α; 20 nM), for 12 h and 24 h, and the typical hallmarks of autophagy and apoptosis were examined by fluorescence/immunofluorescence microscopy and electron microscopy, real-time PCR, and Western blotting. The results indicate that colistin had a stimulatory effect on the expression levels of the target genes and proteins involved in autophagy and apoptosis, including LC3-II/I, p53, DRAM (damage-regulated autophagy modulator), PUMA (p53 upregulated modulator of apoptosis), Bax, p-AMPK (activated form of AMP-activated protein kinase), and caspase-3. In contrast, colistin appeared to have an inhibitory effect on the expression of p-mTOR (activated form of mammalian target of rapamycin), which is another target protein in autophagy. Importantly, analysis of the levels of p53 in the cells treated with colistin revealed an increase in nuclear p53 at 12 h and cytoplasmic p53 at 24 h. Pretreatment of colistin-treated cells with PFT-α inhibited autophagy and promoted colistin-induced apoptosis. This is the first study to demonstrate that colistin-induced autophagy and apoptosis are associated with the p53-mediated pathway.

Effects of Stress, Reactive Oxygen Species, and the SOS Response on De Novo Acquisition of Antibiotic Resistance in Escherichia coli.

Strategies to prevent the development of antibiotic resistance in bacteria are needed to reduce the threat of infectious diseases to human health. The de novo acquisition of resistance due to mutations and/or phenotypic adaptation occurs rapidly as a result of interactions of gene expression and mutations (N. Handel, J. M. Schuurmans, Y. Feng, S. Brul, and B. H. Ter Kuile, Antimicrob Agents Chemother 58:4371-4379, 2014, http://dx.doi.org/10.1128/AAC.02892-14). In this study, the contribution of several individual genes to the de novo acquisition of antibiotic resistance in Escherichia coli was investigated using mutants with deletions of genes known to be involved in antibiotic resistance. The results indicate that recA, vital for the SOS response, plays a crucial role in the development of antibiotic resistance. Likewise, deletion of global transcriptional regulators, such as gadE or soxS, involved in pH homeostasis and superoxide removal, respectively, can slow the acquisition of resistance to a degree depending on the antibiotic. Deletion of the transcriptional regulator soxS, involved in superoxide removal, slowed the acquisition of resistance to enrofloxacin. Acquisition of resistance occurred at a lower rate in the presence of a second stress factor, such as a lowered pH or increased salt concentration, than in the presence of optimal growth conditions. The overall outcome suggests that a central cellular mechanism is crucial for the development of resistance and that genes involved in the regulation of transcription play an essential role. The actual cellular response, however, depends on the class of antibiotic in combination with environmental conditions.

Ibrutinib—a new standard treatment for relapsed mantle cell lymphoma?

728 www.thelancet.com Vol 387 February 20, 2016 In The Lancet, Martin Dreyling and colleagues present the results of a large, international, randomised phase 3 trial comparing the only two drugs approved for previously treated mantle cell lymphoma in Europe: temsirolimus and ibrutinib. Among 280 patients, those randomly assigned to daily oral ibrutinib 560 mg (n=139) showed a signifi cant improvement in progression-free survival, the trial’s primary endpoint, compared with patients (n=141) assigned to daily intravenous temsirolimus 175 mg (14·6 months vs 6·2 months; hazard ratio 0·43 [95% CI 0·32–0·58]). Ibrutinib was also better tolerated than temsirolimus, with fewer study discontinuations because of adverse events. Therefore, the results from this trial clearly establish ibrutinib as a new standard for treatment of relapsed mantle cell lymphoma. Representing only 5% of all non-Hodgkin lymphomas, mantle cell lymphoma is not the most epidemiologically relevant disease. Its natural history and poor prognosis, however, have garnered substantial attention. After an initial chemotherapy-induced remission of varying duration, patients with mantle cell lymphoma generally undergo a series of subsequent therapies, with successes measured in months as the disease and treatment-related side-eff ects slowly take their toll. A constant unmet need, mantle cell lymphoma has been a model for the accelerated development of novel targeted drugs. The US Food and Drug Administration (FDA) approved bortezomib and lenalidomide for patients with mantle cell lymphoma who had received previous treatments, on the basis of results from phase 2 trials that showed an overall response rate of about 30% and equally high occurrences of study discontinuation because of adverse events. The development of temsirolimus was less straightforward. Results from two clinical trials showed that temsirolimus possessed substantial activity against mantle cell lymphoma (with overall response rates of about 40%), but also a therapeutic index that favoured lower doses. An international phase 3 trial compared two doses of temsirolimus against investigator’s choice of treatment (a variety of single chemotherapy drugs), and showed that 22% of patients receiving higher-dose temsirolimus (175 mg per week for 3 weeks followed by 75 mg per week thereafter) achieved an objective response, with a median progression-free survival of 4·8 months, compared with investigator’s choice (2% and 1·9 months, respectively). 22% of patients receiving the higher dose of temsirolimus discontinued treatment because of an adverse event, compared with 11% of patients receiving the investigator’s choice who discontinued for the same reason. These results were suffi cient for approval of temsirolimus for the treatment of mantle cell lymphoma by the European Medicines Agency (EMA) in 2008, but not by the FDA. In 2009, the fi rst-in-class, oral, small molecule inhibitor of Bruton’s tyrosine kinase, ibrutinib, entered clinical development. On the basis of promising results in seven of nine patients with mantle cell lymphoma treated in a phase 1 trial, a non-pivotal, phase 2 trial (PCYC-1104) was designed with the intention of better Ibrutinib—a new standard treatment for relapsed mantle cell lymphoma? 4 Marr KA, Schlamm HT, Herbrecht R, et al. Combination antifungal therapy for invasive aspergillosis: a randomized trial. Ann Intern Med 2015; 162: 81–89. 5 Miceli MH, Kauff man CA. Isavuconazole: a new broad-spectrum triazole antifungal agent. Clin Infect Dis 2015; 61: 1558–65. 6 Teusink A, Vinks AA, Zhang K, et al. Genotype-directed dosing leads to optimized voriconazole levels in pediatric patients receiving hematopoietic stem cell transplantation. Biol Blood Marrow Transplant 2015; published oline Nov 23. DOI:10.1016/j.bbmt.2015.11.011. 7 Lutsar I, Hodges MR, Tomaszewski K, Troke PF, Wood ND. Safety of voriconazole and dose individualization. Clin Infect Dis 2003; 36: 1087–88. 8 Ashbee HR, Barnes RA, Johnson EM, Richardson MD, Gorton R, Hope WW. Therapeutic drug monitoring (TDM) of antifungal agents: guidelines from the British Society for Medical Mycology. J Antimicrob Chemother 2014; 69: 1162–76. 9 Ananda-Rajah MR, Cheng A, Morrissey CO, et al. Attributable hospital cost and antifungal treatment of invasive fungal diseases in high-risk hematology patients: an economic modeling approach. Antimicrob Agents Chemother 2011; 55: 1953–60. 10 Munoz P, Valerio M, Vena A, Bouza E. Antifungal stewardship in daily practice and health economic implications. Mycoses 2015; 58 (suppl 2): 14–25. 11 Ananda-Rajah MR, Slavin MA, Thursky KT. The case for antifungal stewardship. Curr Opin Infect Dis 2012; 25: 107–15. 12 Herbrecht R, Denning DW, Patterson TF, et al. Voriconazole versus amphotericin B for primary therapy of invasive aspergillosis. N Engl J Med 2002; 347: 408–15.

Eradication of Helicobacter pylori with 10-day and 14-day Rifabutin-based Triple Therapy as a Third- or Fourth-line Rescue Therapy: An Open-label Randomized Pilot Trial

Introduction: Recently, we reported that few Helicobacter pylori strains are resistant to rifabutin in Japan (Antimicrob Agents Chemother. 55:5374-5, 2011). This prospective study was designed to assess the efficacy of 10-day and 14-day rifabutin-based triple therapy as a third- or fourth-line rescue therapy. Methods: From October 2013 to May 2015, a total of 28 patients in whom eradication treatment with clarithromycin-based first-line therapy and metronidazole-based second-line therapy failed were enrolled. Furthermore, 19 of the 28 patients had failed to third-line sitafloxacin-based triple therapy. Before beginning the treatment, H. pylori were isolated from gastric biopsy specimens, and the minimum inhibitory concentrations (MICs) of sitafloxacin and metronidazole were determined using agar dilution method. The susceptibility-resistance cutoff values of the MICs for rifabutin were defined as 0.25 μg/mL. Enrolled patients were randomly assigned to receive 10-day or 14-day eradication therapy with esomeprazole, amoxicillin, and rifabutin. Poor compliance was defined as intake of 13C urea breath test or a stool antigen test, 12 weeks after the end of therapy. Results: In ITT analysis, the eradication rate of 10-day therapy was 81.8% (9/11), and that of 14-day therapy was 94.1% (16/17). Only 1 patient were infected with the rifabutin resistant strain (MIC=1.0μg/mL) that were eradicated with 14-day therapy finally. The medication adherence rates of 14-day therapy were 64.7% (11/17), whereas that of 10-day therapy were 100%(11/11) (P=0.05). Major adverse events were diarrhea/soft stool, fever, headache, liver, rush, stomatitis and leucopoenia. As the most serious adverse events, 1 patient developed neutropenia (250/mm3) with 10-day treatment, but after the eradication treatment she spontaneously recovered. Other all adverse events were also recovered after the cessation of eradication therapy. Conclusion: Both of the 10-day and 14-day therapies were most effective as rescue regimens, especially 14-day therapy achieved over 90 % eradication. On the other hand, 10-day treatment were more tolerable than 14-day therapy.

001.4 Recent rise in reduced susceptibility to ceftriaxone inneisseria gonorrhoeaeis not caused by strains with apenamosaic gene

Background Resistance of Neisseria gonorrhoeae against third generation cephalosporins is a threat to public health. A known determinant is the presence of a mosaic penA gene in N.gonorrhoeae , partially derived from commensal Neisseria spp. We report resistance figures of N.gonorrhoeae against ceftriaxone from 2010 to 2013 and looked at penA characteristics of specific strains. Methods MICs for ceftriaxone were assesed from 2010–13 (4191 strains). A specific PCR identifying strains with a mosaic penA gene and partial sequence analysis (aa 180 – 550) of the penA gene were used for further characterisation of specific strains. Results Strains resistant to ceftriaxone were not found during the study period. The frequency of strains with an increased MIC (>0.032) to ceftriaxone was 5.2% in 2010, this rate dropped to 2.0 and 3.1% in 2011 and 2012 respectively, but increased to 7.8% in 2013. In 2010, 46/48 (96%) strains with an increased MIC against ceftriaxone contained a mosaic penA gene; in 2013, only 15/68 (22%) of such strains contained this gene. Sequence analysis of 16 of the strains isolated in 2013 with reduced susceptibility to ceftriaxone and lacking a mosaic penA gene showed that they all had an identical penA gene which was similar to type XVIII, including a 502 A-T mutation, but lacking the 543 G-S mutation. 1 Conclusion The recent increase of the frequency of strains with reduced susceptibility to ceftriaxone in 2013 is due to strains with a penA sequence not yet found in the Netherlands in 2010 among strains with reduced susceptibility to ceftriaxone. Disclosure of interest statement Nothing to declare Reference Whiley DM, Limnios EA, Ray S, et al . Diversity of penA alterations and subtypes in Neisseria gonorrhoeae strains from Sydney, Austrlia, that are less susceptible to ceftriaxone. Antimicrob Agents Chemother . 2007; 51 :3111–6

Respiratory Syncytial Virus Inhibitor AZ-27 Differentially Inhibits Different Polymerase Activities at the Promoter.

Respiratory syncytial virus (RSV) is the leading cause of pediatric respiratory disease. RSV has an RNA-dependent RNA polymerase that transcribes and replicates the viral negative-sense RNA genome. The large polymerase subunit (L) has multiple enzymatic activities, having the capability to synthesize RNA and add and methylate a cap on each of the viral mRNAs. Previous studies (H. Xiong et al., Bioorg Med Chem Lett, 23:6789-6793, 2013, http://dx.doi.org/10.1016/j.bmcl.2013.10.018; C. L. Tiong-Yip et al., Antimicrob Agents Chemother, 58:3867-3873, 2014, http://dx.doi.org/10.1128/AAC.02540-14) had identified a small-molecule inhibitor, AZ-27, that targets the L protein. In this study, we examined the effect of AZ-27 on different aspects of RSV polymerase activity. AZ-27 was found to inhibit equally both mRNA transcription and genome replication in cell-based minigenome assays, indicating that it inhibits a step common to both of these RNA synthesis processes. Analysis in an in vitro transcription run-on assay, containing RSV nucleocapsids, showed that AZ-27 inhibits synthesis of transcripts from the 3' end of the genome to a greater extent than those from the 5' end, indicating that it inhibits transcription initiation. Consistent with this finding, experiments that assayed polymerase activity on the promoter showed that AZ-27 inhibited transcription and replication initiation. The RSV polymerase also can utilize the promoter sequence to perform a back-priming reaction. Interestingly, addition of AZ-27 had no effect on the addition of up to three nucleotides by back-priming but inhibited further extension of the back-primed RNA. These data provide new information regarding the mechanism of inhibition by AZ-27. They also suggest that the RSV polymerase adopts different conformations to perform its different activities at the promoter. Currently, there are no effective antiviral drugs to treat RSV infection. The RSV polymerase is an attractive target for drug development, but this large enzymatic complex is poorly characterized, hampering drug development efforts. AZ-27 is a small-molecule inhibitor previously shown to target the RSV large polymerase subunit (C. L. Tiong-Yip et al., Antimicrob Agents Chemother, 58:3867-3873, 2014, http://dx.doi.org/10.1128/AAC.02540-14), but its inhibitory mechanism was unknown. Understanding this would be valuable both for characterizing the polymerase and for further development of inhibitors. Here, we show that AZ-27 inhibits an early stage in mRNA transcription, as well as genome replication, by inhibiting initiation of RNA synthesis from the promoter. However, the compound does not inhibit back priming, another RNA synthesis activity of the RSV polymerase. These findings provide insight into the different activities of the RSV polymerase and will aid further development of antiviral agents against RSV.

A mutation of RNA polymerase β' subunit (RpoC) converts heterogeneously vancomycin-intermediate Staphylococcus aureus (hVISA) into "slow VISA".

Various mutations in the rpoB gene, which encodes the RNA polymerase β subunit, are associated with increased vancomycin (VAN) resistance in vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneously VISA (hVISA) strains. We reported that rpoB mutations are also linked to the expression of the recently found "slow VISA" (sVISA) phenotype (M. Saito, Y. Katayama, T. Hishinuma, A. Iwamoto, Y. Aiba, K Kuwahara-Arai, L. Cui, M. Matsuo, N. Aritaka, and K. Hiramatsu, Antimicrob Agents Chemother 58:5024-5035, 2014, http://dx.doi.org/10.1128/AAC.02470-13). Because RpoC and RpoB are components of RNA polymerase, we examined the effect of the rpoC(P440L) mutation on the expression of the sVISA phenotype in the Mu3fdh2*V6-5 strain (V6-5), which was derived from a previously reported hVISA strain with the VISA phenotype. V6-5 had an extremely prolonged doubling time (DT) (72 min) and high vancomycin MIC (16 mg/liter). However, the phenotype of V6-5 was unstable, and the strain frequently reverted to hVISA with concomitant loss of low growth rate, cell wall thickness, and reduced autolysis. Whole-genome sequencing of phenotypic revertant strain V6-5-L1 and comparison with V6-5 revealed a second mutation, F562L, in rpoC. Introduction of the wild-type (WT) rpoC gene using a multicopy plasmid resolved the sVISA phenotype of V6-5, indicating that the rpoC(P440L) mutant expressed the sVISA phenotype in hVISA. To investigate the mechanisms of resistance in the sVISA strain, we independently isolated an additional 10 revertants to hVISA and VISA. In subsequent whole-genome analysis, we identified compensatory mutations in the genes of three distinct functional categories: the rpoC gene itself as regulatory mutations, peptidoglycan biosynthesis genes, and relQ, which is involved in the stringent response. It appears that the rpoC(P440L) mutation causes the sVISA phenotype by augmenting cell wall peptidoglycan synthesis and through the control of the stringent response.

Prevalence of fecal carriage of extended-spectrum- and metallo-β-lactamase-producing gram-negative bacteria among neonates born in a hospital setting in central Saudi Arabia.

BACKGROUND AND OBJECTIVECommensal neonatal fecal flora constitute a reservoir of antibiotic resistance. The aim of this study was to characterize the prevalence of fecal carriage of extended spectrum beta-lactamases (ESBLs) and carbapenemase producing gram-negative bacteria among 150 neonates who were born in two hospitals in central Saudi Arabia.PATIENTS AND METHODSFrom June 2012 to Janauary 2013, 150 healthy neonates ≤7 days of age were screened for intestinal enteric bacteria colonization and the influence of age, mode of delivery, body weight and breast feeding of neonates on colonzation rates. The isolates were identified manually and by VITEK 2 and antibiotic susceptibility was tested. Phenotypic tests were performed to seek ESBL and metallo-β-lactamase (MBL) producers in recovered isolates.RESULTSAmong 150 fecal specimens, 188 gram-negative rods were recovered. E coli (n=130; 69.1%) was the commonest organism followed by Klebsiella pneumoniae (n=23; 12.2%), Pseudomonas aeuroginosa (n=14; 7.5%), Acinetobacter baumannii (n=9; 4.8%), Enterobacter spp. (n=9; 4.8%) and Morganella morganii (n=3; 1.6%). E coli colonization during the first day of life was 95.5% (n=43/45), which was relatively higher than in subsequent days. The colonization rate of E coli among low weight babies (≤3 kg) was significantly higher than fully grown neonates (≥4 kg)(P=.03). The prevalence of ESBL and MBL was 15.0% (n=28/188) and 1.6% (n=3/188). The prevalence rates of ESBL in E coli, K pneumoniae, E cloacae, M morganii and E aerogenes were 16.9% (n=22/130), 4.3 % (n=1/23), 60% (n=3/5), 33.3% (n=1/3), and 25% (n=1/4), respectively. All E cloacae with ESBLs and MBLs were resistant to all tested antibiotics including carbapenems.CONCLUSIONWithin the first week of life, the most important determinants of gut enteric bacteria composition in neonates were age in days, body weight, mode of delivery, and type of neonatal feeding. The findings of ESBLs- and MBLs-producing enteric bacteria as neonate-gut colonizers may have wider implication or linkage to prevention of nosocomial and community-acquired infections by these strains.

Pharmacokinetics of a novel sublingual spray formulation of the antimalarial drug artemether in African children with malaria.

The pharmacokinetics of sublingual artemether (ArTiMist) was investigated in 91 young African children with severe malaria or who could not tolerate oral antimalarial therapy. Each received 3.0 mg/kg of body weight of artemether at 0, 8, 24, 36, 48, and 60 h or until the initiation of oral treatment. Few blood samples were drawn postdose. Plasma artemether and dihydroartemisinin (DHA) levels were measured using liquid chromatography-mass spectrometry, and the data were analyzed using established population compartmental pharmacokinetic models. Parasite clearance was prompt (median parasite clearance time, 24 h), and there were no serious adverse events. Consistent with studies in healthy adults (S. Salman, D. Bendel, T. C. Lee, D. Templeton, and T. M. E. Davis, Antimicrob Agents Chemother 59:3197-3207, 2015, http://dx.doi.org/10.1128/AAC.05013-14), the absorption of sublingual artemether was biphasic, and multiple dosing was associated with the autoinduction of the metabolism of artemether to DHA (which itself has potent antimalarial activity). In contrast to studies using healthy volunteers, pharmacokinetic modeling indicated that the first absorption phase did not avoid first-pass metabolism, suggesting that the drug is transferred to the upper intestine through postdose fluid/food intake. Simulations using the present data and those from an earlier study in older Melanesian children with uncomplicated malaria treated with artemether-lumefantrine tablets suggested that the bioavailability of sublingual artemether was at least equivalent to that after conventional oral artemether-lumefantrine (median [interquartile range] areas under the concentration-time curve for artemether, 3,403 [2,471 to 4,771] versus 3,063 [2,358 to 4,514] μg · h/liter, respectively; and for DHA, 2,958 [2,146 to 4,278] versus 2,839 [1,812 to 3,488] μg · h/liter, respectively; P ≥ 0.42). These findings suggest that sublingual artemether could be used as prereferral treatment for sick children before transfer for definitive management of severe or moderately severe malaria.

Auranofin: repurposing an old drug for a golden new age.

Drug discovery, development and registration is an expensive and time-consuming process associated with a high failure rate [Pessetto et al. (Mol Cancer Ther 12:1299–1309, 2013), Woodcock and Woosley (Annu Rev Med 59:1–12, 2008)]. Drug ‘repurposing’ is the identification of new therapeutic purposes for already approved drugs and is more affordable and achievable than novel drug discovery [Pessetto et al. (Mol Cancer Ther 12:1299–1309, 2013)]. Auranofin is a drug that is approved for the treatment of rheumatoid arthritis but is being investigated for potential therapeutic application in a number of other diseases including cancer, neurodegenerative disorders, HIV/AIDS, parasitic infections and bacterial infections [Tejman-Yarden et al. (Antimicrob Agents Chemother 57:2029–2035, 2013)]. The main mechanism of action of auranofin is through the inhibition of reduction/oxidation (redox) enzymes that are essential for maintaining intracellular levels of reactive oxygen species. Inhibition of these enzymes leads to cellular oxidative stress and intrinsic apoptosis [Pessetto et al. (Mol Cancer Ther 12:1299–1309, 2013), Fan et al. (Cell Death Dis 5:e1191, 2014), Fiskus et al. (Cancer Res 74:2520–2532, 2014), Marzano et al. (Free Radic Biol Med 42:872–881, 2007)]. Drugs such as auranofin that have already been approved for human use [Tejman-Yarden et al. (Antimicrob Agents Chemother 57:2029–2035, 2013)] can be brought into clinical use for other diseases relatively quickly and for a fraction of the cost of new drugs.

Effect of ethyl acetate fraction of urucum extract on cell viability of peripheral blood mononuclear cells and antimicrobial activity in human pathogenic bacteria.

Effect of ethyl acetate fraction of urucum extract on cell viability of peripheral blood mononuclear cells and antimicrobial activity in human pathogenic bacteria.

Target-Based Resistance in Pseudomonas aeruginosa and Escherichia coli to NBTI 5463, a Novel Bacterial Type II Topoisomerase Inhibitor

In a previous report (T. J. Dougherty, A. Nayar, J. V. Newman, S. Hopkins, G. G. Stone, M. Johnstone, A. B. Shapiro, M. Cronin, F. Reck, and D. E. Ehmann, Antimicrob Agents Chemother 58:2657-2664, 2014), a novel bacterial type II topoisomerase inhibitor, NBTI 5463, with activity against Gram-negative pathogens was described. First-step resistance mutations in Pseudomonas aeruginosa arose exclusively in the nfxB gene, a regulator of the MexCD-OprJ efflux pump system. The present report describes further resistance studies with NBTI 5463 in both Pseudomonas aeruginosa and Escherichia coli. Second-step mutations in P. aeruginosa arose at aspartate 82 of the gyrase A subunit and led to 4- to 8-fold increases in the MIC over those seen in the parental strain with a first-step nfxB efflux mutation. A third-step mutant showed additional GyrA changes, with no changes in topoisomerase IV. Despite repeated efforts, resistance mutations could not be selected in E. coli. Genetic introduction of the Asp82 mutations observed in P. aeruginosa did not significantly increase the NBTI MIC in E. coli. However, with the aspartate 82 mutation present, it was possible to select second-step mutations in topoisomerase IV that did lead to MIC increases of 16- and 128-fold. As with the gyrase aspartate 82 mutation, the mutations in topoisomerase IV did not by themselves raise the NBTI MIC in E. coli. Only the presence of mutations in both targets of E. coli led to an increase in NBTI MIC values. This represents a demonstration of the value of balanced dual-target activity in mitigating resistance development.

PC-FACS

PC-FACS

Contribution of human immunodeficiency virus type 1 minority variants to reduced drug susceptibility in patients on an integrase strand transfer inhibitor-based therapy.

The role of HIV-1 minority variants on transmission, pathogenesis, and virologic failure to antiretroviral regimens has been explored; however, most studies of low-level HIV-1 drug-resistant variants have focused in single target regions. Here we used a novel HIV-1 genotypic assay based on deep sequencing, DEEPGEN (Gibson et al 2014 Antimicrob Agents Chemother 58∶2167) to simultaneously analyze the presence of minority variants carrying mutations associated with reduced susceptibility to protease (PR), reverse transcriptase (RT), and integrase strand transfer integrase inhibitors (INSTIs), as well as HIV-1 coreceptor tropism. gag-p2/NCp7/p1/p6/pol-PR/RT/INT and env/C2V3 PCR products were obtained from twelve heavily treatment-experienced patients experiencing virologic failure while participating in a 48-week dose-ranging study of elvitegravir (GS-US-183-0105). Deep sequencing results were compared with (i) virological response to treatment, (ii) genotyping based on population sequencing, (iii) phenotyping data using PhenoSense and VIRALARTS, and (iv) HIV-1 coreceptor tropism based on the phenotypic test VERITROP. Most patients failed the antiretroviral regimen with numerous pre-existing mutations in the PR and RT, and additionally newly acquired INSTI-resistance mutations as determined by population sequencing (mean 9.4, 5.3, and 1.4 PI- RTI-, and INSTI-resistance mutations, respectively). Interestingly, since DEEPGEN allows the accurate detection of amino acid substitutions at frequencies as low as 1% of the population, a series of additional drug resistance mutations were detected by deep sequencing (mean 2.5, 1.5, and 0.9, respectively). The presence of these low-abundance HIV-1 variants was associated with drug susceptibility, replicative fitness, and coreceptor tropism determined using sensitive phenotypic assays, enhancing the overall burden of resistance to all four antiretroviral drug classes. Further longitudinal studies based on deep sequencing tests will help to clarify (i) the potential impact of minority HIV-1 drug resistant variants in response to antiretroviral therapy and (ii) the importance of the detection of HIV minority variants in the clinical practice.