Surgical Resection of Retrosternal Goitre: The Four-Finger Technique

Retrosternal goitre (RSG) is a thyroid gland with more than 50% of its mass located below the thoracic inlet. Pre-operative Computed Tomography can visualise the anatomical relations between the RSG and each mediastinal component, and the level of extension. Most cases of RSG can be resected via the cervical approach, as the thoracic approach carries a greater risk of complications. We describe a four finger technique for total thyroidectomy in five cases of RSG through a neck incision, without the need for a sternotomy. The recurrent laryngeal nerve (RLN) was identified early in the Baehr's triangle. The thyroid was mobilised in the neck by ligation of the feeding vessels and separated from the tracheal attachments. The retrosternal portion was then delivered into the neck by blunt dissection, keeping two fingers of each hand close to the thyroid gland. The RLN and parathyroids were identified early in the surgery to avoid the complications of hoarseness and hypoalcemia, respectively.

Unveiling the ESR1 Conformational Stability and Screening Potent Inhibitors for Breast Cancer Treatment

BACKGROUND

The current study recognizes the significance of estrogen receptor alpha (ERα) as a member of the nuclear receptor protein family, which holds a central role in the pathophysiology of breast cancer. ERα serves as a valuable prognostic marker, with its established relevance in predicting disease outcomes and treatment responses.

METHOD

In this study, computational methods are utilized to search for suitable drug-like compounds that demonstrate analogous ligand binding kinetics to ERα.

RESULTS

Docking-based simulation screened out the top 5 compounds - ZINC13377936, NCI35753, ZINC35465238, ZINC14726791, and NCI663569 against the targeted protein. Further, their dynamics studies reveal that the compounds ZINC13377936 and NCI35753 exhibit the highest binding stability and affinity.

CONCLUSION

Anticipating the competitive inhibition of ERα protein expression in breast cancer, we envision that both ZINC13377936 and NCI35753 compounds hold substantial promise as potential therapeutic agents. These candidates warrant thorough consideration for rigorous In vitro and In vivo evaluations within the context of clinical trials. The findings from this current investigation carry significant implications for the advancement of future diagnostic and therapeutic approaches for breast cancer.

Tailoring epoxy coating with acetoxime derivative of zinc for advanced anticorrosive performance on mild steel: experimental and computational insights

CONTEXT

In this work, the corrosion inhibitive effect of acetoxime derivative of zinc chloride, (ZnCl2.2HON=C(CH3)2) (ZA), was investigated on mild steel in epoxy/polyamide coating. ZA was used to modify diglycidyl ether of bisphenol A (DGEBA) to yield novel anticorrosive coating (epoxy-ZA) with excellent barrier characteristic. The dispersal of ZA may lead to the formation of Zn-O-C and O-Zn-O linkages in the polymer framework which act as inorganic fillers producing a dense structure of hybrid coating. In electrochemical findings, electrochemical impedance spectroscopy (EIS) and Tafel polarization (TP) indicate higher protection efficiency for epoxy-ZA coatings (99.99 and 99.93 % for EIS and TP, respectively) as compared to others. Using surface analysis and electrochemical data, it was concluded that an inhibition synergy was developed when ZA was taken instead of acetoxime or zinc chloride (ZC) alone in the coating formulation.

METHODS

Fourier transform infrared (FT-IR) was used to investigate epoxy interaction with zinc compounds and scanning electron microscopy (SEM) was used to investigate morphology of the samples. To reinforce the experimental results, reactivity of crosslinked epoxy and epoxy-ZA coatings with metallic surface was also explored using density functional theory (DFT) with basis set B3LYP/6-311G(d,p) and molecular dynamics (MD) methods by using Forcite module. Modification of epoxy with ZA enhances its interaction with steel surface in dry as well as in wet conditions as indicated by the adhesion energy calculated by MD simulations.

Structure-Based Virtual Screening, Molecular Docking, Molecular Dynamics Simulation of EGFR for the Clinical Treatment of Glioblastoma

Glioblastoma (GBM) is a WHO Grade IV tumor with poor visibility, a high risk of comorbidity, and exhibit limited treatment options. Resurfacing from second-rate glioma was originally classified as either mandatory or optional. Recent interest in personalized medicine has motivated research toward biomarker stratification-based individualized illness therapy. GBM biomarkers have been investigated for their potential utility in prognostic stratification, driving the development of targeted therapy and customizing therapeutic treatment. Due to the availability of a specific EGFRvIII mutational variation with a clear function in glioma-genesis, recent research suggests that EGFR has the potential to be a prognostic factor in GBM, while others have shown no clinical link between EGFR and survival. The pre-existing pharmaceutical lapatinib (PubChem ID: 208,908) with a higher affinity score is used for virtual screening. As a result, the current study revealed a newly screened chemical (PubChem CID: 59,671,768) with a higher affinity than the previously known molecule. When the two compounds are compared, the former has the lowest re-rank score. The time-resolved features of a virtually screened chemical and an established compound were investigated using molecular dynamics simulation. Both compounds are equivalent, according to the ADMET study. This report implies that the virtual screened chemical could be a promising Glioblastoma therapy.

High Frequency Hearing Loss in Chronic Renal Disease: A Cross-Sectional Study

Introduction Chronic kidney disease (CKD) patients face multiple complications. One of them is involvement of the auditory system and it deserves more attention than is paid by the current approaches as hearing loss has major repercussions on the quality of life. Early detection can prevent further deterioration of hearing and improve the quality of life of patients suffering from CKD. Material and methods The high frequency (8-18 kHz) audiometry with pure tones was performed in 82 patients with CKD and compared with age and sexes matched healthy control group of 90 patients. Individual ear were used for statistical calculations. Results This study clearly observed that the hearing thresholds for frequencies 8-18 kHz increased in CKD patients when compared to sex and aged matched healthy control group, the thresholds significantly increased in CKD with diabetes mellitus as compared to nondiabetic with CKD. The high frequency thresholds significantly increased in patients on hemodialysis, and were significantly correlated with age, stage of CKD and duration of CKD. Conclusion This study highlights the presence of high frequency (8-18 kHz) hearing loss in patients of CKD. The severity is significantly correlated with age, stage and duration of CKD.

Expression of Cyclin-D1 and p53 as Prognostic Markers in Treatment of Oral Squamous Cell Carcinoma

Cyclin D1 and p53 play an important role in tumorigenesis of human cancers. The present study aims to evaluate cyclin D1 and p53 expression in resectable OSCC, and to determine their prognostic significance at the end of 5 year follow-up: A total of 100 patients aged 31-74 years, stage 3/4 were recruited. Cyclin D1 and p53 expression in the tumour tissue was estimated by IHC and was statistically correlated with demographic and clinicopathological data and prognosis was evaluated at the end of 5 year outcome. The positive expression rate of cyclin D1 was 50% and p53 it was 40% and they neither showed any statistical significant correlation with each other nor with demographic or clinicopathological data. The OS was 32%.Negative and weak expression predicted better outcomes with regard to DFS and OS. DFS and OS were significantly worse in patients of overexpressed cyclin D1 (p < 0.001) and p53 (p = 0.008). Cyclin D1 is a better prognostic marker as compared to p53 for both DFS and OS. p53 expression (high versus low) for disease free non-survival and overall nonsurvival showed an OR of 3.576 (p = 0.003) and 8.803(p < 0.001) respectively for strong expression while in case of cyclin D1 it showed an OR of 13.067(p < 0.001) and 37.465(p < 0.001) for strong expression.So higher the level of expression of tumour markers higher is the odds ratio so poorer is the prognosis. Overexpression of cyclin D1 and p53 was significantly associated with poor prognosis in terms of DFS and OS.

Venous thromboembolism in adult elective spinal surgery

Aims

To evaluate the incidence of primary venous thromboembolism (VTE), epidural haematoma, surgical site infection (SSI), and 90-day mortality after elective spinal surgery, and the effect of two protocols for prophylaxis.

Patients and Methods

A total of 2181 adults underwent 2366 elective spinal procedures between January 2007 and January 2012. All patients wore anti-embolic stockings, mobilised early and were kept adequately hydrated. In addition, 29% (689) of these were given low molecular weight heparin (LMWH) while in hospital. SSI surveillance was undertaken using the Centers for Disease Control and Prevention criteria.

Results

In patients who only received mechanical prophylaxis, the incidence of VTE was 0.59% and that of SSI 2.1%. In patients who were additionally given LMWH, the incidence of VTE was 0% and that of SSI 0.7%. The unadjusted p-value was 0.04 for VTE and 0.01 for SSI. There were no cases of epidural haematoma or 90-day mortality in either group. When adjusted for case-mix, LMWH remained a significant factor (p = 0.006) for VTE, but not for SSI.

Conclusion

A peri-operative protocol involving mechanical anti-embolism stockings, adequate hydration, and early post-operative mobilisation is effective in significantly reducing the incidence of VTE. The addition of LMWH is safe in patients at higher risk of developing VTE. Cite this article: Bone Joint J 2017;99-B:1204–9.

Antibacterial activity and mode of action of tert-butylhydroquinone (TBHQ) and its oxidation product, tert-butylbenzoquinone (TBBQ)

OBJECTIVES

The antioxidant tert-butylhydroquinone (TBHQ) is a food additive reported to have antibacterial activity, and may therefore have application in the healthcare setting. This study sought to characterize the antibacterial activity and mode of action of TBHQ and its oxidation product, tert-butylbenzoquinone (TBBQ).

METHODS

The stability of TBHQ/TBBQ was studied in buffer. Susceptibility testing was performed by broth microdilution, and killing and lytic activity were evaluated by viable counting and culture turbidity measurements. Mode of action studies included following the incorporation of radiolabelled precursors into macromolecules. The effect of TBHQ/TBBQ upon bacterial and mammalian membranes was assessed using the BacLight(TM) assay and by monitoring the haemolysis of equine erythrocytes.

RESULTS

TBHQ underwent oxidation in solution to form TBBQ. When oxidation was prevented, TBHQ lacked useful antibacterial activity, indicating that TBBQ is responsible for the antibacterial activity attributed to TBHQ. TBBQ demonstrated activity against Staphylococcus aureus SH1000 (MIC 8 mg/L) and against a panel of clinical S. aureus isolates (MIC90 16 mg/L). TBBQ at 4× MIC caused a >4 log10 drop in cell viability within 6 h without lysis, and eradicated staphylococcal biofilms at 8× MIC. TBBQ did not display preferential inhibition of any single macromolecular synthetic pathway, but caused loss of staphylococcal membrane integrity without haemolytic activity.

CONCLUSIONS

TBBQ is responsible for the antibacterial activity previously ascribed to TBHQ. TBBQ prompts loss of staphylococcal membrane integrity; it is rapidly and extensively bactericidal, but is non-lytic. In view of the potent and selective bactericidal activity of TBBQ, this compound warrants further investigation as a candidate antistaphylococcal agent.

Pilocytic astrocytoma mimicking craniopharyngioma: a case series

Although they are one of the most common brain tumours in childhood, pilocytic astrocytomas are rare in adulthood. We report a series of three pilocytic astrocytomas presenting as an intra/suprasellar mass in the fourth to sixth decades of life. All three radiologically mimicked the appearance of a craniopharyngioma, thus representing a potential radiological and diagnostic pitfall. In this series all three patients underwent successful operative management and have remained well throughout follow-up. The majority of information concerning pilocytic astrocytomas is derived from paediatric populations and so only limited and often conflicting data exist for pilocytic astrocytomas developing in adulthood. Decisions regarding treatment of pilocytic astrocytomas in adults must be made on a multidisciplinary, case-by-case basis.

Phosphorylation of the insulin receptor by AMP-activated protein kinase (AMPK) promotes ligand-independent activation of the insulin signalling pathway in rodent muscle

AIMS/HYPOTHESIS

Muscle may experience hypoglycaemia during ischaemia or insulin infusion. During severe hypoglycaemia energy production is blocked, and an increase of AMP:ATP activates the energy sensor and putative insulin-sensitiser AMP-activated protein kinase (AMPK). AMPK promotes energy conservation and survival by shutting down anabolism and activating catabolic pathways. We investigated the molecular mechanism of a unique glucose stress defence pathway involving AMPK-dependent, insulin-independent activation of the insulin signalling pathway.

METHODS

Cardiac or skeletal myocytes were subjected to glucose and insulin-free incubation for increasing intervals up to 20 h. AMPK, and components of the insulin signalling pathway and their targets were quantified by western blot using phosphor-specific antibodies. Phosphomimetics were used to determine the function of IRS-1 Ser789 phosphorylation and in vitro [³²P]ATP kinase assays were used to measure the phosphorylation of the purified insulin receptor by AMPK.

RESULTS

Glucose deprivation increased Akt-Thr308 and Akt-Ser473 phosphorylation by almost tenfold. Phosphorylation of glycogen synthase kinase 3 beta increased in parallel, but phosphorylation of ribosomal 70S subunit-S6 protein kinase and mammalian target of rapamycin decreased. AMPK inhibitors blocked and aminoimidazole carboxamide ribonucleotide (AICAR) mimicked the effects of glucose starvation. Glucose deprivation increased the phosphorylation of IRS-1 on serine-789, but phosphomimetics revealed that this conferred negative regulation. Glucose deprivation enhanced tyrosine phosphorylation of IRS-1 and the insulin receptor, effects that were blocked by AMPK inhibition and mimicked by AICAR. In vitro kinase assays using purified proteins confirmed that the insulin receptor is a direct target of AMPK.

CONCLUSIONS/INTERPRETATION

AMPK phosphorylates and activates the insulin receptor, providing a direct link between AMPK and the insulin signalling pathway; this pathway promotes energy conservation and survival of muscle exposed to severe glucose deprivation.

Towards new business models for R&D for novel antibiotics

In the face of a growing global burden of resistance to existing antibiotics, a combination of scientific and economic challenges has posed significant barriers to the development of novel antibacterials over the past few decades. Yet the bottlenecks at each stage of the pharmaceutical value chain-from discovery to post-marketing-present opportunities to reengineer an innovation pipeline that has fallen short. The upstream hurdles to lead identification and optimization may be eased with greater multi-sectoral collaboration, a growing array of alternatives to high-throughput screening, and the application of open source approaches. Product development partnerships and South-South innovation platforms have shown promise in bolstering the R&D efforts to tackle neglected diseases. Strategies that delink product sales from the firms' return on investment can help ensure that the twin goals of innovation and access are met. To effect these changes, both public and private sector stakeholders must show greater commitment to an R&D agenda that will address this problem, not only for industrialized countries but also globally.

Haemangioblastoma: a rare cause of a cerebellar mass in the elderly

In the elderly, cerebellar lesions are commonly metastatic tumours with poor prognosis. We describe two octogenarians who presented with obstructive hydrocephalus, secondary to posterior fossa tumours that, on computed tomography, were thought to be cerebellar metastases. Both lesions were excised and the histology proved them to be cerebellar haemangioblastomas, primary benign tumours of the posterior fossa, which are rare in the elderly.

Delayed postoperative intracerebral abscess caused byProprionibacterium acnes: case report and review of the literature

A case of delayed intracerebral abscess due to Proprionibacterium acnes (P. acnes), 18 months after an uneventful excision of a parasagittal haemangiopericytoma in a 61-year-old female is reported. This is highly unusual as cerebral abscess by P. acnes is rare and it occurred so late postoperatively in the absence of known risk factors. We propose the inclusion of cerebral abscess by P. acnes in the differential diagnosis of lesions that mimic tumour recurrences, after clean craniotomies.

Increased mutability of Pseudomonas aeruginosa in biofilms

OBJECTIVES

Isolates of Pseudomonas aeruginosa from cystic fibrosis (CF) patients are frequently hypermutable due to selection of mutants with defects in DNA repair genes such as mutS. Since P. aeruginosa grows as a biofilm within the infected CF lung, it is possible that this mode of growth enhances the mutability of the organism thereby increasing the opportunity to derive permanent hypermutators through mutation in DNA repair genes. We have now conducted experiments to examine this possibility.

METHODS

Using established procedures, we examined the mutability of P. aeruginosa PA01 in planktonic cultures and in biofilm cultures generated by growth in a Sorbarod system. Transcriptional profiling by DNA microarray was used to compare gene expression in planktonic and biofilm cells.

RESULTS

Mutation frequency determinations for resistance to rifampicin and ciprofloxacin demonstrated that biofilm cultures of P. aeruginosa displayed up to a 105-fold increase in mutability compared with planktonic cultures. Several genes (ahpC, katA, sodB and PA3529, a probable peroxidase) that encode enzymes conferring protection against oxidative DNA damage were down-regulated in biofilm cells. In particular, katA, which encodes the major pseudomonal antioxidant catalase, was down-regulated 7.7-fold.

CONCLUSIONS

Down-regulation of antioxidant enzymes in P. aeruginosa biofilms may enhance the rate of mutagenic events due to the accumulation of DNA damage. Since P. aeruginosa forms biofilms in the CF lung, this mode of growth may enhance the direct selection of antibiotic-resistant organisms in CF patients and also increase the opportunity to derive permanent hypermutators thereby providing a further source of antibiotic-resistant mutants in the CF lung.

An association between thyroid disease and breast cancer

21063

Background: Anecdotal studies and isolated case reports have observed an association of thyroid disease and breast cancer. This purported association remains controversial. We describe a retrospective case-control study on the prevalence of breast cancer in patients with abnormal thyroid function studies. Age-matched subjects served as controls. Methods: We reviewed 6211 cases of abnormal TSH values between 1/04 and 12/05 and determined the number of cases with breast cancer. We compared those data to 3,151 control subjects with normal TSH seen during the same period. We excluded patients with thyroid cancer from the total number of malignancies in both groups because abnormal TSH would be expected to result from its treatment. We also reviewed the ER, PR, her 2 neu status and free thyroxine of patients with breast cancers. Results: Breast cancer rate of 36% of all cancers (37/102) in the abnormal TSH group was significantly higher than that of 18% (14/77) in the normal TSH group. (p = 0.012). Breast cancers in the study group with abnormal thyroid function were more frequently hormone receptor positive (74% vs. 67%) and her 2 neu negative (67% vs. 50%). Conclusions: The data suggest that there is an increased rate of breast cancer in patients with abnormal thyroid function. The trend of hormone receptor positive disease in the abnormal TSH group suggests that the IGF receptor may play an important role in the relationship between thyroid disease and breast cancer. The IGF receptor may be a potential target for therapeutic drug development for breast cancer prevention and management. Further studies are warranted.

No significant financial relationships to disclose.

Emergence and maintenance of resistance to fluoroquinolones and coumarins in Staphylococcus aureus: predictions from in vitro studies

OBJECTIVES

Fluoroquinolones and coumarins interfere with the activity of bacterial type II topoisomerase enzymes. We examined the development of resistance to these agents in Staphylococcus aureus and determined the effect of simultaneous topoisomerase IV and DNA gyrase mutations on the biological fitness of the organism. This work aimed to gain insight into how such mutants might arise and survive in the clinical environment.

METHODS

Spontaneous mutants resistant to fluoroquinolones and coumarins were selected in S. aureus. Resistance mutations were identified by DNA sequencing of PCR amplicons corresponding to the genes encoding topoisomerase IV and DNA gyrase. In vitro fitness of resistant mutants was compared with the antibiotic-susceptible progenitor strain using pair-wise competition assays.

RESULTS

Mutants simultaneously resistant to both a fluoroquinolone and either of the coumarins, novobiocin or coumermycin A1, could not be recovered following a single-step selection. However, mutants concurrently resistant to both classes of antimicrobial could be generated by step-wise selections. These mutants demonstrated reductions in competitive fitness of up to 36%.

CONCLUSIONS

Dual-targeting of topoisomerase IV and DNA gyrase enzymes, for example with the combination of a fluoroquinolone and a coumarin agent, could minimize the emergence of resistance to these drugs in S. aureus. However, resistance-associated fitness costs may not be sufficient to limit the survival of mutants with dual resistance, if they arose in the clinical setting.

Characterization of the epidemic European fusidic acid-resistant impetigo clone of Staphylococcus aureus

Resistance to the antibiotic fusidic acid in European strains of Staphylococcus aureus causing impetigo has increased in recent years. This increase appears to have resulted from clonal expansion of a strain we have designated the epidemic European fusidic acid-resistant impetigo clone (EEFIC), which carries the fusidic acid resistance determinant fusB on its chromosome. To understand better the properties of the EEFIC responsible for its success, we have performed detailed phenotypic and genotypic characterization of this clone. Molecular typing revealed the EEFIC to be ST123, spa type t171, and agr type IV and therefore unrelated to earlier prevalent fusB(+) strains found in the United Kingdom. EEFIC strains exhibited resistance to fusidic acid, penicillin, and, in some cases, erythromycin, which are all used in the treatment of impetigo. PCR analysis of the EEFIC and complete DNA sequencing of the 39.3 Kb plasmid it harbors identified genes encoding several toxins previously implicated in impetigo (exfoliative toxins A and B and EDIN-C). The location of fusB was mapped on the chromosome and found to be associated with a novel 16.6-kb genomic island integrated downstream of groEL. Although this element is related to classical staphylococcal pathogenicity islands, it does not encode any known virulence factors and consequently has been designated SaRI(fusB) (for "S. aureus resistance island carrying fusB").

Genetic basis of resistance to fusidic acid in staphylococci

Resistance to fusidic acid in Staphylococcus aureus often results from acquisition of the fusB determinant or from mutations in the gene (fusA) that encodes the drug target (elongation factor G). We now report further studies on the genetic basis of resistance to this antibiotic in the staphylococci. Two staphylococcal genes that encode proteins exhibiting ca. 45% identity with FusB conferred resistance to fusidic acid in S. aureus. One of these genes (designated fusC) was subsequently detected in all fusidic acid-resistant clinical strains of S. aureus tested that did not carry fusB or mutations in fusA, and in strains of S. intermedius. The other gene (designated fusD) is carried by S. saprophyticus, explaining the inherent resistance of this species to fusidic acid. Fusidic acid-resistant strains of S. lugdunensis harbored fusB. Thus, resistance to fusidic acid in clinical isolates of S. aureus and other staphylococcal species frequently results from expression of FusB-type proteins.

Molecular genetic and structural modeling studies of Staphylococcus aureus RNA polymerase and the fitness of rifampin resistance genotypes in relation to clinical prevalence

The adaptive and further evolutionary responses of Staphylococcus aureus to selection pressure with the antibiotic rifampin have not been explored in detail. We now present a detailed analysis of these systems. The use of rifampin for the chemotherapy of infections caused by S. aureus has resulted in the selection of mutants with alterations within the beta subunit of the target enzyme, RNA polymerase. Using a new collection of strains, we have identified numerous novel mutations in the beta subunits of both clinical and in vitro-derived resistant strains and established that additional, undefined mechanisms contribute to expression of rifampin resistance in clinical isolates of S. aureus. The fitness costs associated with rifampin resistance genotypes were found to have a significant influence on their clinical prevalence, with the most common clinical genotype (H481N, S529L) exhibiting no fitness cost in vitro. Intragenic mutations which compensate for the fitness costs associated with rifampin resistance in clinical strains of S. aureus were identified for the first time. Structural explanations for rifampin resistance and the loss of fitness were obtained by molecular modeling of mutated RNA polymerase enzymes.

N-alkyl-substituted glycopeptide antibiotics

The glycopeptide antibiotic vancomycin has proved valuable in the treatment of staphylococcal and enterococcal infections, particularly those caused by strains resistant to other antibiotics. The emergence of high-level resistance to vancomycin within the enterococci, and its potential for transfer to other pathogenic Gram-positive cocci, has led to interest in developing new glycopeptide antibiotics with activity against vancomycin resistant organisms. The N-alkylated glycopeptide antibiotics, under development by Lilly Research Laboratories, represent a new series of compounds possessing these properties. The lead compound in this series, LY 333328, is reported to be in Phase I trials.

Protein synthesis as a target for antibacterial drugs: current status and future opportunities

The discovery and development of clinically useful antibiotic classes, such as the aminoglycosides, macrolides and tetracyclines, have clearly demonstrated that bacterial protein synthesis is a suitable target for drug intervention. New information on the binding of classical protein synthesis inhibitors to ribosomal RNA provides a rational explanation for their selective action against bacteria and also explains why chromosomal point mutations conferring resistance by structural changes at the target site are relatively rare in the majority of bacteria. These principles will be helpful when considering strategies for the screening or design of novel protein synthesis inhibitors that could be developed as new antibiotics. Recent progress in the discovery and development of bacterial protein synthesis inhibitors is illustrated by consideration of the glycylcyclines, ketolides, oxazolidinones and streptogramins.

Prospects for antisense agents in the therapy of bacterial infections

Antisense agents have received widespread interest as potential therapeutic agents for a number of diseases, including cancer, inflammatory conditions and viral infections. However, less emphasis has been placed on their potential application in the therapy of bacterial infections. This review considers the reported effects of backbone modified oligonucleotides (phosphorothioate and methyl phosphonate analogues) as well as peptide nucleic acids (PNAs) on gene expression and bacterial growth. In addition to suppressing bacterial growth by decreasing the expression of essential genes, it is also evident that antisense agents can be specifically targeted to genes that control expression of antibiotic resistance mechanisms, thereby potentially restoring an antibiotic-sensitive phenotype to the cell. Despite observations from several studies that antisense agents can interfere with bacterial gene expression in a sequence specific manner, their uptake into bacteria is poor. At present this is a limiting factor in their potential application as therapeutic agents for bacterial infections.

Approaches to antibacterial drug discovery

The discovery of new antibacterial drugs can be based either upon empirical screening methods or structure-based design. Empirical methods utilise both intact bacteria and isolated biochemical targets for high throughput screening of natural product or chemical libraries to detect inhibitor leads. Structure-based methods for drug design are based upon understanding the molecular architecture of the active site in an appropriate target molecule. Empirical methods have been widely applied to screen for antibacterial agents and the introduction of combinatorial methods for the synthesis of chemical libraries considerably expands the potential of empirical screening methods. In contrast, structure-based drug design has not yet been widely applied to the development of antibacterial drugs, although it has proved to be a successful approach in other therapeutic areas. Recent advances in the sequencing of bacterial genomes will assist both empirical and structure-based approaches by identifying new, essential bacterial genes whose products may become the targets of new agents with selective antibacterial activity.

Intradural metastatic spinal cord compression from ACTH-secreting pituitary carcinoma

Pituitary carcinomas are uncommon and intradural metastatic spread to the spine is rarer still. We describe a 27-year old man with metastatic spinal cord compression from an adrenocorticotrophic hormone (ACTH) cell pituitary carcinoma, 16 years following the initial presentation. He had three previous resections of the pituitary tumour and post-operative radiotherapy. The intradural, extramedullary spinal metastases causing thoracic and lumbar cord compression were excised, with neurological improvement. Spinal metastases in pituitary carcinoma are uncommon, but aggressive surgical resection of the spinal metastases produces good symptomatic relief.

A knot in the catheter--an unusual cause of ventriculo-peritoneal shunt blockage

A 25-year-old woman, who was 25 weeks pregnant, underwent insertion of a VP shunt for hydrocephalus, secondary to a bithalamic glioma. Two months later, she represented with symptoms of raised intracranial pressure and MR scan revealed increased ventricular size. On exploration of the shunt, manometry with saline confirmed blockage of the catheter distal to the valve. On re-opening the abdominal wound, the peritoneal catheter was found to be knotted, 2 cm from the end. This segment of the catheter was replaced, with resolution of symptoms, post-operatively. The present case illustrates that a knot in the peritoneal catheter is an extremely rare cause of shunt malfunction. Possible mechanisms underlying it are discussed.

Antimicrobial activity and mechanisms of resistance to cephalosporin P1, an antibiotic related to fusidic acid

The antimicrobial properties of cephalosporin P1, an antibiotic structurally related to fusidic acid, were examined. Cephalosporin P1 exhibited potent activity against methicillin-sensitive Staphylococcus aureus, methicillin-resistant S. aureus and vancomycin-intermediate S. aureus. Mutants of S. aureus resistant to cephalosporin P1 arose with a frequency of 1.6 x 10(-6) for selections at 4 x MIC, a frequency similar to that for fusidic acid. The mutations conferred cross-resistance to fusidic acid and mapped in fusA, the gene encoding elongation factor G. Cross-resistance between cephalosporin P1 and fusidic acid also occurred for S. aureus fusA mutants selected with fusidic acid, and in fusidic acid-resistant clinical isolates. Plasmid pUB101, which mediates resistance to fusidic acid in S. aureus, also conferred resistance to cephalosporin P1. Escherichia coli was intrinsically resistant to both fusidic acid and cephalosporin P1, but deletion of the AcrAB efflux pump resulted in susceptibility to both antibiotics. Although complete cross-resistance between fusidic acid and cephalosporin P1 was demonstrated, the nature and location of fusA mutations in S. aureus when cephalosporin P1 was the selective agent frequently differed from those selected with fusidic acid. This may reflect differences in the interaction of the two antibiotics with the translational apparatus, which results in the selection of separate mutation classes for each antibiotic. Furthermore, in three of 14 mutants selected with fusidic acid, resistance was attributed to mutations lying outside fusA. In contrast, mutations in 10 mutants selected with cephalosporin P1 were all located in fusA.

Exploiting current understanding of antibiotic action for discovery of new drugs

The introduction of antibiotics for the chemotherapy of bacterial infections has been one of the most important medical achievements of the past 50 years. However, the emergence of bacterial resistance to antibiotics undermines the therapeutic utility of existing agents, creating a requirement for the discovery of new antibacterial drugs. Several drug discovery strategies have emerged, including incremental improvements to existing antibiotics by chemical manipulation and the search for novel drug targets based on genomic approaches. An alternative strategy seeks to exploit opportunities for drug discovery arising from an understanding of the mode of action of existing antibiotics. Thus biochemical pathways or processes inhibited by antibiotics already in clinical use may nevertheless contain key functions that represent unexploited targets for further drug discovery. A major benefit of employing pathways or processes that are already known to contain drug targets is that proof of principle for drug intervention is already established. This approach to drug discovery is illustrated by reviewing target sites for existing antibiotics and considering how this information might be applied for the discovery of new agents inhibiting peptidoglycan synthesis, tRNA synthesis, transcription and DNA replication

Exploiting current understanding of antibiotic action for discovery of new drugs

The introduction of antibiotics for the chemotherapy of bacterial infections has been one of the most important medical achievements of the past 50 years. However, the emergence of bacterial resistance to antibiotics undermines the therapeutic utility of existing agents, creating a requirement for the discovery of new antibacterial drugs. Several drug discovery strategies have emerged, including incremental improvements to existing antibiotics by chemical manipulation and the search for novel drug targets based on genomic approaches. An alternative strategy seeks to exploit opportunities for drug discovery arising from an understanding of the mode of action of existing antibiotics. Thus biochemical pathways or processes inhibited by antibiotics already in clinical use may nevertheless contain key functions that represent unexploited targets for further drug discovery. A major benefit of employing pathways or processes that are already known to contain drug targets is that proof of principle for drug intervention is already established. This approach to drug discovery is illustrated by reviewing target sites for existing antibiotics and considering how this information might be applied for the discovery of new agents inhibiting peptidoglycan synthesis, tRNA synthesis, transcription and DNA replication.

Glycylcyclines: third-generation tetracycline antibiotics

Although tetracycline antibiotics have some roles in human and veterinary medicine, the widespread emergence of microbial resistance has severely limited their effectiveness. A new generation of tetracyclines, the glycylcyclines, is being specifically developed to overcome problems of resistance to earlier tetracyclines. One of the glycylcyclines, 9-t-butylglycylamido-minocycline (GAR-936, tigilcycline), is currently undergoing clinical trials and microbiological, pharmacodynamic and pharmacokinetic data have recently been presented for several glycylcyclines, including GAR-936. An ongoing concern is whether resistance to glycylcyclines might arise in the future.

Tetracycline antibiotics: mode of action, applications, molecular biology, and epidemiology of bacterial resistance

Tetracyclines were discovered in the 1940s and exhibited activity against a wide range of microorganisms including gram-positive and gram-negative bacteria, chlamydiae, mycoplasmas, rickettsiae, and protozoan parasites. They are inexpensive antibiotics, which have been used extensively in the prophlylaxis and therapy of human and animal infections and also at subtherapeutic levels in animal feed as growth promoters. The first tetracycline-resistant bacterium, Shigella dysenteriae, was isolated in 1953. Tetracycline resistance now occurs in an increasing number of pathogenic, opportunistic, and commensal bacteria. The presence of tetracycline-resistant pathogens limits the use of these agents in treatment of disease. Tetracycline resistance is often due to the acquisition of new genes, which code for energy-dependent efflux of tetracyclines or for a protein that protects bacterial ribosomes from the action of tetracyclines. Many of these genes are associated with mobile plasmids or transposons and can be distinguished from each other using molecular methods including DNA-DNA hybridization with oligonucleotide probes and DNA sequencing. A limited number of bacteria acquire resistance by mutations, which alter the permeability of the outer membrane porins and/or lipopolysaccharides in the outer membrane, change the regulation of innate efflux systems, or alter the 16S rRNA. New tetracycline derivatives are being examined, although their role in treatment is not clear. Changing the use of tetracyclines in human and animal health as well as in food production is needed if we are to continue to use this class of broad-spectrum antimicrobials through the present century.

Tetracycline antibiotics: mode of action, applications, molecular biology, and epidemiology of bacterial resistance

Tetracyclines were discovered in the 1940s and exhibited activity against a wide range of microorganisms including gram-positive and gram-negative bacteria, chlamydiae, mycoplasmas, rickettsiae, and protozoan parasites. They are inexpensive antibiotics, which have been used extensively in the prophlylaxis and therapy of human and animal infections and also at subtherapeutic levels in animal feed as growth promoters. The first tetracycline-resistant bacterium, Shigella dysenteriae, was isolated in 1953. Tetracycline resistance now occurs in an increasing number of pathogenic, opportunistic, and commensal bacteria. The presence of tetracycline-resistant pathogens limits the use of these agents in treatment of disease. Tetracycline resistance is often due to the acquisition of new genes, which code for energy-dependent efflux of tetracyclines or for a protein that protects bacterial ribosomes from the action of tetracyclines. Many of these genes are associated with mobile plasmids or transposons and can be distinguished from each other using molecular methods including DNA-DNA hybridization with oligonucleotide probes and DNA sequencing. A limited number of bacteria acquire resistance by mutations, which alter the permeability of the outer membrane porins and/or lipopolysaccharides in the outer membrane, change the regulation of innate efflux systems, or alter the 16S rRNA. New tetracycline derivatives are being examined, although their role in treatment is not clear. Changing the use of tetracyclines in human and animal health as well as in food production is needed if we are to continue to use this class of broad-spectrum antimicrobials through the present century.

Mutation frequencies for resistance to fusidic acid and rifampicin in Staphylococcus aureus

Frequencies at which mutants resistant to fusidic acid and/or rifampicin arose in vitro were determined in Staphylococcus aureus strains including methicillin-susceptible S. aureus (MSSA), methicillin-resistant S. aureus (MRSA), vancomycin-intermediate resistant S. aureus (VISA) and hetero-VISA. The concentrations of fusidic acid (30 and 15 mg/L) and rifampicin (16 and 1 mg/L) used for selection were equal to the expected maximum and minimum serum concentrations after an oral regimen of rifampicin 900 mg od, together with fusidic acid 500 mg tds. Resistant mutants arose at a frequency of around 10(-8) for selections with rifampicin, but were undetectable (frequency <10(-11)) for selections with fusidic acid. Mutants were not recovered (frequency <10(-11)) after selections in the presence of both fusidic acid and rifampicin at 30/16 and 15/1 mg/L. Our results suggest that these antibiotics, when used in combination, could have a wider role in the management of staphylococcal infections.

Antimicrobial properties and mode of action of the pyrrothine holomycin

Holomycin, a member of the pyrrothine class of antibiotics, displayed broad-spectrum antibacterial activity, inhibiting a variety of gram-positive and gram-negative bacteria, with the exception of Enterobacter cloacae, Morganella morganii, and Pseudomonas aeruginosa. The antibiotic lacked activity against the eukaryotic microorganisms Saccharomyces cerevisiae and Candida kefyr. Holomycin exhibited a bacteriostatic response against Escherichia coli that was associated with rapid inhibition of RNA synthesis in whole cells. Inhibition of RNA synthesis could have been a secondary consequence of inhibiting tRNA aminoacylation, thereby inducing the stringent response. However, the levels of inhibition of RNA synthesis by holomycin were similar in a stringent and relaxed pair of E. coli strains that were isogenic except for the deletion of the relA gene. This suggests that inhibition of RNA synthesis by holomycin could reflect direct inhibition of DNA-dependent RNA polymerase. Examination of the effects of holomycin on the kinetics of the appearance of beta-galactosidase in induced E. coli cells was also consistent with inhibition of RNA polymerase at the level of RNA chain elongation. However, holomycin only weakly inhibited E. coli RNA polymerase in assays using synthetic poly(dA-dT) and plasmid templates. Furthermore, inhibition of RNA polymerase was observed only at holomycin concentrations in excess of those required to inhibit the growth of E. coli. It is possible that holomycin is a prodrug, requiring conversion in the cell to an active species that inhibits RNA polymerase.

Affinities of beta-lactams for penicillin binding proteins of Chlamydia trachomatis and their antichlamydial activities

Binding affinities of beta-lactam antibiotics for the three penicillin binding proteins (PBPs) from Chlamydia trachomatis were determined in vitro and compared with their antichlamydial activities. Mecillinam selectively inhibited PBP1, with a 50% inhibitory concentration for PBP1 binding (0.2 microg/ml) similar to the MIC (0.1 microg/ml) and minimum bactericidal concentration (0.25 microg/ml). Although the other beta-lactams inhibited a wider range of PBPs than mecillinam, their antichlamydial activities were inferior to that of mecillinam.

RNA polymerase inhibitors with activity against rifampin-resistant mutants of Staphylococcus aureus

A collection of rifampin-resistant mutants of Staphylococcus aureus with characterized RNA polymerase beta-subunit (rpoB) gene mutations was cross-screened against a number of other RNA polymerase inhibitors to correlate susceptibility with specific rpoB genotypes. The rpoB mutants were cross-resistant to streptolydigin and sorangicin A. In contrast, thiolutin, holomycin, corallopyronin A, and ripostatin A retained activity against the rpoB mutants. The second group of inhibitors may be of interest as drug development candidates.

Antibacterial spectra of drugs used for chemotherapy of mycobacterial infections

The mechanism of action of many antimycobacterial agents is poorly understood. To obtain preliminary information on whether the targets for some of these drugs might also occur in other bacteria, the in vitro activities of selected agents against Escherichia coli, Bacillus subtilis and Staphylococcus aureus were determined. Dapsone, p-aminosalicylic acid and thiacetazone failed to inhibit the above organisms (MIC values > 100 micrograms/ml) that may therefore lack targets for these drugs. Capreomycin, viomycin and clofazimine demonstrated activity against some of the organisms (MIC values < 100 micrograms/ml) suggesting that the targets of these drugs may not be restricted to mycobacterial species. The agents were all potent inhibitors of Mycobacterium bovis bacille Calmette-Guérin (MIC values 0.08-0.5 microgram/ml).

Expression of the Staphylococcus aureus UDP-N-acetylmuramoyl- L-alanyl-D-glutamate:L-lysine ligase in Escherichia coli and effects on peptidoglycan biosynthesis and cell growth

The monomer units in the Escherichia coli and Staphylococcus aureus cell wall peptidoglycans differ in the nature of the third amino acid in the L-alanyl-gamma-D-glutamyl-X-D-alanyl-D-alanine side chain, where X is meso-diaminopimelic acid or L-lysine, respectively. The murE gene from S. aureus encoding the UDP-N-acetylmuramoyl-L-alanyl-D-glutamate: L-lysine ligase was identified and cloned into plasmid vectors. Induction of its overexpression in E. coli rapidly results in abnormal morphological changes and subsequent cell lysis. A reduction of 28% in the peptidoglycan content was observed in induced cells, and analysis of the peptidoglycan composition and structure showed that ca. 50% of the meso-diaminopimelic acid residues were replaced by L-lysine. Lysine was detected in both monomer and dimer fragments, but the acceptor units from the latter contained exclusively meso-diaminopimelic acid, suggesting that no transpeptidation could occur between the epsilon-amino group of L-lysine and the alpha-carboxyl group of D-alanine. The overall cross-linking of the macromolecule was only slightly decreased. Detection and analysis of meso-diaminopimelic acid- and L-lysine-containing peptidoglycan precursors confirmed the presence of L-lysine in precursors containing amino acids added after the reaction catalyzed by the MurE ligase and provided additional information about the specificity of the enzymes involved in these latter processes.