Cell-wall recycling and synthesis in Escherichia coli and Pseudomonas aeruginosa - their role in the development of resistance.

The bacterial cell-wall that forms a protective layer over the inner membrane is called the murein sacculus - a tightly cross-linked peptidoglycan mesh unique to bacteria. Cell-wall synthesis and recycling are critical cellular processes essential for cell growth, elongation and division. Both de novo synthesis and recycling involve an array of enzymes across all cellular compartments, namely the outer membrane, periplasm, inner membrane and cytoplasm. Due to the exclusivity of peptidoglycan in the bacterial cell-wall, these players are the target of choice for many antibacterial agents. Our current understanding of cell-wall biochemistry and biogenesis in Gram-negative organisms stems mostly from studies of Escherichia coli. An incomplete knowledge on these processes exists for the opportunistic Gram-negative pathogen, Pseudomonas aeruginosa. In this review, cell-wall synthesis and recycling in the various cellular compartments are compared and contrasted between E. coli and P. aeruginosa. Despite the fact that there is a remarkable similarity of these processes between the two bacterial species, crucial differences alter their resistance to ß-lactams, fluoroquinolones and aminoglycosides. One of the common mediators underlying resistance is the amp system whose mechanism of action is closely associated with the cell-wall recycling pathway. The activation of amp genes results in expression of AmpC ß-lactamase through its cognate regulator AmpR which further regulates multi-drug resistance. In addition, other cell-wall recycling enzymes also contribute to antibiotic resistance. This comprehensive summary of the information should spawn new ideas on how to effectively target cell-wall processes to combat the growing resistance to existing antibiotics.

Overview on the Current Status of Zika Virus Pathogenesis and Animal Related Research.

There is growing evidence that Zika virus (ZIKV) infection is linked with activation of Guillan-Barré syndrome (GBS) in adults infected with the virus and microcephaly in infants following maternal infection. With the recent outpour in publications by numerous research labs, the association between microcephaly in newborns and ZIKV has become very apparent in which large numbers of viral particles were found in the central nervous tissue of an electively aborted microcephalic ZIKV-infected fetus. However, the underlying related mechanisms remain poorly understood. Thus, development of ZIKV-infected animal models are urgently required. The need to develop drugs and vaccines of high efficacy along with efficient diagnostic tools for ZIKV treatment and management raised the demand for a very selective animal model for exploring ZIKV pathogenesis and related mechanisms. In this review, we describe recent advances in animal models developed for studying ZIKV pathogenesis and evaluating potential interventions against human infection, including during pregnancy. The current research directions and the scientific challenges ahead in developing effective vaccines and therapeutics are also discussed.

Muropeptides in Pseudomonas aeruginosa and their Role as Elicitors of ß-Lactam-Antibiotic Resistance.

Muropeptides are a group of bacterial natural products generated from the cell wall in the course of its turnover. These compounds are cell-wall recycling intermediates and are also involved in signaling within the bacterium. However, the identity of these signaling molecules remains elusive. The identification and characterization of 20 muropeptides from Pseudomonas aeruginosa is described. The least abundant of these metabolites is present at 100 and the most abundant at 55,000 molecules per bacterium. Analysis of these muropeptides under conditions of induction of resistance to a ß-lactam antibiotic identified two signaling muropeptides (N-acetylglucosamine-1,6-anhydro-N-acetylmuramyl pentapeptide and 1,6-anhydro-N-acetylmuramyl pentapeptide). Authentic synthetic samples of these metabolites were shown to activate expression of ß-lactamase in the absence of any ß-lactam antibiotic, thus indicating that they serve as chemical signals in this complex biochemical pathway.

Comparison of the efficacy of carbamazepine, gabapentin and lamotrigine for neuropathic pain in rats.

BACKGROUND: Neuropathic pain in cancer patients remain a treatment challenge. Many of the anticancer drugs have to be abandoned because patients develop neuropathic pain. Several antiepileptic drugs like carbamazepine, phenytoin, lamotrigine, felbamate are effective in neuropathic pain and trigeminal neuralgia. However, their efficacy varies. AIM: The aim of this study is to compare the efficacy of antiepileptic drugs in neuropathic pain induced by anticancer drugs. MATERIALS AND METHODS: Neuropathic pain was induced in rats by injecting 4 doses of paclitaxel. The rats were divided into four groups of six animals each. Group I was treated with oral carbamazepine (cbz) 100 mg/kg, group II received oral gabapentin (gbp) 60 mg/kg, and group III was treated with oral lamotrigine (lam) 40 mg/kg and group IV was the control group. Behavioural testing for thermal hyperalgesia and mechanical hyperalgesia was assessed from 26(th) day of paclitaxel administration to next five days by hot plate method and Randall Siletto test, respectively, in all the four groups. One way analysis of variance followed by Scheffe's post hoc test was used for statistical analysis. RESULTS: In thermal hyperalgesia lam treated group was found to be significantly (P < 0.001) superior to cbz and gbp treated group. In mechanical hyperalgesia, lam group showed significant response (P < 0.05) as compared to gbp group. However, the gbp treated group showed a significant (P < 0.01) improvement after three days of treatment. CONCLUSIONS: In paclitaxel induced neuropathic pain, lamotrigine appears to be a promising drug. The difference in responses shown by different antiepileptics' depends on the etiology of the underlying mechanisms in neuropathic pain.