The linkage between prevalence of integron I and reduced susceptibility to biocides in MDR Klebsiella pneumoniae isolated from neonates

Background and Objectives: Klebsiella pneumoniae causes challenging nosocomial fatal infections including neonatal sepsis. Our study aims at clarifying the contribution of integrons in the observed reduced susceptibility of multidrug-resistant (MDR) K. pneumoniae isolated from septicemic neonates to the clinically used antimicrobial agents and biocides. Materials and Methods: Eighty-six K. pneumoniae isolates were collected from Mansoura University Children’s Hospital from septicemic neonates. Isolates were subjected to antibiotic and biocide susceptibility using disk diffusion and the agar dilution method, respectively. The distribution of different classes of integrons was screened in the isolates by PCR. Detected inegron I was sequenced in selected isolates. Results: Fifty-seven isolates (66.27%) were MDR. In the MDR isolates, class I integron was detected in 23 (40.3%), inte- gron III was detected in 20 (35%), whereas integron II could not be detected. Sequencing results of integron I from MDR K. pneumoniae isolates revealed that only aminoglycoside and folate synthesis inhibitors gene cassettes were detected, while the rest of the resistance genes were not associated with integron I. Conclusion: The presence of integron I in MDR K. pneumoniae tested isolates may contribute only to some biocide resistance, however, it does not seem to be the only contributor in multiple drug resistance.

A small fragment of factor B as a potential inhibitor of complement alternative pathway activity

BACKGROUND

The complement system is a key player in innate immunity and a modulator of the adaptive immune system. Among the three pathways of complement, the alternative pathway (AP) accounts for most of the complement activation. Factor B (FB) is a major protease of the AP, making it a promising target to inhibit the AP activity in conditions of uncontrolled complement activation.

METHODS

Based on the data obtained from sequence analysis and conformational changes associated with FB, we expressed and purified a recombinant FB fragment (FBfr). We tested the inhibitory activity of the protein against the AP by in vitro assays.

RESULTS

FBfr protein was proven to inhibit the complement AP activity when tested by C3b deposition assay and rabbit erythrocyte hemolytic assay.

CONCLUSION

Our recombinant FBfr was able to compete with the native human FB, which allowed it to inhibit the AP activity. This novel compound is a good candidate for further characterization and testing to be used in complement diagnostic tests and as a drug lead in the field of complement therapeutics.

Dasatinib mitigates renal fibrosis in a rat model of UUO via inhibition of Src/STAT-3/NF-κB signaling

This research aimed to investigate the reno-protective impact of the tyrosine kinase inhibitor dasatinib (DAS) against renal fibrosis induced by unilateral ureteral obstruction (UUO) in rats. DAS administration improved renal function and mitigated renal oxidative stress with paralleled reduction in the ligated kidney mass index, significant retraction in renal histopathological alterations and suppression of renal interstitial fibrosis. Nevertheless, DAS administration attenuated renal expression of phosphorylated Src (p-Src), Abelson (c-Abl) tyrosine kinases, nuclear factor-kappaB (NF-κB) p65, and phosphorylated signal transducer and activator of transcription-3 (p-STAT-3)/STAT-3 with paralleled reduction in renal contents of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and monocyte chemoattractant protein-1 (MCP-1). DAS diminished interstitial macrophage infiltration and decreased renal profibrotic transforming growth factor-β1 (TGF-β1) levels and suppressed interstitial expression of renal α-smooth muscle actin (α-SMA) and fibronectin. Collectively, DAS slowed the progression of renal interstitial fibrosis, possibly via attenuating renal oxidative stress, impairing Src/STAT-3/NF-κB signaling, and reducing renal inflammation.

Antioxidant and anti-inflammatory activities of berberine attenuate hepatic fibrosis induced by thioacetamide injection in rats

Berberine (BBR) is an isoquinoline alkaloid extracted from the roots, rhizomes and stems of coptis. Liver fibrosis is a worldwide health problem with no established therapy until now. The aim of our study is to investigate the efficacy of BBR on hepatic fibrosis induced in rats and to uncover other mechanisms. Rats were injected with thioacetamide (TAA) (200 mg/kg, i.p) twice per week for 6 weeks to induce fibrosis. Treated groups were gavaged with BBR (50 mg/kg/day, p.o) simultaneously with TAA injection. Hepatic antioxidant enzymes (catalase, SOD, GPx) were assessed in hepatic homogenate. Their activities were attenuated by TAA injection and elevated by BBR administration. Additionally, serum IL-6 and mRNA levels of IL-1β, IL-6, IL-10 and IFN-γ were evaluated as inflammatory markers. Our results showed that BBR suppressed the inflammation induced by TAA injection. Tissue expression of α-SMA (marker of activated HSCs), TGF-β1 and fibronectin were measured by immunohistochemistry as well as mRNA expressions of TGF-β1 and fibronectin were quantified as fibrotic markers. The collagen deposition in hepatic tissues was assessed by Masson's trichome staining. BBR significantly alleviated TGF-β1 production, decreased collagen and fibronectin deposition and consequently attenuated hepatic fibrogenesis. Akt pathway controls cell survival, proliferation, migration and adhesion. The relative phosphorylation of Akt was determined in hepatic homogenates that was increased with TAA injection and decreased by BBR treatment. Inhibition of Akt pathway has been linked to the intrinsic pathway of apoptosis. Caspase-3, caspase-9, Bcl-2 and Bax were quantified as apoptotic markers using qPCR and also caspase-3 by immunohistochemistry. BBR-treated rats showed an increase in the expression of apoptotic markers. Moreover, BBR-treated rats showed restoration of normal liver lobular architecture as shown by H&E staining. In conclusion, BBR is a potential therapeutic candidate for liver fibrosis owing to its antioxidant and anti-inflammatory activities.

Complement-Coagulation Cross-Talk: A Potential Mediator of the Physiological Activation of Complement by Low pH

The complement system is a major constituent of the innate immune system. It not only bridges innate and adaptive arms of the immune system but also links the immune system with the coagulation system. Current understanding of the role of complement has extended far beyond fighting of infections, and now encompasses maintenance of homeostasis, tissue regeneration, and pathophysiology of multiple diseases. It has been known for many years that complement activation is strongly pH sensitive, but only relatively recently has the physiological significance of this been appreciated. Most complement assays are carried out at the physiological pH 7.4. However, pH in some extracellular compartments, for example, renal tubular fluid in parts of the tubule, and extracellular fluid at inflammation loci, is sufficiently acidic to activate complement. The exact molecular mechanism of this activation is still unclear, but possible cross-talk between the contact system (intrinsic pathway) and complement may exist at low pH with subsequent complement activation. The current article reviews the published data on the effect of pH on the contact system and complement activity, the nature of the pH sensor molecules, and the clinical implications of these effects. Of particular interest is chronic kidney disease (CKD) accompanied by metabolic acidosis, in which therapeutic alkalinization of urine has been shown significantly to reduce tubular complement activation products, an effect, which may have important implications for slowing progression of CKD.

Absence of the lectin activation pathway of complement does not increase susceptibility to Pseudomonas aeruginosa infections

Pseudomonas aeruginosa remains one of the major clinical pathogens that burden immuno-compromised patients and patients with cystic fibrosis. The present study aimed to define the role of the lectin pathway of complement in the immune-defence against P. aeruginosa in a mouse model of invasive pneumonia. Using in vitro assays specific for each of the three complement pathways, we demonstrate that some strains of P. aeruginosa bind lectin pathway recognition sub-components and initiate complement activation in a lectin pathway-specific mode. All of the tested strains activated complement via classical and alternative pathways. We assessed the importance of lectin pathway activation in fighting P. aeruginosa infections by testing a lectin pathway activating strain in a mouse model of intra-nasal infection. MASP-2 (mannan binding lectin associated serine protease-2) deficient mice, which have no lectin pathway activity, had no significant survival disadvantage compared to wild type littermates (72.7% and 81.8% survival, respectively, p=0.48). Likewise, no difference in opsonising activity was seen between MASP-2 sufficient and MASP-2 deficient mouse sera. Moreover, cytokine expression profiles in the lungs of WT mice and MASP-2-/- mice were similar throughout the course of P. aeruginosa infection. We conclude that the lectin pathway does not play an essential role in fighting P. aeruginosa infection in mice.