Mechanisms of virus resistance and antiviral activity of snake venoms

Viruses depend on cell metabolism for their own propagation. The need to foster an intimate relationship with the host has resulted in the development of various strategies designed to help virus escape from the defense mechanisms present in the host. Over millions of years, the unremitting battle between pathogens and their hosts has led to changes in evolution of the immune system. Snake venoms are biological resources that have antiviral activity, hence substances of significant pharmacological value. The biodiversity in Brazil with respect to snakes is one of the richest on the planet; nevertheless, studies on the antiviral activity of venom from Brazilian snakes are scarce. The antiviral properties of snake venom appear as new promising therapeutic alternative against the defense mechanisms developed by viruses. In the current study, scientific papers published in recent years on the antiviral activity of venom from various species of snakes were reviewed. The objective of this review is to discuss the mechanisms of resistance developed by viruses and the components of snake venoms that present antiviral activity, particularly, enzymes, amino acids, peptides and proteins.

Prevalence and genetic characterization of blaCTX-M among Klebsiella pneumoniae isolates collected in an intensive care unit in Brazil.

Thirteen (44.8%) CTX-M-2-producing K. pneumoniae clinical isolates were identified among 29 strains collected from single patients with serious infection hospitalized in an intensive care unit of a tertiary hospital located in São Paulo, Brazil. These isolates belonged to 9 different typing clusters and showed great diversity of plasmid content. Their bla(CTX-M-2)was carried in an ISCR1/sul1-type integron structure located in transferable plasmids of different sizes or in the chromosome.

Health and economic outcomes of the detection of Klebsiella pneumoniae-produced extended-spectrum beta-lactamase (ESBL) in a hospital with high prevalence of this infection.

INTRODUCTION: Klebsiella pneumoniae is of high prevalence in hospital infections, mainly in bloodstream infections (BSI), and some produce extended-spectrum beta-lactamase (ESBL). For hospitals with a high prevalence of strains producing this enzyme, there is no reference material to show whether the use of the E-test method for their detection, which can be quite expensive, is actually required. OBJECTIVE: To evaluate the cost-benefit of the disk diffusion and E-test methods for the detection of ESBL-producing K. pneumoniae strains in hospitals where a high prevalence of this resistance mechanism in BSI is found. METHODS: One hundred and eight patients with K. pneumoniae BSI were evaluated retrospectively. ESBL-producing strains were identified by the disk diffusion method and by the E-test method. We estimated the costs of both diagnostic methods based on antimicrobial therapy adequacy. RESULTS: Fifty-two percent of K. pneumoniae infections were due to ESBL-producing strains. The disk diffusion method yielded a positive predictive value (PPV) of 94.7% (95% CI: 88.9-100%) and a negative predictive value (NPV) of 96.1% (CI 95%: 90.8-101.4%) in relation to the E-test. We evaluated cost-effectiveness, i.e., we analyzed the cost of both E-test and disk diffusion methods with carbapenem and cephalosporins, and found that the use of the disk diffusion method accounts for approximately US$3300. CONCLUSIONS: In hospitals with a high prevalence of ESBL-producing strains, the disk diffusion method can be used to detect ESBL-producing K. pneumoniae without compromising the clinical progression of patients with BSI. The E-test showed higher accuracy but this method was more expensive than the disk diffusion method. However, the use of the E-test method was demonstrated to be more cost-effective, as we evaluated cost based on antimicrobial therapy adequacy.