Host Defense Antimicrobial Peptide

Overwhelming, deleterious host immune response to an infection due to release of chemicals to fight the infection 2• 1

Based on research and observation, we now know that infectious diseases are caused by microorganisms (pathogens) and that the immune system provides defense against infectious diseases.

“Bacterial illness is a result of complex interactions between bacteria and the host. During evolution, humans developed many ways to protect themselves against bacterial pathogens. On the other hand, bacteria have developed strategies to evade, subvert or circumvent these defenses” (Sousa, 2003) “One of the most important characteristics of bacterial pathogenicity is the various strategies developed by prokaryotic organisms to use host molecules for their own benefit” (Sousa, 2003). “To accomplish this, bacteria have evolved elaborate control mechanisms to turn genes on and off, varying the transcriptional activator or

Not all bacteremias lead to sepsis. People have everyday bacteremia, particularly, from oral cavity, but sepsis develops rarely [27-31]. It occurs when the infection is resistant to host antibacterial defense. The latter is different in the bloodstream and tissues. If the infection develops locally (tissue, cavity, etc.) and then enters the bloodstream, there are two stages of sepsis: pre-septic (local) and septic (generalized). If infection enters the bloodstream directly from an external source (contaminated intravenous injection, bite, etc.), the pre-septic stage is absent. Local antibacterial defense is provided by phagocytosis (leukocytes and their local versions: resident macrophages), complement, NETs, etc., whereas in the bloodstream

1 and 3). This antibiotic is effective against both gram positive and negative bacteria, so it would be effective against Staphylococcus epidermidis. This antibiotic is able to kill bacteria by interfering with the cell wall synthesis, weakening it, and causing its death. However, just like with Penicillin, some bacteria have become resistant to this antibiotic (6). The hypothesis stated that Staphylococcus epidermidis would be susceptible to Ampicillin because although some bacteria have become resistant this one has not (7). According to the class data, two of the tests resulted in in susceptibility, one resulted in an intermediate effect, and the rest were resistant (see Figs. 2 and 5). It seems that Staphylococcus epidermidis is in the process of becoming resistant to Ampicillin because of the varied data. However, the group data did not support the hypothesis that the bacteria would still be

Peptides of the innate immune system have a broad range of microbicidal activities and can affect Gram positive and Gram negative bacteria as well as mycobacteria, spirochetes, fungi, and some enveloped bacteria. The same can be said of magainin-2 and melittin.(Mark, 601)

Although a vaccine does exist, its cost and multiple doses needed to achieve immunity have limited its acceptability by the medical community [20, 21]. Antimicrobial therapy has been at the forefront of research in trying to identify if prophylactic treatment is necessary, what drug is most successful, and what dosing is most appropriate.

It also helps with the prevention of PCP in HIV-positive patients, but should be used cautiously due to the incidence of adverse reactions. This drug is also active against many strains of gram-positive pathogens including: Streptococcus pneumoniae, Staphylococcus aureus, Group A beta-hemolytic streptococci, Nocardia, Enterococcus. It also has activity against many gram-negative pathogens, such as: Acinetobacter, Enterobacter, Klebsiella pneumoniae, Escherichia coli, Proteus mirabilis, Shigella, Xanthomonas maltophilia, and Haemophilus influenzae, including ampicillin-resistant

S. aureus responsible for 70% skin infection in children, moreover, the incidence of skin infection caused by MRSA is in a continuous increasing (Nataraj et al., 2014). Pseudomonas aeruginosa is gram-negative bacteria, it is classic opportunistic bacteria and are often severe, life-threatening and difficult to treat due to it has an innate resistance to many of antibiotic and disinfection (Bangera D et al., 2015; Wendell Lou B. Ladion et al., 2015). P. aeruginosa recently acquired significant as one of the most important organisms that cause nosocomial infection due to having an ability to survive in hospital environments, in addition, it has the ability to develop resistance against many antimicrobial agents (Nagoba et al., 2013). Wound infection caused by P. aeruginosa rapidly deteriorating and lead to systemic spread and therefore death within days or weeks (Turner et al., 2014). Escherichia coli is gram negative bacteria and considered as a member of the Enterobacteriaceae, it is innocuous resident in a gastrointestinal tract, but at the same time has the ability to cause

Humans such as us alike cannot live in a world without a highly effective defense system that helps us to resist against infections and toxins caused by microorganisms. The immune system is a complex network of consorting cells, tissues and organs that defend the body from pathogens and other harmful substances. This essential complex consists of two subsections : the innate immune system and the adaptive immune system.

By cloning the LPS locus, he was able to identify a ‘toll-like receptor’ (TLR4) which acted sense the presence of invading microbes bearing LPS. Receptors of the same family, ten of which are now known to exist in humans, each ‘tuned’ to detect different kinds of microbes, also initiate inflammation to combat infection, but sometimes shock as well. It was for this work that Beutler won the Nobel Prize, and his team at the University of Texas Southwestern Medical Center continues to search for proteins that protect mammals against defined infections. In the process, they have identified genes required for other functions, including the regulation of iron absorption, hearing and the development of embryos

Antibiotics are amongst the most important medical discoveries and their introduction represents a remarkable success story (Hedin, 2011). The term antibiotics literally means against life (Walsh, 2000). Thus antibiotics can be used against any microbe such as bacteria, viruses, fungi, and protozoa. However, some people use the term to only apply to bacteria, but in this paper, the more appropriate term will be used.

To date, the following groups of peptides have been identified: tryptophyllins (Ge et al. 2014, Wang et al. 2015), tachykinins (Mignogna et al. 1997, Wang et al. 2008), bradykinins, caerulein, sauvagine (Mignogna et al. 1997, Wang et al. 2008), and opioid peptides (Mignogna et al. 1997). In more recent years, investigators discovered adenoregulin, caerin homologs, dermaseptins (Wang et al. 2008), and medusin (Xi et al. 2013). The primary function of these peptides is to kill pathogenic bacteria, but they inhibit the growth of other parasitic microorganisms as well (Clarke 1997, Wang et al. 2015). To carry out their antimicrobial activity, most peptides interfere with the plasma membrane of the bacterium (Nicolas and Amiche 2006, Rollins-Smith et al. 2005). These peptides are cationic, or positively charged, and attach to the negatively charged heads on the microbe’s phospholipid bilayer (Nicolas and Amiche 2006, Rollins-Smith et al. 2005). Complex steps then occur, but in the end, the orientation of the bacterium’s cell membrane is disturbed, which leads to cell destruction (Nicolas and Amiche 2006, Rollins-Smith et al. 2005). While some scientists researched how these peptides attacked microbes, others investigated and identified new types of peptides in the red-eye leaf frog’s

Question 1. I remember hearing in your video something about our body natural immunity and it eradicates the virus. The immune system includes physical barriers, such as the skin and mucous membranes that prevent pathogens from entering the body, and cellular responses, such as circulating macrophages that respond to foreign invaders. Our acquired immune system mounts a specific antibody response when the body is exposed to a foreign invader, and our immune cells attack the invader

Antimicrobial peptides (AMPs) are small proteins with potent antibacterial activity that are found in a variety of organisms, including humans [23]. AMPs can be classified according to their size of length, α or β conformational and predominant amino acid. Table 1.1 shows the different classification of AMPs with examples.Among the four groups of AMPs, the cationic antimicrobial peptides with amphipathic α-helical structure accounts for the most of natural AMPs [25]. The major difference within amphipathic α-helical structure AMPs lays in the sequences despite their common cationic and amphiphilic nature are similar [26]. Cathelicidins and defensins peptides are the two most frequently studied AMPs, these AMPs are positive charged and have the ability to kill microbes. They can function charged residues to separate from hydrophobic resides, associate with negative charged acidic polymers and molecules on the bacterial cell surfaces (Figure 1.5). It can disrupt the cell membrane’s physical integrity by the means of membrane thinning and transient pore formation [27]. Studies show that these AMPs can translocate through the membrane to kill bacteria [28].