Pathogenic, bacteria, adherence

The capacity of pathogenic bacteria to adhere to mucosal membranes has been exploited in the modification of new mucoadhesive polymers. The ability of bacteria to adhere to a specific target is rooted from particular cell-surface components or appendages, known as fimbriae, which promote adhesion to other cells or inanimate surfaces. Fimbriae are extracellular, long thread-like protein polymers of bacteria that play a major role in many diseases. It has been reported that Escherichia coli adheres specifically to the lymphoid follicle epithelium of the ileal Peyer s patch in rabbits. Similarly, different staphylococci possess the ability to adhere specifically to the surface of mucus gel layers and not mucus-free surfaces. Thus, polymers have been modified by the attachment of these fimbriae to enhance mucoadhesion. An attachment protein derived from E. coli, K99-fimbriae, has been covalently attached to polyacrylic acid networks in an attempt to provide a novel polymer with enhanced adhesive properties (Figure 52.7). ... 

The potential advantages of biocontrol agents compared to antibiotics were discussed by Moriarty (1998), with most attention directed towards the production of inhibitory substances by the beneficial bacterial strains. The possibility of selecting for biocontrol-resistant pathogens must not be underestimated, and it is particularly important to search for strains that express diverse antagonistic properties that may lower the risk of resistance. For example, the ability of some bacteria to adhere to the intestinal epithelium may inhibit the intestinal infection route common to many pathogens (Evelyn, 1996 Gatesoupe, 1999). 

In all antiseptic testing, it is recognized that skin and mucous membranes to which products ate appHed cannot be disinfected or sterilized but it is possible to significantly reduce the population of transient and resident pathogenic bacterial flora. AH in vivo test methods requite a deterrnination of the bacteria on the skin before and after treatment. Because of the normal variation in bacterial population of the skin of different people, a number of people must be tested in order to make a statistical analysis of the results. Different parts of the body are used for different tests. In aH of the tests the details of the protocol ate extremely important and must be strictly adhered to in order to obtain reproducible results. 

Enteric bacterial pathogens must maneuver through a lengthy stretch of hazardous terrain before they reach their intended target or infection site within a host. Initially, they must tolerate salivary enzymes having various hydrolytic activities in the mouth, followed by exposure to shedded epithelial cells in the esophagus that may prevent local bacterial adherence (Pearson and Brownlee, 2005). In the stomach, bacteria must endure another severe environment created by the secretion of digestive enzymes and hydrochloric acid (up to 0.1 M concentration and a pH as low as 1.0). Once bacteria reach the intestines, they then encoimter mechanical. 

As the main surface component of the bacterial cell envelope LPS is thought to contribute to the restrictive Gram-negative membrane permeability, allowing bacterial growth in unfavourable environments such as those that may be encountered within or on plants. The exclusion of antimicrobial substances of plant origin probably contributes to the ability of pathogenic bacteria to parasitize plants. LPS-defective mutants show increased in vitro sensitivity to antibiotics and antimicrobial peptides and the numbers of viable bacteria often decline very rapidly upon introduction into plants. LPS may also promote bacterial adherence to plant surfaces (Newman et al., 2007). 

E. coli infections. If a prebiotic can be added to the daily feed and it subsequently stimulates the beneficial bacteria in the colon at the expense of pathogens, it is most probable that these bacteria, namely bifidobacteria and lactobacilli, adhere to sites on epithelial cells and ultimately prevent the binding of pathogenic bacteria [112]. In diets containing reasonable quantities of carbohydrates saccharolytic fermentation will prevail, thus the pH of the GIT will remain stable and subsequently reduce the onset of Clostridia infections, as a more alkaline pH is required by species of this genus. Inulin added to rabbit feed was fermented in the cecum, produced SCFA, and reduced the risk of clostridiosis [113]. 

Neutrophils arc the primary innate defense against pathogenic bacteria. They make up most (SO to 75(3>) of the leukocyte fraction in the bhxid. Micro.scopically. neutrophils have mullilobcd nuclei. They respond to chemical motility factors such as complement mediators released from infected i>r inflamed tissues and migrate to a site of infection by the process of chemotaxis. There, they recognize, adhere to, and phagocytose invading microbes. 

---