Biofilms: - are formed when microbes adhere to a surface which usually moist and contains organic matter. The microbe secretes glycocalyx allowing other microbes to adhere a large mass is formed. The biofilms are resistant to disinfectants and antibiotics.

Prevention of Host Defenses:-

Some pathogenic bacteria are inherently able to resist the bactericidal components of host tissues. For example, the poly-D-glutamate capsule of Bacillus anthracis protects the organisms against cell lysis by cationic proteins in sera or in phagocytes. The outer membrane of Gram-negative bacteria is a formidable permeability barrier that is not easily penetrated by hydrophobic compounds such as bile salts which are harmful to the bacteria. Pathogenic mycobacteria have a waxy cell wall that resists attack or digestion by most tissue bactericides. And intact lipopolysaccharides (LPS) of Gram-negative pathogens may protect the cells from complement-mediated lysis or the action of lysozyme.

Enzymes (exoenzymes):- The microbes produce many enzymes to prevent host defenses are-

Coagulases: clot fibrin in blood to create protective barrier against host defenses.

Kinases: dissolve clots (fibrinolysis) to allow escape from isolated wounds e.g.Streptokinase (Streptococcus pyogenes) Staphylokinase (Staphylococcus aureus)

Hyaluronidase: Hydrolyzes hyaluronic acid (‘glue' that holds together connective tissues and epithelium barriers) allowing deeper invasion e.g. Clostridium species: allows them to cause gangrene (tissue necrosis).

Collagenase: breaks down collagen (fibrous part of connective tissue) for invasion into muscles and organs e.g. Clostridium species

IgA proteases : destroy host IgA antibodies found in mucous secretions to allow adherence and passage at mucus membranes e.g. Neisseria species that infect CNS.

Antigenic Variation  

There are many pathogens which alter its surface antigens to escape attack by antibodies and immune cells e.g. Neisseria gonorrhoeae has many variety of Opa gene, which can alter one is being expressed e.g. influenza virus constant genetic recombination between flu viruses always new spike proteins.  

Penetration into Host Cytoskeleton 

Many a time the pathogen penetrates into host cytoskeleton and use actin of host cell to penetrate and move within the cells of host. The invasins a surface proteins produced by bacteria to control actin e.g. Salmonella rearrange actin to cause the cell membrane to wrap around the microbe and take it into the cell (endocytosis) allows Salmonella to penetrate intestinal epithelium e.g. Shigella and Listeria trigger endocytosis.