Peptide cross-resistance

Capreomycin (capasiat) is an antimycobacterial cyclic peptide elaborated by Streptococcus capreolus. Bacterial resistance to capreomycin develops when it is given alone such microorganisms show cross-resistance with kanamycin and neomycin. Capreomycin is used only in conjunction with other appropriate drugs in treatment of pulmonary tuberculosis when bactericidal agents cannot be tolerated or when causative organisms have become resistant. 

Under certain circumstances, many bacteria produce capsules outside their ceU envelopes. Capsules are usually made of polysaccharide however, some Bacillus capsules are composed of D-glutamic acid polypeptide. Certain Gram positive bacteria, most notably strains of Bacillus and Clostridium, produce modified ceUs (endospores) capable of surviving in adverse environments. Spore PG is found between an inner and outer membrane and differs from that in the normal vegetative cell muramic acid is mostly in the lactam form the spore PG has fewer peptide cross-links and the ceU exterior is coated with keratin. The spore also contains large quantities of calcium dipicolinate, a substance involved in microbial heat resistance. 

The bacterial cell wall surrounds the plasma membrane and provides the mechanical strength that enables bacteria to resist shear and osmotic shock. The cell wall is composed of a network of linear heteropolysaccharides cross-linked by peptides (fig. 16.15). 

Blood Alkaline phosphatase (bone-specific) Osteocalcin Procollagen type I carboxy-terminal propeptide (PICP) Procollagen type I amino-terminal propeptide (PINP) Procollagen type III amino-terminal propeptide (PIIINP) Blood Acid phosphatase (acid-resistant) Type I collagen carboxy-terminal telopeptide (ICTP) Urine Calcium Hydroxyproline Cross-linked peptides (pyridinium and deoxypyridinoline)... 

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