Example problems bacterial strains

Because the natural penicillins have been used for many years, drug-resistant strains of microorganisms have developed, making the natural penicillins less effective than some of the newer antibiotics in treating a broad range of infections. Bacterial resistance has occurred within tire penicillins. Bacterial resistance is the ability of bacteria to produce substances that inactivate or destroy the penicillin. One example of bacterial resistance is tiie ability of certain bacteria to produce penicillinase, an enzyme that inactivates penicillin. The penicillinase-resistant penicillins were developed to combat this problem. 

The refractory nature of some pollutants, notably, persistent polyhalogenated compounds, has raised problems of bioremediation of contaminated sites (e.g., sediments and dumping sites). There has been interest in the identification, or the production by genetic manipulation, of strains of microorganisms that can metabolically degrade recalcitrant molecules. For example, there are bacterial strains that can reductively dechlorinate PCBs under anaerobic conditions. 

Resistance to erythromycin is becoming a serious clinical problem. For example, most strains of staphylococci in hospital isolates are resistant to this drug. Several mechanisms have been identified (1) the inability of the organism to take up the antibiotic (2) a decreased affinity of the 50S ribosomal subunit for the antibiotic resulting from the methylation of an adenine of the 23S bacterial ribosomal RNA and (3) presence of a plasmid-associated erythromycin esterase. Both clarithromycin and azithromycin show cross-resistance with erythromycin. 

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