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Effect of resistance to chloramphenicol on bacteriophage sensitivity of group A streptococci
Abstract:
Several phage hosts of group A streptococci became resistant to lysis by bacteriophage as a consequence of having acquired the ability to grow in the presence of chloramphenicol. The phage was adsorbed to the streptococcal cell, and P(32)-labeling of the phage showed that the phage genome penetrated the chloramphenicol (CM)- resistant cells as it did the parent cells. However, artificial lysis of the infected CM-resistant cells with chloroform or enzymes revealed no intracellular mature phage particles. Lysates of infected CM-resistant cells contained no phage-related antigenic materials which possessed serum-blocking power, although they were readily detected in lysates of infected parent cells. The CM-resistant cells were not lysogenized by the phage. Only cells resistant to more than 10 mug/ml of chloramphenicol were resistant to phage, and this threshold effect was taken as an indication of at least two different loci of chloramphenicol resistance on the streptococcal genome. Strains resistant to high levels of other antibiotics, such as streptomycin and erythromycin, showed no resistance to lysis by phage. Evidence indicated that the mutant cells were deficient in an essential function associated with the phage genome.
Insights
Group A streptococci resistant to chloramphenicol (CM) also resisted phage lysis. Phage DNA entered these resistant cells, but no new phage particles formed, indicating a defect in phage replication.
Area of Science:
- Microbiology
- Bacteriology
- Virology
Background:
- Group A Streptococcus (GAS) is a significant human pathogen.
- Bacteriophages (phages) are viruses that infect bacteria and can be used to lyse specific bacterial hosts.
- Antibiotic resistance in bacteria poses a growing public health threat.
Purpose of the Study:
- To investigate the mechanism by which chloramphenicol resistance affects phage susceptibility in Group A Streptococcus.
- To determine if phage infection is blocked at entry or during intracellular replication in chloramphenicol-resistant strains.
Main Methods:
- Group A Streptococcus strains were made resistant to chloramphenicol (CM).
- Phage adsorption and genome penetration were assessed using P(32)-labeled phage.
- Intracellular phage development was examined through artificial lysis of infected cells.
- Phage-related antigens were detected using serum blocking assays.
Main Results:
- CM-resistant GAS strains showed resistance to phage lysis.
- Phage DNA successfully penetrated CM-resistant cells.
- No mature phage particles or phage antigens were detected in infected CM-resistant cells.
- A threshold level of CM resistance (>10 µg/ml) correlated with phage resistance.
Conclusions:
- Chloramphenicol resistance in GAS confers resistance to phage lysis by inhibiting intracellular phage replication, not entry.
- The resistance mechanism suggests a deficiency in a phage genome-dependent function within the resistant host cells.
- This study highlights a potential link between antibiotic resistance mechanisms and phage susceptibility in bacteria.