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Septicemia with two distinct strains of Staphylococcus aureus and dwarf variants of both
Abstract:
A patient with erythema multiforme developed septicemia with two strains of Staphylococcus aureus. Six blood cultures, obtained during 14 days, yielded a mixture of both strains. The strains differed in the ability to hemolyze human erythrocytes, in the production of beta-lactamase and in the susceptibility to antibiotics and bacteriophages. Following therapy with gentamicin, a Dwarf colony variant auxotrophic for vitamin K, tryptophan and p-aminobenzoic acid appeared in some of the blood cultures. This variant was apparently derived from one of the offending strains (phage Type 55/71). From other blood cultures, a different type of Dwarf colony variant was obtained; this variant was of the same phage type as the other offending S. aureus strain (Type 85). The metabolic deficiencies of this strain were not unraveled. Both events, the double infection with distinct S. aureus strains, and the emergence of Dwarf variants during antibiotic therapy, are unusual in clinical practice, and will be detected only if laboratory staff pays particular attention to the possible occurrence of such events.
Insights
A patient with erythema multiforme experienced septicemia from two Staphylococcus aureus strains. Antibiotic therapy led to unusual Dwarf colony variants, highlighting the need for vigilant laboratory detection of complex infections.
Area of Science:
- Medical Microbiology
- Infectious Diseases
Background:
- Erythema multiforme can be associated with severe infections.
- Staphylococcus aureus is a common cause of hospital-acquired infections.
Observation:
- A patient presented with septicemia involving two distinct Staphylococcus aureus strains.
- These strains exhibited differential hemolytic activity, beta-lactamase production, and antibiotic/bacteriophage susceptibility.
Findings:
- During gentamicin therapy, a Dwarf colony variant auxotrophic for vitamin K, tryptophan, and p-aminobenzoic acid emerged from one strain (phage Type 55/71).
- A second Dwarf colony variant, derived from the other strain (phage Type 85), also appeared, though its metabolic deficiencies were uncharacterized.
Implications:
- The co-infection with multiple Staphylococcus aureus strains is clinically uncommon.
- The emergence of antibiotic-induced Dwarf colony variants during treatment presents a diagnostic challenge.
- Enhanced laboratory vigilance is crucial for detecting such complex microbial dynamics and variant emergence.