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Serious infections due to penicillin-resistant strains of viridans streptococci with altered penicillin-binding
J P Quinn1, C A DiVincenzo, D A Lucks
1Department of Medicine, Michael Reese Hospital, Chicago, Illinois 60616.
Abstract:
We investigated the mechanism of resistance to penicillin in two penicillin-resistant clinical isolates of viridans streptococci that caused life-threatening infections in two patients not receiving chronic penicillin therapy. The first was a strain of Streptococcus intermedius that was isolated from the cerebrospinal fluid of a patient with post-neurosurgical meningitis. The second was a strain of Streptococcus mitis recovered from the bloodstream of a leukemic patient with neutropenia. Both patients failed to respond to penicillin. The mechanism of resistance in these strains was associated with diminished affinity for penicillin of their penicillin-binding proteins, as compared with those of penicillin-susceptible control strains. We conclude that penicillin-resistant viridans streptococci may cause serious infections even in patients not receiving chronic penicillin therapy, that this resistance is clinically significant and may result in failure of penicillin therapy, and that the mechanism of resistance in these strains is associated with diminished affinity of the penicillin-binding proteins for penicillin.
Insights
Penicillin-resistant viridans streptococci, including Streptococcus intermedius and Streptococcus mitis, can cause severe infections. Resistance stems from altered penicillin-binding proteins, leading to treatment failure even without prior penicillin exposure.
Area of Science:
- Microbiology
- Infectious Diseases
- Clinical Medicine
Background:
- Viridans streptococci are common causes of opportunistic infections.
- Penicillin is a primary treatment for many streptococcal infections.
- Understanding resistance mechanisms is crucial for effective treatment.
Observation:
- Two patients with life-threatening infections (meningitis, bloodstream infection) had penicillin-resistant viridans streptococci.
- These isolates were Streptococcus intermedius and Streptococcus mitis.
- Neither patient was undergoing chronic penicillin therapy.
Findings:
- Penicillin resistance in these strains was linked to reduced affinity of penicillin-binding proteins (PBPs) for penicillin.
- Control strains showed normal PBP affinity, confirming the resistance mechanism.
Implications:
- Penicillin-resistant viridans streptococci pose a significant clinical threat, even in non-chronically treated patients.
- This resistance can lead to therapeutic failure with standard penicillin treatment.
- Altered PBPs are a key mechanism driving this clinically relevant penicillin resistance.