Study Finds Significant Antimicrobial, Multi-Drug Resistance Towards Key Pneumococcal Serotypes

Investigators of a study published in the Journal of Global Antimicrobial Resistance have found significant antimicrobial resistance (AMR) and multi-drug resistance (MDR) towards both vaccine and non-vaccine pneumococcal serotypes, reaffirming the need for extensive surveillance and novel treatment modalities to combat resistant serotypes.¹

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Dangers of Antimicrobial Resistance

AMR is one of the most pertinent emerging public health threats today. When antimicrobial drugs are misused or overused, pathogens are exposed to subtherapeutic levels of these drugs, resulting in the pathogen adapting to reduce the effect of the antimicrobials. Accordingly, this can translate into difficult-to-treat, drug-resistant infections that can cause significant morbidity and mortality.^1,2

The chief concern regarding AMR is the bacteria Streptococcus pneumoniae—a leading cause of pneumococcal pneumonia, meningitis, and other diseases. This bacterium has a unique genetic structure, allowing it to express multiple different forms of its serotypes; to date, 100 distinct pneumococcal serotypes have been identified.^1,3

Pneumococcal conjugate vaccines (PCVs) have been developed to target a series of the most highly invasive pneumococcal serotypes, but the sheer number of serotypes—and varying patient susceptibility or resistance—complicates efforts to provide effective coverage to the public. For antimicrobial treatments, investigators identified varying resistance rates to certain drugs depending on the serotype. The lack of consensus on AMR patterns necessitates a detailed review of these dynamics to better inform strategies to reduce the burden of pneumococcal disease.¹

For this review, the investigators aimed to summarize findings from studies conducted among children and adults to highlight resistance patterns of pneumococcal serotypes in the global population. Through this review, the authors aimed to determine the most resistant pneumococcal serotypes to antimicrobial drugs.¹

Both Vaccine, Non-Vaccine Pneumococcal Serotypes Resistant to Numerous Treatments

The systemic review included a total of 90 studies, with 66 pneumococcal serotypes identified throughout the trials. Most reported pneumococcal serotypes were vaccine types, including 19A (n = 67), 19F (n = 57), 6B (n = 50), 23F (n = 50), 14 (n = 47, 52.2%), and 6A (n = 44, 48.9%), along with 4 non-vaccine serotypes, such as 15A, 6C, 23A, 23B, and 35B. The primary antimicrobial drugs that serotypes were resistant to included sulfonamides, lincosamides, and penicillin.¹

For the sulfonamides class of medications, co-trimoxazole resistance was observed across 30 serotypes, most prominently among serotype 5, followed by 9V, 33F, 19F, 19A, 6B, and others. For the lincosamide class, 24 serotypes exhibited resistance against clindamycin, with non-vaccine serotypes 24F and 20 having the highest rates of resistance. And for penicillin, resistance was reported for 27 pneumococcal serotypes, with 35B and 15A having the highest rate of resistance.¹

MDR rates were also estimated for 24 pneumococcal serotypes. The highest prevalence was observed in serotype 23F, followed by 15C, with notable rates observed among serotypes 23A, 19F, 19A, 15B, 23F, 15A, and 6B. The lowest MDR rates were observed for serotypes 22F and 8, with high heterogeneity across the studies for almost all included serotypes.¹

Antimicrobial Resistance: A Key Consideration for Pneumococcal Disease

Although the widespread use of PCVs has significantly reduced the predominance of their targeted serotypes, the investigators still found that serotypes predominant in their analysis were vaccine types. The authors wrote that this indicates that vaccine serotypes continue circulating in the post-vaccination era and emphasizes the need for future vaccine candidates to target serotypes accordingly. Furthermore, the high MDR resistance rates among vaccine serotypes could result from frequent encounters with antimicrobials, as they are most often used in the treatment of pneumococcal disease.¹

Given the significant prevalence of AMR and MDR, pharmacists should act carefully when prescribing antimicrobials to patients that may be susceptible to pneumococcal disease. If a patient presents with pneumococcal disease, conducting medication reconciliation and ensuring all medications a patient is taking are not negatively contributing to their disease is critical.¹

“This study highlights significant AMR and MDR among both vaccine and non-vaccine pneumococcal serotypes, emphasizing the importance of ongoing surveillance and targeted interventions to address these challenges in public health,” the study authors concluded. “We hope that future studies will provide the necessary data to enable the estimation of pooled AMR among these serotypes.”¹

REFERENCES

1. Ntim OK, Awere-Doudo AA, Akwetey SA, Kotey FCN, Donkor ES. Relationship Between Pneumococcal Serotypes and Antimicrobial Resistance: A Systematic Review and Meta-analysis. Journ Global Antimicro Res. Published Online July 14, 2025. Accessed July 31, 2025. doi:10.1016/j.jgar.2025.07.008

2. Salam A, Al-Amin Y, Salam MT, et al. Antimicrobial resistance: A growing serious threat for global public health. Healthcare. 2023;11(13):1946. doi:10.3390/healthcare11131946

3. Ganaie F, Saad JS, McGee L, et al. A New Pneumococcal Capsule Type, 10D, is the 100th Serotype and Has a Large cps Fragment from an Oral Streptococcus. mBio. Published Online May 19, 2020. Accessed July 31, 2025. doi:11:10.1128/mbio.00937-20.