Study Finds High Antimicrobial Resistance Against Pneumococcal Diseases, Despite Vaccination


Investigators found high incidences of non-susceptibility with penicillin and increasing resistance to macrolides for pneumococcal diseases.

Despite immunization with pneumococcal conjugate vaccines (PCV), there was a high incidence of non-susceptibility for pneumococcal diseases, especially for penicillin, and increasing resistance to macrolides, according to a systematic review published in Antibiotics. However, investigators found that there are still drugs that pneumococci are sensitive to.

Streptococcus pneumonia bacteria cells | Image Credit: Jezper -

Jezper -

In the study, investigators aimed to determine the effects of pre- and post-vaccination with PCV10 in preventing antimicrobial resistance. Isolates that were associated with colonization were recovered from all age groups, according to the study authors. The year 2000 was the starting point due to the introduction of PCV10 in Brazil 10 years later.

In 2011 and 2022, the investigators said that the average vaccination coverage with the primary and booster doses was 88.5% and 80.6%, respectively. Typically, Beta-lactams, including penicillin and amoxicillin, are the main antibiotics used, but macrolides, fluoroquinolones, and lacosamide can also be used against pneumococcal diseases according to the investigators. For those with allergies, cefdinir or azithromycin can be prescribed. In addition, the authors said, “penicillin non-susceptible pneumococci are considered a medium priority risk to human health by the World Health Organization” and is a serious threat in the United States.

3 Key Takeaways

  1. Despite immunization with pneumococcal conjugate vaccines (PCV), there is a significant incidence of non-susceptibility among pneumococcal strains, particularly to penicillin, and increasing resistance to macrolides, highlighting a concerning trend in antimicrobial resistance.
  2. While the vaccination rates were relatively high, the introduction of PCV10 led to changes in the susceptibility patterns of various antibiotics, with some showing increased resistance post-vaccination.
  3. Despite the rise in resistance to certain antibiotics, the study identifies several drugs to which pneumococci remain sensitive, such as vancomycin, linezolid, and fluoroquinolones.

The study authors used 17 articles and academic research to retrieve data for the total analysis. Only 2 cases were classified negatively, according to the authors. Approximately 41.2% describe the sampling in a clear way, but all articles described the tests and referenced the standard used. Only 5 used internal quality control. The data were divided into 3 parts: a pre-PCV-10 period, post-PCV10, and extended period with data from both periods. Investigators used 18,273 isolates, with 14.7% associated with colonization 0.6% with non-invasive diseases, and 0.2% with invasive disease, according to the investigators. Approximately 49.2% were from the pre-period and 50.8% were from the post-period.

Investigators found that there were higher frequencies of resistance for sulfamethoxazole-trimethoprim in the invasive isolates pre-PCV10 at 60.1%. The proportion of susceptibility was higher among isolates in the post-PCV10 period.

There were no cases of non-susceptibility in the pre-PCV period for vancomycin, linezolid, trovafloxacin, telithromycin, and quinupristin-dalfopristin, and resistance to amoxicillin, according to the authors. In the post-PCV10 period, there was no resistance to vancomycin, linezolid, telithromycin, and quinupristin-dalfopristin.

Ceftriaxone and penicillin had higher proportions of resistance after the post-PCV10 introduction period at 6.5% and 44.6%, respectively. Furthermore, among isolates for meningitis and non-meningitis, the proportion of both penicillin and ceftriaxone was higher after the induction of PCV10, according to the study. However, the frequency of penicillin non-susceptibility was among carriage isolates in the post-period.

For macrolides, erythromycin had a high susceptibility for colonization isolates at 95.2% pre-PCV10, declining to 82% post-PCV10, according to the investigators. For invasive samples, investigators found that the drug was susceptible at 94.5% and 81.1%, respectively. The non-susceptibility of erythromycin was among carriage and invasive isolates in the post-PCV10 period.

There was only a small number of fluoroquinolones, including ofloxacin and trovafloxacin, which only showed susceptibility for the pre-PCV10 period in all isolates for the respective drugs, according to the investigators. For invasive disease, the susceptibility was also 100%, according to the results. Levofloxacin also had a high number of susceptible isolates with 98.8% in the pre-period and 100% in the post-period, as well as all invasive isolates in the pre-PCV10 period. All non-invasive diseases were also susceptible to the drug, according to the results of the study.


Knupp-Pereira PA, Cabral AS, Dolores ÍM, da Silva AB, Póvoa HCC, Neves FPG. Antimicrobial Resistance in Streptococcus pneumoniae before and after the Introduction of Pneumococcal Conjugate Vaccines in Brazil: A Systematic Review. Antibiotics (Basel). 2024;13(1):66. doi:10.3390/antibiotics13010066

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