Respiratory review

Review of antibiotic resistance, antibiotic treatment and prevention of pneumococcal pneumonia

Streptococcus pneumoniae is an important causal agent of pneumonia, meningitis, sepsis, bacteremia, and otitis media. Penicillin resistance rates in S. pneumoniae have remained stable in Argentina in the last years. In the late ‘90s more isolates with MIC of penicillin ≥2 μg/ml were observed; however, their frequency has decreased in recent years. The phenotypic expression of penicillin resistance is due to a modification in penicillin-binding proteins associated with a mosaic structure in the coding genes. The expansion of successful resistant clones varies among the different regions and is influenced by the use of antibiotics, vaccines, particularly conjugated ones, as well as population density. Parenteral treatment with high doses of penicillin G continues to be effective for the treatment of pneumonia and bacteremia, oral aminopenicillins for otitis media and sinusitis and third generation cephalosporins for meningitis.

Streptococcus pneumoniae es un importante agente causal de neumonía, meningitis, sepsis, bacteriemia y otitis media. En la Argentina, las tasas de resistencia a penicilina en Streptococcus pneumoniae se mantuvieron estables durante los últimos años. Hacia finales de los años noventa, un mayor número de aislamientos presentaban CIM de penicilina ≥2 μg/ml, pero su frecuencia disminuyó en los últimos años. La expresión fenotípica de resistencia a penicilina se debe a una modificación en las proteínas de unión a la penicilina, asociada a una estructura en mosaico en los genes codificantes. La expansión de clones resistentes exitosos varía entre diferentes regiones y está influida por el uso de antibióticos y de vacunas, particularmente de las conjugadas, así como por la densidad de la población. El tratamiento por vía parenteral con altas dosis de penicilina G continúa siendo eficaz para el tratamiento de las neumonías y bacteriemias, con aminopenicilinas por vía oral para otitis media y sinusitis, y con cefalosporinas de tercera generación para meningitis.

Streptococcus pneumoniae (S. pneumoniae) is an important pathogen in causing global morbidity and mortality among children. This study aimed to determine phenotypic and molecular characteristics of S. pneumoniae causing infections in children under five years in China.

A hospital-based retrospective study was conducted. All 537 S. pneumoniae isolates were tested for antimicrobial susceptibility by E-test method, molecular characteristics including resistance genes, virulence genes and serotypes by multiplex polymerase chain reaction (PCR) method, and sequence types (STs) by sequencing seven housekeeping genes. Minimum spanning tree and correspondence analysis were used to reveal the potential relationship between serotypes and STs.

Most of S. pneumoniae isolates were resistant to erythromycin (93.9%) and tetracycline (86.4%), with the predominant resistance genes being erm(B) (92.6%) and tet(M) (95.5%). The prevalent serotypes were 19F, 6B, 19A, 23F and 14, the coverage rate of PCV13 was high in 85.8%, and the predominant STs were ST271, ST320, ST3173, ST81 and ST876. A significant correlation existed between STs and serotypes, with ST271/19F and ST320/19A as the most prevalent clones. Notably, ST271/19F and ST320/19A isolates were associated with resistance to specific antibiotics and carrying of mef(A/E), rlrA and sipA genes.

Our findings suggest the introduction of PCV13 vaccine to Chinese children, and underscore the value of monitoring multiple characteristics to detect new epidemiologic trends and provide implications for the formulation of multivalent pneumococcal vaccines.