Clonal distribution of pneumococcal serotype 19F isolates from Ghana

Area of Science:

• Microbiology
• Epidemiology
• Genetics

Background:

• Streptococcus pneumoniae causes significant global morbidity and mortality.
• Over 90 pneumococcal serotypes are known, classified by capsular polysaccharide.
• Pneumococcal carriage studies are vital for understanding disease epidemiology and vaccine impact.

Purpose of the Study:

• To investigate pneumococcal carriage isolates from Ghana, focusing on serotype 19F.
• To characterize the genetic diversity and clonal structure of serotype 19F isolates using Multi-Locus Sequence Typing (MLST).
• To identify novel sequence types (STs) and assess their distribution in Ghana.

Main Methods:

• Analysis of pneumococcal isolates from healthy children and hospital outpatients in Tamale and Accra, Ghana.
• Previous characterization included Gram staining, serotyping, and penicillin susceptibility testing.
• Multi-Locus Sequence Typing (MLST) was performed on serotype 19F isolates to determine genetic relatedness.

Main Results:

• Fourteen distinct Sequence Types (STs) were identified among serotype 19F isolates.
• Nine of the identified STs were novel, not previously recorded in the international MLST database.
• Two dominant clones, a known ST (ST 4194) and a novel ST (ST 9090), were identified circulating in Ghana.
• ST 9090 was exclusive to healthy children in Accra, while ST 4194 was found across all groups and linked to other West African isolates.
• The majority of isolates exhibited intermediate resistance to penicillin.

Conclusions:

• Two dominant clones of Streptococcus pneumoniae serotype 19F circulate in Ghanaian populations.
• The clonal distribution of serotype 19F in Ghana appears diverse, with a significant number of novel clones identified.
• Ongoing surveillance of pneumococcal carriage in Ghana is essential to monitor antimicrobial resistance and the impact of vaccines like PCV-13.