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Phenotypic and molecular study of pneumococci causing respiratory tract infections. A 3-year prospective cohort
1Department of Medical Microbiology, College of Medicine, University of Dammam, Dammam, Kingdom of Saudi Arabia. E-mail. amalnimr@uod.edu.sa.
Insights
Emerging pneumococcal serotype 11A and non-typeable strains show high resistance to penicillin and macrolides post-vaccine introduction in Saudi Arabia. This highlights challenges in antimicrobial resistance and vaccine coverage for respiratory infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Vaccinology
Background:
- The 13-valent pneumococcal conjugate vaccine (PCV13) was introduced in Saudi Arabia to reduce pneumococcal disease burden.
- Surveillance of pneumococcal serotypes and antimicrobial resistance is crucial post-vaccine implementation.
Purpose of the Study:
- To determine the serotype distribution of pneumococci causing respiratory infections.
- To assess antimicrobial resistance patterns to beta-lactams and macrolides.
- To evaluate the impact of PCV13 on serotype prevalence and resistance.
Main Methods:
- A prospective, hospital-based surveillance study was conducted from 2012 to 2014.
- Respiratory pneumococcal isolates were serotyped using multiplex sequential polymerase chain reaction (PCR) and Pneumotest-Latex.
- Resistance genes for beta-lactams and macrolides were identified via multiplex PCR.
Main Results:
- Serotypes 11A, 19A, 17F, 23F, 3, and 19F were most common (64% of typeable strains).
- A significant proportion (24%) of isolates were non-typeable, with 18% lacking the housekeeping gene cpsA.
- High rates of resistance to both penicillin and macrolides were observed in typeable (67.9%) and non-typeable isolates (62.5% penicillin, 47% macrolides).
Conclusions:
- Serotype 11A has emerged as a significant cause of pneumococcal disease.
- The high prevalence of non-typeable pneumococci suggests the emergence of serotypes not covered by current vaccines.
- Sustained surveillance is necessary to monitor evolving pneumococcal resistance and vaccine effectiveness.
Objectives:
To study serotype distribution and antimicrobial resistance to beta-lactams and macrolides in pneumococci causing respiratory diseases after the introduction of the 13-valent pneumococcal conjugate vaccine in Saudi Arabia. Methods: This is a hospital-based and a cross-sectional prospective surveillance study conducted at King Fahad Hospital of the University, AlKhobar, Kingdom of Saudi Arabia, in which respiratory pneumococcal isolates collected between 2012 and 2014 were serotyped by multiplex sequential polymerase chain reaction (PCR) and Pneumotest-Latex. Resistance genes to beta-lactams and macrolides were detected by multiplex PCR. Results: The most common serotypes encountered were 11A, 19A, 17F, 23F, 3, and 19F, representing 64% of the typeable strains. Interestingly, 24% of the 94 isolates were not typeable and 18% were negative for the housekeeping gene cpsA. Among the 53 typeable pneumococci isolates, 36 (67.9%) carried genes encoding resistance to both penicillin and macrolides, 9 (17%) were penicillin-monoresistant, 3 (5.6%) were macrolide-monoresistant, and 5 (9.4%) were designated non-resistant. The high rate of resistance genes did not significantly differ according to serotype (p=0.76). Similarly, non-typeable pneumococci (cpsA+ and cpsA-) had high rates of resistance to both penicillin (62.5%) and macrolides (47%). Conclusion: These data highlight the emergence of a previously rare capsular type, 11A (mean patient age, 29 years; p=0.001). Moreover, the high percentage of non-typeable isolates shows the emergence of possible atypical pneumococcal serotypes not covered by available vaccines.