Seasonality and outbreak of a predominant Streptococcus pneumoniae serotype 1 clone from The Gambia: Expansion of ST217 hypervirulent clonal complex in West Africa

BACKGROUND: Streptococcus pneumoniae serotype 1 causes > 20% of invasive disease, among all age groups combined, in The Gambia. In contrast, it is rarely detected in carriage studies. This study compares the molecular epidemiology of S. pneumoniae serotype 1 causing invasive disease in The Gambia between 1996 and 2005 to those carried in the nasopharynx between 2004 and 2006. RESULTS: A total of 127 invasive and 36 nasopharyngeal carriage serotype 1 isolates were recovered from individuals of all age groups and were analyzed by serotyping, antibiotic susceptibility testing and MLST. MLST analysis revealed 23 different sequence types (STs), 18 of which were novel. The most prevalent clone among the 163 isolates was ST618 (70.5%), followed by ST3575 (7.4%), ST2084 (2.5%) and ST612 (2.5%). A single ST (ST618), previously shown to belong to the ST217 hypervirulent clonal complex, was frequent among carriage (61.1%) and invasive (72.7%) serotype 1 isolates. ST618 causing both paediatric and adult disease peaked annually in the hot dry season and caused outbreak in 1997 and 2002. CONCLUSION: For over a decade, isolates of ST618 have been the dominant lineage among serotype 1 carriage and disease isolates circulating in the Gambia. This lineage shows similar epidemiological features to those of the meningococcus in the African meningitis belt being able to cause outbreaks of disease

Nasopharyngeal carriage of Streptococcus pneumoniae in Gambian infants: a longitudinal study.

BACKGROUND: To prepare for national introduction of a pneumococcal conjugate vaccine of restricted valency, we studied nasopharyngeal carriage of Streptococcus pneumoniae in Gambian infants. METHODS: We studied 236 infants in 21 villages. We collected nasopharyngeal swab samples at birth, twice per month for 6 months, and every second month until 1 year of age. We studied time to acquisition and duration of pneumococcal carriage according to serotype. RESULTS: All infants carried S. pneumoniae at some point. Sixty-five serotypes were found, and the 5 most common serotypes (6B, 19F, 6A, 14, and 23F) accounted for 51% of isolates. The mean age at first acquisition of carriage was 33 days (95% confidence interval, 29-36 days). There were no significant differences in acquisition rates between the 6 most common serotypes (P = .067) or between vaccine serotypes, vaccine-related serotypes, or nonvaccine serotypes (P = .317). However, the duration of carriage differed significantly between the 6 most common serotypes (P = .004). The rate of reacquisition of carriage and the duration of carriage did not differ significantly between the 6 most common serotypes (P = .229 and P = .669 respectively). However, nonvaccine types were acquired faster (P = .004) and were carried for a shorter duration (P < .001) than were vaccine serotypes. A previous episode of serotype 14 carriage was associated with delayed reacquisition of this serotype (P = .005) and longer duration of carriage (P = .017). CONCLUSIONS: The data provided in this study regarding time to acquisition and duration of pneumococcal carriage in Gambian infants provide an important baseline for evaluating the impact of the introduction of a pneumococcal conjugate vaccine in The Gambia and elsewhere in Africa

Nasopharyngeal carriage of Streptococcus pneumoniae in Gambian villagers.

BACKGROUND: To prepare for the introduction of a pneumococcal conjugate vaccine of restricted valency, we studied the nasopharyngeal carriage of Streptococcus pneumoniae in Gambian villagers. METHODS: A cross-sectional survey was conducted in 21 villages after a census. We recorded demographic characteristics, information on medical history, and data on possible risk factors for carriage from subjects. We collected a nasopharyngeal swab specimen from each subject for isolation and serotyping of S. pneumoniae and for antibiotic susceptibility testing. RESULTS: The prevalence of S. pneumoniae carriage among 2872 villagers was 72%. It was highest among infants (i.e., children aged <1 year; 97%); the rate was 93% among babies aged <1 month and decreased with increasing age (P<.001). Prevalence of carriage was linked to proximity to another village. Sixty-three percent of isolates recovered from children aged <5 years were covered by the 7-valent vaccine or were of a vaccine-related serotype, compared with 43% of isolates overall. Forty-three isolates (14.3%) tested were initially penicillin resistant; none had high-level resistance, and 4 had intermediate resistance. The rates of resistance to other antibiotics were as follows: trimethoprim-sulfamethoxazole, 39%; tetracycline, 32.3%; chloramphenicol, 6.3%; cefotaxime, 0.3%; and erythromycin, 0%. The rates were highest for isolates of vaccine serotypes. CONCLUSIONS: Pneumococcal carriage rates among Gambian villagers are very high. A pneumococcal conjugate vaccine of restricted valency should reduce the pool of antibiotic-resistant pneumococci. The large reservoir of pneumococci of nonvaccine serotypes will require close monitoring when the vaccine is introduced

Seasonality and outbreak of a predominant Streptococcus pneumoniae serotype 1 clone from The Gambia: expansion of ST217 hypervirulent clonal complex in West Africa.

BACKGROUND: Streptococcus pneumoniae serotype 1 causes > 20% of invasive disease, among all age groups combined, in The Gambia. In contrast, it is rarely detected in carriage studies. This study compares the molecular epidemiology of S. pneumoniae serotype 1 causing invasive disease in The Gambia between 1996 and 2005 to those carried in the nasopharynx between 2004 and 2006. RESULTS: A total of 127 invasive and 36 nasopharyngeal carriage serotype 1 isolates were recovered from individuals of all age groups and were analyzed by serotyping, antibiotic susceptibility testing and MLST. MLST analysis revealed 23 different sequence types (STs), 18 of which were novel. The most prevalent clone among the 163 isolates was ST618 (70.5%), followed by ST3575 (7.4%), ST2084 (2.5%) and ST612 (2.5%). A single ST (ST618), previously shown to belong to the ST217 hypervirulent clonal complex, was frequent among carriage (61.1%) and invasive (72.7%) serotype 1 isolates. ST618 causing both paediatric and adult disease peaked annually in the hot dry season and caused outbreak in 1997 and 2002. CONCLUSION: For over a decade, isolates of ST618 have been the dominant lineage among serotype 1 carriage and disease isolates circulating in the Gambia. This lineage shows similar epidemiological features to those of the meningococcus in the African meningitis belt being able to cause outbreaks of disease

Evaluation of sequential multiplex PCR for direct detection of multiple serotypes of Streptococcus pneumoniae from nasopharyngeal secretions.

Sequential multiplex PCR was evaluated for detection of multiple Streptococcus pneumoniae serotypes directly from nasopharyngeal secretions. A total of 279 nasopharyngeal swab samples were tested blindly. When limited to the 29 serotypes identifiable by the molecular method, the mean number of serotypes identified by the conventional latex/Quellung method was 0.85, which was significantly lower than that by the molecular method (P <0.0001). The multiplex PCR method identified significantly more serotypes than the latex/Quellung method if limited to the 29 serotypes (P=0.001 and P=0.014, respectively)