GAS has remained a significant human pathogen for centuries. It causes a wide variety of infections in humans, which range from mild upper respiratory and skin infections to non-suppurative sequelae like Acute Rheumatic Fever (ARF) and Rheumatic Heart Disease (RHD). Although ARF and RHD have declined in many parts of the world, they continue to be major causes of the cardiovascular morbidity and mortality in India [4].
A preliminary study was undertaken to identify the GAS carriers among healthy school children.
MATERIALS AND METHODS
A total of 2000 (1347 boys and 653 girls) apparently healthy school children who were studying in 8 schools in and around B.G.Nagara, a village which is 60 kms away from the city, formed Sectionthe study group. About 6000 students are studying in 20 schools in and around B.G. Nagar. The study period was from December 2010 to March 2012. The age of the study group ranged from 5-15 years. This study was conducted in the Department of Microbiology, AIMS, B.G.Nagara, which was established in 1986.
The school children were selected for the study if they met the inclusion criteria.
No history of tonsillectomy
Absence of any signs or symptoms which showed upper respiratory infections.
No antibiotic usage during the past two weeks before the sampling.
Those who received an antimicrobial therapy or those who had suffered from sore throat in the previous three months, were excluded from the study.
An ethical clearance was obtained from the institution. Consents were obtained from the school authority and the parents of the children.
The throat swabs which were collected were inoculated onto 5% sheep blood agar plates on the spot itself. The streaked plates were incubated at 37°C in a candle jar for 24 to 48 hours. All the beta haemolytic colonies were identified and sero grouped by the latex agglutination method (HiStrep Latex Test Kit, Hi-Media, Mumbai). The latex kit identifies the groups A, B, C, D, F and G of the Lancefield group of Streptococci.
Two more throat swabs were studied from the GAS positive students at intervals of 3 months, to classify them as transient (first culture- positive and the subsequent two cultures- negative), recurrent (first two cultures- positive and the third culture- negative) and chronic carriers (all the three cultures positive) [2].
RESULT
The mean age of the study group was 10.6 years. The beta-haemolytic Streptococci were isolated from 44 (2.20%) samples. Among the 44 beta haemolytic Streptococci, 38 (86.36%) were GAS, 5 (11.36%) were Group C Streptococci and one (2.27%) was Group G Streptococci. Among the 38 GAS positive children, 24 (63.16%) were transient carriers, 10 (26.32%) were recurrent carriers and 4 (10.52%) were chronic carriers.
[Table/Fig-1] shows the prevalence of GAS with respect to the age and sex.
Prevalence of GAS in relation to age and sex of study group (2000)
| Age in years | Boys No.1347 | Girls No.653 | Number Studied | Positives (%) |
|---|
| Positive | Negative | Positive | Negative |
|---|
| 5-8 | 2 | 248 | 2 | 176 | 428 | 04 (0.9%) |
| 9-12 | 14 | 597 | 7 | 261 | 879 | 21 (2.38%) |
| 13-15 | 08 | 478 | 5 | 202 | 693 | 13 (1.87%) |
| Total | 24 | 1323 | 14 | 639 | 2000 | 38 (1.9%) |
DISCUSSION
Throat cultures have always been considered as the “gold standard” for diagnosing the presence of GAS [1]. The healthy carriers of GAS are the sources of a bacterial dissemination and they are able to communicate the disease and even lead to severe epidemics [5]. According to different studies, GAS is seen more in the pharynges of children as compared to that in adults [5]. In the present study, Beta Haemolytic Streptococci (BHS) were isolated from 44 (2.2%) children, which was less than those which were isolated in other studies [3,6–8]. GAS was isolated from 38 children (1.9%) in the present study, while other studies had reported higher incidences [3,6–10].
[Table/Fig-2] shows the prevalence of the asymptomatic carriage of GAS, as was reported by various studies. The low prevalence of the GAS carriage in the present study may be explained by the geographical location and the setting of the study, it being free from air pollution and overcrowding and 60 kms away from the city, with a population of approximately 25,000. This study was undertaken in an agricultural area and the people of the area mainly belonged to the middle and the lower socio economic groups. The high prevalence rates which were reported by others could be due to the high population density, the hot and humid climate, air pollution and more number of students in the class rooms, which may have contributed to the spread of the GAS infection [3,6–10].
Prevalence of asymptomatic carriage of GAS as reported in various studies
| Reference | Year of study | Number of children | Age range (years) | Place of study | Sample collection | Prevalence of GAS carriage % |
|---|
| Present study | 2011 | 2000 | 5-15 | B.G.Nagara, Karnataka | Three cultures | 1.9 |
| Dumre [9] 2009 | 2007 | 350 | 5-15 | Nepal | Single culture | 10.9 |
| Lloyd [3] 2006 | 2004 | 1102 | 5-17 | Chennai | Single culture | 8.4 |
| Thangam [7] 2004 | 2004 | 230 | 5-14 | Chennai | Single culture | 7.8 |
| Navaneeth [8] 2001 | 1998 | 481 | 5-15 | Salem | Single culture | 6.2 |
| Rajkumar [10] 2001 | 1991 | 178 | 5-15 | Chennai | Single culture | 3.7 |
| Gupta [6] 1992 | 1991 | 749 | 5-15 | Delhi | Single culture | 13.7 |
The variations in the carriage rates among different schools in the same village may be explained on the basis of the location which was studied [9]. The maximum number of GAS was found in the age group of 9-12 years (2.38%) and a minimum number was found in the age group of 5-8 years(0.9%), which was similar to the report of Dumre et al., [9] Rijal et al.,reported the maximum number of GAS in the age group of 5-8 years (11.8%) and a minimum in the age group of 9-12 years (7.8%) [11].
The GAS carrier rate was higher in girls (2.14%) than in boys (1.76%), which was similar to other reports [6,9,10]. Fatemah Nabipour (54.4%) and Navneeth (55.7%) reported higher GAS carriage rates among boys [5,8].
Among the BHS (44) which were isolated, 5(0.25%) were Group C Streptococci and one (0.25%) was Group G Streptococcus, which were lower in number than those which were reported in the studies of others [3,6–8]. GCS and GGS are primarily animal pathogens and they may cause infections in humans [3].
The GAS throat carriage is an important public health issue, as the infection often leads to post streptococcal sequelae and as the individuals who are colonized with GAS can serve as a source of the infection for other children and their family members in the community [9].
The chronic carriers of GAS were given a course of antibiotics, with the aim of preventing the non-suppurative complications and the spread of GAS to their family members and other children. Health education regarding the GAS infections, their sequelae and their prevention, was given to the children, their teachers and their parents. The magnitude of the problem of ARF and RHD in India is high [12]. To prevent this, all the Microbiology Departments have to be upgraded for the isolation of GAS. Once this is achieved, the GAS associated disease and sequelae will narrow down.
CONCLUSIONS
The present study which was done on the prevalence of the asymptomatic GAS carriers among school children in the community, may provide useful information about the prevalence of GAS in this location. This study highlighted the importance of a regular surveillance to keep the GAS carriage in check, by treating the children with antibiotics.