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Nasopharyngeal Carriage of Streptococcus pneumoniae

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Original Article



Nasopharyngeal Carriage of Streptococcus pneumoniae
C. Wattal, J.K. Oberoi, P.K. Pruthi1 and Suresh Gupta1

Department of Clinical Microbiology and 1Department of Pediatrics, Sir Ganga Ram Hospital, New Delhi, India



                                                          ABSTRACT
Objective. To determine nasopharyngeal carriage rate and prevalent serogroups/ types (SGT) of S. pneumoniae in healthy
children, assess their antimicrobial susceptibility and its implications over the heptavalent pneumococcal conjugate vaccine.

Methods. 200 healthy children aged between 3 months and 3 years attending Pediatric OPD at Sir Ganga Ram Hospital, New
Delhi were studied. A nasopharyngeal swab was collected from each child which was processed to isolate Streptococcus
pneumoniae. Serotyping was performed by the Quellung reaction. Antimicrobial susceptibility patterns were determined by disk
diffusion and E test methods.

Results. S. pneumoniae carriage rate was 6.5%. Isolates belonged to serotypes 1, 6, 14 and 19, of which serotype 19 was the
most common. None of the strains were totally resistant to penicillin though 2 (15.4%) were intermediately resistant. Overall,
84.6% of the isolates belonged to the strains covered by the heptavalent pneumococcal vaccine.

Conclusion. The heptavalent conjugate vaccine covers most isolated strains, but since the number of strains is very small, it
is suggested that there is need for further studies in different regions to assess the usefulness of this vaccine. [Indian J Pediatr
2007; 74 (10) : 905-907] E-mail : chandwattal@sgrh.com

Key words : S. pneumoniae serotype; Nasopharyngeal carriage; Antimicrobial susceptibility


Acute respiratory infection is a serious problem in India           overuse has been identified as the major risk factor for
accounting for 14.3% deaths during infancy and 15.9%                this phenomenon, especially frequent and prophylactic
deaths between 1-5 years. 1 Streptococcus pneumoniae                use of antibiotics. The serotype distribution data of
remains the major cause of invasive disease, pneumonia              invasive isolates from India is scarce. Hence, there is need
and otitis media, in young children. The nasopharynx of             for additional data on the prevalence of Streptococcus
children has resident microbial flora that do not usually           pneumoniae serotype from India. This study was
harm the child but, sometimes may act as a reservoir of             undertaken to evaluate drug resistance and
pathogens. Moreover, the organisms can easily spread                nasopharyngeal carriage of prevalent serogroups/ types
from one child to another. Therefore, nasopharyngeal                (SGT) of Streptococcus pneumoniae in healthy children at
carriage is a major factor in the pathogenesis of                   New Delhi (India).
pneumococcal disease and its transmission. Studies of the
prevalence of different pathogens and their resistance
                                                                                  MATERIALS AND METHODS
patterns can provide useful information for rational
therapeutic and preventive strategies.
   Strains of S. pneumoniae resistant to antibiotics,               Study was performed on 200 healthy children attending
especially penicillin and co-trimoxazole have been                  Pediatric OPD at Sir Ganga Ram Hospital, New Delhi
reported worldwide. 2Also, nasopharyngeal colonisation              over a period of 4 months. Informed consent was taken
by antibiotic-resistant Streptococcus pneumoniae has                from the parent/guardian prior to inclusion of the subject
steadily increased over the last few years. Antibiotic              in the study. Only one member per family was included
                                                                    to avoid bias of siblings living in the same family
                                                                    environment.
                                                                    Inclusion Criteria
Correspondence and Reprint requests : Dr. C. Wattal, Chairman,
Department of Clinical Microbiology, Sir Ganga Ram Hospital,
                                                                    Criteria of inclusion within the study was children aged
Rajinder Nagar, New Delhi-110060, India, Phone - 011-42251049;      between 3 months and 3 years considered healthy after
Fax : 011- 25730343                                                 general examination by the pediatrician. Recent and past
[Received October 18, 2006; Accepted January 1, 2007]               history of the subject including history of upper

Indian Journal of Pediatrics, Volume 74—October, 2007                                                                          905
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                                                              C. Wattal et al

respiratory tract infection, head injury, hospitalisation,             method as per CLSI (Clinical Laboratory Standards
antibiotic usage, immunisation status, family history and              Institute, formerly known as National committee for
environmental history were taken.                                      Clinical Laboratory Standards) guidelines. 3 Estimation of
                                                                       minimum inhibitory concentration (MIC) of various
Exclusion Criteria
                                                                       antibiotics was also determined using E test (biodisk,
Children less than 3 months of age, grade II, III or IV                Solna, Sweden).
malnourishment, underlying clinical illness
(immunologic diseases; neoplastic disorders; renal,
                                                                                               RESULTS
cardiac, hepatic, or hematologic diseases;
bronchodysplasia; Down syndrome; chronic otitis media
with effusion) or even a mild acute upper or lower                     Out of the two hundred nasopharyngeal swabs cultured,
respiratory tract infection at the time of enrollment                  13 (6.5%) grew S. pneumoniae. The median age of
(children with rhinitis without fever were however                     acquisition of S. pneumoniae was 16 months. The youngest
included in the study) were excluded from the study.                   and the oldest child colonized with S. pneumoniae were 8
Children who had received antibiotic treatment in the                  months and 3 years old, respectively.
previous 2 weeks were also excluded from the study.
                                                                          The serogroups/serotypes (SGT) isolated were 1, 6, 14,
Bacteriology                                                           and 19, the most common being SGT 19. Eight (61.5%)
                                                                       cases belonged to SGT 19. One isolate was untypeable.
Nasopharyngeal swabs were obtained from each subject
with calcium alginate swabs (BD, USA) on a flexible                       Majority of the isolates were susceptible to penicillin,
aluminum wire. The swabs were transported                              only 2 (15.4%) were resistant to 1 µg oxacillin disc and
immediately and were inoculated on trypticase soy agar                 were having MICs for penicillin falling in the moderately
with 5% sheep blood and 5µg of gentamicin sulphate per                 susceptible range, viz. 0.125 and 0.75 µg/ml. None was
ml of the medium. Plates were incubated at 37ºC                        totally resistant to Penicillin. The strain with an MIC of
overnight in the CO2 extinction jar and examined for the               0.125 µg/ml to penicillin belonged to SGT 6 and the other
presence of colonies of S. pneumoniae. Morphologically                 with an MIC of 0.75 µg/ml could not be typed. All the
suggestive colonies were examined microscopically using                isolates were resistant to co-trimoxazole. Erythromycin
gram stain. Colonies were further identified by                        and ciprofloxacin resistance was observed in 1 (7.7%) and
susceptibility to optochin and Latex agglutination test for            2 (15.4%) isolates respectively. All isolates were sensitive
S. pneumoniae (BD, USA). Such isolates of S. pneumoniae                to amoxycillin and cefotaxime. Three (23.07%) strains
were subsequently serotyped by Quellung reaction using                 were resistant to two or three antibiotics and none were
Pneumotest kit containing pneumococcal antiserum                       resistant to more than three antibiotics (Table 1).
supplied by the Statens Serum Institute, Copenhagen,
Denmark
                                                                                             DISCUSSION
   Antimicrobial susceptibility testing to crystalline
penicillin (1 µg oxacillin disc was used to screen penicillin
susceptibility), cefotaxime (30µg), erythromycin (15µg),               S. pneumoniae nasopharyngeal carriage was observed in
ciprofloxacin (5µg), cotrimoxazole (25µg) and amoxycillin              6.5% of the 200 healthy children enrolled in the study. A
(10µg) was done using Kirby Bauer disk diffusion                       similar study reported a colonization rate of 74% in

TABLE 1. MIC of the S. pneumoniae Isolates to Various Antibiotics

SN            serotype         Penicillin MIC       Erythromycin         Ciprofloxacin   Co-trimoxazole MIC Cefotaxime MIC
                                  (µg/ml)            MIC (µg/ml)         MIC (µg/ml)           (µg/ml)          (µg/ml)

1              19                  0.012 S                 0.064 S              1S             >32 R              0.016 S
2              19                  0.012 S                 0.125 S             1S              >32 R              <.012 S
3              19                  0.008 S                 0.094 S          0.75 S             >32 R            < 0.016 S
4               6                  0.012 S                 0.094 S          0.75 S             >32 R               0.32 S
5              19                  0.008 S                 0.032 S          0.50 S             >32 R              0.016 S
6              19                  0.012 S                 0.016 S           0.5 S             >32 R              <.016 S
7              19                  0.012 S                 0.016 S           0.5 S             >32 R              <.016 S
8              19                  0.023 S                 0.125 S          0.75 S             >32 R              <.016 S
9              19                  0.012 S                 0.064 S           0.5 S             >32 R              0.016 S
10         Nontypeable             0.75 M                      2R              2S              >32 R               0.38 S
11             14                  0.047 S                 0.032 S           0.5 S             >32 R              0.047 S
12              1                  0.012 S                 0.032 S          >32 R              >32 R               0.19 S
13              6                 0.125 M                  0.032 S             8R              >32 R               0.125S

S = Sensitive, M = Moderately susceptible, R = Resistant

906                                                                        Indian Journal of Pediatrics, Volume 74—October, 2007
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                               Nasopharyngeal Carriage of Streptococcus pneumoniae

Mumbai, which is much higher than that of our study              causing invasive disease. Most isolated serotypes are
(Mathur et al, abstract at 5th International Symposium on        covered by the heptavalent conjugate vaccine, but since
Pneumococci and Pneumococcal diseases, Alice Springs,            the number of strains is very small and they may not be
Australia, 2-6 April, 2006). Also, the most common               representative of all geographical regions in India, it is
serogroups isolated were SGT 6 and 1 in contrast to our          suggested that there is need for further studies in
study that documents SGT 19 and 6. The study from                different regions to assess the usefulness of this vaccine.
Mumbai depicts the data obtained from children living in
                                                                 Acknowledgements
slums as compared to this study, which mainly consisted
of subjects living in an urban area and belonging                We are grateful to Pharmaceuticals, Wyeth Limited for their support
primarily to nuclear families. It appears socioeconomic          in funding this project.
factors may influence Streptococcus pneumoniae
colonization rate and serotype prevalence in India.                                      REFERENCES
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                                                                      pneumoccal serogroups cause the most invasive disease:
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                                                                   8. Kar UK, Satpathy S, Nayak N, Das BK, Panda SK. Serotype
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Indian Journal of Pediatrics, Volume 74—October, 2007                                                                           907

								
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