Association between ocular bacterial carriage and follicular trachoma following mass azithromycin distribution in The Gambia.
BACKGROUND
Trachoma, caused by ocular Chlamydia trachomatis infection, is the leading infectious cause of blindness, but its prevalence is now falling in many countries. As the prevalence falls, an increasing proportion of individuals with clinical signs of follicular trachoma (TF) is not infected with C. trachomatis. A recent study in Tanzania suggested that other bacteria may play a role in the persistence of these clinical signs.


RESULTS
We examined associations between clinical signs of TF and ocular colonization with four pathogens commonly found in the nasopharnyx, three years after the initiation of mass azithromycin distribution. Children aged 0 to 5 years were randomly selected from 16 Gambian communities. Both eyes of each child were examined and graded for trachoma according to the World Health Organization (WHO) simplified system. Two swabs were taken from the right eye: one swab was processed for polymerase chain reaction (PCR) using the Amplicor test for detection of C. trachomatis DNA and the second swab was processed by routine bacteriology to assay for the presence of viable Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus and Moraxella catarrhalis. Prevalence of TF was 6.2% (96/1538) while prevalence of ocular C. trachomatis infection was 1.0% (16/1538). After adjustment, increased odds of TF were observed in the presence of C. trachomatis (OR = 10.4, 95%CI 1.32-81.2, p = 0.03), S. pneumoniae (OR = 2.14, 95%CI 1.03-4.44, p = 0.04) and H. influenzae (OR = 4.72, 95% CI 1.53-14.5, p = 0.01).


CONCLUSIONS
Clinical signs of TF can persist in communities even when ocular C. trachomatis infection has been controlled through mass azithromycin distribution. In these settings, TF may be associated with ocular colonization with bacteria commonly carried in the nasopharnyx. This may affect the interpretation of impact surveys and the determinations of thresholds for discontinuing mass drug administration.
Department of Clinical Research, Faculty of Infectious and Tropical Disease, London School of Hygiene and Tropical Medicine, London, United Kingdom. sburr@mrc.gm
Sarah E
SE
Burr
John D
JD
Hart
Tansy
T
Edwards
Ignatius
I
Baldeh
Ebrima
E
Bojang
Emma M
EM
Harding-Esch
Martin J
MJ
Holland
Thomas M
TM
Lietman
Sheila K
SK
West
David C W
DC
Mabey
Ansumana
A
Sillah
Robin L
RL
Bailey
D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D017963:Azithromycin / Q000627:therapeutic use*; D001419:Bacteria / Q000145:classification / Q000302:isolation & purification*; D001424:Bacterial Infections / Q000453:epidemiology* / Q000382:microbiology; D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D015818:Eye Infections, Bacterial / Q000453:epidemiology* / Q000382:microbiology; D005260:Female; D005714:Gambia / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D015995:Prevalence
D000900:Anti-Bacterial Agents; D017963:Azithromycin