Is there evidence for resistance of ocular Chlamydia trachomatis to azithromycin after mass treatment for trachoma control?
BACKGROUND
Trachoma, caused by repeated infections with ocular Chlamydia trachomatis, is targeted for elimination using multiple annual rounds of mass drug administration (MDA) in endemic communities. Infection rates do not decline as expected in some communities, leading to concerns about azithromycin resistance.


METHODS
After 3 yearly MDAs in 32 communities in Tanzania, 107 children were identified 1 year later with infection. All were provided MDA again, and 90 were seen again at 2 months, of whom 30 had infection. Chlamydia trachomatis isolates were obtained before and after MDA in 15 paired samples and were tested for antimicrobial susceptibility. The infectious load of C. trachomatis before MDA was determined in 30 children who had infection at both times and 60 whose infection cleared.


RESULTS
The median load was 8.6 genome copies per polymerase chain reaction in the consistently infected, and 8.4 in those whose infection cleared (P = .86). For the consistently infected, the average minimum inhibitory concentration was 0.26 µg/mL for azithromycin before and 0.20 µg/mL after MDA. All isolates had minimum inhibitory concentration ≤0.50 µg/mL.


CONCLUSIONS
There is no evidence that continued infection after MDA was due either to resistance to azithromycin or to a heavier load of organism before treatment. Other potential causes of persistent infection need to be evaluated.
Sheila K
SK
West
Jeanne
J
Moncada
Beatriz
B
Munoz
Harran
H
Mkocha
Philip
P
Storey
Justin
J
Hardick
Charlotte A
CA
Gaydos
Thomas C
TC
Quinn
Julius
J
Schachter
D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000494:pharmacology; D017963:Azithromycin / Q000008:administration & dosage* / Q000494:pharmacology; D002648:Child; D002675:Child, Preschool; D002692:Chlamydia trachomatis / Q000187:drug effects* / Q000302:isolation & purification; D024881:Drug Resistance, Bacterial; D004358:Drug Therapy / Q000379:methods; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008826:Microbial Sensitivity Tests; D055502:Secondary Prevention; D013636:Tanzania / Q000453:epidemiology; D014141:Trachoma / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology* / Q000517:prevention & control
D000900:Anti-Bacterial Agents; D017963:Azithromycin