Oral antimicrobial rinse to reduce mycobacterial culture contamination among tuberculosis suspects in Uganda: a prospective study.
BACKGROUND
Contamination by bacterial or fungal organisms reduces the effectiveness of mycobacterial culture for diagnosis of pulmonary tuberculosis (TB). We evaluated the effect of an anti-microbial and an anti-fungal oral rinse prior to expectoration on culture-contamination rates.


METHODS
We enrolled a consecutive random sample of adults with cough for ≥ 2 weeks and suspected TB admitted to Mulago Hospital (Kampala, Uganda) between October 2008 and June 2009. We randomly assigned patients to oral rinse (60 seconds with chlorhexidine followed by 60 seconds with nystatin) vs. no oral rinse prior to initial sputum collection. Uganda National Tuberculosis Reference Laboratory technicians blinded to the method of sputum collection (with or without oral rinse) processed all sputum specimens for smear microscopy (direct Ziehl-Neelsen) and mycobacterial culture (Lowenstein-Jensen media).


RESULTS
Of 220 patients enrolled, 177 (80%) were HIV-seropositive (median CD4-count 37 cells/uL, IQR 13-171 cells/uL). Baseline characteristics were similar between patients in the oral-rinse (N = 110) and no oral-rinse (N = 110) groups. The proportion of contaminated cultures was significantly lower in the oral-rinse group compared to the no oral-rinse group (4% vs. 15%, risk difference -11%, 95% CI -18 to -3%, p = 0.005). Oral rinse significantly reduced the proportion of contaminated cultures among HIV-infected patients (3% vs. 18%, risk difference -14%, 95% CI -23 to -6%, p = 0.002) but not HIV-uninfected (6% vs. 4%, risk difference 2%, 95% CI -12 to +15%, p = 0.81) patients. However, the proportion of smear-positive specimens (25% vs. 35%, p = 0.10) and culture-positive specimens (48% vs. 56%, p = 0.24) were lower in the oral-rinse compared to the no oral-rinse group, although the differences were not statistically significant.


CONCLUSIONS
Oral rinse prior to sputum expectoration is a promising strategy to reduce mycobacterial culture contamination in areas with high HIV prevalence, if strategies can be devised to reduce the adverse impact of oral rinse on smear- and culture-positivity.
Makerere University - University of California San Francisco Research Collaboration, Kampala, Uganda. kalemanelson@gmail.com
Nelson
N
Kalema
Saskia Den
SD
Boon
Adithya
A
Cattamanchi
J Lucian
JL
Davis
Alfred
A
Andama
Winceslaus
W
Katagira
Charles
C
Everett
Nicholas
N
Walter
Patrick
P
Byanyima
Sylvia
S
Kaswabuli
William
W
Worodria
Laurence
L
Huang
D000328:Adult; D000890:Anti-Infective Agents / Q000494:pharmacology*; D018791:CD4 Lymphocyte Count; D002710:Chlorhexidine / Q000494:pharmacology*; D060085:Coinfection; D015169:Colony Count, Microbial; D003371:Cough / Q000503:physiopathology; D005260:Female; D006678:HIV; D015658:HIV Infections / Q000821:virology*; D006801:Humans; D008297:Male; D008853:Microscopy; D009067:Mouthwashes; D009169:Mycobacterium tuberculosis / Q000254:growth & development / Q000302:isolation & purification*; D009761:Nystatin / Q000494:pharmacology*; D011446:Prospective Studies; D016037:Single-Blind Method; D013048:Specimen Handling; D013183:Sputum / Q000382:microbiology; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000382:microbiology*; D014454:Uganda
D000890:Anti-Infective Agents; D009067:Mouthwashes; D009761:Nystatin; D002710:Chlorhexidine