Abstract:
Actinomycetes are organisms belonging to the order Actinomycetale. Most of them are
opportunistic pathogens causing infections in immunocompromised patients. In most
cases, respiratory infections caused by Actinomycetes display symptoms that mimic
tuberculosis. This can lead to misdiagnosis resulting to delayed or inappropriate
treatment. Therefore, this study aimed at isolating, characterizing and determining drug
susceptibility of Actinomycetes from the sputum of TB smear negative patients from
selected referral facilities in Kenya. This employed a cross-sectional study design where
a total of three hundred and eight-five (385) sputum samples from TB smear negative
patients were collected and screened for the presence of Actinomycetes. Phenotypic
identification was done by Gram staining, culture and biochemical test. Genotypic
identification was done using rDNA primers to amplify 16S rRNA gene as well as
Phylogenetic analysis for confirmation. Antimicrobial susceptibility testing was done by
minimum inhibition concentration method (MIC) using 9 antimicrobial agents; amikacin
(64 μg/ml), amoxicillin-clavulanate (64/32 μg/ml), ceftriaxone (256 μg/ml),
ciprofloxacin (64 μg/ml), clarithromycin (64 μg/ml), gentamycin (64 μg/ml), co trimoxazole (trimethoprim-sulfamethoxazole) (8/152 μg/ml), doxycycline (64 μg/ml)
and linezolid (64 μg/ml). Data was analyzed by statistical package, R Windows using
the Kruskal-Wallis test, a P value of less than 0.05 was considered significant. Fifty two
(13.5%) of 385, were identified as Actinomycetes using the phenotypic methods. Of the
52 Actinomycetes isolates, 32 (8.3%) were amplified for16S rRNA gene. Nine of the
amplified genes were sequenced and compared with those in National Center for
Biotechnology Information (NCBI). Phylogenetic analysis confirmed the 9 sequenced
genes were members of Actinomycetes. Eight of them were members of the genus
Streptomyces while only one was a Nocardiopsis species. Antimicrobial susceptibility
testing was done on the 52 isolates. The isolates showed highest susceptibility to
Gentamycin and Ciprofloxacin at 100% and 98% respectively. Highest resistance was
observed in Ceftriazone and Clarithromycin at 11.5% and 26.9% respectively.
Multidrug resistance was observed in four isolates. Staphylococcus aureus ATCC 25923
was used for quality control. There is Actinomycetes infections in TB smear negative
patients hence it is important to investigate suspected pulmonary pathologies for
potential Actinomycetes infection for proper diagnosis and interventions
