Characterization of plasmids in bacterial isolates in a tertiary health care facility in Kilimanjaro region, Tanzania

Abstract

Plasmids are infectious extra-chromosomal DNA molecules found within bacteria. Their detection is important for guiding clinical treatment and controlling resistant disease outbreaks in hospital and community settings. Plasmids were characterized in bacterial isolates recovered from inpatient retrospective specimens admitted at the Kilimanjaro Christian Medical Centre (KCMC) from August 2013 to August 2015 in Kilimanjaro, Tanzania; to determine their prevalence, effects on the risks of antibiotic resistance development and spread. Bacterial isolates were fully genome sequenced. The risk factors for infections with pathogens resistant to at least one antibiotic were examined using logistic regression models. Results showed that, 56.2% (159/283) of bacterial isolates were found to carry plasmids. Twenty-six (86.7%) multiple replicon plasmids and 4 (13.3%) single-replicon plasmids were found to carry both resistance and virulence genes. There was no statistically significant correlation found between the number of antibiotic resistance and virulence genes in plasmids (r = -0.14, p > 0.05). Moreover, adjusted for other factors, lower odds of infection with pathogens resistant to at least one antibiotic for males (0.16 [95% CI, 0.05 - 0.49]; p= 0.001) was found. However, non-significant difference odds of carrying resistant pathogens was found between those transferred and non-transferred patients, and those sought and did not sought medical services. The findings show a relatively high proportion of plasmid-carrying isolates in the study area, suggesting selection pressure due to antibiotic use in the hospital. Co-occurrence of antibiotic resistance and virulence genes found in the studied clinical isolates, affirming that this is a public health concern that needs an immediate attention.