BACKGROUND: HIV transmitted drug resistance (TDR) surveillance is usually 
conducted by sampling from a large population. However, overall TDR prevalence 
results may be inaccurate for many individual clinical setting. We analyzed HIV 
genotypes at a tertiary care setting in Ottawa, Ontario in order to evaluate 
local TDR patterns among sub-populations.
METHOD: Genotyping reports were digitized from ART naïve patients followed at 
the Immunodeficiency Clinic at the Ottawa Hospital, between 2008 and 2010. 
Quality controlled, digitized sequence data were assessed for TDR using the 
Stanford HIV Database. Patient characteristics were analyzed according to TDR 
patterns. Finally, a phylogenetic tree was constructed to elucidate the observed 
pattern of HIV TDR.
RESULTS: Among the 155 clinic patients there was no statistically significantly 
difference in demographics as compared to the Ontario provincial HIV population. 
The clinic prevalence of TDR was 12.3%; however, in contrast to the data from 
Ontario, TDR patterns were inverted with a 21% prevalence among MSM and 5.5% 
among IDU. Furthermore, nearly 80% of the observed TDR was a D67N/K219Q pattern 
with 87% of these infections arising from a distinct phylogenetic cluster.
CONCLUSIONS: Local patterns of TDR were distinct to what had been observed 
provincially. Phylogenetic analysis uncovered a cluster of related infections 
among MSM that appeared more likely to be recent infections. Results support a 
paradigm of routine local TDR surveillance to identify the sub-populations under 
care. Furthermore, the routine application of phylogenetic analysis in the TDR 
surveillance context provides insights into how best to target prevention 
strategies; and how to correctly measure outcomes.