Background: Salmonella enterica subsp. enterica serovar Blockley (antigenic formula 6,8:k:1,5) is a serovar of the O:8 (C2-C3) serogroup. Serovar Blockley was first isolated from the stool from a 60-year-old patient in the United States in 1955. This serovar was involved in a case of cardiac device infection in China. Interestingly, serovar Blockley was suggested to be associated with long-term reactive arthritis. Serovar Blockley was among the five most common isolated serotypes from both avian and human sources in Japan, Thailand, and Malaysia.
NCBI PD link for serovar Blockley: https://www.ncbi.nlm.nih.gov/pathogens/isolates/#(taxgroup_name:%22Salmonella%20enterica%22)%20AND%20computed_types:(%22serotype=Blockley%22)
Genetic characteristics: Serovar Blockley has been found to be polyphyletic with three lineages identified. Izumiya et al. found that 264 Blockley isolates can be classified to 10 distinct groups (BAPS A to BAPS J), further categorized into two lineages, R and S. Lineage R was made of six BAPS clusters (BAPSs A-F), primarily found in Africa and Asia, all of which possessed the azithromycin resistance gene mph(A) and other resistance patterns. Lineage R was found to harbor a genomic island with mph(A), aph(3')-Ia, aph(3")-Ib, aph(6)-Id, and tet(A).
Animal reservoir: Chickens are the main reservoir for serovar Blockley. This serovar was also found in turkey, cattle, and pigs.
Geographical distribution: Serovar Blockley has been reported worldwide periodically.
Human outbreaks:
Year | Location | Associated source | Number of cases |
| 2019 | US: NY | Chicken | 10 |
| 1998 | Germany | Smoked eel | 13 |
| 1998 | Greece | Unknown | 35 |
| 1966 | US: MA | Frozen unpasteurized egg yolks | 167 |
Border rejections: There have been no recent border rejections linked to this serovar.
Recalls: There have been no recent recalls linked to this serovar.
Relevant links: