Investigation of extramammary sources of Group B Streptococcus reveals its unusual ecology and epidemiology in camels

Abstract

Camels are vital to food production in the drylands of the Horn of Africa, with milk as their main contribution to food security. A major constraint to camel milk production is mastitis, inflammation of the mammary gland. The condition negatively impacts milk yield and quality as well as household income. A leading cause of mastitis in dairy camels is Streptococcus agalactiae, or group B Streptococcus (GBS), which is also a commensal and pathogen of humans and cattle. It has been suggested that extramammary reservoirs for this pathogen may contribute to the occurrence of mastitis in camels. We explored the molecular epidemiology of GBS in camels using a cross-sectional study design for sample collection and phenotypic, genomic and phylogenetic analysis of isolates. Among 88 adult camels and 93 calves from six herds in Laikipia County, Kenya, GBS was detected in 20% of 50 milk samples, 25% of 152 nasal swabs, 8% of 90 oral swabs and 3% of 90 rectal swabs, but not in vaginal swabs. Per camel herd, two to four sequence types (ST) were identified using Multi Locus Sequence Typing (MLST). More than half of the isolates belonged to ST617 or its single-locus variant, ST1652, with these STs found across all sample types. Capsular serotype VI was detected in 30 of 58 isolates. In three herds, identical STs were detected in milk and swab samples, suggesting that extramammary sources of GBS may contribute to the maintenance and spread of GBS within camel herds. This needs to be considered when developing prevention and control strategies for GBS mastitis. The high nasal carriage rate, low recto-vaginal carriage rate, and high prevalence of serotype VI for GBS in camels are in stark contrast to the distribution of GBS in humans and in cattle and reveal hitherto unknown ecological and molecular features of this bacterial species.

Molecular typing and prevalence of antibiotic resistance and virulence genes in Streptococcus agalactiae isolated from Chinese dairy cows with clinical mastitis

“…The bacterium invades the mammary glands of dairy cows via the skin and teat and causes mastitis [1]. Mastitis caused by S. agalactiae is generally a chronic disease with few acute outbreaks and no significant clinical symptoms but reduces the milk yield and has severe economic consequences for dairy farms [2,3]. The financial impact of mastitis includes the costs of treatment, milk that must be discarded, increased workload, reduced milk production, and culling and replacement [4].…”

The landscape of antimicrobial resistance in the neonatal and multi-host pathogen group B Streptococcus: review from a One Health perspective

“…The GBS population is classified in several lineages that can be differentiated according to niche adaptation, virulence potential, and genetic relatedness. For example, ST17 is a hypervirulent lineage associated with meningitis in infants; CC61 is a bovine-adapted lineage known for causing mastitis in dairy cattle; CC552 represents a lineage that is unique to coldblooded species (fish and frogs); and CC616 is limited to camels ( Delannoy et al, 2013 ; Gori et al, 2020 ; Crestani et al, 2021 ; Seligsohn et al, 2021b ). In addition to such host-adapted lineages, the species includes host-generalists, such as CC10, which includes GBS of human, dog, rat, cattle, dolphin, fish, and frog origin ( Delannoy et al, 2013 ; Da Cunha et al, 2014 ; Leal et al, 2019 ; Crestani et al, 2021 ; Maeda et al, 2022 ).…”

“…In the medical literature, host adaptation is mostly considered in the context of host age, i.e., pediatric vs. adult GBS ( Raabe and Shane, 2019 ; Watkins et al, 2019 ), but GBS is also a cause of infectious diseases among food-producing animals, including cattle ( Pinto et al, 2013 ; Cobo-Angel et al, 2019 ), fishes ( Delannoy et al, 2013 ; Leal et al, 2019 ) and camels ( Fischer et al, 2013 ; Seligsohn et al, 2021b ) and it has been detected in companion animals ( Maeda et al, 2022 ), laboratory animals ( Bodi Winn et al, 2018 ), and wildlife ( Bowater et al, 2012 ). There is evidence for GBS transmission between humans and animals from evolutionary ( Barkham et al, 2019 ; Richards et al, 2019 ; Crestani et al, 2021 ) as well as epidemiological studies ( Kalimuddin et al, 2017 ; Sørensen et al, 2019 ; Seligsohn et al, 2021a ) with transmission via multiple routes and in both directions ( Botelho et al, 2018a ; Crestani et al, 2021 ).…”

Proteomics and metabolomics analyses of Streptococcus agalactiae isolates from human and animal sources

“…GBS invades the mammary glands of dairy cattle through the skin and teats 4 . Mastitis caused by GBS is a chronic illness with few acute epidemics and no notable associated symptoms, but it affects milk output 5 .…”