Bacterial Pathogens: Streptococci BT10 Lecture 10 PDF

Bacterial Pathogens: Streptococci BVM&S Module 2 Prof. Ross Fitzgerald  Streptococcus Gram-positive cocci Gram-positive diplococcus chain diplococcus...

Bacterial Pathogens: Streptococci BVM&S Module 2 Prof. Ross Fitzgerald  Streptococcus Gram-positive cocci Gram-positive diplococcus chain diplococcus PMN  Streptococcus spp. Over 40 species Most species usually restricted to single host species Loosely clustered into groups based on common characteristics eg haemolytic activity/surface antigens, also fermentation properties  Haemolysis (horse blood agar) Pyogenic- γ - no haemolysis β - complete haemolysis: SLO & SLS  Haemolysis Pyogenic- γ - no β - complete haemolysis haemolysis: SLO & SLS viridans - partial haemolysis (α): (hydrogen peroxide)  Grouping of streptococcal species chain Lancefield length haemolysis group(s) pyogenic long β A, B, C, G, L viridans long α not typeable pneumococci pairs α not typeable (diplococcus) enterococci short β, α or γ D  Lancefield groupings Serological classification pioneered by american bacteriologist Rebecca Lancefield Based on variants of major cell wall polysaccharide Extracted with hot HCl and precipitated with Ab raised in rabbits Referred to as group polysacch., and assigned a letter 21 groups identified, but limited practical value M- protein subgroupings (n=~120) Streptococci and host preference Lancefield species host preference A Str. pyogenes human G Str. canis dog C Str. equi horse Str. equisimilis horse Str. zooepidemicus horse, cattle, other NT Str. pneumoniae human, horse, dog B Str. agalactiae cattle,human C Str. dysgalactiae cattle NT Str. uberis cattle D Str. suis pig E Str. porcinus pig  Equine strangles One of the most important respiratory diseases of the horse Highly contagious Usually horses 5 years indicates that with high level of immunity by vaccination should be feasible Vaccines against SeM effective ? Bacterins have shown limited efficacy Adjuvanted extracts – disappointing Multivalent M-protein - candidate immunogen Attenuated live vaccine ? Intervet: strangles vaccine Mutation in aroA gene: poor growth in vivo Vaccination through upper lip route Yard in Kent: 19 horses became infected with strangles, despite being vaccinated against the disease. Combination of 7 recombinant antigens- 5 surface proteins 2 secreted IgG endopeptidases Protective experimental strangles infections of horses  Treatment Most isolates: AmpicillinS; aminoglycosideR is a problem eg streptomycin Treat with penicillin Not always completely effective Control of Strangles outbreaks During infection Stop all movement of horses in and out quarantine infected horses and contacts Antibiotic treatment After clinical Recovery >3 swabs taken at 1 wk intervals - quarantine Strict hygiene measures introduced  Aetiology & pathogenesis of streptococcal mastitis Str. agalactiae Str. dysgalactiae Str. uberis B NT C udder “commensal” skin & GI commensal mouth & udder invades teat & duct commensal faecal contamination mild, chronic invades wounds, etc. teat duct colonisation duct blockage acute, permanent May be severe damage ENVIRONMENTAL SUMMER MASTITIS MASTITIS possible co-infection On the increase along with Arcanobacterium with E. coli pyogenes environmental mastitis  Streptococcus suis Pig disease: Usually asymptomatic in pigs but can result in septicaemia, meningitis, pneumonia Young pigs most at risk Intensive farming leads to stress and subsequent immune suppression Zoonotic infection of humans: 2005- Sichuan- 204 human cases, 38 fatalities The human outbreak coincided with local epidemic of pigs No human-to-human transmission Streptococcal toxic shock syndrome Underlying reasons unknown eg new virulent strain  Bacterial Pathogens 3: Summary and learning outcomes Know the general characteristics of the streptococci in terms of their host tropism and phenotypic characteristics Understand the clinical signs of early and advanced equine strangles Understand the molecular pathogenesis of equine strangles including the features of the most important virulence factors Understand the different ways employed for controlling and preventing strangles