Objectives: A previously unidentified mecA homologue, mecA LGA251 , has recently been described in methicillinresistant Staphylococcus aureus (MRSA) from humans and dairy cattle. The origin and epidemiology of this novel homologue are unclear. The objective of this study was to provide basic descriptive information of MRSA isolates harbouring mecA LGA251 from a range of host animal species.Methods: A number of S. aureus isolates from historical animal isolate collections were chosen for investigation based on their similarity to known mecA LGA251 MRSA isolates. The presence of mecA LGA251 was determined using a multiplex PCR and antimicrobial susceptibility testing performed by disc diffusion.Results: MRSA harbouring mecA LGA251 were found in isolates from a domestic dog, brown rats, a rabbit, a common seal, sheep and a chaffinch. All of the isolates were phenotypically MRSA, although this depended on which test was used; some isolates would be considered susceptible with certain assays. All isolates were susceptible to linezolid, rifampicin, kanamycin, norfloxacin, erythromycin, clindamycin, fusidic acid, tetracycline, trimethoprim/sulfamethoxazole and mupirocin. Five multilocus sequence types were represented (2273, 130, 425, 1764 and 1245) and six spa types (t208, t6293, t742, t6594, t7914 and t843). Conclusions:The discovery of MRSA isolates possessing mecA LGA251 from a diverse range of host species, including different taxonomic classes, has important implications for the diagnosis of MRSA in these species and our understanding of the epidemiology of this novel mecA homologue.

Necrotic enteritis in broilers is caused by Clostridium perfringens type A strains that produce the NetB toxin. Necrotic enteritis is one of the gastrointestinal diseases in poultry that has gained worldwide importance during the last decade due to efforts to improve broiler performance. Prevention strategies include avoiding predisposing factors, such as coccidiosis, and in-feed supplementation with a variety of feed additives. However, vaccination with modified toxin or other secreted immunogenic proteins seems a logical preventive tool for protection against a toxin-producing bacterium. Formalin-inactivated crude supernatant has been used initially for vaccination. Several studies have been carried out recently to identify the most important immunogenic and protective proteins that can be used for vaccination. These include the NetB toxin, as well as a number of other proteins. There is evidence that immunization with single proteins is not protective against severe challenge and that combinations of different antigens are needed. Most published studies have used multiple dosage vaccination regimens that are not relevant for practical use in the broiler industry. Single vaccination regimens for 1-day-old chicks appear to be non-protective. This review describes the history of vaccination strategies against necrotic enteritis in broilers and gives an update on future vaccination strategies that are applicable in the field. These may include breeder hen vaccination, in ovo vaccination and live attenuated vectors to be used in feed or in drinking water

HighlightsNetB from Clostridium perfringens is the major virulence factor in avian necrotic enteritis.Vaccination with a NetB genetic or formaldehyde toxoid protects chicken in an in vivo disease model.NetB toxoids could form the bases of an efficient vaccine against necrotic enteritis.

Necrotic enteritis toxin B (NetB) is a pore-forming toxin produced by Clostridium perfringens and has been shown to play a key role in avian necrotic enteritis, a disease causing significant costs to the poultry production industry worldwide. The aim of this work was to determine whether immunization with a non-toxic variant of NetB (NetB W262A) and the C-terminal fragment of C. perfringens alpha-toxin (CPA247–370) would provide protection against experimental necrotic enteritis. Immunized birds with either antigen or a combination of antigens developed serum antibody levels against NetB and CPA. When CPA247–370 and NetB W262A were used in combination as immunogens, an increased protection was observed after oral challenge by individual dosing, but not after in-feed-challenge.

Necrotic enteritis, caused by netB toxin-producing Clostridium perfringens type A, is an important disease in broiler chickens worldwide. Earlier attempts to prevent necrotic enteritis by vaccination have not sufficiently taken into account the practical limitations of broiler vaccination. In most published studies on vaccination against necrotic enteritis, multiple doses at different ages are administered, which is not practical for broilers. The aim of this study was to compare the efficacy of subcutaneous single vaccination at day 1 or day 3 and double vaccination at day 3 and day 12, using crude supernatant containing active toxin or formaldehydeinactivated supernatant (toxoid) of a netB-positive C. perfringens strain in a subclinical necrotic enteritis model. Double vaccination with crude supernatant resulted in a significant decrease in the number of chickens with necrotic enteritis lesions. The efficacy of vaccination using toxoid was lower compared with crude supernatant. Single vaccination with crude supernatant at day 3 resulted in significant protection, while vaccination of 1-day-old chickens with crude supernatant or toxoid, as envisaged for practical field application, did not induce protection.