Staphylococcus aureus in commercial laying flocks: incidence and characteristics of strains isolated from chicks, pullets and hens in an integrated commercial enterprise

Review on skeletal disorders caused by Staphylococcus spp. in poultry

Lameness or leg weakness is the main cause of poor poultry welfare and serious economic losses in meat-type poultry production worldwide. Disorders related to the legs are often associated with multifactorial aetiology which makes diagnosis and proper treatment difficult. Among the infectious agents, bacteria of genus Staphylococcus are one of the most common causes of bone infections in poultry and are some of the oldest bacterial infections described in poultry. Staphylococci readily infect bones and joints and are associated with bacterial chondronecrosis with osteomyelitis (BCO), spondylitis, arthritis, tendinitis, tenosynovitis, osteomyelitis, turkey osteomyelitis complex (TOC), bumblefoot, dyschondroplasia with osteomyelitis and amyloid arthropathy. Overall, 61 staphylococcal species have been described so far, and 56% of them (34/61) have been isolated from clinical cases in poultry. Although Staphylococcus aureus is the principal cause of poultry staphylococcosis, other Staphylococcus species, such as S. agnetis, S. cohnii, S. epidermidis, S. hyicus, S. simulans, have also been isolated from skeletal lesions. Antimicrobial treatment of staphylococcosis is usually ineffective due to the location and type of lesion, as well as the possible occurrence of multidrug-resistant strains. Increasing demand for antibiotic-free farming has contributed to the use of alternatives to antibiotics. Other prevention methods, such as better management strategies, early feed restriction or use of slow growing broilers should be implemented to avoid rapid growth rate, which is associated with locomotor problems. This review aims to summarise and address current knowledge on skeletal disorders associated with Staphylococcus spp. infection in poultry.

Enterotoxigenicity and genetic relatedness of Staphylococcus aureus in a commercial poultry plant and poultry farm

Raw (fresh) and frozen poultry products are frequently associated with Staphylococcus aureus contamination. New Zealand is among the developed countries with high incidences of staphylococcal food poisoning. The study investigated the S. aureus isolates obtained from various stages of poultry production, to determine the primary source of contamination. Viable cell counts of S. aureus were enumerated using Petrifilm™ Staph Express Count Plates, and the isolates were confirmed by Gram-stain and coagulase-positive test. Sixty S. aureus isolates were further confirmed by PCR. The PCR analysis used primers that specifically amplifies a fragment of the femA gene, unique to S. aureus. The confirmed S. aureus strains were further examined for enterotoxigenicity by PCR. Multilocus Sequence Typing (MLST) was then used to identify sequence types (STs) of the sixty isolates of S. aureus. The relatedness of the sequence types was investigated by eBURST. In this study, it was observed that all samples from the processing plant and live chickens at the farm were contaminated by S. aureus. Fifty-nine (59) of the 60 isolates were enterotoxigenic carrying enterotoxin genes: seg, sei, seh, sek, sel, sem, sen, or seo. The sixty isolates were categorised into six different sequence types: ST5, ST2594, ST101, ST83, ST398, ST1; where ST5, ST83 and ST2594 belonged to the Clonal Complex (CC) 5 with ST5 being the clonal ancestor. The sources of S. aureus contamination in the final poultry products were linked to fresh mechanically separated meat, fresh skin, fresh skin-on-breast fillet, rubber fingers on mechanical pluckers, and live chickens at the farm. The skin of live chickens at the farm was most likely the origin of S. aureus contamination on equipment and final products. Not all identified S. aureus strains at the farm were observed in the final products. Therefore, further investigation on other potential contamination sources such as gloves and knives used at the processing plant, and feeders and drinkers at the farm level is recommended.

Loop-mediated isothermal amplification assays for Enterococcussp., Escherichiacoli and Staphylococcusaureus in chicken

Bacterial chondronecrosis with osteomyelitis (BCO) is a major cause of lameness in broiler chicken, and results in serious economic losses worldwide. Although the pathogenesis mechanism leading to lameness is not entirely understood, some strains of Enterococcussp., avian pathogenic Escherichia coli or Staphylococcus aureus have been long recognized as important causative pathogens. To prevent the progression of Enterococcussp., avian pathogenic E. coli or S. aureus infections, we developed rapid, sensitive and convenient diagnostic assays using loop-mediated isothermal amplification (LAMP). Entero-Common-LAMP assays were developed for simultaneous detection of eight Enterococcus species. To target specific microorganisms, seven Entero-Specific-LAMP assays for E. faecalis, E. faecium, E. hirae, E. gallinarum, E. avium, E. duransand E. cecorum were developed, as well as E. coli-LAMP and S. aureus-LAMP assays. Considering the prevalence and economic impact of Enterococcussp., E. coli and S. aureus, the 10 different LAMP assays which were developed have considerable potential as routine diagnostic methods in the field or in resource-limited environments.

Bacterial chondronecrosis with osteomyelitis ('femoral head necrosis') of broiler chickens: a review

Bacterial chondronecrosis with osteomyelitis (BCO) in chickens was first reported in 1972 and is now recognized as an important cause of lameness in broiler chickens. Recent systematic studies of causes of lameness in birds reared in Northern Ireland have shown that it was the most common cause of lameness, being present in 17.3% of lame birds. Furthermore, it was also detected in birds presented as ''found dead''. Overall losses in male birds due to BCO were estimated to be 0.75% of all birds placed, which, in addition to welfare concerns, represents considerable economic loss. The disease has been seen in birds ranging from 14 to 70 days of age, but most cases occurred around 35 days old. It is most commonly caused by Staphylococcus aureus, but Escherichia coli, coagulase-negative staphylococci and Enterococcus spp. are sometimes involved, as are, rarely, other bacteria. The lesions are most commonly found associated with the growth plates of long bones, particularly the proximal growth plate of the femur and tibiotarsus, but other bones may also be affected. Since lesions were visible to the naked eye in only 40 to 67% of cases, histological examination is recommended where no lesions are visible macroscopically. As the lesion may be present in only one growth plate, and because histological examination is often not carried out, BCO is almost certainly underdiagnosed. The exact pathogenesis of the condition is unknown, but it is thought that adherence of blood-borne bacteria to exposed cartilage at the tips of metaphyseal blood vessels is fundamental. Under controlled experimental conditions, infection of birds with the immunosuppressive viruses chicken anaemia virus and infectious bursal disease virus increased the incidence of the disease, while restricting feed intake reduced the incidence of disease. S. aureus strains identical to, or closely related to, isolates recovered from naturally occurring cases of the disease (as determined by pulsed-field gel electrophoresis) have been recovered from fluff-debris in hatcheries, and also from the environment of breeding flocks, indicating that infection in the breeding farm and in the hatchery could be an important source of infection. It has also been shown that humans can carry poultry strains of S. aureus on their hands. There is a higher incidence of BCO in birds hatched from floor eggs. Thus, hygiene and management practice on breeder farms and in the hatchery may influence the occurrence of the disease. Bacteraemia is a prerequisite for BCO. Indeed, in some flocks suffering losses due to BCO, there are also losses due to staphylococcal septicaemia. Thus, appropriate treatment of affected flocks should reduce losses due to septicaemia. It should also reduce the occurrence of bacteraemia and the development of further cases of BCO. However, birds in which BCO has already developed, are unlikely to respond to treatment. Control of BCO by vaccination seems unlikely in the short term. Simple bacterins have not been effective and much basic research is needed to identify the important virulence factors. Furthermore, more than one type of bacterium is capable of causing the disease. Bacterial interference has been used successfully in humans and turkeys to prevent staphylococcal diseases, and warrants investigation for the prevention of BCO in chickens. This may have an advantage in that the interfering bacterium may also exclude some of the other bacteria that can cause BCO. The recent development of a disease model in which S. aureus is given by a natural route allows the potential for further investigation of the role of predisposing factors, and intervention strategies, including vaccination and bacterial interference, for the prevention of BCO.

The anti-nuclease humoral immune response of broiler chickens exposed to Staphylococcus aureus, infectious bursal disease virus and chicken anaemia virus in an experimental model for bacterial chondronecrosis and osteomyelitis

This study aimed to develop an enzyme-linked immunosorbent assay to detect antibody associated with Staphylococcus aureus that is produced during the chicken immune response to this organism. The protein nuclease was tested for suitability as an antigen to detect antibody in sera from broiler chickens that had been exposed to aerosolized S. aureus on day 1 post hatch during experiments to reproduce bacterial chondronecrosis and osteomyelitis. An enzyme-linked immunosorbent assay was developed to measure the levels of nuclease antibody in 509 chicken sera from various experiments, which also enabled the examination of the influence of factors such as the S. aureus infection status and co-infection with chicken anaemia virus (CAV) and infectious bursal disease virus (IBDV) on nuclease antibody levels. Positive levels of nuclease antibody were detected in 71% of serum samples from chickens inoculated with S. aureus, CAV and IBDV, while positive levels were detected in 35% of chickens inoculated with S. aureus only. The influence of CAV and IBDV on the number of chickens with positive levels was most prominent in chickens aged up to 42 days. The study showed that nuclease-specific antibodies form part of the humoral immune response in broiler chickens that have been exposed to S. aureus. Co-infection with CAV and IBDV appeared to promote development of antibody in birds younger than 42 days; however, the presence of antibody did not necessarily prevent systemic infection.

Neonatal Osteomyelitis Associated with Staphylococcus aureus in Turkey Poults

A case of Staphylococcus aureus infection causing osteomyelitis in young turkey poults is described. Mortality during the first week after hatching was 12.6%. Poults showed leg weakness, inflammation of all four toes, swelling of feet and hock joints, and osteomyelitis of the proximal tibiotarsus. Staphylococcus aureus was isolated from exudate in the hock joints and footpads. Granulocytic infiltration and colonies of gram-positive coccoid bacteria compatible with S. aureus were found on microscopic examination of the lesions. Toe trimming after hatching is believed to have provided a portal of entry for S. aureus, which resulted in infection of the toes and spread along tendons to joints and bones of the leg. Neonatal staphylococcal osteomyelitis should be considered when recently placed turkey flocks experience increased mortality, especially if they develop severe swelling and inflammation of toes following trimming and have enlarged swollen feet, tendons, or joints.

Comparison of Staphylococcus aureus recovered from personnel in a poultry hatchery and in broiler parent farms with those isolated from skeletal disease in broilers

Personnel from one broiler hatchery, and workers on 18 separate broiler parent farms which supply the hatchery, were tested for hand and nasal carriage of Staphylococcus aureus. In both locations, nasal carriage of S. aureus was more common than hand carriage. A total of 63 S. aureus strains were characterised by biotyping, protein A analysis and pulsed field gel electrophoresis (PFGE) typing. Of these, 36 were recovered from broiler hatchery personnel, 14 from broiler parent farm personnel and 13 from cases of skeletal disease in commercial broilers. Biotyping and protein A analysis indicated that none of the strains recovered from hatchery personnel were of the poultry biotype, but that two strains recovered from the hands of two broiler parent farm personnel could be grouped together with 12/13 of strains recovered from skeletal disease in broilers, as poultry biotypes. PFGE-typing could not distinguish 9/13 strains recovered from skeletal disease in broilers and one of the strains from the broiler parent farm personnel from isolate 24 (I. 24), which is the predominant S. aureus strain type associated with clinical disease in N. Ireland broiler flocks. The present study found no evidence of nasal carriage of S. aureus strains of poultry biotype by humans. The finding of hand carriage by broiler parent farm personnel, suggests that handling by personnel may contribute to the dissemination of I. 24 or other S. aureus strains associated with skeletal disease in broilers.

The use of pulsed field gel electrophoresis to investigate the epidemiology of Staphylococcus aureus infection in commercial broiler flocks

Pulsed field gel electrophoresis (PFGE) analysis of SmaI restriction patterns was used to type 109 isolates of Staphylococcus aureus collected from broiler farms and hatcheries in Northern Ireland. Forty-seven isolates from clinical conditions in broilers and 62 strains from hatcheries, were examined. The PFGE patterns demonstrated a similarity between 85% of strains from clinical sources and 71% of the hatchery isolates. The association of disease with the predominant strain type and presence of these same strains in the hatchery, indicates that the hatchery is a potential source of the infection for clinical broiler disease.

Use of plasmid profiles to detect changes in strains of Staphylococcus aureus during poultry processing

The plasmid profiles of Staphylococcus aureus strains isolated at different stages in three poultry processing plants have been examined. Changes in profiles were seen in two plants after the plucking stage and the appearance of these new profiles correlated with the presence of an endemic strain, as suggested previously by increases in bacterial counts and changes in biotypes at the same stage. A third plant in which such changes did not occur showed no change in profiles. Plasmid profiles are therefore a rapid and sensitive method for distinguishing endemic strains within a plant from the flora of the incoming birds. Certain profiles also appeared to correspond with particular biotypes and certain phage types.

Plasmids of Staphylococcus aureus associated with live and processed poultry

A series of 23 strains of Staphylococcus aureus originally isolated from processed poultry was screened for the presence of plasmids. Plasmids were more common in strains of Staph. aureus characteristically associated with live poultry than with strains endemic in poultry plants and strains of human origin. Two plasmids with sizes of 1.65 and 18.2 kilobase pairs (kBp) were present in three strains considered typical of Staph. aureus forma specialis 'altilis' and two plasmids with sizes of 1.65 and 17 kBp were present in three of four strains of Staph. aureus var. gallinae. A 1.65 kBp plasmid was present in all seven strains of these poultry biotypes and in three of 14 'endemic' strains. All the 1.65 kBp plasmids were shown by blot hybridization to share sequence homology. There was also some sequence homology between the 18.2 kBp and 17 kBp plasmids. These results were supported by restriction enzyme digest analyses. A study of cured derivatives of strain PS221 f.sp. 'altilis' suggested that the 18.2 kBp plasmid encoded the genetic determinant(s) responsible for caseolysis. Both the 1.65 and the 18.2 kBp plasmids also exerted an effect on the production of acid from lactose. In no other characteristic did cured strains resemble the plasmid-free 'endemic' strains. This was therefore consistent with the notion that the genetic determinants associated with the cultural characteristics of endemic strains are chromosomally located.

Incidence and properties of Staphylococcus aureus associated with turkeys during processing and further-processing operations

The incidence of Staphylococcus aureus on turkeys sampled at various stages of processing and further-processing was determined on four occasions at each of three different processing plants. For freshly-slaughtered birds, counts from neck skin varied from plant to plant over the range less than 10(2) to greater than 10(5)/g but in all cases the corresponding counts obtained from carcasses sampled after chilling rarely exceeded 10(3)/g and the same was true for samples of mechanically recovered meat (MRM), the final raw product examined. Despite the limited susceptibility of isolates from the different factories to typing by means of either standard human or poultry bacteriophages (55-94% untypable), evidence was obtained with the aid of biotyping for the presence of both human and animal-derived strains. However, some biotypes isolated from MRM were not detected at earlier stages of processing. At one processing plant, an "indigenous' type of S. aureus was clearly demonstrated. It occurred in high numbers in the defeathering machines (up to 10(5)/swab), was found on carcasses at all subsequent stages of processing over the survey period and was shown to survive routine cleaning and disinfection procedures. Isolates of this type produced unusually large amounts of extracellular "slime' in artificial culture. Two of the three processing plants yielded isolates which were enterotoxigenic. Of 55 strains from Plant 1, 60% produced enterotoxin C and all were of the "indigenous' type. In the case of Plant 2, only two type D- and one type F-producing strain were found.

Staphylococcus aureus isolated from poultry in Australia. I. Phage typing and cultural characteristics

The phage typing and cultural characteristics of 574 strains of S. aureus of poultry origin in Australia were examined. With the avian phage set of Shimizu (1979) it was possible to type 74.2% of strains. A number of significant variations in the phage typing patterns of Australian strains compared to those reported from Japan and Europe were observed. A lower proportion of Australian strains were of avian phage group I and a higher proportion of group III. A high proportion of strains were of mixed lytic groups. No locally isolated phages were able to increase significantly the percentage of typeable strains, although four local phages appeared to be of greater value for phage typing poultry strains of S. aureus than some other phages of the avian phage set. The international (human) phage set was of limited value in typing Australian strains of poultry origin although four strains were identified which were indistinguishable from strains of human origin. Using cultural characteristics of the strains in conjunction with phage typing, the Australian strains of S. aureus were assigned to one of three major groups and nine subgroups. A list of typing phages considered to be valuable for use on Australian poultry strains of S. aureus is given.