Pathogenic staphylococci in poultry

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.

A Review of Current Knowledge on Staphylococcus agnetis in Poultry

Simple Summary

This literature review provides a synthesis and evaluation of the current knowledge on Staphylococcus agnetis (S. agnetis) and its implications in poultry pathology. Recent studies revealed that S. agnetis can cause bacterial chondronecrosis with osteomyelitis (BCO), endocarditis, and septicemia in broiler chickens. Lameness constitutes one of the major health and welfare problems causing huge economic losses in the poultry industry. To date, a range of infectious and non-infectious factors have been associated with lameness in poultry. Among bacteria of the genus Staphylococcus, Staphylococcus aureus is the main species associated with locomotor problems. This contrasts with S. agnetis, which until recently had not been considered as a poultry pathogen. Previously only reported in cattle, S. agnetis has expanded its host range to chickens, and due to its unique characteristics has become recognized as a new emerging pathogen. The genotypic and phenotypic similarities between S. agnetis and other two staphylococci (S. hyicus and S. chromogenes) make this pathogen capable of escaping recognition due to misidentification. Although a significant amount of research on S. agnetis has been conducted, many facts about this novel species are still unknown and further studies are required to understand its full significance in poultry pathology.

Abstract

This review aims to summarize recent discoveries and advancements regarding the characteristics of Staphylococcus agnetis (S. agnetis) and its role in poultry pathology. S. agnetis is an emerging pathogen that was primarily associated with mastitis in dairy cattle. After a presumed host jump from cattle to poultry, it was identified as a pathological agent in broiler chickens (Gallus gallus domesticus), causing lameness induced by bacterial chondronecrosis with osteomyelitis (BCO), septicemia, and valvular endocarditis. Economic and welfare losses caused by lameness are global problems in the poultry industry, and S. agnetis has been shown to have a potential to induce high incidences of lameness in broiler chickens. S. agnetis exhibits a distinct repertoire of virulence factors found in many different staphylococci. It is closely related to S. hyicus and S. chromogenes, hence infections caused by S. agnetis may be misdiagnosed or even undiagnosed. As there are very few reports on S. agnetis in poultry, many facts about its pathogenesis, epidemiology, routes of transmission, and the potential impacts on the poultry industry remain unknown.

Screening of genes encoding adhesion factors and biofilm formation in Staphylococcus aureus isolates from poultry

Staphylococcus aureus isolates recovered from poultry between 1970 and 1972 (90 old isolates) and in 2006 (81 recent isolates) were screened for the presence of bap, icaA and icaD genes associated with biofilm formation, and for bbp, cna, ebpS, eno, fib, fnbA, fnbB, clfA and clfB genes that encode microbial surface components recognizing adhesive matrix molecules (MSCRAMMs). Most of the old isolates were collected from broiler breeders affected by staphylococcal tenosynovitis and arthritis, whilst nearly all recent isolates were derived from the nose and cloaca of healthy broilers. Ten recent isolates belonged to the animal-associated methicillin-resistant S. aureus (MRSA) ST398. All isolates were positive for clfA, clfB, eno and fnbA, and were negative for bap and bbp. All recent isolates were also positive for ebpS and cna, and all old isolates were positive for fib. The average number of genes encoding adhesins and biofilm-associated proteins in both groups was eight per isolate. All MRSA ST398 isolates in this study were positive for icaD, cna, ebpS, eno, fnbA, fnbB, clfA and clfB. No relevant differences were found between the presence of adhesin and biofilm formation genes in old and recent S. aureus isolates or in isolates from healthy compared with diseased chickens. From this study, there is no indication that the presence of these genes has changed over time and no specific association could be found between the presence of certain MSCRAMM or biofilm genes in poultry S. aureus isolates and the isolate's capacity to cause disease.

Staphylococcus hyicus associated with pox in chickens and in turkeys

Staphylococcus hyicus was isolated in profuse and often pure culture from skin lesions, and from internal organs of chickens and turkeys suffering from pox. Most cases were seen in backyard stock, but similar observations were made in laying hens from an industrial farm.

Comparative molecular analysis of erythromycin-resistance determinants in staphylococcal isolates of poultry and human origin

The ermA, ermB, ermC and msrA/msrB genes were detected in multidrug-resistant Staphylococcus spp. strains by PCR. Among 25 human clinical staphylococcal isolates the ermA, ermB, ermC and the msrA/msrB genes were detected in 88, 72, 4 and 100% of the strains, respectively. Among 24 poultry isolates the ermA, ermB, ermC and the msrA/msrB genes were detected in 100, 16.6, 50 and 12.5% of the strains, respectively. The ermA gene was found exclusively on the chromosome, whereas the ermC gene was found on 2.4-4.2 kb plasmids. Restriction fragment length polymorphism (RFLP) analysis of the ermA gene with Eco RI revealed five patterns (25.0, 21.0, 10.5, 6.2 and 4. 8 kb) for the clinical strains and two (8.0 and 6.2 kb) for the poultry strains. The 6.2 kb RFLP pattern, in both the poultry and human clinical isolates, indicates a common lineage for the ermA gene.

Delayed-type hypersensitivity reaction induced in broilers by killed Staphylococcus aureus

A trial was conducted to determine whether the delayed footpad reaction (DFR) induced by killed Staphylococcus aureus in chickens is a delayed-type hypersensitivity (DTH) reaction. Five criteria were used to assess DTH: 1) DFR with a peak response at 24 to 48 h postchallenge, 2) inhibition of monocyte/macrophage migration, 3) lymphocyte blastogenic response, 4) mononuclear cell infiltration at the challenge site, and 5) passive transfer of DFR by splenic lymphocytes. Broilers were sensitized twice with a s.c. injection in the neck of S. aureus antigen (150 microg/bird) diluted in polyethylene glycol at 3 and 4 wk of age. Controls were s.c. injected with polyethylene glycol. At 6 wk of age, a migration inhibition test was conducted before the birds were challenged intradermally with S. aureus antigen (75 microg/bird) in PBS in the right footpad. The left footpad was injected with PBS. The thickness of the footpad was measured at 0, 4, 24, and 48 h postchallenge to evaluate the DFR. After challenge, blood was collected for the lymphocyte blastogenesis assay. Birds were euthanatized, and both footpads were removed for histology. The spleens were collected aseptically; splenic lymphocytes were injected i.v. into recipient birds. Sensitized birds showed an increase in the DFR (P < 0.02) and blastogenic response (P < 0.01) compared with nonsensitized birds. Delayed footpad reaction reached a maximum response at 24 h postchallenge. The in vitro migration of monocytes/macrophages from sensitized birds was significantly inhibited (P < 0.01). The histological appearance of S. aureus-injected footpads was characterized by dermal edema and perivascular infiltrates of small lymphocytes and macrophages. Birds that received sensitized splenic lymphocytes had a significantly pronounced DFR following challenge with S. aureus when compared with birds that received nonsensitized lymphocytes (P < 0.0001). These results indicated that the DFR can be used as a standard in vivo test for cell-mediated DTH reaction induced by killed S. aureus antigen in chickens.

Delayed-type hypersensitivity reaction induced in broilers via trachea inoculation of killed Staphylococcus aureus

A study was conducted to determine whether the delayed-type hypersensitivity (DTH) reaction to killed Staphylococcus aureus antigen in chickens could be induced through multiple intratracheal inoculations. Three criteria were used to assess DTH: 1) delayed footpad reaction (DFR) with a peak response at 24 to 48 h postchallenge, 2) inhibition of monocyte/macrophage migration, and 3) mononuclear cell infiltration at the challenge site. Broilers were sensitized three times with a s.c. injection in the neck or intratracheal inoculation of killed S. aureus in polyethylene glycol at 2, 3, and 4 wk of age. Controls were given polyethylene glycol with a s.c. injection in the neck or intratracheal inoculation. Migration inhibition tests were conducted at 6 wk of age. At 7 wk of age, all birds were challenged intradermally with S. aureus antigen in PBS in the right footpad. The left footpad was injected with PBS. The thickness of the footpad was measured at 0, 4, 24, and 48 h postchallenge to evaluate the DFR. Birds were euthanatized, and both footpads were removed for histopathological examination. Subcutaneously or intratracheally sensitized birds showed significant DFR compared with nonsensitized birds (P < 0.0001), which reached maximum response at 24 h postchallenge. The s.c. sensitization resulted in an inhibition of the in vitro migration of monocytes/macrophages (P < 0.0001), whereas intratracheally sensitized birds did not show migration inhibition of monocytes/macrophages. Histological examination showed typical perivascular infiltration of small lymphocytes in S. aureus-injected footpads from s.c. and intratracheally sensitized birds. These results indicate that multiple intratracheal inoculation, as well as s.c. injection of killed S. aureus antigen, can be used to induce a cell-mediated DTH reaction in chickens.

Biochemical and molecular characterization of erthromycin-resistant avian Staphylococcus spp. isolated from chickens

The epidemiology of the two common erythromycin-resistant methylase (erm) genes ermC and ermA was analyzed in 12 coagulase-negative Staphylococcus spp. and 34 coagulase-positive Staphylococcus spp. isolated from chicken. Southern hybridization indicated that only 2 of the 12 coagulase-negative Staphylococcus spp. strains contained the ermC gene on the plasmid; 1 strain of Staphylococcus xylosus harbored the ermC gene on a 2.5-kb plasmid, and 1 strain of Staphylococcus cohnii harbored the gene on a 4.0-kb plasmid. Twelve of the 34 strains of Staphylococcus aureus contained the ermC gene. Eleven of these strains had the ermC gene on a 2.5-kb plasmid, and 1 strain had the gene on a 4.0-kb plasmid. Ten of the 12 coagulase-negative Staphylococcus spp. and 22 of the 34 coagulase-positive Staphylococcus spp. harbored the ermA gene exclusively on the chromosome. Two different ermA EcoRI restriction fragment length polymorphisms (RFLP) were identified. A majority of the isolates was found to have two chromosomal inserts (8.0- and 6.2-kb EcoRI fragments) of ermA. One strain of S. aureus had different chromosomal inserts (6.4- and 5.8-kb EcoRI fragments) of ermA. Our results indicate that either the ermC or ermA gene, homologous to those described in human isolates, was present in all avian Staphylococcus spp. and that ermA was the predominant gene in coagulase-negative and coagulase-positive avian Staphylococcus spp. The size and copy numbers of the ermA gene were different from its human counterpart.

Induction of the delayed footpad and wattle reaction to killed Staphylococcus aureus in chickens

Two experiments were conducted to induce the delayed footpad reaction (DFR) to killed Staphylococcus aureus antigen. In Experiment 1, tracheal, cloacal, and choanal swabs were collected from chickens prior to sensitization with S. aureus to determine the carrier status of S. aureus. The second experiment compared the DFR to the delayed wattle reaction (DWR). Chickens were subjected to single or multiple sensitizations in the neck with S. aureus antigen between 4 and 6 wk of age. One week later, birds were challenged with S. aureus either in the right footpad or wattle. The left footpad or wattle was injected with PBS. The thicknesses of the footpad or the wattle were measured up to 96 h postchallenge. The recoveries of S. aureus from the choanal slit and trachea were significantly higher than that of the cloaca (P < 0.001). Birds of Experiment 1 showed a significant DFR (P < 0.0001) following intradermal challenge with killed S. aureus that was sustained through 48 h postchallenge with no difference in the DFR between carrier and noncarrier birds. In Experiment 2, the thicknesses of the footpad and wattle were significantly increased following challenge with S. aureus (P < 0.0001), with the footpad showing a greater response than the wattle (P < 0.001). Three sensitizing dosages, as compared to two dosages, resulted in a less pronounced DFR and DWR (P < 0.02). These results indicate that the DFR can be used as a delayed reaction model in the study of staphylococcosis in poultry.

The role of environment and management on leg abnormalities in meat-type fowl

Continuous light with 1 h of darkness at midnight is a common photoperiod for raising meat-type fowl. The logic behind the 1 h of darkness, usually provided between midnight and 0100 h, is to acclimate the birds to darkness in the event of a power failure. Increasing evidence from several research laboratories indicates that lighting regimens other than continuous light, such as intermittent or step-up lighting, can lower the incidence of leg abnormalities in meat-type fowl. Some evidence suggests that increased exercise contributes in part to the reduction in lameness due to lighting. Management can influence the incidence of leg and foot problems via effects on rate of gain, flooring systems, and litter moisture. Rapid weight gains have been correlated with tibial dyschondroplasia (TD), although more evidence is needed to determine whether other types of leg deformities, such as long bone distortion, are related to rapid growth rates. Using low intensity X-ray imaging (hand-held lixiscope), live breeders with TD lesions can be identified and the incidence of TD can be reduced in breeder flocks through genetic selection. In addition, turkeys can be selected for wider shanks to improve walking ability. Slippery surfaces should be avoided to prevent spraddled legs. With the exception of TD, broilers reared in cages have more leg deformities than floor-reared birds. Dry litter conditions can help prevent foot pad dermatitis caused by Staphylococcus aureus and other bacteria.

Assay of protein A in Staphylococcus hyicus subsp. hyicus by ELISA and immunoelectron microscopy

The presence and quantity of protein A in Staphylococcus hyicus subsp. hyicus isolates were examined by an enzyme-linked immunosorbent assay (ELISA) and immunoelectron microscopy. Cell-bound protein A was demonstrated in 45 (94%) of 48 isolates from diseased pigs and in 113 (86%) of 132 isolates from healthy pigs by ELISA using peroxidase-conjugated rabbit antibody, but was not found in isolates from chickens and cows. Most of these swine isolates contained about 100 to 300 ng of cell-bound protein A/ml. Extracellular protein A was not detected in any isolates from pigs, chickens or cows. In the immunoelectron microscopy assay, swine isolates were labeled with goat anti-mouse IgG conjugated to colloidal gold particles, but chicken and cow isolates were not labeled.

Health effects of exposure to endotoxins and organic dust in poultry slaughter-house workers

Twenty-three dust-exposed shacklers in the hanging departments of four poultry slaughter-house plants were examined immediately before work on a Monday morning with a standardized interview, pulmonary function tests (VC and FEV1), and blood sampling for analysis of complement factors. The examinations were repeated immediately after work the same day. Further, the individual breathing zone levels of both total dust and endotoxins were monitored during the whole work-shift. Moreover, spot samples of airborne bacteria and fungi were collected. The mean level of total dust was 6.3 mg/m3 (range 0.4-15.3 mg/m3) and of endotoxins 0.40 micrograms/m3 (range 0.02-1.50 micrograms/m3). Total levels of 4 x 10(5)-4 x 10(6) cfu/m3 of airborne bacteria, mainly coagulase-negative staphylococcal strains, but only 500-4000 cfu/m3 of fungi were found in the hanging departments. An over-shift increase in respiratory symptoms was found, but none of the workers had experienced any symptoms indicating extrinsic allergic alveolitis (EAA) or organic dust toxic syndrome (ODTS). Further, mean over-shift decreases of VC (3.1%) and FEV1 (4.1%) were found, indicating a harmful effect on the bronchi. There were, however, no associations between these over-shift decreases and the individual time-weighted average breathing zone levels of either total dust or of endotoxins. No over-shift change in serum complement factors was observed.

Acute fibrinopurulent blepharitis and conjunctivitis associated with Staphylococcus hyicus, Escherichia coli, and Streptococcus sp. in chickens and turkeys

Multiple outbreaks of acute severe fibrinopurulent lesions of the eyelids occurred in chickens and turkeys. Lesions began as tiny foci of epidermal necrosis and ulceration and spread to involve the entire eyelid. Scabs overlying the epidermis contained large gram-positive cocci; lesser numbers of small cocci and gram-negative bacilli were in more superficial areas. Staphylococcus hyicus was isolated from birds in all stages of the disease. Escherichia coli and Streptococcus sp. were isolated only during severe stages; no anaerobic bacterial pathogens were isolated. Vasculitis and perivascular lymphocytic infiltrates in deep layers of the dermis suggested that a staphylococcal toxin may have been involved. The disease was not reproduced by scarifying S. hyicus onto the eyelids or by intravenous inoculation of retrovirus-infected chickens.

Proteolytic zymograms of Staphylococcus hyicus subsp. hyicus isolated from pigs, chickens and cows

The extracellular proteases of Staphylococcus hyicus subsp. hyicus were assayed by a zymogram showing caseinolysis and gelatinolysis. Four bands were associated with caseinolysis or with gelatinolysis. The patterns shown by strains isolated from pigs, chickens and cows were compared; isolates from pigs differed from those isolated from chickens or cows but strains isolated from diseased and healthy pigs could not be differentiated.

Gordon memorial lecture. Poultry disease and public health

The development of the poultry industry and the consumption of poultry meat is traced over the past quarter of a century and related to the increased incidence of food poisoning in man. Factors affecting the spread of the main poultry pathogens which are of human significance are discussed. The pathogens considered are salmonella, campylobacter, staphylococci and clostridia. Various preventative measures are considered including rearing procedures for poultry, decontamination methods and education of the public. It is concluded that one of the most effective measures is irradiation of poultry and poultry products. The difficulties of introducing this control measure are recognised. It is concluded that more effective application of existing control methods would greatly reduce the hazards to public health.

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.

Lysogeny and other characteristics of Staphylococcus hyicus isolated from chickens

Lysogeny was readily demonstrated among strains of Staphylococcus hyicus that were isolated from chickens. Susceptibility to phage lysis was affected by prophage immunity, but lipase activity and erythromycin resistance were not affected by the presence of temperate phage. In contrast to previously published results, lipase-negative strains of S. hyicus were relatively common and the use of selective media based on lipase activity would have been unsuitable for detection of the S. hyicus strains examined.

Staphylococcus aureus isolated from poultry in Australia. II. Epidemiology of strains associated with tenosynovitis

Bacteriophage typing of Staphylococcus aureus from different outbreaks of tenosynovitis in broiler breeder replacement chickens showed that, although a mixture of phage types was present on affected farms, there was a predominant phage type isolated from lesions of affected chickens. The predominant phage type isolated from chickens in different outbreaks was variable. The source of S. aureus associated with tenosynovitis appeared to be a resident population present on the skin.

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.