The Characteristics of Staphylococcus aureus Isolated from Cases of Staphylococcosis in Poultry

Phylogenomic Analyses of Three Distinct Lineages Uniting Staphylococcus cohnii and Staphylococcus urealyticus from Diverse Hosts

We sequenced and assembled genomes for 17 isolates of Staphylococcus cohnii isolated from osteomyelitis lesions in young broilers from two separate experiments where we induced lameness using a hybrid wire-litter flooring system. Whole genome comparisons using three different methods support a close relationship of genomes from both S. cohnii and Staphylococcus urealyticus. The data support three different lineages, which we designated as Lineage 1, Lineage 2, and Lineage 3, uniting these two species within an evolving complex. We present evidence for horizontal transfer between lineages of genomic regions from 50-440 kbp. The transfer of a 186 kbp region from Lineage 1 to Lineage 2 appears to have generated Lineage 3. Human-associated isolates appear to be limited to Lineages 2 and 3 but Lineage 2 appears to contain a higher number of human pathogenic isolates. The chicken isolates from our lameness trials included genomically diverse isolates from both Lineage 1 and 2, and isolates from both lineages were obtained from osteomyelitis lesions of individual birds. Our results expand the diversity of Staphylococci associated with osteomyelitis in poultry and suggest a high diversity in the microbiome of day-old chicks. Our data also support a reevaluation and unification of the taxonomic classifications of S. cohnii and S. urealyticus.

Horizontal transfer of probable chicken-pathogenicity chromosomal islands between Staphylococcus aureus and Staphylococcus agnetis

Staphylococcus agnetis is an emerging pathogen in chickens but has been most commonly isolated from sub-clinical mastitis in bovines. Previous whole-genome analyses for known virulence genes failed to identify determinants for the switch from mild ductal infections in cattle to severe infections in poultry. We now report identification of a family of 15 kbp, 17-19 gene mobile genetic elements (MGEs) specific to chicken osteomyelitis and dermatitis isolates of S. agnetis. These MGEs can be present in multiple copies per genome. The MGE has been vectored on a Staphylococcus phage that separately lysogenized two S. agnetis osteomyelitis strains. The S. agnetis genome from a broiler breeder case of ulcerative dermatitis contains 2 orthologs of this MGE, not associated with a prophage. BLASTn and phylogenetic analyses show that there are closely related intact MGEs found in genomes of S. aureus. The genome from a 1980s isolate from chickens in Ireland contains 3 copies of this MGE. More recent chicken isolates descended from that genome (Poland 2009, Oklahoma 2010, and Arkansas 2018) contain 2 to 4 related copies. Many of the genes of this MGE can be identified in disparate regions of the genomes of other chicken isolates of S. aureus. BLAST searches of the NCBI databases detect no similar MGEs outside of S. aureus and S. agnetis. These MGEs encode no proteins related to those produced by Staphylococcus aureus Pathogenicity Islands, which have been associated with the transition of S. aureus from human to chicken hosts. Other than mobilization functions, most of the genes in these new MGEs annotate as hypothetical proteins. The MGEs we describe appear to represent a new family of Chromosomal Islands (CIs) shared amongst S. agnetis and S. aureus. Further work is needed to understand the role of these CIs/MGEs in pathogenesis. Analysis of horizontal transfer of genetic elements between isolates and species of Staphylococci provides clues to evolution of host-pathogen interactions as well as revealing critical determinants for animal welfare and human diseases.

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.

Characteristics of Staphylococcus intermedius Isolates from Diseased and Healthy Dogs

Staphylococcus intermedius isolates from diseased and healthy dogs were examined for production of extracellular enzymes and toxins, and phage patterns. There were no significant differences between the two groups of isolates in the production rates of DNase, protease, lipase, gelatinase, hyaluronidase, hemolysins, protein A, and TSST-1, or in phage patterns. But the production rate of enterotoxins in isolates from diseased dogs was significantly higher than that in isolates from healthy dogs. PFGE analysis was performed with isolates from different body sites in individual dogs. In 3 of 6 healthy dogs, identical PFGE patterns were seen in isolates from the nares, external auditory meatus or skin. The remaining 3 dogs yielded isolates of different patterns. In 4 of 6 diseased dogs, identical patterns were seen in isolates from lesions as well as from the other normal sites.

Characterization of Staphylococcus aureus isolated from poultry meat in Spain

Ninety-six Staphylococcus aureus isolates from retail chicken carcasses in Spain were characterized using cultural and biochemical tests. The strains were phage typed with the international bacteriophage set for typing S. aureus of human origin. Eighty-eight (91.7%) strains were of the poultry ecovar. Strains of human ecovar were not found. These facts are congruent with findings of other authors. Ninety (93.7%) strains were phage typeable. Lysis by phages of Group III was the most frequent with 66 (68.7%) sensitive strains. Twenty-eight (29.2%) strains were sensitive at 100 routine test dilution (RTD) and only 16 (16.7%) at RTD. By using reversed phage typing, we managed to increase the number of phage typeable strains by 46 (47.9%). More than one S. aureus phage type was detected in 14 (35%) carcasses, which emphasizes the convenience of subtyping several S. aureus isolates from the same food sample in epidemiological studies. Two phage patterns (75/84 and 6/1030/ W57) were the most common. The S. aureus isolates were closely related, as 78 strains showed the most common or indistinguishable (<2 phage reaction differences) phage patterns.

Systemic distribution of Staphylococcus aureus following intradermal footpad challenge of broilers

We conducted an experiment with broilers to determine if prior exposure to Staphylococcus aureus would facilitate the systemic infiltration of this pathogen following intradermal footpad challenge with live S. aureus. Litter-raised broilers were sensitized at 3 and 4 wk of age with s.c. injections in the neck with heat-killed S. aureus diluted in polyethylene glycol (PEG). Equal numbers of control birds were injected at the same times with PEG. At 7 wk of age, chicks previously sensitized to killed S. aureus or injected with PEG were injected intradermally in the right footpad with PBS or live S. aureus. The left footpads of all birds were injected with PBS. The difference in thickness between the right and left footpads was determined at 0, 24, and 48 h postchallenge. Blood, liver, spleen, lung, and synovial fluid were collected six times between 1 and 48 h postchallenge to determine the recovery of S. aureus. Sensitized and non-sensitized birds showed footpad swelling following challenge with live S. aureus in the right footpad (P < 0.001). Injection of PBS did not induce footpad swelling. Birds injected in the footpads with live S. aureus as compared to PBS had significantly higher isolation rates of S. aureus in the spleen, liver, and blood; however, recovery of S. aureus from S. aureus-sensitized and PEG-injected birds was not significantly different. Time postchallenge (1, 3, 7, 11, 24, and 48 h) had no significant effect on the recovery of S. aureus. It was concluded that the intradermal challenge of the footpad with S. aureus resulted in systemic infiltration of S. aureus into the spleen, liver, and blood. Prior exposures to killed S. aureus as compared to PEG controls did not affect the systemic distribution of S.

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.

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 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.

Antimicrobial drug resistance in Staphylococcus aureus isolated from cattle in Brazil

Isolates of Staphylococcus aureus obtained from apparently healthy cattle in the State of Paraiba, Brazil were characterized in relation to resistance to 21 antimicrobial agents. Among the 46 isolates obtained, resistance to penicillin was most frequent, followed by resistance to cadmium, streptomycin, arsenate, tetracycline, mercury, erythromycin and kanamycin/neomycin. All isolates were susceptible to fusidic acid, ethidium bromide, cetrimide, chloramphenicol, benzalkonium chloride, doxycycline, gentamicin, methicillin, minocycline, novobiocin, rifamycin, tylosin and vancomycin. Only six isolates were susceptible to all the drugs tested. With respect to the antibiotics, multi-resistant isolates were uncommon. These results are probably a consequence of the peculiarities of local drug usage pressures. In relation to metal ions, resistance to mercury was rare while resistance to arsenate was relatively frequent, which contrasts with the situation for human Staph. aureus strains. After treatment with ethidium bromide, elimination of resistance to penicillin, tetracycline, streptomycin, erythromycin and cadmium was observed, which was consistent with the genetic determinants being plasmid-borne.

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.

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

1. Staphylococcus aureus was able to colonise the surface of chicks as young as 1 d old. 2. The organism was detected in a hatchery particularly in the debris from the hatchers and on the working surfaces at the sexing and vaccination areas. 3. The degree of surface colonisation of chicks and pullets was low during rearing but rose to a maximum at mid-lay (50 weeks) when the organism was readily detectable on almost all hens. 4. Strains of Staphylococcus aureus were characterised by phage-typing and cultural characteristics and found to belong predominantly to poultry phage group B2 of Gibbs et al. (1978a). 5. A detailed description of poultry phage group B2 strains is presented; strains of this type can be considered as a second "live-bird" ecovar when compared with Staph. aureus var. gallinae of Witte et al. (1977).

The use of a new phage set for typing poultry strains of Staphylococcus aureus obtained from seven countries

1. Eighty per cent of poultry strains of Staphylococcus aureus tested from French, Belgian, English, West German, Japanese and Argentinian sources were typable using a set of typing phages isolated in this laboratory. Strains from Bulgaria, however, with few exceptions were not typable with this phage set. 2. Strains isolated from lesions generally resembled those from apparently healthy poultry. 3. The existence of two distinct Staph. aureus biotypes on poultry was confirmed by isolates from six of the countries; one of these biotypes closely resembled Staph. aureus variety gallinae as described by Witte et al. (1977).

Quantitative aspects of the Staphylococcus aureus flora of poultry

Important populations of Staphylococcus aureus were found to be present on the body surfaces of live poultry originating from flocks without history of staphylococcal disease. Their sized increased considerably until approximately the seventh week of life after which time they were maintained at equally high levels. Significant correlations were found between the populations recovered from superficial wash samples and skin-tissue samples. Similarly the numbers isolated from the nasal cavities were correlated with other surface counts. Low numbers were present in the intestinal tract. Birds with staphylococcal synovitis had higher numbers in all sampling regions. The counts were very high in subjects suffering from staphylococcal dermatitis. Higher rates of positive birds and higher numbers of staphylococci were detected with a whole body sampling method than with a nasal swab technique. The isolates obtained in this study belonged to the S. aureus biotype B which is associated with poultry and pigs.