Encephalomalacia in first-week chicks

The application of the loop-mediated isothermal amplification (LAMP) method for diagnosing Enterococcus hirae-associated endocarditis outbreaks in chickens

BACKGROUND

Enterococcus hirae is considered a part of the normal intestinal biota of several domestic animals, including poultry. However, this species is also associated with infective endocarditis in chickens, a disease that leads to unexpected deaths and serious economical losses. Enterococcus hirae is identified predominantly with the use of conventional bacteriological methods, biochemical tests and PCR. Rapid, sensitive and specific methods for detecting E. hirae in clinical samples are required in poultry production. The aim of this study was to use the Loop-Mediated Isothermal Amplification (LAMP) for the identification and quantification of E. hirae in heart samples from broiler chickens.

RESULTS

The specificity of the LAMP method was confirmed for 7 enterococcal strains and 3 non-enterococcal strains. E. hirae was detected in all of the 22 analyzed clinical bacterial isolates and in all of the 9 heart samples. Three sets of primers supported the detection of E. hirae with high sensitivity and specificity within one hour. The highest detection rate of a LAMP product was approximately 7 min for an E. hirae strain and 12 min for a positive heart sample. The detection limit for the E. hirae ATCC 10541 standard was 1.3 × 10² CFU (43.4 fg) or 13.8 copies of the E. hirae genome equivalent per reaction. The reaction was 10-fold more sensitive than conventional species-specific PCR. The LAMP assay supported the determination of the E. hirae load in chicken hearts with endocarditis in field cases. The average number of E. hirae cells in hearts was 5.19 × 10⁷ CFU/g of tissue, and the average number of E. hirae genome equivalents in hearts was 5.51× 10⁶ copies/g of tissue. Bacterial counts were significantly higher in the LAMP assay than in the standard plate count.

CONCLUSIONS

The LAMP assay is a useful diagnostic tool and an effective alternative to conventional methods for the detection of this enterococcal species. The sodA-based LAMP assay supported direct identification of E. hirae from pure cultures and heart samples without previous bacterial cultivation. This is the first study to apply the LAMP method for the purpose of diagnosing E. hirae-associated endocarditis in poultry.

Genetic diversity and antimicrobial resistance profile of Enterococcus faecalis isolated from broilers with vertebral osteomyelitis in Southeast Brazil

Vertebral osteomyelitis (VO) is a worldwide emerging disease that affects broilers. Recently, the isolation of Enterococcus faecalis in cases of the disease has been described. This study aimed at determining the genetic diversity and antimicrobial resistance profile of 12 E. faecalis strains isolated from broilers with VO. Strains were isolated from nine flocks from six farms in a high-density poultry production area in Southeast Brazil and were evaluated using multilocus sequence typing and phylogenetic analysis. Antimicrobial susceptibility tests and PCR were performed to detect antimicrobial resistance genes. E. faecalis isolates belonged to different sequence types (ST), six of which (ST49, ST100, ST116, ST202, ST249, and ST300) have been previously described. Strains ST708 and ST709 were newly identified in this study. Strain ST49 was most frequently isolated (50% of the flocks) from the analysed VO cases. No phylogenetic or phylogeographic relationship was found among the strains. The VO isolated E. faecalis strains showed highest resistance to aminoglycosides, mainly gentamicin (40%), but were highly susceptible to vancomycin (10%). Aminoglycoside resistance genes were detected in seven E. faecalis strains, and AAC6'-APH2″ genes were most frequently detected. The results showed that E. faecalis strains isolated from recently reported VO cases were highly diverse genetically. The diversity of genotypes in circulation in the analysed flocks, without apparent relationship among them, raises questions on aetiopathogenesis of the disease in broilers and evolutionary aspects of E. faecalis.

Antimicrobial resistance, virulence determinants and genetic profiles of clinical and nonclinical Enterococcus cecorum from poultry

Enterococcus cecorum has been implicated as a possible cause of disease in poultry. However, the characteristics that contribute to pathogenesis of Ent. cecorum in poultry have not been defined. In this study, Ent. cecorum from carcass rinsates (n = 75) and diseased broilers and broiler breeders (n = 30) were compared based upon antimicrobial resistance phenotype, the presence of virulence determinants and genetic relatedness using pulsed-field gel electrophoresis (PFGE). Of the 16 antimicrobials tested, Ent. cecorum from carcass rinsates and clinical cases were resistant to ten and six of the antimicrobials, respectively. The majority of Ent. cecorum from carcass rinsates was resistant to lincomycin (54/75; 72%) and tetracycline (46/75; 61.3%) while the highest level of resistance among clinical Ent. cecorum was to tetracycline (22/30; 73.3%) and erythromycin (11/30; 36.7%). Multidrug resistance (resistance to ≥2 antimicrobials) was identified in Ent. cecorum from carcass rinsates (53/75; 70.7%) and diseased poultry (18/30; 60%). Of the virulence determinants tested, efaAfm was present in almost all of the isolates (104/105; 99%). Using PFGE, the majority of clinical isolates clustered together; however, a few clinical isolates grouped with Ent. cecorum from carcass rinsates. These data suggest that distinguishing the two groups of isolates is difficult based upon the characterization criteria used.

Genetic mechanisms of antimicrobial resistance identified in Salmonella enterica, Escherichia coli, and Enteroccocus spp. isolated from U.S. food animals

The prevalence of antimicrobial resistance (AR) in bacteria isolated from U.S. food animals has increased over the last several decades as have concerns of AR foodborne zoonotic human infections. Resistance mechanisms identified in U.S. animal isolates of Salmonella enterica included resistance to aminoglycosides (e.g., alleles of aacC, aadA, aadB, ant, aphA, and StrAB), β-lactams (e.g., bla_{CMY−2, TEM−1, PSE−1}), chloramphenicol (e.g., floR, cmlA, cat1, cat2), folate pathway inhibitors (e.g., alleles of sul and dfr), and tetracycline [e.g., alleles of tet(A), (B), (C), (D), (G), and tetR]. In the U.S., multi-drug resistance (MDR) mechanisms in Salmonella animal isolates were associated with integrons, or mobile genetic elements (MGEs) such as IncA/C plasmids which can be transferred among bacteria. It is thought that AR Salmonella originates in food animals and is transmitted through food to humans. However, some AR Salmonella isolated from humans in the U.S. have different AR elements than those isolated from food animals, suggesting a different etiology for some AR human infections. The AR mechanisms identified in isolates from outside the U.S. are also predominantly different. For example the extended spectrum β-lactamases (ESBLs) are found in human and animal isolates globally; however, in the U.S., ESBLs thus far have only been found in human and not food animal isolates. Commensal bacteria in animals including Escherichia coli and Enterococcus spp. may be reservoirs for AR mechanisms. Many of the AR genes and MGEs found in E. coli isolated from U.S. animals are similar to those found in Salmonella. Enterococcus spp. isolated from animals frequently carry MGEs with AR genes, including resistances to aminoglycosides (e.g., alleles of aac, ant, and aph), macrolides [e.g., erm(A), erm(B), and msrC], and tetracyclines [e.g., tet(K), (L), (M), (O), (S)]. Continuing investigations are required to help understand and mitigate the impact of AR bacteria on human and animal health.

Adherence of Enterococcus hirae to the duodenal epithelium of chicks with diarrhoea

A flock of commercial layer chicks in Hokkaido, Japan experienced mortality of 3.53% over the first 7 days of life. Affected chicks were depressed, anorexic and had diarrhoea. The striking pathological feature was dense colonization of epithelial surface of the duodenum by Enterococcus hirae. There was no obvious damage to the enterocytes associated with bacterial adherence. Enterococcus hirae organisms were isolated in large numbers from the small intestines, together with Escherichia coli.

Enterococcus hirae-associated endocarditis outbreaks in broiler flocks: clinical and pathological characteristics and molecular epidemiology

BACKGROUND

Enterococcus hirae-associated endocarditis, characterized by a peak in mortality during the second week of the grow-out, and occasionally lameness, was diagnosed at Dutch broiler farms.

OBJECTIVES

Field cases were studied to increase knowledge on clinical and pathological characteristics, pathogenesis and epidemiology of these infections.

ANIMALS AND METHODS

In total, 1266 birds of 25 flocks from 12 farms were examined. Post-mortem examinations, bacteriology, histopathology, PCR and DNA fingerprinting was carried out. Six flocks were followed longitudinally (n = 1017 birds).

RESULTS

Average mortality was 4.1% for the entire grow-out, of which 36% was attributed to endocarditis. Fibrinous thromboendocarditis of the right atrioventricular (AV) valve was found in 24% of hearts, compared to 7% and 4% with lesions of left and both AV valves, respectively. Thrombotic lesions were found in 24% (n = 432) of lungs, but only in larger branches of the Arteria pulmonalis. Occasionally, thrombi were found in the Arteria ischiadica externa and in liver and brain vessels. Enterococcus was cultured from 54% (n = 176) of heart and in 75% (n = 28), 62% (n = 106) and 31% (n = 16) of liver, bone marrow and lung samples, respectively. Further identification, using the Rapid ID Strep 32 API system and a PCR targeting mur-2 and mur-2(ed) genes was carried out on a subset of Enterococcus positive isolates (n = 65): both techniques identified the isolates as Enterococcus hirae. Pulsed-field gel electrophoresis did not indicate evidence of clonality between farms and flocks.

CONCLUSIONS

The relevance of these findings for pathogenesis and epidemiology of E. hirae infections is discussed. CLINICAL IMPORTANCE. This study may facilitate diagnosis of field cases and may contribute to the design of further research and development of control measures.

Enterococcus hirae infections in psittacine birds: epidemiological, pathological and bacteriological observations

Cases of Enterococcus hirae septicaemia are described in 10 different species of psittacine birds. In most of the cases other disease causes were not detected, and cytological examination confirmed the aetiological role of the bacteria isolated. Despite these findings, attempts to reproduce the disease in young budgerigars failed. The bacterium was isolated frequently from the faeces of healthy psittacine birds belonging to a wide range of species, and appeared to be member of the normal intestinal flora of these birds. The bacteriological diagnosis of E. hirae, and especially its differentiation from Enterococcus durons, is discussed.

Encephalomalacia with Enterococcus durans Infection in the Brain Stem and Cerebral Hemisphere in Chicks in Japan

Fourteen chicks, 7-12 days old, that died or had neurological signs (depression, paralysis, torticollis, incoordination, and rolling) were investigated pathologically and microbiologically. Variably sized foci of malacia were present within the parenchyma of the brain stem (cerebral peduncle, optic lobe, and medulla oblongata) and the cerebral hemisphere. Capillary thrombosis with congestion and hemorrhage was frequently observed within the malacia lesions. Gram-positive cocci were recognized in the blood capillary of malacia lesions. Bacteriologically, Enterococcus durans was isolated from the brain, liver, kidney, lung, and spleen. Detection of gram-positive cocci within the blood vessels in the malacia lesions observed in these cases may more strongly suggest the pathogenic role of E. durans on the malacia lesions in the brain stem and cerebral hemisphere.

Reproduction of sepsis and endocarditis by experimental infection of chickens with Streptococcus gallinaceus and Enterococcus hirae

This study describes experimental infections in 4-week-old chickens inoculated intravenously with approximately 10(8) colony-forming units Streptococcus gallinaceus strain CCUG 42692T (C13156) or Enterococcus hirae strain DSM 20160 (C17410). Birds were necropsied following death and obvious clinical signs of disease or were euthanized weekly after infection for up to 4 weeks. At necropsy, lesions included splenomegaly, hepatomegaly, valvular and/or mural endocarditis. Cardiac lesions included focal necrotizing myocarditis and/or yellow-white vegetative valvular endocarditis or greyish proliferations associated with the mitral valves in 35% (6/20) and 79% (19/24) of birds infected with S. gallinaceus and in 20% (4/20) and 55% (12/22) of birds infected with E. hirae via the brachial and jugular veins, respectively. S. gallinaceus was reisolated from heart valves in 45% (9/20) and 75% (18/24) and E. hirae in 35% (7/20) and 73% (16/22) after inoculation via brachial and jugular veins, respectively. Both challenge strains were also isolated from liver, spleen, bone marrow and hock joints. A significant difference between the infections with the two strains was seen only with reisolation of E. hirae from hock joints (P < 0.007). Significant differences were apparent between the two inoculation routes only with E. hirae, where infection via the jugular vein was associated with higher culture positive isolations from the heart (P = 0.029), bone marrow (P = 0.002) and hock joints (P < 0.001) compared with the brachial vein. Birds injected with sterile phosphate-buffered saline were negative for culture of the challenge strains and no lesions were observed in these controls. The results confirm that both S. gallinaceus and E. hirae can cause endocarditis in experimentally infected chickens.

Characterization of Enterococcus hirae Outbreaks in Broiler Flocks Demonstrating Increased Mortality Because of Septicemia and Endocarditis and/or Altered Production Parameters

In Denmark, increased problems associated with streptococci and enterococci have been observed in broilers and broiler parent flocks, resulting in increased mortalities, uneven flocks, and subsequent downgrading and increased condemnations. Postmortem lesions associated with recent outbreaks due to Enterococcus hirae have been accompanied or dominated by septicemia and endocarditis. As a result of infection at an early age and relatively low mortality rates, outbreaks are not always clearly defined and may go unnoticed or may be attributed to poor chick quality. For the same reasons, the pathogenesis and epidemiology of observed outbreaks has only remained speculative. Four separate outbreaks associated with E. hirae infections in broiler flocks occurring between 1998 and 2002 have been investigated. Two of the outbreaks indicated evidence of two separate clones, with 89% and 79% of isolates involved in the individual outbreaks belonging to a single pulsed-field gel electrophoresis (PFGE) profile, respectively. Another outbreak (outbreak 4) demonstrated clear clonality, with all isolates demonstrating affinity to one of two PFGE profiles that differed by only two bands. However, all three outbreaks demonstrated a different clone. The remaining outbreak was nondonal, with isolates distributed between six separate PFGE profiles. One of the outbreaks (outbreak 4) was descended from a parent broiler flock previously associated with an outbreak of Streptococcus gallinaceus; the flock also exhibited septicemia and endocarditis. Initial indications suggested the possibility of vertical transmission of S. gallinaceus to the current broiler flock, causing infection. By extended phenotypic characterization and subsequent genetic characterization, including 16S rRNA sequencing, all strains from the four outbreaks were confirmed as E. hirae. This investigation highlights the problems associated with characterizing enterococci infections in broiler flocks.

Pathogenicity of Enterococcus hirae for chicken embryos and betamethasone-treated chicks

An isolate Enterococcus hirae was used to determine its pathogenicity for chicken embryos and for chicks treated with betamethasone. E hirae was inoculated intravenously into four-day-old chicks which had been treated for three consecutive days with betamethasone, and chick embryos were inoculated into the allantoic cavity with 10(2) and 10(3) bacteria. E hirae was not pathogenic for the chicks or for the embryos.