Development and application of a multiplex polymerase chain reaction for avian respiratory agents

A multiplex polymerase chain reaction (PCR) was developed and optimized to simultaneously detect 6 avian respiratory pathogens. Six sets of specific oligonucleotide primers for infectious bronchitis virus (IBV), avian influenza virus (AIV), infectious laryngotracheitis virus (ILTV), Newcastle disease virus (NDV), Mycoplasma gallisepticum (MG), and Mycoplasma synoviae (MS) were used respectively in the test. With the use of agarose gel electrophoresis for detection of the PCR-amplified DNA products, the sensitivity of detection was between 10 pg for IBV, AIV, MG, and ILTV and 100 pg for NDV and MS after 35 cycles of PCR. Similar sensitivity of these primers was achieved with chickens experimentally infected with respiratory pathogens. In experimental infections, the multiplex PCR was able to detect all the infected chickens in each group at I and 2 wk postinfection as compared with serologic tests at 2 wk postinfection that confirmed the presence of specific antibodies. The multiplex PCR was also able to detect and differentiate coinfections with two or more pathogens. No specific DNA amplification for respiratory avian pathogens was observed among noninoculated birds kept separately as a negative control group.     

鸡毒支原体PCR检测方法的建立

根据已发表的鸡毒支原体种特异性序列fMG-2设计1对引物,建立检测鸡毒支原体的PCR方法.该法对鸡毒支原体能特异性扩增726 bp的目的片段,而对其他禽病原DNA模板的扩增结果为阴性.建立的PCR方法对鸡毒支原体的最少检出量为3 Pg.用建立的PCR方法对临床采集的样品进行检测,同时对相应的样品进行细菌分离,结果临床样品PCR的阳性检出率为20.5%,细菌分离培养的阳性率为0.9%,表明PCR的敏感性高于细菌分离鉴定.     

Molecular characterization of Mycoplasma gallisepticum isolates from Jordan

Two groups of Mycoplasma gallisepticum (MG) isolates (n = 24) from Jordan were analyzed by molecular methods and compared with other Middle Eastern isolates, related international isolates, and reference strains. The first group (n = 19) was isolated from July 2004 to January 2005 (isolation period A), and the newer group (n = 5) from June 2007 to April 2008 (isolation period B). The groups of isolates are from chicken flocks from northern Jordan, but are not from the same farms. None of the flocks were vaccinated for MG. Random amplified polymorphic DNA analysis, targeted sequencing of the partial MG cytadhesin 2 (mgc2), and the MG 16S-23S rRNA intergenic spacer region (IGSR) divided the Jordanian isolates into two groups. All of the 19 isolates from time period A, in addition to two isolates from time period B, were indistinguishable from the F strain. Three of five isolates from time period B were characterized as wild types and were indistinguishable from each other. The wild-type field strain was readily distinguished from the F strain. It was 91% and 96.4% similar to the F strain based on Clustal-W alignments of sequences of mgc2 and IGSR, respectively. Sequence similarity of mgc2 gene of the Jordan wild-type strain to isolates from Israel and Egypt ranged from 96.5% to 100%, whereas for IGSR it was 99.4%-100%. We theorize that the F-strain live MG vaccine, commonly used in Jordan prior to 2007, was transmitted to nonvaccinated poultry in the region and was a predominant genotype during time period A.     

Use of mgc2-polymerase chain reaction-restriction fragment length polymorphism for rapid differentiation between field isolates and vaccine strains of Mycoplasma gallisepticum in Israel

Increasing use of Mycoplasma gallisepticum (MG) live vaccines has led to a need for a rapid test for differentiation of MG field strains from the live vaccine strains ts-11 and 6/85. We examined the differentiating potential of diagnostic polymerase chain reaction (PCR) primers targeted to the gene mgc2, encoding a cytadherence-related surface protein uniquely present in MG. The mgc2-PCR diagnostic primers are specific for MG in tests of all avian mycoplasmas or bacteria present in the chicken trachea and are sensitive enough to readily detect MG in tracheal swabs from field outbreaks. Differentiation of vaccine strain ts-11 was based on identification of restriction enzyme sites in the 300-base-pair (bp) mgc2-PCR amplicon present in ts-11 and missing in MG isolates from field outbreaks in Israel. Restriction sites for the enzymes HaeII and SfaN1 were identified in the amplified region in strain ts-11 and were not found in 28 field isolates of MG, comprising a representative cross section of all the MG isolates from the period 1997-2003. In practice, differential diagnosis of MG is achieved within 1 day of submission of tracheal swab samples by mgc2-PCR amplification and restriction of the amplicon with HaeII, giving a 270-bp fragment for ts-11 or no restriction for other MG strains tested. Application of the mgc2-PCR-restriction fragment length polymorphism (mgc2-PCR-RFLP) assay enabled differential diagnosis of both components of a mixture of ts-11 and non-ts-11 DNA, detecting the field strain in the presence of a large excess of ts-11. The test was successfully applied in vivo for monitoring vaccinates in a ts-11 vaccine trial. In principle, the test may also be used to identify the 6/85 vaccine strain, which yields a 237-bp product, readily differentiated from the approximately 300-bp PCR product of all other strains tested. Further testing of field isolates will be necessary to determine the applicability of this test in the United States and other countries.     

Evaluation and comparison of various PCR methods for detection of Mycoplasma gallisepticum infection in chickens

Four genetic Mycoplasma gallisepticum (MG) polymerase chain reactions (PCRs) (16s rRNA PCR, three newly developed PCR methods that target surface protein genes [mgc2, LP (nested) and gapA (nested)]) were compared for analytical specificity and sensitivity and for diagnostic sensitivity (Se) and specificity of detection from tracheal swabs. The licensed MG DNA Test Kit Flock Chek test (IDEXX, Laboratories, Inc., Westbrook, ME) was as well evaluated for the diagnostic specificity and sensitivity of detection from tracheal swabs. Analytical specificity was evaluated for the four generic PCR methods using a panel of DNA samples from microorganisms that may be isolated from the trachea of commercial poultry and other fowl. PCR methods mgc2, nLP, and ngapA only amplified DNA from MG, whereas 16S rRNA PCR amplified DNA from MG and Mycoplasma imitans. The analytical sensitivity of the four generic PCR methods expressed in color-changing units (CCU)/amplification reaction was estimated for each PCR method and ranged from 4 to 400 CCU/reaction; the sensitivities of single PCR methods 16S rRNA and mgc2 were estimated at 40 CCU/reaction, the nLP at 400 CCU/reaction, and the ngapA at 4 CCU/reaction. The diagnostic sensitivity and specificity of MG detection from tracheal swab pools, as compared to isolation from choanal cleft swabs, was evaluated for the five PCR methods using three groups of birds exposed to vaccine strains ts-11 and 6/85 and to challenge strain R. All PCR methods were able to detect the vaccine strains and the challenge strain R directly from tracheal swabs, indicating that PCR primers from the different methods amplified divergent MG strains. Isolation and PCR results correlated satisfactorily among the three experimentally infected groups, with agreement values (k) ranging from 0.52 to 1.00. The ngapA, IDEXX, and mgc2 PCRs showed the best sensitivity (Se) ratios for detection of M. gallisepticum strains as compared to isolation. Compared to the ngapA and IDEXX PCR methods, the mgc2 PCR has a faster turnaround time, since this test consists of a single amplification reaction and the amplification product is detected by gel electrophoresis. Therefore, among the PCR methods evaluated in this study, the mgc2 PCR is the method of choice to further validate in the field.     

Separating Mycoplasma gallisepticum field strains from nonpathogenic avian mycoplasmas

Mycoplasma gallisepticum (MG) has repeatedly emerged as a serious problem in U.S. broiler, layer, and turkey industries. Tracing the source of an outbreak is essential if MG control is to be accomplished. Amplified fragment length polymorphism (AFLP), random amplification of polymorphic DNA (RAPD), and restriction fragment length polymorphism (RFLP) are valuable tools used to study MG epidemiology, allowing diagnosticians to determine the source of MG infections. In some past outbreaks, AFLP, RAPD, and RFLP fingerprinting, which require pure MG cultures, were not successful because of contaminating nonpathogenic mycoplasmas from field samples. The objective of this research was to develop a method to separate rapidly growing nonpathogenic avian mycoplasma species from slower-growing MG field strains. Mixtures of MG and three separate nonpathogenic avian mycoplasmas were inoculated onto chick embryo fibroblasts cells (CEF) allowing MG to penetrate the CEF cells. Later, gentamicin sulphate was added to the culture, eliminating the nonpathogenic mycoplasmas and allowing MG to be isolated in pure culture. Mixtures of Mycoplasma synoviae (MS) and MG could not be separated in this assay. However, removal of nicotinamide adenine dinucleotide and cysteine hydrochloride during serial passage in Frey broth medium successfully eliminated growth of MS.     

Microbial pathogens in ticks, rodents and a shrew in northern Gyeonggi-do near the DMZ, Korea

A total of 1,618 ticks [420 individual (adults) and pooled (larvae and nymphs) samples], 369 rodents (Apodemus agrarius, Rattus norvegicus, Tscherskia triton, Mus musculus, and Myodes regulus), and 34 shrews (Crocidura lasiura) that were collected in northern Gyeonggi-do near the Demilitarized Zone (DMZ) of Korea during 2004-2005, were assayed by PCR for selected zoonotic pathogens. From a total of 420 individual and pooled tick DNA samples, Anaplasma (A.) phagocytophilum (16), A. platys (16), Ehrlichia (E.) chaffeensis (63), Borrelia burgdorferi (16), and Rickettsia spp. (198) were detected using species-specific PCR assays. Out of 403 spleens from rodents and shrews, A. phagocytophilum (20), A. platys (34), E. chaffeensis (127), and Bartonella spp. (24) were detected with species-specific PCR assays. These results suggest that fevers of unknown causes in humans and animals in Korea should be evaluated for infections by these vector-borne microbial pathogens.     

鸡毒支原体PCR检测试剂盒的研制与应用

根据基因库中鸡毒支原体 1 6SrRNA的序列研制PCR检测试剂盒 ,用于检测鸡毒支原体 (MG)。结果表明该MG PCR检测试剂盒对不同MG参考菌株和地方分离株均能特异性地扩增出 732bp条带 ,而对其他禽支原体和禽病病原体的扩增结果为阴性。该MG PCR试剂盒最低能检测出 1 0 0fg的MGDNA模板。保存期测定结果表明 ,该MG PCR试剂盒在 - 2 0℃条件下保存至 1 ,3 ,6和 9个月时 ,其敏感性无明显变化 ,仍能检测到 1 0 0fg至 1pg的MGDNA模板。保存至 1 2个月时其敏感度虽降低了 1个滴度 ,但仍能 1 0 0 %检出人工感染鸡的临床样品     

3种禽支原体多重PCR检测方法的建立及应用

从鸡毒支原体、鸡滑液囊支原体和火鸡支原体 3种致病性支原体液体培养物中提取DNA,用特定引物分别和组合进行PCR,均得到了特异性扩增产物,片段大小分别为732、207和850 bp。直接用液体培养物进行PCR亦得到了一致的电泳条带。试验结果表明,建立的PCR方法可用于上述3种支原体临床感染的鉴别诊断。ELISA血清学检测和气管拭子PCR检测的比较结果表明,该PCR方法可用于临床MG检测。     

Use of an avidin-biotin enhanced dot-immunobinding assay to detect antibodies for avian mycoplasma in sera from Iowa market turkeys

A dot-immunobinding assay, amplified with avidin and biotin (DAB assay), was used to detect serum antibodies to Mycoplasma iowae in immunized turkeys. The DAB assay was used to test serum samples from 122 commercial market turkey flocks obtained from four Iowa processing plants. The samples were pooled and tested for the presence of antibodies to four species of Mycoplasma spp. considered to be important pathogens for turkeys: M. gallisepticum (MG), M. iowae (MI), M. meleagridis (MM), and M. synoviae (MS). The occurrence of antibodies against these mycoplasmas, as determined by the DAB assay, were 5.7% for MG, 18.0% for MI, 77.9% for MM, and 9.8% for MS.     

Charting the proteome of Cryptosporidium parvum sporozoites using sequence similarity-based BLAST searching

Cryptosporidium (C.) spp. are important zoonotic parasites causing widespread diarrhoeal disease in man and animals. The recent release of the complete genome sequences for C. parvum and C. hominis has facilitated the comprehensive global proteome analysis of these opportunistic pathogens. The well-known approach for mass spectrometry (MS) based data analysis using the BLAST tool (MS BLAST) is a database search protocol for identifying unknown proteins by sequence similarity to homologous proteins using peptide sequences produced by mass spectrometry. We have used several complementary approaches to explore the global sporozoite proteome of C. parvum with available proteomic tools. To optimize the output of the MS data, a sequence similarity-based MS BLAST strategy was employed for bioinformatic analysis. Most significantly, almost all the constituents of glycolysis and several mitochondrion-related proteins were identified. In addition, many hypothetical Cryptosporidium proteins were validated by the identification of their constituent peptides. The MS BLAST approach was found to be useful during the study and could provide valuable information towards a complete understanding of the unique biology of Cryptosporidium.     

The Mycoplasma gallisepticum 16S-23S rRNA intergenic spacer region sequence as a novel tool for epizootiological studies

Mycoplasma gallisepticum (MG) contains two sets of rRNA genes (5S, 16S and 23S) in its genome, but only one of the two is organized in an operon cluster and contains a unique 660-nucleotide intergenic spacer region (IGSR) between the 16S and the 23S rRNA genes. We designed a polymerase chain reaction (PCR) for the specific amplification of the complete MG IGSR segment. The MG IGSR PCR was tested on 18 avian mollicute species and was confirmed as MG specific. The reaction sensitivity was demonstrated by comparing it to the well-established MG mgc2 PCR. The MG IGSR sequence was found to be highly variable (discrimination [D] index of 0.950) among a variety of MG laboratory strains, vaccine strains, and field isolates. The sequencing of the MG IGSR appears to be a valuable single-locus sequence typing (SLST) tool for MG isolate differentiation in diagnostic cases and epizootiological studies.     

用探针杂交法检测鸡毒支原体和滑液囊支原体

根据鸡毒支原体(MG)和滑液囊支原体(MS)的16SrRNA基因序列，设计并合成了探针MG和MS共同目的基因，跨幅为580bP的一对引物。用这对引物对2个标准的MG和1个标准的Ms菌株DNA模板进行聚合酶锭反应(PcR)，结果得到了预期大小约580bP的PcR产物。回收纯化琼脂糖电泳凝肢中的MG扩增产物克隆至T载体中，DIG随机引物法合成核酸探针，斑点杂交试验对MG和MS均呈阳性，检测灵敏度分别为2ng和3ng，其它对照菌(毒)株为阴性。     

鸡毒支原体与鸡滑液囊支原体双重PCR检测方法的建立

为建立能同时检测鸡毒支原体(Mycoplasma gallisepticum, MG)和鸡滑液囊支原体(Mycoplasma synoviae,MS)的双重PCR诊断方法,该研究根据GenBank中登录的MG gapA基因序列和MS heat shock ATP-dependent protease基因序列,设计2对特异性引物,通过对PCR扩增条件的优化,建立了能够同时检测MG和MS的双重PCR诊断方法。特异性检测结果显示,该方法能够扩增出729 bp的MG和309 bp的MS特异性片段,对禽巴氏杆菌、大肠杆菌、鸡白痢沙门菌、副鸡禽杆菌核酸扩增均为阴性;敏感性检测结果显示,对MG和MS DNA的最低检出量均为5×10^-2 ng/μL;临床样品的检测结果显示,所建立的双重PCR方法可同时有效地检测出MG、MS混合感染和单独感染。该研究建立的鸡毒支原体与鸡滑液囊支原体双重PCR方法具有良好的特异性、敏感性、重复性,为快速、高效检测MG和MS提供了技术支持。     

Key role of Chlamydophila psittaci on Belgian turkey farms in association with other respiratory pathogens

Two hundred turkey sera from eight Belgian and two French farms were tested for the presence of antibodies against avian pneumovirus (APV), Ornithobacterium rhinotracheale (ORT), Mycoplasma gallisepticum, Mycoplasma meleagridis and Chlamydophila psittaci. At slaughter, C. psittaci, APV and ORT antibodies were detected in 94, 34 and 6.5% of the turkeys, respectively. No antibodies against M. gallisepticum or M. meleagridis were present. Additionally, turkeys on three Belgian farms were examined from production onset until slaughter using both serology and antigen or gene detection. All farms experienced two C. psittaci infection waves, at 3-6 and 8-12 weeks of age. Each first infection wave was closely followed by an ORT infection starting at the age of 6-8 weeks, which was still detectable when the second C. psittaci infection waves started. Animals on farm A were not vaccinated against APV leading to an APV subtype B outbreak accompanying the first C. psittaci infection wave. Despite subtype A APV vaccination on farms B and C, the second C. psittaci infection waves were accompanied (farm B) or followed (farm C) by a subtype B APV infection. On all farms respiratory signs always appeared together with a proven C. psittaci, APV and/or ORT infection. This study suggests an association between C. psittaci, APV and ORT, and indicates the multi-factorial aetiology of respiratory infections in commercial turkeys. All three pathogens should be considered when developing prevention strategies for respiratory disease.     

应用多重聚合酶链式反应检测鸡毒支原体、鸡滑液囊支原体和禽衣阿华支原体的研究

根据鸡毒支原体 (MG)、禽衣阿华支原体 (MI)、鸡滑液囊支原体 (MS)的基因文库 ,设计了 3对分别与MG、MI、MS某段基因序列互补的引物。用这 3对引物对同一样品中的MG、MI、MSDNA模板进行多重聚合酶链式反应 (PCR)扩增 ,结果均同时得到了 3条特异性的大小与实验设计相符的 732bp (MG)、 2 99bp (MI)、 2 0 7bp (MS)多重的PCR扩增带 ,而对其他 6种禽病病原的PCR扩增结果均为阴性 ;敏感性测定结果能同时检出 1pg的MG、MI和MSDNA模板     

Molecular characterization of Malaysian fowl adenovirus (FAdV) serotype 8b species E and pathogenicity of the virus in specific-pathogen-free chicken

BackgroundInclusion body hepatitis (IBH) is an economically important viral disease primarily affecting broiler and breeder chickens. All 12 serotypes of fowl adenovirus (FAdV) can cause IBH.ObjectivesTo characterize FAdV isolates based on phylogenetic analysis, and to study the pathogenicity of FAdV-8b in specific-pathogen-free (SPF) chickens following virus inoculation via oral and intramuscular (IM) routes.MethodsSuspected organ samples were subjected to virus isolation and polymerase chain reaction (PCR) for FAdV detection. Hexon gene sequencing and phylogenetic analysis were performed on FAdV-positive samples for serotype identification. One FAdV-8b isolate, UPM/FAdV/420/2017, was selected for fiber gene characterization and pathogenicity study and was inoculated in SPF chickens via oral and IM routes.ResultsThe hexon gene phylogenetic analysis revealed that all isolates belonged to FAdV-8b. The fiber gene-based phylogenetic analysis of isolate UPM/FAdV/420/2017 supported the grouping of that isolate into FAdV species E. Pathogenicity study revealed that, chickens infected with UPM/FAdV/420/2017 via the IM route had higher clinical score values, higher percent mortality, higher degree of the liver lesions, higher antibody response (p < 0.05), and higher virus shedding amounts (p < 0.05) than those infected via the oral route. The highest virus copy numbers were detected in liver and gizzard.ConclusionsFAdV-8b is the dominant FAdV serotype in Malaysia, and pathogenicity study of the FAdV-8b isolate UPM/FAdV/420/2017 indicated its ability to induce IBH in young SPF chickens when infected via oral or IM routes.     

Detection of infectious bronchitis virus 793B,avian metapneumovirus, <Emphasis Type="Italic">Mycoplasma gallisepticum</Emphasis> and <Emphasis Type="Italic">Mycoplasma synoviae</Emphasis> in poultry in Ethiopia

A survey was conducted into respiratory infectious diseases of poultry on a chicken breeder farm run by the Ethiopian Institute of Agricultural Research (EIAR), located in Debre Zeit, Ethiopia. Oropharyngeal swabs were collected from 117 randomly selected birds, and blood was taken from a subset of 73 of these birds. A combination of serological and molecular methods was used for detection of pathogens. For the first time in Ethiopia, we report the detection of variant infectious bronchitis virus (793B genotype), avian metapneumovirus subtype B and Mycoplasma synoviae in poultry. Mycoplasma gallisepticum was also found to be present; however, infectious laryngotracheitis virus was not detected by PCR. Newcastle disease virus (NDV) was not detected by PCR, but variable levels of anti-NDV HI antibody titres shows possible exposure to virulent strains or poor vaccine take, or both. For the burgeoning-intensive industry in Ethiopia, this study highlights several circulating infectious respiratory pathogens that can impact on poultry welfare and productivity.     

Characterization of the in vitro core surface proteome of Mycoplasma mycoides subsp. mycoides, the causative agent of contagious bovine pleuropneumonia

Contagious bovine pleuropneumonia (CBPP), caused by Mycoplasma mycoides subsp. mycoides (Mmm) is a severe cattle disease, present in many countries in sub-Saharan Africa. The development of improved diagnostic tests and vaccines for CBPP control remains a research priority. Polyacrylamide gel electrophoresis and mass spectrometry were used to characterize the Triton X-114 soluble proteome of nine Mmm strains isolated from Europe or Africa. Of a total of 250 proteins detected, 67 were present in all strains investigated. Of these, 44 were predicted to be lipoproteins or cytoplasmic membrane-associated proteins and are thus likely to be members of the core in vitro surface membrane-associated proteome of Mmm. Moreover, the presence of all identified proteins in other ruminant Mycoplasma pathogens were investigated. Two proteins of the core proteome were identified only in other cattle pathogens of the genus Mycoplasma pointing towards a role in host–pathogen interactions. The data generated will facilitate the identification and prioritization of candidate Mycoplasma antigens for improved control measures, as it is likely that surface-exposed membrane proteins will include those that are involved in host–pathogen interactions.