Antigenic diversity of Chlamydia psittaci of mammalian origin determined by microimmunofluorescence

Efficacy of a prepared tissue culture-adapted vaccine against Chlamydia psittaci experimentally in mice

Background and Aim

Chlamydia psittaci is an intracellular pathogen with a broad range of hosts and endemic in nearly all bird species as well as many mammalian species. Outbreaks contribute to economic losses, especially due to infection of pet birds, poultry, and livestock. Worse, the organism has a zoonotic effect, and transmission to humans results in severe illness. Therefore, proper control measures need to be applied. We conducted a trial for the preparation and evaluation of inactivated vaccine against C. psittaci.

Materials and Methods

Three C. psittaci strains (accession nos.: KP942827, KP942828, and KP942829) were grown in embryonated chicken eggs and then propagated for purification in Vero cells. The immunization experiment was experimentally performed in mice, which then were challenged with a virulent C. psittaci strain.

Results

The immunization trial revealed nearly 100% protection after the challenge. The histopathological and immunofluorescence examinations of internal organs revealed that the prepared killed vaccines can effectively reduce chlamydial infection and shedding in animals with the proper level of protection.

Conclusion

Our vaccine can be used to control economic and financial losses resulting from avian chlamydiosis, especially those in poultry industries. The zoonotic transmission risk highlights the need for proper control measures.

Antimicrobial Resistance in Chlamydiales, Rickettsia, Coxiella, and Other Intracellular Pathogens

This article will provide current insights into antimicrobial susceptibilities and resistance of an important group of bacterial pathogens that are not phylogenetically related but share lifestyle similarities in that they are generally considered to be obligate intracellular microbes. As such, there are shared challenges regarding methods for their detection and subsequent clinical management. Similarly, from the laboratory perspective, susceptibility testing is rarely undertaken, though molecular approaches might provide new insights. One should also bear in mind that the highly specialized microbial lifestyle restricts the opportunity for lateral gene transfer and, consequently, acquisition of resistance.

The Chlamydia suis Genome Exhibits High Levels of Diversity, Plasticity, and Mobile Antibiotic Resistance: Comparative Genomics of a Recent Livestock Cohort Shows Influence of Treatment Regimes

Chlamydia suis is an endemic pig pathogen, belonging to a fascinating genus of obligate intracellular pathogens. Of particular interest, this is the only chlamydial species to have naturally acquired genes encoding for tetracycline resistance. To date, the distribution and mobility of the Tet-island are not well understood. Our study focused on whole genome sequencing of 29 C. suis isolates from a recent porcine cohort within Switzerland, combined with data from USA tetracycline-resistant isolates. Our findings show that the genome of C. suis is very plastic, with unprecedented diversity, highly affected by recombination and plasmid exchange. A large diversity of isolates circulates within Europe, even within individual Swiss farms, suggesting that C. suis originated around Europe. New World isolates have more restricted diversity and appear to derive from European isolates, indicating that historical strain transfers to the United States have occurred. The architecture of the Tet-island is variable, but the tetA(C) gene is always intact, and recombination has been a major factor in its transmission within C. suis. Selective pressure from tetracycline use within pigs leads to a higher number of Tet-island carrying isolates, which appear to be lost in the absence of such pressure, whereas the loss or gain of the Tet-island from individual strains is not observed. The Tet-island appears to be a recent import into the genome of C. suis, with a possible American origin.

Prevalence of lung lesions in slaughtered cattle in the Eastern Cape Province, South Africa

Information obtained from abattoirs on the causes of lung condemnation is important in preventing the spread of zoonotic diseases and for promoting food security. In this study, we assessed the causes of lung condemnation in cattle at three abattoirs represented as ANA, QTA and EBA to evaluate the financial losses associated with lung condemnation. A retrospective study (n = 51 302) involving the use of abattoir slaughter records of 2010-2012 and an active abattoir survey (n = 1374) was conducted from July to December 2013. The retrospective study revealed the main causes of lung condemnation as pneumonia (1.09%, 2.21% and 0.77%), emphysema (1.12%, 1.14% and 1.1.6%) and abscessation (0.71%, 1.06% and 0.77%), from ANA, QTA and EBA, respectively. The combined monetary loss because of lung condemnation during the period 2010 to 2012 was estimated as ZAR 85 158 (USD 7939) for the abattoirs surveyed. Conversely, during the active abattoir survey, agonal emphysema (15%, 15% and 23%) and improper eviscerations with faecal contamination (10%, 38% and 42%) were the major factors that led to lung condemnation at ANA, QTA and EBA, respectively. Other causes of lung condemnations were haemorrhage (10%) for QTA and pleurisy (12%) for EBA. The weight loss of lungs during the active abattoir survey was 6450 kg, while the associated monetary loss was estimated as ZAR 29 025 (USD 2706). This study identified major causes of lung condemnation as pleuritis, improper evisceration, pneumonia, abscesses, haemorrhages and lung worms and their associated monetary losses. The results of this study may be useful as baseline data for future comparison in similar surveys, for tracking of some zoonotic diseases affecting lungs and for further research in the Eastern Cape Province or other provinces of South Africa.

Penicillin G-Induced Chlamydial Stress Response in a Porcine Strain of Chlamydia pecorum

Chlamydia pecorum causes asymptomatic infection and pathology in ruminants, pigs, and koalas. We characterized the antichlamydial effect of the beta lactam penicillin G on Chlamydia pecorum strain 1710S (porcine abortion isolate). Penicillin-exposed and mock-exposed infected host cells showed equivalent inclusions numbers. Penicillin-exposed inclusions contained aberrant bacterial forms and exhibited reduced infectivity, while mock-exposed inclusions contained normal bacterial forms and exhibited robust infectivity. Infectious bacteria production increased upon discontinuation of penicillin exposure, compared to continued exposure. Chlamydia-induced cell death occurred in mock-exposed controls; cell survival was improved in penicillin-exposed infected groups. Similar results were obtained both in the presence and in the absence of the eukaryotic protein translation inhibitor cycloheximide and at different times of initiation of penicillin exposure. These data demonstrate that penicillin G induces the chlamydial stress response (persistence) and is not bactericidal, for this chlamydial species/strain in vitro, regardless of host cell de novo protein synthesis.

Molecular and pathological insights into Chlamydia pecorum-associated sporadic bovine encephalomyelitis (SBE) in Western Australia

Background

Despite its global recognition as a ruminant pathogen, cases of Chlamydia pecorum infection in Australian livestock are poorly documented. In this report, a C. pecorum specific Multi Locus Sequence Analysis scheme was used to characterise the C. pecorum strains implicated in two cases of sporadic bovine encephalomyelitis confirmed by necropsy, histopathology and immunohistochemistry. This report provides the first molecular evidence for the presence of mixed infections of C. pecorum strains in Australian cattle.

Case presentation

Affected animals were two markedly depressed, dehydrated and blind calves, 12 and 16 weeks old. The calves were euthanized and necropsied. In one calf, a severe fibrinous polyserositis was noted with excess joint fluid in all joints whereas in the other, no significant lesions were seen. No gross abnormalities were noted in the brain of either calf. Histopathological lesions seen in both calves included: multifocal, severe, subacute meningoencephalitis with vasculitis, fibrinocellular thrombosis and malacia; diffuse, mild, acute interstitial pneumonia; and diffuse, subacute epicarditis, severe in the calf with gross serositis. Immunohistochemical labelling of chlamydial antigen in brain, spleen and lung from the two affected calves and brain from two archived cases, localised the antigen to the cytoplasm of endothelium, mesothelium and macrophages. C. pecorum specific qPCR, showed dissemination of the pathogen to multiple organs. Phylogenetic comparisons with other C. pecorum bovine strains from Australia, Europe and the USA revealed the presence of two genetically distinct sequence types (ST). The predominant ST detected in the brain, heart, lung and liver of both calves was identical to the C. pecorum ST previously described in cases of SBE. A second ST detected in an ileal tissue sample from one of the calves, clustered with previously typed faecal bovine isolates.

Conclusion

This report provides the first data to suggest that identical C. pecorum STs may be associated with SBE in geographically separated countries and that these may be distinct from those found in the gastrointestinal tract. This report provides a platform for further investigations into SBE and for understanding the genetic relationships that exist between C. pecorum strains detected in association with other infectious diseases in livestock.

Molecular evidence for chlamydial infections in the eyes of sheep

Ocular infections by chlamydiae are associated with ocular disease manifestations such as conjunctivitis and keratitis in humans and animals. Limited evidence exists that members of the order Chlamydiales can also cause ocular disease in sheep. In the current study, the prevalence of chlamydiae in the eyes of sheep was investigated by using PCR methods. Data obtained in sheep by broad-range 16S rRNA order Chlamydiales-specific PCR were compared to the prevalence of antibodies against chlamydiae detected by a competitive enzyme-linked immunosorbent assay (cELISA). Flocks tested included a clinically healthy flock and two flocks suffering from ocular disease and with histories of Ovine Enzootic Abortion (OEA). PCR detected DNA of Chlamydophila (Cp.) abortus and Cp. pecorum in the eyes of both healthy and sick animals but also identified Chlamydia (C.) suis and a variety of uncultured chlamydia-like organisms. Good correlation was found between the presence of Cp. abortus DNA in sheep conjunctival samples and seropositivity detected by cELISA. Despite these findings, no association was found between the presence of chlamydial DNA in the sheep conjunctival samples and the onset of clinical disease. These results suggest that the biodiversity of chlamydiae in the eyes of sheep is greater than that previously thought. Further investigations are needed to determine whether a causal relationship between infection by chlamydiae and ocular disease exists in these animals.

Chlamydophila psittaci in free-living Blue-fronted Amazon parrots (Amazona aestiva) and Hyacinth macaws (Anodorhynchus hyacinthinus) in the Pantanal of Mato Grosso do Sul, Brazil

Chlamydophila psittaci (C. psittaci) infection was evaluated in 77 free-living nestlings of Blue-fronted Amazon parrots (Amazona aestiva) and Hyacinth macaws (Anodorhynchus hyacinthinus) in the Pantanal of Mato Grosso do Sul, Brazil. Tracheal and cloacal swab samples from 32 wild parrot and 45 macaw nestlings were submitted to semi-nested PCR, while serum samples were submitted to complement fixation test (CFT). Although all 32 Amazon parrot serum samples were negative by CFT, cloacal swabs from two birds were positive for Chlamydophila DNA by semi-nested PCR (6.3%); these positive birds were 32 and 45 days old. In macaws, tracheal and cloacal swabs were positive in 8.9% and 26.7% of the samples, respectively. Complement-fixing antibodies were detected in 4.8% of the macaw nestlings; macaw nestlings with positive findings were between 33 and 88 days old. These results indicate widespread dissemination of this pathogen in the two evaluated psittacine populations. No birds had clinical signs suggestive of chlamydiosis. To the best of our knowledge, this is the first report on C. psittaci in free-living Blue-fronted Amazon parrots and Hyacinth macaws in Brazil.

Microbiological Monitoring of Guinea Pigs Reared Conventionally at Two Breeding Facilities in Korea

In this study, microbiological monitoring of guinea pigs reared conventionally in two facilities was performed twice in 2004, with a three-month-interval between surveys. This study was based on the recommendations of the FELASA Working Group, with some modifications. In serological tests in the first survey, some animals from facility A showed positive results for Encephalitozoon cuniculi, Sendai virus, pneumonia virus of mice (PVM), and Reovirus-3 (Reo-3); facility B showed a positive result only for E. cuniculi. The results of the second survey were similar to the first, except for the presence of Sendai virus; all animals from the two facilities were Sendai virus-negative in the second experiment. No pathogenic bacteria were cultured in the organs of any of the animals in the first survey. However, in the second survey, Bordetella bronchiseptica was cultured from the lung tissue of two 10-week-old animals from facility A. Chlamydial infection was examined by the Macchiavello method, but no animal showed positive results. Tests using fecal flotation or the KOH wet mount method showed no infection of endoparasites, protozoa, ectoparasites, or dermatophytes in any animal in both surveys. However, in the histopathological examination, an infection of protozoa-like organisms was observed in the cecum of some animals from facility A. The present study revealed that microbiological contamination was present in guinea pigs reared conventionally in two facilities in Korea, suggesting that there is a need to improve environmental conditions in order to eradicate microbial contamination.

Bovine Chlamydophila spp. infection: do we underestimate the impact on fertility?

Classical methods for detection of Chlamydophila species, and of antibodies against these agents, have indicated that these bacteria are highly prevalent in cattle and associated with numerous disease conditions. These methods demonstrated acute Chlamydophila-induced diseases such as epizootic bovine abortion, as well as worldwide variable, but generally high, Chlamydophila seroprevalence. However, it was impossible to consistently detect the low levels of these organisms which were suspected to be present in endemic infections. Application of highly sensitive real-time PCR and ELISA methods for detection of Chlamydophila spp. DNA and of antibodies against Chlamydophila spp., respectively, in a series of prospective cohort studies revealed a high prevalence of Chlamydophila spp. genital infections in female calves (61%) and adult heifers (53%). These infections were acquired by extragenital transmission in the first weeks of life, and infection frequency was increased by crowding of the animals. A challenge study demonstrated that infection with C. abortus resulted in decreased fertility of heifers. The experimental use of a C. abortus vaccine provided evidence for immunoprotection against C. abortus-induced suppression of bovine fertility. The results of these investigations suggest that bovine Chlamydophila infection should be viewed more as pervasive, low-level infection of cattle than as rare, severe disease. Such infections proceed without apparent disease or with only subtle expressions of disease, but potentially have a large impact on bovine herd health and fertility.

High prevalence of natural Chlamydophila species infection in calves

We investigated the acquisition and prevalence of Chlamydophila sp. infection in calves. Specimens were collected at weekly intervals from birth to week 12 postpartum from 40 female Holstein calf-dam pairs in a dairy herd. Real-time PCR detected, quantified, and differentiated Chlamydophila 23S rRNA gene DNA from vaginal cytobrush swabs and milk samples. Chemiluminescence enzyme-linked immunosorbent assay with lysed Chlamydophila abortus or Chlamydophila pecorum elementary body antigens quantified antibodies against Chlamydophila spp. in sera. Chlamydophila sp. DNA was found in 61% of calves and 20% of dams in at least one positive quantitative PCR. In calves, clinically inapparent C. pecorum infection with low organism loads was fivefold more prevalent than C. abortus infection and was most frequently detected by vaginal swabs compared to rectal or nasal swabs. In dams, C. abortus dominated in milk and C. pecorum dominated in the vagina. The group size of calves correlated positively (P < 0.01) with Chlamydophila infection in quadratic, but not linear, regression. Thus, a doubling of the group size was associated with a fourfold increase in frequency and intensity of Chlamydophila infection. For groups of 14 or 28 calves, respectively, logistic regression predicted a 9 or 52% probability of infection of an individual calf and a 52 or 99.99% probability of infection of the group. Anti-Chlamydophila immunoglobulin M antibodies in Chlamydophila PCR-positive calves and dams and in dams that gave birth to calves that later became positive were significantly higher than in PCR-negative animals (P </= 0.02). Collectively, crowding strongly enhances the frequency and intensity of highly prevalent Chlamydophila infections in cattle.

Growth characteristics of porcine chlamydial strains in different cell culture systems and comparison with ovine and avian chlamydial strains

Porcine Chlamydiaceae were cultivated under various culture conditions and we compared their growth characteristics with those of ruminant and avian strains. The combination of centrifugation assisted cell culture infection and cycloheximide treatment of Vero cell coverslip cultures provided the highest inclusion numbers with all chlamydial strains. Interestingly, the use of Iscove's modified Dulbecco's medium instead of Eagle's minimal essential medium significantly increased Chlamydia suis inclusion counts. C. suis and Chlamydophila pecorum inclusion numbers were markedly increased in CaCo cells, compared with Vero cells. This accelerated growth of porcine Chlamydiaceae under certain cultivation conditions may be helpful for the propagation of low chlamydial numbers or for their isolation from field samples. The intracellular distribution of porcine Chlamydiaceae in polarised CaCo cells clearly demonstrated differences between the chlamydial strains: C. pecorum 1710S inclusions were predominantly localised in the apical cytoplasm, C. suis S45 inclusions, however, were mostly situated in lower cytoplasmatic compartments. These findings might reflect biological differences in vivo.

Reinfection with Chlamydophila abortus by uterine and indirect cohort routes reduces fertility in cattle preexposed to Chlamydophila

This study investigated the effects of controlled reinfection on fertility of cattle naturally preexposed to Chlamydophila abortus. All animals had high prechallenge levels of immunoglobulin M (IgM), IgG, IgG1, and IgG2 serum antibodies against ruminant C. abortus in a chemiluminescent enzyme-linked immunosorbent assay. Twenty virgin heifers were estrus synchronized with prostaglandin F2, artificially inseminated 2 to 3 days later, and challenged immediately by intrauterine administration of 0, 10(4), 10(5), 10(6), or 10(8) inclusion-forming units (IFU) of C. abortus. Ten heifers were estrus synchronized, inseminated, and uterine challenged 2 weeks later. These animals were also indirectly exposed to C. abortus infection (cohort challenged) by contact with their previously challenged cohorts. Pregnancy was determined by rectal palpation 42 days after insemination. All anti-C. abortus antibody isotypes increased in heifers following uterine challenge with 10(8) IFU. A total of 11, 83, 50, 66, and 0% of heifers were pregnant after uterine challenge with 0, 10(4), 10(5), 10(6), and 10(8) IFU of C. abortus, respectively. A total of 50 and 65% of heifers were pregnant with and without cohort challenge, respectively. Uterine inoculum dose and cohort challenge (or, alternatively, a negative pregnancy outcome [infertility]) correlated highly significantly with a rise in postchallenge anti-C. abortus IgM levels over prechallenge levels. Logistic regression modeled fertility, with uterine challenge dose and cohort challenge or prechallenge IgM as predictors (P < 0.05). The models predict that the uterine C. abortus inoculum causing infertility is 8.5-fold higher for heifers without cohort exposure and 17-fold higher for heifers with high IgM levels than for heifers with cohort exposure or with low IgM levels.

Efficacy of live Chlamydophila abortus vaccine 1B in protecting mice placentas and foetuses against strains of Chlamydophila pecorum isolated from cases of abortion

The efficacy of Chlamydophila abortus vaccine strain 1B in protecting against two selected Chlamydophila pecorum strains, isolated from an aborted goat (M14) in Morocco and a ewe (AB10) in France, was investigated in a mouse model, by comparing the reduction in number of bacteria in the placentas of vaccinated mice challenged intraperitoneally at 11 days of pregnancy with the reference C. abortus (AB7) and C. pecorum (M14, or AB10) strains, to those of unvaccinated mice. Vaccine 1B was shown to provide effective protection against the field strains of C. pecorum, since it significantly reduced the placental Chlamydophila colonisation. The two C. pecorum strains were not sufficiently abortifacient in mice to use reduction in abortion as a criterion of protection.

Missing links in the divergence of Chlamydophila abortus from Chlamydophila psittaci

Pathological and serological evidence and DNA-DNA reassociation data indicate that Chlamydophila psittaci and Chlamydophila abortus are separate species. C. psittaci causes avian systemic disease and C. abortus causes abortion. Both previously belonged to Chlamydia psittaci are associated with zoonotic and enzootic outbreaks. Genetic studies suggest that they are closely related and because of the recent availability of diverse C. psittaci strains and comparative data for several genes, it was possible to explore this relationship. The parrot C. psittaci strain 84/2334 was found to have DNA sequences that were identical to an extrachromosomal plasmid in duck C. psittaci strain N352, to rnpB in strain R54 from a brown skua and to the rrn intergenic spacer in parakeet strain Prk/Daruma (from Germany, Antarctica and Japan, respectively). Analysis of ompA and the rrn spacer revealed progressive diversification of the strains, with 84/2334 resembling what might have been a recent ancestor of C. abortus. Another C. psittaci strain (VS225) showed evidence of having undergone convergent evolution towards the C. abortus-like genotype, whereas strain R54 diverged independently. For the first time, these studies link C. abortus in an evolutionary context to the C. psittaci lineage. It has been concluded that C. abortus diverged from C. psittaci, and so strain R54 was designated a C. psittaci strain. It is recommended that characterization of C. psittaci and C. abortus strains should utilize more than a single method and more than a single gene.

Subspecies variation in Greek strains of Chlamydophila abortus

The Greek chlamydial strains FAS, FAG, VPG and LLG, isolated from aborted sheep or goat foetuses, had been previously characterized as divergent on the basis of mouse cross-protection experiments, with LLG and its homologous POS significantly different from the rest in inclusion morphology, polypeptide profiles and reactivity with monoclonal antibodies. To determine the genetic basis of their divergence the 16S-23S ribosomal intergenic spacer was analysed by RFLP analysis of PCR 16SF2/23R amplicons. Using the restriction enzymes BfaI, SfcI, HpaI, BclI, DdeI and AclI, the strains were classified as Chlamydophila abortus. However, digestion with RsaI made it possible to differentiate strains FAS, FAG and VPG from strains LLG and POS, generating DNA fragments of 530/55 and 585bp, respectively. By subsequent sequence analysis of the 23S domain I rRNA gene only strain FAS was identical to reference strain A22 of C. abortus. Strains FAG and VPG presented an identical nucleotide deviation at position 593 of signature sequences. Strains LLG and POS presented three identical nucleotide deviations at positions 156, 186 and 307. Variation within the domain I signature sequences for the examined abortion strains was < or =0.69%. In conclusion, substantial genetic and biological diversity among strains of C. abortus was demonstrated, suggesting that subspecies variation status for certain strains may be applicable. Our findings suggest that differentiation may be possible at a subspecies level by RFLP analysis.

Prevalence of Chlamydophila abortus infection in domesticated ruminants in Taiwan

This study is to (1) investigate the prevalence of Chlamydophila abortus infection in cows and goats in Taiwan, and (2) compare the genetic properties of Taiwanese isolates with abortion strains from other sources. Approximately 71% of aborted cows and 58% of aborted does had IgG against C. abortus in their sera. The seroprevalence rate in cows may be overestimated, because a certain degree of cross-reactivity with C. pecorum cannot be ruled out. Only 22.7% (from aborted cows) and 33.3% (from aborted dogs) of vaginal swabs that tested positive by polymerase chain reaction led to successful isolation of C. abortus by inoculation into chicken embryos, equivalent to 7.1% and 7.9% of isolation rates, respectively. The major outer membrane protein gene of 15 Taiwanese abortion isolates was compared with that of various strains by restriction fragment length polymorphism (RFLP) and nucleotide sequencing. Restriction enzyme CfoI was able to distinguish Taiwanese ruminant isolates, which have identical RFLP patterns, from C. felis (feline) and C. psittaci (avian) strains. Taiwanese isolates had 98.8-100% homology with known ruminant abortion strains and were phylogenetically closest to bovine LW508 strain.

Seroepidemiological investigation of feline chlamydiosis in cats and humans in Japan

The prevalence of chlamydia antibodies in Japan was investigated in 215 cat sera, consisting of 88 sera of stray cats and 127 sera of pet cats, and 2,184 human sera, taken from 2,003 general persons and 181 small animal clinic veterinarians, by microimmunofluorescence (MIF) testing with Chlamydia psittaci Fe/Pn1 of feline origin and Prk/6BC of avian origin as antigens. The prevalence rates of anti-Fe/Pn1 antibodies were 45.5% in stray cats, 17.3% in pet cats, 1.7% in general persons and 8.8% in small animal clinic veterinarians. The prevalence rates of anti-Prk/6BC antibodies were 51.1% in stray cats, 15.0% in pet cats, 3.1% in general persons and 5.0% in small animal clinic veterinarians. These results suggested that feline chlamydia infection is widely spread in cats especially in stray cats in Japan, and suggested that feline chlamydiosis could be transmitted to people who are in close contact with infected cats.

Fulminant psittacosis requiring mechanical ventilation and demonstrating serological cross-reactivity between Legionella longbeachae and Chlamydia psittaci

Chlamydia psittaci infection typically causes a mild respiratory illness in humans. Severe respiratory failure requiring mechanical ventilation or intensive care therapy is an uncommon development. The aetiological agents causing severe community acquired pneumonia often remain undetermined. Serological tests may aid in diagnosis. We present two cases of fulminant psittacosis, one demonstrating early cross-reactivity with Legionella longbeachae.

Neuropathological and aetiological studies of sporadic non-suppurative meningoencephalomyelitis of cattle

Sporadically occurring non-suppurative encephalitis appears to be a frequent condition of Swiss cattle. Fifty-one such cases diagnosed over a period of 10 years were examined retrospectively to investigate whether they constituted one or more distinct diseases, and to search for aetiological agents. Three cases were characterised by periventricular granulomatous encephalitis, and most probably represented a different disease, but the remaining 48 cases had disseminated non-suppurative encephalitis with widespread neuronal changes. Neuronal degeneration was very marked in the hippocampus of 10 cases and in the cerebellar Purkinje cells of 11. It was thought that the latter cases represented morphological variations of the same disease rather than a different disease because of their overlapping morphological features. The 48 cases had the following features in common: the disease had primarily neurological signs affecting mostly adult cattle, it was a sporadic condition, and there was a clear tendency for it to have a subacute to chronic course. Polymerase chain reaction (PCR) amplification for chlamydial DNA was negative except in one of 32 specimens, and immunohistochemistry did not demonstrate the presence of chlamydial antigens either in the one PCR-positive case or in the other cases examined. Immunohistochemistry for rabies virus, Borna disease virus, and central European tickborne encephalitis virus was negative. In four cases, immunolabelled cells were found in the lesions with antibodies against paramyxovirus antigens.

In vitro susceptibility of Chlamydia pecorum to macrolides, tetracyclines, quinolones and beta-lactam

The in vitro susceptibility of Chlamydia pecorum to two macrolides (clarithromycin and erythromycin), two tetracyclines (doxycycline and minocycline), two quinolones (ofloxacin and ciprofloxacin) and one beta-lactam (ampicillin) was determined. The MICs were 0.004 to 0.008 microg/ml for clarithromycin, 0.008 to 0.031 microg/ml for doxycycline and minocycline, 0.063 to 0.125 microg/ml for erythromycin, 0.25 to 0.5 microg/ml for ofloxacin and 0.25 to 1.0 microg/ml for ciprofloxacin. The MIC for ampicillin was greater than 1,024 microg/ml. The results show clarithromycin and doxycycline are the two most effective drugs against C. pecorum.

Serological diagnosis of chlamydial abortion in sheep and goats: comparison of the complement fixation test and an enzyme-linked immunosorbent assay employing solubilised proteins as antigen

A new ELISA for antibodies against chlamydial abortion of ewes which uses detergent solubilised proteins (dsp) of Chlamydia psittaci as antigen (Anderson, I.E., Herring, A.J., Jones, G.E., Low, J.C., Greig, A., 1995. Development and evaluation of an indirect ELISA to detect antibodies to abortion strains of Chlamydia psittaci in sheep sera. Vet. Microbiol., 43, pp. 1-12] was compared with the complement fixation test (CFT) in screening 1000 ovine and caprine sera obtained from selected flocks/herds ('flocks') and submitted to a veterinary diagnostic laboratory. Fifteen of the 17 'flocks' had a history of abortion while the remaining two did not and were classified as 'negative flocks'. Infection with Chlamydia was confirmed during the study period in five 'flocks' using direct immunofluorescence and the modified Ziehl Neelsen stain on pathological material. The dspELISA and CFT identified 37 and 45 positive sera on 158 samples tested from these 'flocks'. Chlamydia antibodies were not detected in one of the two negative flocks, in two other flocks where the cause of abortion was undetermined and in three flocks in which the causes of abortion were diagnosed as Listeriosis and/or Salmonellosis. One of the 'negative flocks' yielded two positive reactors by CFT and five by dspELISA, suggesting infection with a cross-reactive subtype of C. pecorum. Of the five 'flocks' in which a definitive diagnosis from pathological material was not possible, four were positive by both serological tests, suggesting that the abortions were due to Chlamydia. The fifth flock, though negative by dspELISA and marginally positive in two samples by CFT, had experienced confirmed chlamydial abortions in previous lambing seasons, but culling and tetracycline treatment have prevented further abortions in the study period. Overall, the proportions of samples positive by CFT and dspELISA were similar (9.1% and 8.8%). These studies confirmed the value of the dspELISA as a screening test for chlamydial abortion. Furthermore, the dspELISA compared to the CFT is easier to perform, does not require reagent titration at each testing and uses automated assessment of results.

Comparison of five tests for the detection of antibodies against chlamydial (enzootic) abortion of ewes

Five tests for antibodies against chlamydial (enzootic) abortion of ewes were compared using 255 sera from experimentally (group 1) or naturally (group 2) infected animals, flocks free of the disease (group 3) and individual animals testing positively by the complement fixation test but from flocks with no evidence of chlamydial abortion (group 4). Sera from five specific pathogen-free lambs vaccinated with two different subtypes of Chlamydia pecorum were also included (group 5). All tests used some form of processed culture of C psitiaci as antigen. Specificities, established with group 3 and 4 sera, ranged between 96 per cent (ELISA using lipopolysaccharide antigen) and 59 per cent (Immunocomb). Reactions with group 5 sera suggested that the cause of false positive results in the field might be cross-reactive antibodies against the arthritogenic subtype of C pecorum. Sensitivities, established with groups 1 and 2 sera, ranged between 81 per cent (Immunocomb) and 51 per cent (ELISA using solubilised protein antigen). The minimum sample sizes required to be 95 per cent certain of detecting at least five seropositives in two infected flocks (combined data) were 15 to 48, dependent on the test applied. The Western blot test, applied to a proportion of samples, yielded no false positives with group 3 sera but 31.7 per cent with group 4 sera. Thus, none of the tests in this comparison emerged as sufficiently satisfactory in all respects, suggesting that further improvements in chlamydial serology must come through the use of non-native antigens or in the form of a competitive ELISA.

Comparison of Chlamydia psittaci from cats with upper respiratory tract disease by polymerase chain reaction analysis of the ompA gene

Conjunctival swabs were taken from 168 cats with clinical signs of acute or chronic upper respiratory tract disease and tested for Chlamydia psittaci by the polymerase chain reaction (PCR) to amplify the ompA gene coding region. Twenty-two (13 per cent) were positive for C psittaci. The PCR products from positive samples were subjected to restriction endonuclease analysis with the restriction enzymes Alu I and Mse I. The fragments of DNA were detected on silver-stained polyacrylamide gels and the results were compared with the results obtained from chlamydial isolates from cats in Japan, France, the USA and the UK. All the strains had identical restriction patterns. When PCR is used as an epidemiological tool, feline chlamydial strains worldwide appear very similar.

Detection of Chlamydia psittaci DNA in avian clinical samples by polymerase chain reaction

A polymerase chain reaction (PCR) assay was developed to detect. Chlamydia psittaci DNA in faeces and tissue samples from avian species. Primers were designed to amplify a 264 bp product derived from part of the 5' non-translated region and part of the coding region of the ompA gene which encodes the major outer membrane protein. Amplified sequences were confirmed by Southern hybridization using an internal probe. The sensitivity of the combined assay was found to be between 60 to 600 fg of chlamydial DNA (approximately 6 to 60 genome copies). The specificity of the assay was confirmed since PCR product was not obtained from samples containing several serotypes of C. trachomatis, strains of C. pneumoniae, the type strain of C. pecorum, nor from samples containing microorganisms commonly found in the avian gut flora. In this study, 404 avian faeces and 141 avian tissue samples received by the Central Veterinary Laboratory over a 6 month period were analysed by PCR, antigen detection ELISA and where possible, cell culture isolation. PCR performed favourably compared with ELISA and cell culture, or with ELISA alone. The PCR assay was especially suited to the detection of C. psittaci DNA in avian faeces samples. The test was also useful when applied to tissue samples from small contact birds associated with a case of human psittacosis where ELISA results were negative and chlamydial isolation was a less favourable method due to the need for rapid diagnosis.

Diversity of feline Chlamydia psittaci revealed by random amplification of polymorphic DNA

DNA samples from C. psittaci including 6 strains of feline origin, 10 strains of avian origin, 1 strain of ovine origin and 1 strain of guinea pig origin were amplified each with three 10-nucleotide (nt) primers and four > 18-nt primers. Amplified products were separated by polyacrylamide gel electrophoresis. Eight patterns were recognized by random amplification of polymorphic DNA (RAPD) fingerprinting of C. psittaci: 2 patterns of feline origin, 5 patterns of avian origin and 1 pattern of guinea pig origin. DNA of feline or guinea pig origin was clearly distinguished from the other strains of C. psittaci by RAPD analysis, as shown by the absence of any common fragments in electrophoresis. The RAPD analysis indicated at least 2 types of feline C. psittaci. The RAPD typing is suggested as a convenient tool for molecular epidemiology of chlamydial infection.

Seroepidemiology of feline chlamydiosis by microimmunofluorescence assay with multiple strains as antigens

The prevalence of anti-chlamydia antibodies was examined in 232 cat sera collected in 1985 and from 1993 to 1995 from laboratories and veterinary hospitals located in 11 prefectures of Japan. The antibodies were determined by an indirect microimmunofluorescence test using six strains of feline Chlamydia: one strain each of avian- and guinea pig-derived C. psittaci and one strain each of C.pecorum, C.pneumoniae and C.trachomatis. Positive rates of IgG antibodies to chlamydiae were 34.4% in 1985 and 16.5-21.4% from 1993 to 1995. Positive rates of IgM antibodies to chlamydiae were 8.2% in 1985 and 6.6-14.3% from 1993 to 1995. Variations in antibody reactivity to the different feline strains were observed. The results suggest the wide prevalence of chlamydial infection in cats in Japan, and antigenic diversity in the feline strains of C.psittaci.

Diversity among abortion strains of Chlamydia psittaci demonstrated by inclusion morphology, polypeptide profiles and monoclonal antibodies

Twenty eight C. psittaci abortion strains had been previously classified in to 4 immunologically distinct groups on the basis of cross-protection experiments in a mouse model. To identify the molecular basis of their immunological divergence 4 representative strains were investigated by cellular, molecular and immunological techniques. An identical pattern was obtained by Alul digestion of the amplified major outer membrane protein gene (MOMP) by the polymerase chain reaction (PCR) of the 4 strains. However, inclusion morphology and polypeptide profiles clearly distinguished one strain, named LLG, and its homologous strain POS from the other prototypes by the presence of a unique protein at 26.5 kDa and the absence of a polypeptide at 23 kDa. Six out of 10 monoclonal antibodies (mAbs) raised against abortion strains failed to react with inclusions of the 2 strains. All 6 mAbs reacted with the chlamydial outer membrane complex (COMC). Two of these mAbs, one against the MOMP and one against an antigen at 90 kDa, did not react with immunoblots of LLG and POS. The data provide direct demonstration of the existence of strain variation in the field and classify strains LLG and POS as a distinct C. psittaci serotype 1-subtype. The antigenic diversity among abortion strains should be taken into consideration when designing a subunit vaccine.

Serological diagnosis of ovine enzootic abortion by comparative inclusion immunofluorescence assay, recombinant lipopolysaccharide enzyme-linked immunosorbent assay, and complement fixation test

Since the 1950s, serological diagnosis of ovine enzootic abortion (OEA), caused by strains of Chlamydia psittaci, has been based mainly on the complement fixation test (CFT), which is neither particularly sensitive nor specific since antibodies to other chlamydial and enterobacterial pathogens may be detected. In this study. a recombinant enzyme-linked immunosorbent assay (rELISA) (medac, Hamburg, Germany), based on a unique chlamydial genus-specific epitope of Chlamydia trachomatis L2 lipopolysaccharide, was evaluated for sensitivity and specificity as a primary screening assay for OEA by comparison with the CFT. A comparative inclusion immunofluorescence assay (IFA), in which antibody titers to C. psittaci and Chlamydia pecorum were examined, was used as the reference test for 573 serum samples from four flocks. Reactivity to C. pecorum was measured since inapparent intestinal infections by C. pecorum are believed to be common in British flocks. In detecting positive sera from an abortion-affected flock, in which a C. pecorum infection was also suggested by IFA, the rELISA outperformed the CFT with significant evidence for increased sensitivity (P = 0.003). In two flocks in which C. pecorum infections alone were suggested by IFA, the rELISA and CFT were prone to detect low levels of false-positive results, but the values were not significant. The rELISA provided results in one flock in which sera that were anticomplementary could not be resolved by the CFT. In another flock in which abortion had not occurred but infection by both chlamydial species was suspected, no significant difference was found between the sensitivities of the rELISA and CFT. The rELISA could not differentiate ovine C. psittaci and C. pecorum infections but was shown to be a more sensitive primary screening test for OEA than was the CFT, particularly where abortion had occurred and even when antibodies due to additional inapparent infection(s) by C. pecorum were present.

Serotype 2-specific antigens from ruminant strains of Chlamydia pecorum detected by monoclonal antibodies

A panel of 25 monoclonal antibodies (MAbs) selected from seven different cellular fusions was used to study the antigenic relationships among a group of 18 ruminant serotype 2 strains of Chlamydia pecorum by indirect microimmunofluorescence test. The antigenic relationships between the strains of C. psittaci serotype 1 and strains of serotype 2 C. pecorum were also studied, as well as the C. pecorum strains and an avian and a feline strain of C. psittaci. Only the genus-specific MAb, used as a positive control, reacted with all the tested strains. Six MAbs reacted with all the C. pecorum serotype 2 strains, but only one of them recognized an 80 kDa protein in Western blot. With these 18 serotype 2 strains, 16 different patterns were established, underlying the high heterogeneity of this group. Only the three caprine strains exhibited the same profile. None of the MAbs reacted with the serotype I strains, or the feline isolate of C. psittaci, but two of them recognized the avian strain. We discuss the possibility that the serotype 2-specific antigens represent C. pecorum species-specific antigens that could be used for diagnosis.

Epizootic bovine abortion in a dairy herd: characterization of a Chlamydia psittaci isolate and antibody response

A chlamydial agent was recovered from the placental cotyledons of an aborting cow from a 100-cow dairy herd in Cumbria. Immunoblotting analysis of purified elementary bodies of the isolate revealed a reactivity pattern typical of serotype I Chlamydia psittaci strains. Nucleotide sequencing of the major outer membrane protein (MOMP) gene further confirmed the isolate, BA1, as a serotype I strain. The sequence was identical to that of the type strain of ovine enzootic abortion, B577. In both the antigenic and MOMP sequencing analyses BA1 was distinguishable from serotype II C. pecorum strains. A sequential series of sera obtained from the aborting cow, from which BA1 was recovered, was analysed by immunoblotting against the homologous isolate, and demonstrated reactivity to major chlamydial antigens over a 110-day period. Close contact between ruminant species on the farm suggested that the C. psittaci strain may have been transmitted to cattle from infected sheep.

Chlamydia psittaci infections: a review with emphasis on avian chlamydiosis

In the first part of this article the general characteristics of Chlamydia psittaci namely the history, taxonomy, morphology, reproductive cycle, metabolism and genetics are reviewed. For the taxonomy in particular, a considerable amount of new information has become available in recent years, following the application of monoclonal antibodies and restriction enzymes. Using these techniques isolates of Chlamydia psittaci from birds have been subdivided in different serovars, a number of isolates have been classified in a new species (Chlamydia pecorum) and isolates from animals have been classified as Chlamydia trachomatis. In the second part of the article, the current knowledge on avian chlamydiosis is summarized. Emphasis is put on clinical signs, lesions, pathogenesis, epizootiology, immunity, diagnosis, prevention and treatment. Also the public health considerations are reviewed. It is concluded that the diagnosis of avian chlamydiosis is laborious and that there is still a need for more accurate, simple and rapid diagnostic tools, both for antigen and antibody detection in various species of birds.

Usefulness of omp1 restriction mapping for avian Chlamydia psittaci isolate differentiation

Sixty-five avian Chlamydia psittaci isolates collected worldwide, including 27 previously characterized reference strains, were analysed by restriction mapping of the major outer membrane protein gene (omp1) obtained after DNA amplification by PCR. They were compared to 2 ruminant isolates, a feline pneumonitis and a guinea pig inclusion conjunctivitis (GPIC) isolate. According to their omp1 restriction patterns, avian strains were heterogeneous in that they exhibited 6 and 4 distinct patterns using AluI and MboII restriction enzymes, respectively, thus defining 7 groups. However, 84% of the studied strains belonged to groups 1 to 4, which share a specific fragment triplet of 411, 282 and 102 base pairs in their AluI digestion patterns. Comparisons with serological classifications showed a strict correlation and allowed further intraserovar differentiation. Furthermore, this classification based upon a single gene (omp1) roughly correlated with the data obtained by RFLP of native DNA and DNA/DNA hybridization studies. There was no host or geographic specificity in the pattern exhibited by these strains. The ruminant, feline pneumonitis and GPIC C. psittaci isolates were clearly distinguished from each other and the avian strains. Moreover, this method was clearly able to identify dubiously designated strains as well as mixtures of isolates within a single sample. In conclusion, this PCR approach based upon omp1 restriction mapping enables the differentiation of avian C. psittaci isolates and can be proposed as a taxonomic and epidemiologic tool.

Utility of complement fixation and microimmunofluorescence assays for detecting serologic responses in patients with clinically diagnosed psittacosis

The serodiagnosis of human psittacosis was considerably improved by a microimmunofluorescence (MIF) assay that uses selected strains of Chlamydia psittaci, C. pneumoniae, and C. trachomatis as antigens. The 78 patients examined in the study were clinically diagnosed as having psittacosis on the basis of compatible clinical symptoms following exposure to sick birds. The conventional complement fixation (CF) test identified 36 patients, or 46% (36 of 78) of the total, as positive. Antibody responses to C. psittaci were demonstrated by the MIF test in all 36 CF-positive patients. The MIF test also detected antibody responses to C. psittaci in 12 patients (15% of the total) whose sera were negative or anticomplementary in the CF test. Seven patients, or 9% (7 of 78) of the total, were identified by the MIF test as having C. pneumoniae infections. About 30% of the study patients (23 of 78) showed no serologic evidence of either C. psittaci or C. pneumoniae infection by both the CF and the MIF tests. Four distinctive serologic reaction patterns were observed in the study patients. Recognition of these reaction patterns and judicious corroboration of serologic responses to the chlamydial species by the MIF test with epidemiologic and clinical information will increase the efficiency and accuracy of serodiagnosis for human psittacosis.

An indirect microimmunofluorescence test for detection of chlamydial antibodies in ovine fetal fluids

The objective of this study was to evaluate an indirect microimmunofluorescence test (IMIF) for detection of chlamydial antibodies in serum and/or thoracic fluids of aborted ovine fetuses. One hundred eighty-two ovine fetuses, including 64 fetuses from 40 ewes that were experimentally infected with an ovine abortion strain of Chlamydia psittaci at gestation days 90-100, 10 fetuses from 6 normal ewes, and 108 fetuses selected from those received at the Iowa Veterinary Diagnostic Laboratory, were evaluated in this study. Fetuses from experimentally infected ewes were examined 4-60 days after inoculation. The IMIF findings were compared with the results of complement fixation serology for chlamydiae and concentrations of immunoglobulin (IgG). Chlamydiae-specific antibodies were detected by IMIF in 28 of 38 fetuses infected with C. psittaci. Elevated levels of IgG and IMIF titers > or = 1:8 were consistent findings in ovine fetuses infected with chlamydiae for more than 24 days. IgG levels and titers of chlamydial antibodies increased with maturity of the fetus and duration of chlamydial infection. Chlamydial antibodies were not detected with the complement fixation test. Fluids from ovine fetuses aborted as a result of other causes also were examined, and IMIF results were negative. The results of this study indicate that the IMIF is a useful and relatively rapid test for identification of chlamydial antibodies in ovine fetuses.

Primary pathogenicity of an European isolate of Chlamydia psittaci from turkey poults

Chlamydia psittaci was isolated as the sole pathogenic agent from a severe outbreak of respiratory disease in a commercial broiler turkey farm in the Netherlands. The mortality rate in the flocks was 65%. Clinical signs included conjunctivitis, swelling of the sinus infraorbitalis and sneezing. Cloacal excretion of chlamydia was demonstrated in twelve out of fifteen birds examined by a direct immunofluorescence test. In all the fifteen birds antibodies against Chlamydia psittaci were detected in the sera by a competitive ELISA. At necropsy sinusitis, rhinitis, airsacculitis, pneumonia, pericarditis and enlargement of the liver and spleen were found. Chlamydiae were demonstrated in the sinus material of all and in conjunctival smears of eight of the fifteen examined birds. Chlamydiae were isolated from all the examined birds after one to three passages on Buffalo Green Monkey (BGM) cell cultures using samples taken from lung, liver and spleen. No other pathogens were isolated. The chlamydia isolate was typed using a panel of serovar-specific monoclonal antibodies in a micro-immunofluorescence test. The isolate belonged to the avian Chlamydia psittaci serovar D. Experimental inoculation with this isolate of 7-day-old specific pathogen free (SPF) turkeys resulted in severe clinical signs, with mortality and extensive pathological lesions, similar to those seen in turkeys from the examined broiler turkey farm. From the data it was concluded that this Chlamydia psittaci isolate can cause severe disease in turkeys.

Typing Chlamydia psittaci--a review of methods and recent findings

When the present chlamydial classification was established it was recognized that a wide variety of types were contained within the arbitrary designation Chlamydia psittaci. Early workers relied mostly on observations of growth characteristics to differentiate the types of C. psittaci isolated from a wide range of different hosts. The differences between isolates were confirmed serologically using a variety of tests of which the most sensitive was the micro-immunofluorescence (MIF) test which was able to recognize nine immunotypes among the mammalian isolates alone. This approach has recently been improved by the use of monoclonal antibodies in the MIF test which has confirmed most of the mammalian immunotypes and divided the avian strains into four groups. Studies on the nucleic acid of C. psittaci isolates show clear differences in the size distribution of DNA fragments produced by restriction endonuclease digestion of the genomes of the various types. Most importantly, studies of DNA/DNA homologies showed that at least four of the types identified by biological, serological and restriction endonuclease tests were sufficiently different to be considered separate species. Most recently, attention has been focused on DNA sequence comparisons of C. psittaci genes amplified by the polymerase chain reaction (PCR). The usual target has been the major outer membrane protein gene for which much sequence information is now available. The combination of PCR and MIF with monoclonals has provided a set of practical techniques with which all chlamydial isolates can be detected and typed with relative ease. It is likely that these developments will lead to the reclassification of the genus and, hopefully, a rapid increase of our understanding of the diseases caused by C. psittaci.