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J Nicolet

Publications and source records attributed to J Nicolet.

At least 19 recordsLinked to original sources
PubMed2005

Modifications of spontaneous cerebral blood flow oscillations during cardiopulmonary bypass.

UNLABELLED: Spontaneous slow waves are present in the systemic circulation including the intracranial compartment. They are supposed to reflect the cerebral autoregulation. We hypothesised that in the absence of cardio respiratory variability, during cardiopulmonary bypass (CPB), we should reveal extreme physiologic controls. MATERIAL/METHODS: Ten patients were included. Arterial blood pressure (ABP, radial invasive), extracorporeal circuitry pressure and cerebral blood flow velocity (CBFV, middle cerebral artery) were recorded. We analysed the slow waves in the B (8 to 50) and the UB (>50 to 200) bands (in milli-Hz). The analysis, before and during CPB, was performed in the tine domain (correlation coefficient, entropy, mean quantity of mutual information, relative entropy) and in the frequency domain (spectrogram, frequency spectrum, coherence). RESULTS: CPB dramatically changed monitored signals decreasing their entropy and revealing a dominant CBFV 70 mHz-frequency and a dominant ABP 9 mHz-frequency. There was no association between the signals (p < 0.05). Before CPB we found complex patterns where B and UB waves were present. CONCLUSION: We hypothesised that CPB provoked a highly protective mechanism, reducing the fluctuations of CBF, by a deactivation of B waves, revealing monotonous UB waves.

Biological Clocks↗
PubMed2004

[Seroprevalences of zoonotic diseases in nomads and their livestock in Chari-Baguirmi, Chad].

The seroprevalences of brucellosis and Q-fever were evaluated in humans and livestock in three Chadian nomadic communities, i.e., Fulani cattle breeders and Arab camel and cattle breeders. The survey was carried out in 1999 and 2000. The total number of human sera and animal sera tested were 911 and 1637, respectively, for antibodies against Brucella spp. and 368 and 613, respectively, for Coxiella burnetii. Sixteen brucellosis positive human sera resulted in a seroprevelance rate of 2%. Male participants were significantly more often brucellosis seropositive than females. No association was found between brucellosis serostatus and physical findings or reported symptoms. Positive brucellosis serology was more frequent in cattle (seroprevalence, 7%) than in camels (1.4%) and small ruminants (0.5%). Fifteen human sera from 11 Arab camel breeders and 4 Arab cattle breeders were positive for Q-fever (seroprevalence below 1%). Being a camel breeder was a significant risk factor for Q-fever seropositivity. Camels had the highest Q-fever seroprevalence (73%) among livestock species.

Brucellosis↗
PubMed2003

Brucellosis and Q-fever seroprevalences of nomadic pastoralists and their livestock in Chad.

As a part of a research-and-action partnership between public health and veterinary medicine, the relationships between the seroprevalences of brucellosis and Q-fever in humans and livestock were evaluated in three nomadic communities of Chad (Fulani cattle breeders, and Arab camel and cattle breeders). Nomad camps were visited between April 1999 and April 2000. A total of 860 human and 1637 animal sera were tested for antibodies against Brucella spp., and 368 human and 613 animal sera for Coxiella burnetii. The same indirect ELISA was used for livestock and human sera, and the test characteristics for its use on human sera were evaluated. Twenty-eight people were seropositive for brucellosis (seroprevalence 3.8%). Brucella seroprevalence was higher in cattle (7%) than other livestock, and brucellosis seropositivity was a significant factor for abortion in cattle (OR=2.8). No correlation was found between human brucellosis serostatus and camp proportions of seropositive animals. Q-fever-seropositive blood samples were taken from 11 Arab camel and 4 Arab cattle breeders (seroprevalence 1%). Being a camel breeder was associated with Q-fever seropositivity in humans (OR=9). Camels had the highest Q-fever seroprevalence (80%) among livestock species. Although there was high-risk human behaviour for the acquisition of brucellosis and Q-fever from livestock through raw-milk consumption (98%) and contact with placentas of livestock (62%), we concluded that seroprevalences in humans were relatively low (likely due to limited active foci in livestock).

Adolescent↗
PubMed2002

[The necrotizing enteritis by Clostridium perfringens type C in piglets: II. Molecular epidemiology study].

Investigations were performed on shedding of C. perfringens in sows from four different pig farms. In two farms where no outbreaks of necrotizing enteritis had been observed, no strains of C. perfringens producing beta-toxin were detected in the faeces of sows. In contrast, C. perfringens strains producing beta-toxin were detected in sows on both farms suffering outbreaks of acute necrotizing enteritis. Strains of C. perfringens producing beta-toxin were invariably positive for the beta 2-toxin gene. However, strains carrying the beta 2-toxin gene only (i.e. negative for beta-toxin) were present in animals on all farms with roughly similar frequencies (mean 28.2% carriers). Some sows carried C. perfringens strains of both toxin genotypes simultaneously. Whereas these data further support the role of betatoxin as a cause of necrotizing enteritis, the role of beta 2-toxin in intestinal disease of piglets remains unclear. To establish the role of faecal shedding vs. environmental contamination as reservoirs of C. perfringens type C, strains were isolated from teats and feedlot trough swabs (toxin genotype beta/beta 2), as well as from fodder (genotype beta 2). However, sows carried this pathogen intermittently and in small numbers. This renders an individual, reliable diagnosis of carrier sows very difficult. Ribotyping of 34 C. perfringens isolates of different toxin genotypes showed five distinct profiles. Different toxin genotypes can belong to the same ribotype, and the same toxin genotype can be present in different ribotypes. Thus, even if a majority (79.4%) of strains investigated in a limited geographic region belonged to ribotype 1, ribotyping offered discrimination of strains beyond toxin typing.

Animals↗
PubMed2001

Mycoplasma conjunctivae infection is self-maintained in the Swiss domestic sheep population.

Bacteriological and serological investigations were performed to assess whether the domestic sheep population is a reservoir of Mycoplasma conjunctivae in Switzerland. Among a sample of 69 sheep showing clinical signs of infectious keratoconjunctivitis (IKC) in three Swiss cantons, M. conjunctivae was identified 53 times (76.8%). A commercially prepared indirect ELISA was used to detect M. conjunctivae antibodies in 674 sera of adult sheep. We analysed a stratified random sample of 123 sheep herds from 25 out of the 26 Swiss cantons. At least one positive animal was detected in 89.4% of the herds. In positive herds (n=110), 57.1% of the individual animals tested positive. To assess the importance of sheep's age in the spread of M. conjunctivae, 209 sera of adult sheep and 93 lamb sera among eight sheep herds were analysed using the indirect ELISA. Seroprevalence in 2-6-month-old lambs was 50.5%, indicating that the IKC agent is spread in sheep flocks during raising. Lambs experimentally infected with M. conjunctivae carried the agent for 8 and 23 weeks, respectively, depending on the strain used for challenge. We conclude that the M. conjunctivae-infection is endemic and self-maintained in the domestic sheep population in Switzerland.

Animals↗
PubMed2001

Molecular epidemiology and genetic linkage of macrolide and aminoglycoside resistance in Staphylococcus intermedius of canine origin.

A collection of 77 Staphylococcus intermedius isolates from dogs and cats in Switzerland was examined for resistance to erythromycin. Resistance profiles for 14 additional antibiotics were compared between erythromycin-resistant and susceptible isolates. A resistance prevalence of 27% for erythromycin was observed in the population under study. Complete correlation between resistance to erythromycin, and to spiramycin, streptomycin, and neomycin was observed. The erythromycin-resistant isolates all had a reduced susceptibility to clindamycin when compared to the erythromycin-susceptible isolates. Both constitutive and inducible resistance phenotypes were observed for clindamycin. Ribotyping showed that macrolide-aminoglycoside resistance was randomly distributed among unrelated strains. This suggests that this particular resistance profile is not related to a single bacterial clone but to the horizontal transfer of resistance gene clusters in S. intermedius populations. The erythromycin-resistant isolates were all carrying erm(B), but not erm(A), erm(C), or msr(A). The erm(B) gene was physically linked to Tn5405-like elements known as resistance determinants for streptomycin, streptothricin, neomycin and kanamycin. Analysis of the region flanking erm(B) showed the presence of two different groups of erm(B)-Tn5405-like elements in the S. intermedius population examined and of elements found in Gram-positive species other than staphylococci. This strongly suggests that erm(B) or the whole erm(B)-Tn5405-like elements in S. intermedius originate from other bacterial species, possibly from enterococci.

Aminoglycosides↗
PubMed2001

Identification and detection of Actinobacillus pleuropneumoniae by PCR based on the gene apxIVA.

The apxIVA gene, a recently discovered RTX determinant of Actinobacillus pleuropneumoniae, was shown to be species-specific. DNA hybridization experiments using probes for various regions of apxIVA revealed that the 3'-terminus of this gene was present in all 14 serotypes of A. pleuropneumoniae but absent from phylogenetically related species. A primer pair spanning this region specifically amplified a 422bp fragment in PCR experiments with DNA from the reference strains of the 14 serotypes and 194 field strains isolated from various geographic locations worldwide. DNA sequence analysis of PCR products derived from all serotypes were identical except in serotypes 3, 8, and 10, which showed minor differences. The PCR did not amplify any product when DNA from 17 different bacterial species closely related to A. pleuropneumoniae was used as template. In addition, the PCR was negative with DNA of several Actinobacillus sp. which were initially characterized as A. pleuropneumoniae using routine phenotypic and serological analyses but which were subsequently shown by 16S rRNA sequence analysis to belong to yet undefined Actinobacillus species. The sensitivity of the PCR was determined to be 10pg of A. pleuropneumoniae DNA. A set of nested primers amplified a 377bp fragment specifically with A. pleuropneumoniae DNA. DNA titration experiments using the flanking and nested primer pairs showed an improved level of sensitivity to approximately 10fg of genomic DNA. The nested PCR was used to monitor the spread of A. pleuropneumoniae in pigs experimentally infected with a virulent serotype 1 strain and housed in a controlled environment facility. A. pleuropneumoniae DNA could be detected by nested PCR in nasal swab samples of infected pigs receiving either a high dose (5x10(5)) or a low dose (1x10(4)) challenge and in unchallenged cohorts that were contact-infected by the inoculated animals. Furthermore, PCR confirmed the presence of A. pleuropneumoniae in 16/17 homogenates from necrotic lung lesions, while the bacterium was successfully recovered from 13 of these lesions by culture.

Actinobacillus Infections↗
PubMed2001

Antimicrobial growth promoter ban and resistance to macrolides and vancomycin in enterococci from pigs.

Ninety-six enterococcus isolates from fecal samples of pigs receiving tylosin as an antimicrobial growth promoter and 59 isolates obtained in the same farms 5 to 6 months after the ban of antimicrobial growth promoters in Switzerland were tested for susceptibility to nine antimicrobial agents. A clear decrease in resistance to macrolides, lincosamides, and tetracycline was visible after the ban. Vancomycin-resistant Enterococcus faecium belonged to the same clonal lineage as vancomycin-resistant isolates previously isolated from Danish pigs.

Animals↗
PubMed2001

[Causes of death, zoonoses, and reproduction in the European brown hare in Switzerland].

To elucidate the importance of different causes of mortality which could explain the downward trend of the hare populations in Switzerland and for monitoring selected zoonoses, the health and reproductive status of 167 perished brown hares (Lepus europaeus) was assessed. Concerning causes of mortality, traumas were by far the most frequent diagnosis, 80% of the hares dying because of injuries. Animals killed by road traffic were highly represented. Predators (such as dogs, domestic cats, lynx, martens, buzzards, and golden eagles) killed 16% of the analysed animals. In juveniles, predation was significantly more frequent than in adults. Infectious diseases led to death in 15% of the animals, and cases of pasteurellosis, brucellosis, pseudotuberculosis, tularaemia, listeriosis, and toxoplasmosis were diagnosed. In 5% of the hares, the cause of death pertained to other categories or remained unclear. Reproductive performance was judged to be normal, since mean litter size was 2.5 per female and pregnancy rate in March-June was 74%. We conclude that neither a specific infectious disease, for which adult hares are particularly susceptible, nor an insufficient reproductive performance are responsible for the decline of brown hare populations in Switzerland. This phenomenon is rather a cause of a reduced survival rate in leverets.

Animals↗
PubMed2001

[Pneumonia in calves: characterization of the bacterial spectrum and the resistance patterns to antimicrobial drugs].

The population under study included young calves with pneumonia (group A, n = 13) and their controls (group B, n = 9), as well as older calves from which the lungs with (group C, n = 90) or without (group D, n = 10) lesions were collected after slaughter. Arcanobacterium pyogenes was the organism most commonly isolated from calves in group A (46%), followed by Haemophilus somnus (23%), Mannheimia haemolytica (15%), Streptococcus suis and Pasteurella multocida (7.7% each). Only S. suis (22%) and P. multocida (11%) were found in group B. P. multocida was isolated from 32% group C calves, H. somnus from 11%, A. pyogenes from 7.8%, M. haemolytica from 2.2% and S. suis from 1.1%. No specific pathogens were isolated in group D. Prevalence of Mycoplasma bovis infection was 69% in group A and 37% in group C. Ninety-eight strains were tested for resistAnce to antibiotics. Resistance to penicillin and ampicillin was present only in M. haemolytica (46%). High percentages of resistant strains were observed for streptomycin (48-100%), tetracycline (15-43%), sulfonamides alone (14-100%) or in combination with trimethoprim (0-100%). Therapeutic approaches to bacterial calf pneumonia in the area under study should be modified according to the isolated bacterial population, the observed antimicrobial resistances and the growing importance of Mycoplasma bovis.

Animals↗
PubMed2001

[Epidemiological study of risk factors for Mycoplasma bovis infections in fattening calves].

To establish the role of Mycoplasma bovis as an agent of respiratory disease in fattening calves, an epidemiologic study was undertaken. A recently validated commercially available ELISA was used to diagnose M. bovis infection by seroconversion in paired sera obtained for each animal at entry in the fattening herd and at follow-up seven weeks later. Management data as well as relevant clinical and epidemiological variables were prospectively recorded. The overall seroconversion rate observed among the 415 calves in 23 fattening herds on 13 farms was 54.7%. Significant risk factors for seroconversion were the mixing of fattening herds of different age groups (risk ratio RR 1.70, 95% confidence interval (CI) 1.48 to 1.96), and the presence of at least one seropositive animal in the fattening herd (RR: 2.02; CI: 1.69 to 2.40). The proportion of clinical episodes of respiratory disease attributable to M. bovis infection was 50.3%. The average weight gain during the observation period was reduced by 7.6% in seroconverting calves and these animals had about 2 times more antibiotics prescribed by a veterinarian than calves remaining negative for M. bovis throughout follow-up (RR 1.83). Maternal antibodies against M. bovis were detected in 39% of newborn calves born from seronegative cows and had a half-life of 20 days, potentially limiting the usefulness of vaccines against M. bovis in this age group.

Age Factors↗
PubMed2001

[The current antimicrobial resistance situation in Swiss veterinary medicine].

Antimicrobial susceptibility data (n = 1501) and bacterial isolates (n = 258) of important bacterial pathogens from animals were collected in collaboration with eight Swiss laboratories from May 1999 to February 2000. Using these data, the antimicrobial resistance situation could be assessed for the following bacterial species: Escherichia coli, Salmonella, Haemophilus parasuis, Actinobacillus pleuropneumoniae, Pasteurella multocida, Mannheimia haemolytica, Bordetella bronchiseptica, Campylobacter jejuni, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus intermedius, Streptococci, and enterococci. Differences in the distribution of resistance between animal species could be evidenced in E. coli and salmonella. Some resistance frequency data were compared with those obtained in 1980. A significant increase of resistance frequency was observed for several antibiotics. This includes in particular an increase of ampicillin, gentamicin, and cotrimoxazole resistance in E. coli. A similar increase was observed in salmonella for ampicillin, streptomycin, sulfonamides, and nalidixic acid. Staphylococci from dogs (S. intermedius and S. aureus) also presented a clear increase of resistance for penicillin, neomycin, sulfonamides, cotrimoxazole, and erythromycin. Finally, a comparison with data from abroad shows that the antibiotic resistance situation in Switzerland is relatively favorable.

Animals↗
PubMed2000

Farm and slaughter survey of bovine tuberculosis in captive deer in Switzerland.

In 1998, a survey was conducted by postal questionnaire to gather basic knowledge about the management, health and productivity of captive deer in Switzerland. In addition, lymph nodes were collected from slaughtered deer from 124 of the 262 holdings surveyed, and tested for Mycobacterium bovis and Mycobacterium tuberculosis. The total farmed deer population was 8389 animals kept on 485 holdings; 87 per cent were fallow deer, 8 per cent red deer, 4 per cent sika deer, and there were small numbers of other species. The median herd sizes were 12 for fallow deer and eight for red deer. Few owners had handling facilities or crushes. In none of the lymph nodes examined were lesions typical of bovine tuberculosis observed, and neither M bovis nor M tuberculosis was cultivated from any of the samples.

Animal Husbandry↗
PubMed2000

Apx toxins in Pasteurellaceae species from animals.

Pasteurellaceae species particularly of porcine origin which are closely related to Actinobacillus pleuropneumoniae were analyzed for the presence of analogues to the major A. pleuropneumoniae RTX toxin genes, apxICABD, apxIICA and apxIIICABD and for their expression. Actinobacillus suis contains both apxICABD(var.suis) and apxIICA(var. suis) operons and was shown to produce ApxI and ApxII toxin. Actinobacillus rossii contained the operons apxIICA(var.rossii) and apxIIICABD(var.rossii). However, only the toxin ApxII and not ApxIII could be detected in cultures of A. rossii. The Apx toxins found in A. suis and A. rossi may play a role in virulence of these pathogens. Actinobacillus lignieresii, which was included since it is phylogenetically very closely related to A. pleuropneumoniae, was found to contain a full apxICABD(var.lign.) operon which however lacks the -35 and -10 boxes in the promoter sequences. As expected from these results, no expression of ApxI was detected in A. lignieresii grown under standard culture conditions. Actinobacillus seminis, Actinobacillus equuli, Pasteurella aerogenes, Pasteurella multocida, Haemophilus parasuis, and also Mannheimia (Pasteurella) haemolytica, which is known to secrete leukotoxin, were all shown to be devoid of any of the apx toxin genes and did not produce ApxI, ApxII or ApxIII toxin proteins. However, proteins of slightly lower molecular mass than ApxI, ApxII and ApxIII which showed limited cross-reactions with monospecific, polyclonal anti-ApxI, anti-ApxII and anti-ApxIII were detected on immunoblot analysis of A. equuli, A. seminis and P. aerogenes. The presence of Apx toxins and proteins that imunologically cross react with Apx toxins in porcine Actinobacillus species other than A. pleuropneumoniae can be expected to interfere with serodiagnosis of porcine pleuropneumonia.

Amino Acid Sequence↗
PubMed2000

Detection of the ADP-ribosyltransferase toxin gene (cdtA) and its activity in Clostridium difficile isolates from Equidae.

Clostridium difficile is an antibiotic-associated emerging pathogen of humans and animals. Thus far three toxins of C. difficile have been described: an enterotoxin (ToxA), a cytotoxin (ToxB) and an ADP-ribosyltransferase (CDT). In the present work we describe the first isolation of CDT producing C. difficile from Equidae with gastro-intestinal disease. Out of 17 C. difficile strains isolated from Equidae, 11 were positive for the genes tcdA and tcdB encoding ToxA and ToxB. In addition four of these 11 isolates were positive for the cdtA gene encoding the catalytic subunit of the ADP-ribosyltransferase CDT. Interestingly none of the isolates derived from canines (41 isolates) and felines (4 isolates) harboured the cdtA gene. In C. difficile field isolates which contained the cdtA gene, ADP-ribosyltransferase activity could also be detected in culture supernatants indicating expression and secretion of CDT. All strains were associated with intestinal disorders, but no association was found for the occurrence of toxins with a specific clinical diagnosis.

ADP Ribose Transferases↗
PubMed2000

Antigenic and genetic characterization of lipoprotein LppQ from Mycoplasma mycoides subsp. mycoides SC.

Lipoprotein LppQ, a predominant 48-kDa antigen, and its corresponding gene, lppQ, were characterized in Mycoplasma mycoides subsp. mycoides SC, the etiological agent of contagious bovine pleuropneumonia. The lppQ gene is specific to M. mycoides subsp. mycoides SC and was found in the type strain and in field strains isolated in Europe, Africa, and Australia, as well as in vaccinal strains. LppQ is encoded as a precursor with a consensus sequence for prokaryotic signal peptidase II and a lipid attachment site. The leader sequence shows significant prominent transmembrane helix structure with a predicted outside-to-inside helix formation capacity. The N-terminal domain of the mature LppQ was shown to be surface exposed. It induced a strong, specific, early, and persistent immune response in naturally and experimentally infected animals. The C-terminal domain of LppQ possesses an integral membrane structure built up of repeated units, rich in hydrophobic and aromatic amino acids, which have a pore formation potential. A recombinant peptide representing the N-terminal domain of LppQ was obtained by site-directed mutagenesis of nine Mycoplasma-specific TGA (Trp) codons into universal TGG (Trp) codons and expression in Escherichia coli hosts. It was used for serodetection of cattle infected with M. mycoides subsp. mycoides SC, in which it was detected postinfection for significantly longer than conventional serological test reactions.

Animals↗
PubMed2000

Characterization of PaxA and its operon: a cohemolytic RTX toxin determinant from pathogenic Pasteurella aerogenes.

Pasteurella aerogenes is known as a commensal bacterium or as an opportunistic pathogen, as well as a primary pathogen found to be involved in abortion cases of humans, swine, and other mammals. Using broad-range DNA probes for bacterial RTX toxin genes, we cloned and subsequently sequenced a new operon named paxCABD encoding the RTX toxin PaxA in P. aerogenes. The pax operon is organized analogous to the classical RTX operons containing the activator gene paxC upstream of the structural toxin gene paxA, which is followed by the secretion protein genes paxB and paxD. The highest sequence similarity of paxA with known RTX toxin genes is found with apxIIIA (82%). PaxA is structurally similar to ApxIIIA and also shows functional analogy to ApxIIIA, since it shows cohemolytic activity with the sphingomyelinase of Staphylococcus aureus, known as the CAMP effect, but is devoid of direct hemolytic activity. In addition, it shows to some extent immunological cross-reactions with ApxIIIA. P. aerogenes isolated from various specimens showed that the pax operon was present in about one-third of the strains. All of the pax-positive strains were specifically related to swine abortion cases or septicemia of newborn piglets. These strains were also shown to produce the PaxA toxin as determined by the CAMP phenomenon, whereas none of the pax-negative strains did. This indicated that the PaxA toxin is involved in the pathogenic potential of P. aerogenes. The examined P. aerogenes isolates were phylogenetically analyzed by 16S rRNA gene (rrs) sequencing in order to confirm their species. Only a small heterogeneity (<0.5%) was observed between the rrs genes of the strains originating from geographically distant farms and isolated at different times.

Abortion, Veterinary↗