Comparison of sampling methods used for MRSA-classification of herds with breeding pigs.

Since the first report on methicillin resistant Staphylococcus aureus (MRSA) CC398 in pigs, several countries have determined the prevalence of MRSA-positive pig herds using different sampling and laboratory techniques. The objective of the study was to compare three sampling methods for MRSA-classification of herds. Therefore, nasal swabs of pigs and environmental wipes were collected from 147 herds with breeding pigs. Per herd, laboratory examination was done on 10 pools of 6 nasal swabs (NASAL), 5 single environmental wipes (ENVSINGLE) and one pool of 5 environmental wipes (ENVPOOL). Large differences in apparent prevalence of MRSA-positive herds between methods were found: 19.1% for ENVPOOL, 53.1% for ENVSINGLE, and 70.8% for NASAL. Pairwise comparisons of methods resulted in relative sensitivities of 26.9% (ENVPOOL vs. NASAL), 34.6% (ENVPOOL vs. ENVSINGLE), and 72.1% (ENVSINGLE vs. NASAL) with relative specificities of respectively 100%, 98.6% and 93.0%. Cohen's kappa was respectively 0.18, 0.32 and 0.55, thus varying between very poor and moderate agreement. Examination of environmental wipes is an easy and non-invasive method to classify herds for MRSA. The number of environmental wipes needed depends on e.g. required detection limits and within-herd prevalence. In low prevalent herds (e.g. herds with <3 positive pools of nasal swabs), 25 single environmental wipes are required to be 90% sure that MRSA is detected at a detection limit similar to analyzing 10 pools of nasal swabs. Individual analysis of environmental wipes is highly recommended, as pooling 5 environmental samples resulted in a substantial reduction of the apparent prevalence.

Prevalence of methicillin-resistant Staphylococcus aureus in meat.

Recently the isolation of methicillin-resistant Staphylococcus aureus (MRSA) strains from several food-producing animals has been reported. During slaughtering of MRSA-positive animals, contamination of carcasses with MRSA may occur and consequently the meat of these animals may get contaminated. The aim of this study was to estimate the prevalence of MRSA in raw meat samples from the retail trade. Samples of raw beef, pork, veal, lamb/mutton, chicken, turkey, fowl and game were collected from the retail trade. A detection method including a two-step enrichment in Mueller-Hinton broth+6.5% NaCl and phenol red mannitol broth containing ceftizoxime and aztreonam, followed by isolation on MRSA ID agar (bioMérieux) was evaluated and subsequently applied for the detection of MRSA in samples of raw meats. MRSA strains were isolated from 264 (11.9%) of 2217 samples analyzed. Isolation percentages for the meat species were: beef (10.6%), veal (15.2%), lamb and mutton (6.2%), pork (10.7%), chicken (16.0%), turkey (35.3%), fowl (3.4%) and game (2.2%). The majority (85%) of the isolated strains belonged to spa-types of pulsed-field gel electrophoresis (PFGE) non-typeable (NT)-MRSA, corresponding to the multilocus sequence type ST398, a type also recently isolated in the Netherlands from pigs. However, a smaller part of these strains were found to be of other ST's, possibly of human origin. Further studies are needed to elucidate transmission routes of MRSA in relation to meat and other foods and to provide the tools for preventing the spread of MRSA. At present the high prevalence of MRSA in meat has not been shown to contribute significantly to the dissemination of MRSA to humans and the possible health hazard for consumers of the presence of MRSA in foods should be further elucidated.

Escherichia coli O157 infection associated with a petting zoo.

A young child was admitted to hospital with haemolytic-uraemic syndrome caused by infection with a Shiga toxin 2-producing strain of Escherichia coli (STEC) O157. Five days before he became ill, the child had visited a small petting zoo. STEC O157 strains were isolated from faecal samples from goats and sheep housed on the farm. The human and the animal isolates were indistinguishable by molecular subtyping. The petting zoo voluntarily closed temporarily to prevent further cases of infection. Two out of 11 other, randomly selected petting zoos (including one deer park) visited subsequently, tested positive. Furthermore, during the study period there was one more notification of STEC O157 infection possibly linked with a farm visit. Although STEC O157 was indeed found in the petting zoo associated with this patient, transmission through animal contact could not be confirmed because the human isolate was not available for subtyping. The case study and the results of the other on-farm investigations highlight the risk of acquiring severe zoonotic infections during visits to petting zoos.

Monitoring and estimating concentrations of polychlorinated biphenyls, dioxins, and furans in cattle milk and soils of Rhine-Delta floodplains.

In the Rhine-Delta, accumulation of microcontaminants in floodplain foodwebs has received little attention in comparison with aquatic communities. Here, soil and cattle milk samples were taken from three floodplains and analyzed for polychlorinated biphenyls (PCBs), dibenzodioxins (PCDDs) and dibenzofurans (PCDFs). Based on 2,3,7, 8-tetrachlorodibenzodioxin equivalents, total PCDD and PCDF residues in milk did not exceed the quality standard of 0.006 microg/kg fat weight. This was still the case if non- and mono-ortho PCBs were added to the total. Yet, the floodplains investigated were only moderately polluted according to previous studies and one cannot exclude higher levels in milk from other floodplains. Bioconcentration ratios of milk fat vs soil organic matter were about 0.01 to 0.1 for persistent PCBs. These values are in accordance with a few literature data found for other persistent compounds. Yet, ratios are lower than expected from equilibrium partitioning. Ratios for PCDDs and PCDFs were even lower, possibly due to biotransformation.

Isolation and characterisation of dog uropathogenic Proteus mirabilis strains.

Proteus mirabilis strains isolated from the urine of dogs with urinary tract infections, were characterised with respect to the production of haemolysin and fimbriae. In contrast to healthy dogs, P. mirabilis was also isolated in high numbers from the faeces of dogs suffering from recurrent urinary tract infections. Production of fimbriae was demonstrated by electron microscopy and the presence of genes for two different types of major fimbrial subunits (MR/P-like or UCA-like) was demonstrated by Southern hybridisation. These genes were absent in the Proteus vulgaris, Providentia rettgeri and Morganella morganii strains tested. All but one P. mirabilis strains were haemolytic and most strains produced fimbriae albeit in different amounts. The UCA fimbrial subunits from dog and human isolates have identical molecular weights and N-terminal sequences and are immunologically cross reactive. It was concluded that dog uropathogenic P. mirabilis strains are very similar to human uropathogenic P. mirabilis strains.

Pipemidic acid, a new treatment for recurrent urinary tract infection in small animals.

A new chemotherapeutic agent, pipemidic acid, was used to treat 14 dogs and 2 cats with recurrent urinary tract infection caused by multiresistent strains of Escherichia coli and Proteus spp. Bacterial culture of the urine after treatment revealed disappearance of the microorganisms in all patients. It is concluded that pipemidic acid is a promising chemotherapeutic agent for urinary tract infections caused by multiresistant E. coli and Proteus spp., with the condition that bacterial culture during the course of treatment is obligatory.

Cystourethroscopy in the dog.

The cystourethroscopic examination with cold light cystoscopes forms an essential part of a complete urological examination and is useful for diagnostic as well as surgical procedures. The fast and non-invasive character of the procedure limits the inconvenience to the patient. With the rigid non-flexible scope its use is, however, limited to female dogs, unless in the male dog a urethro(s)tomy is performed.

[A plainly apparent cause of urethral obstruction]. / Een duidelijk aanwijsbare oorzaak van urethra obstructie.

Some mariginal notes regarding possible forms of treatment are made with reference to acute urethral obstruction appearing in a male dog. Although this obstruction was due to a rare cause, the procedure adopted may serve as guidance in planning a scheme of treatment in common cases of urethral obstruction caused by urinary calculi in male dogs.

The immune system of cyprinid fish. Oxytetracycline and the regulation of humoral immunity in carp (Cyprinus carpio).

The antibiotic oxytetracycline (oxyTC) was administered either by mixing with food or by intraperitoneal injections. On oxyTC treated animals decreased serum immunoglobulin levels were found. The primary anti-sheep red blood cells (SRBC) response was measured by enumerating plaque forming cells (PFC). It was observed that the PFC response was depressed by 80-95% in oxyTC treated animals. When an anti-SRBC serum was injected together with SRBC the immunosuppressive effect of oxyTC was absent. A secondary anti-SRBC response was not inhibited by oxyTC. On base of the results a model for antigen presentation and the interaction between macrophages, T- and B-like cells during primary and secondary responses in fish is proposed. In primary responses cellular interaction is needed to develop a proper immune response whereas after a high antigen dose challenge SRBC might behave as a T-independent antigen.

Homogeneous immunoglobulins in the serum of irradiated and bone marrow reconstituted mice: the role of thymus and spleen.

The influence of thymectomy and splenectomy on the frequency and class distribution of homogeneous immunoglobulins (H-Ig) in serum was studied in lethally irradiated (DBA/2 x C57Bl/Rij)F1 mice reconstituted with syngeneic bone marrow. During four follow-up periods in the first 9 months after transplantation, the sham-operated controls and splenectomized animals developed transient H-Ig in an average frequency of 14.2 and 15.7% respectively. There were no marked differences in the incidence of H-Ig within these two groups. In contrast, thymectomized mice and mice both thymectomized and splenectomized showed H-Ig in much higher frequencies (average percentages 31.6 and 36.5, respectively). The highest frequency of H-Ig was observed between 1.5 and 3.5 months after transplantation. H-Ig of the IgG1 and IgG2 subclasses were most frequent in all groups during the first 3.5 months. Later, H-Ig belonging to the IgM class also appeared in somewhat higher numbers. H-Ig of the IgA class was a very rare finding at any time. These results indicate that the presence of the thymus, but not necessarily of the spleen, is an important factor in the regulation of the immunoglobulin heterogeneity during the reconstitution of the immune system in lethally irradiated and bone marrow reconstituted mice.