Transmission of MRSA between humans and animals on duck and turkey farms

OBJECTIVES

The objectives of this study were to estimate the prevalence of MRSA on duck and turkey farms, identify risk factors for human carriage and study transmission between animals and humans.

METHODS

On 10 duck and 10 turkey farms, samples were taken from animals, poultry houses, home residences and humans and cultured using pre-enrichment and selective enrichment. MRSA isolates were typed by spa typing and multiple-locus variable number tandem repeat analysis (MLVA) typing. A subset of isolates from animals and humans was investigated using whole-genome mapping.

RESULTS

MRSA was found on one duck farm and three turkey farms. On duck farms, all humans were MRSA negative. On turkey farms, 5 of 11 farmers, 2 of 32 family members and 15 of 49 samples from the home residences were MRSA positive. Individuals with daily contact with turkeys were significantly more often MRSA positive than individuals without daily contact. All MRSA isolates belonged to livestock-associated MLVA complex 398, belonged to spa type t011, were negative for Panton-Valentine leucocidin, were mecC negative and were mecA positive. Whole-genome mapping proved a valuable tool to study the transmission of livestock-associated MRSA and showed that on two turkey farms the isolates from the animals and humans were indistinguishable or closely related, indicating transmission.

CONCLUSIONS

MRSA carriage in individuals in daily contact with turkeys was significantly higher than that in individuals only living on the farms or than in the general Dutch population. Therefore, persons with a high degree of contact with turkeys have an increased risk of MRSA carriage, and we propose that they should be screened prior to hospitalization in order to decrease the risk of nosocomial transmission.

The Presence of Borrelia miyamotoi, A Relapsing Fever Spirochaete, in Questing Ixodes ricinus in Belgium and in The Netherlands

Borrelia miyamotoi is a tick-borne bacterium that may cause relapsing fever in humans. As this pathogen has been discovered in Europe only recently, only little is known about its local impact on human health and its spatial distribution. In this study, we show the results of PCR screenings for B. miyamotoi in flagged Ixodes ricinus from Belgium and the Netherlands. B. miyamotoi was detected in nine of thirteen, and three of five locations from the Netherlands and Belgium, respectively. These outcomes indicate that B. miyamotoi is more spread than previously thought. The mean infection rate B. miyamotoi was 1.14% for Belgium and 3.84% for the Netherlands.

Iron mobilisation with chelating agents during acute viral hepatitis

During acute viral hepatitis, disturbances in iron metabolism occur. To obtain more insight into this, DFO and DTPA induced urinary iron excretion was studied during acute viral hepatitis. It was found that liver cell damage enhances iron excretion, in proportion to the extent of liver cell disintegration: a highly significant correlation was shown between the DFO as well as DTPA induced urinary iron excretion, and the SGPT. Also, a correlation existed between sideruria and the serum iron level, as well as with the serum bilirubin concentration, provided the test was performed within 10 days after the onset of the jaundice. It is suggested that during liver cell damage, iron, which is liberated during ferritin catabolism, forming a transit pool within the hepatocyte and/or at the cell membrane, is the immediate source of iron donation to DFO and/or DTPA. The practical importance for interpretation of iron mobilisation tests is pointed out.

Some aspects of iron metabolism during acute viral hepatitis

In the acute phase of acute viral hepatitis high serum iron and serum ferritin levels were found in all patients. The normalisation of the serum ferritin concentration parallelled that of the serum glutamic pyruvic transaminase activity. However serum iron levels remained elevated for a long period of time. Chemical analysis of liver tissue showed a low total liver depot iron concentration during the first two weeks of the disease, indicating that the high serum iron levels are caused by iron liberation from disintegrated hepatocytes. Patients studied after two weeks showed higher liver iron concentrations, in particular the non-ferritin iron fraction, reflecting iron accumulation in the reticulo-endothelial system. Indeed, histological examination in the patients studied after two weeks showed sinusoidal lining cell siderosis in addition to "diffuse iron" in clusters lining cells which in electron microscopical studies proved to be macrophages. These cells showed a positive immunohistological reaction for ferritin protein. It is suggested that during acute viral hepatitis two mechanisms act together, i.e. changes in iron metabolism caused by damage of the main iron depot organ (specific liver pathology) and changes in iron metabolism common to all infectious processes.

Follow-up of blood donors positive for hepatitis B surface antigen

From 1973 to 1977 in Amsterdam the incidence of hepatitis B surface antigen (HBsAg) in blood donations from new donors was 0.224 and from known donors 0.034%. 65 donors, previously found positive for HBsAg, were re-examined. Persistence of HBsAg in new donors (28 of 31) occurred significantly (p less than 0.0005) more often than in known donors (15 of 34). All carriers were classified into HBeAg (21%) or anti-HBe (79%) by a sensitive Elisa technique. Abnormal liver function tests (LFTs) were observed in 30% of the carriers and were significantly (p less than 0.005) more often found in HBeAg than in anti-HBe-positive carriers. When the LFTs remained abnormal, in almost all (8 of 9) carriers moderate to severe histological liver disease was diagnosed.

On the iron content of human serum ferritin, especially in acute viral hepaptitis and iron overload

A new method has been developed to measure ferritin iron in human serum. The ferritin is bound to antibodies to ferritin, which are coupled to Sepharose 4-B and separated from the serum by centrifugation. The iron is liberated from the bound ferritin and measured colorimetrically. The detection limit of this method proved to be approx. 15 ng Fe/ml serum. The serum ferritin iron concentration has been compared with the serum ferritin protein concentration. During liver disease with liver cell leakage the mean iron content of serum ferritin proved to be less than the mean iron content in the liver ferritin. The mean iron content in the liver ferritin was 16%, range 7%--32% (n = 8). The mean iron content in serum ferritin from the same patients was 5%, range 0%--14%. Also in two cases of haemosiderosis the serum ferritin iron content was low. It is suggested that ferritin loses part of its iron on passage from the tissue cells to the blood. In some cases of severe liver cell (or other cell) leakage the mean iron content in serum ferritin might be high, because then more or less complete ferritin molecules enter the blood.

An enzyme-linked immunoassay for ferritin in human serum and rat plasma and the influence of the iron in serum ferritin on serum iron measurement, during acute hepatitis

To measure human serum ferritin and rat plasma ferritin a non-competitive enzyme-linked immunoassay has been developed using horseradish peroxidase as the enzyme. In this assay it proved necessary to use heated rat plasma to obtain reproducible ferritin values. The heating procedure caused a loss of 38% of the plasma ferritin. Rat plasma ferritin values have been corrected for this loss. The standard deviation, from duplicate normal human and rat samples is 10 ng ferritin/ml serum and 69 ng/ml plasma, respectively. (The mean ferritin concentrations are: in human sera, 82 ng/ml and in rat plasma 762 ng/ml.) Mean recovery of added liver ferritin in the human serum is 104% +/- 4% (+/-S.E.M') and in the rat plasma 101% +/- 3% (+/- S.E.M.). Normal ferritin concentrations varied in the human material between 30 ng/ml and 300 ng/ml serum, and in the rat plasma between 500 ng/ml and 1300 ng/ml. During increased body iron and acute hepatitis the ferritin concentrations, in patients as well as in rats, exceeded the upper limit of the normal values in most cases. During human hepatitis high serum ferritin levels combined with high serum iron levels were measured. The high serum iron concentrations could not be explained by the high serum ferritin concentrations, even if the iron content of the ferritin is supposed to be high.

A method for measurement of liver iron fractions in needle biopsy specimens and some results in acute liver disease

Methods are described for measurement of total tissue iron, ferritin iron, haem iron and ferritin protein in approx. 15 mg of tissue obtained by liver biopsy. The validity of these methods is examined by comparison with the values observed in larger samples of the same post-mortem derived liver tissue. Correlation coefficients vary between 0.80 and 0.99 (n = 11--16). It appears that in post-mortem liver tissue the haem iron concentration is higher than in biopsy specimens from patients. Analysis of liver biopsy specimens from patients with hepatitis showed a large variation in the mean iron content of the liver ferritin molecules. Also, the non-ferritin depot iron concentration and ferritin protein concentration is quite variable. It is suggested that in cases of advanced ferritin catabolism during hepatitis the mean percentage of iron in ferritin molecules often increases while at the same time the non-ferritin depot iron fraction decreases, probably because of iron release from the liver.