In vitro antibiotic susceptibility of Francisella tularensis isolated from humans and animals.

The in vitro susceptibility of 38 strains of Francisella tularensis (biovar F. tularensis palaearctica) was determined using Etests on cysteine heart agar plates with 2% haemoglobin. All strains were susceptible to the antibiotics traditionally used to treat tularaemia, such as streptomycin (MIC(90) 4.0 mg/L), tetracycline (MIC(90) 0.38 mg/L) and chloramphenicol (MIC(90) 0.38 mg/L), and to aminoglycosides, such as tobramycin (MIC(90) 1.5 mg/L) and gentamicin (MIC(90) 1.0 mg/L). The quinolones examined had low MIC(90)s: ciprofloxacin, 0.016 mg/L; levofloxacin, 0.016 mg/L; grepafloxacin, 0.047 mg/L; and trovafloxacin, 0.032 mg/L. In contrast, all the strains were resistant to beta-lactams and azithromycin. Quinolones thus seem to be promising drugs for the treatment of tularaemia.

Molecular epidemiology of an outbreak caused by Salmonella enterica serovar Newport in Finland and the United Kingdom.

Between December 1997 and January 1998 an increase in the number of isolates of Salmonella enterica serovar Newport, a serotype rarely causing indigenous infections in Finland, was detected. This included two clusters of gastroenteritis following funeral meals. An inquiry via Enter-net revealed a concomitant increase in cases of S. Newport in the United Kingdom. To investigate the Finnish outbreak, a total of 56 S. Newport strains (22 from the outbreak period, 27 from pre- and post-outbreak period, and 7 from imported food producing animals) were studied by pulsed-field gel electrophoresis (PFGE); selected isolates were also phage typed. Two retrospective questionnaire studies evaluating food exposures among the funeral attendants were conducted. All isolates from the clusters had an identical PFGE pattern which was also found in 13 infections temporally close to but not associated with the clusters. The Finnish outbreak was caused by the same phage type as the one in the United Kingdom. In both clusters, an epidemiological link between illness and exposure to cured ham was found. In conclusion, the outbreak was not limited to the two clusters but was more widely spread both in and outside Finland. Early alarm systems of food-borne outbreaks and collaboration between European countries are needed for investigating international outbreaks.

Disease patterns in field and bank vole populations during a cyclic decline in central Finland.

Declining field vole (Microtus agrestis) and bank vole (Clethrionomys glareolus) populations were sampled (117 field voles and 34 bank voles) in south-central Finland during the winter of 1988-89. The last surviving field voles were caught in April and bank voles in February. A subsample (16) of the April field voles were taken live to the laboratory for immunosuppression. The histopathology of the main internal organs and the presence of aerobic bacteria and certain parasites were studied. In the lungs, an increase in lymphoid tissue, probably caused by infections, was the most common finding (52% of all individuals). The prevalences in the voles, in the whole material, of Chrysosporium sp. and Pneumocystis carinii in lungs were 13 and 10% in field voles, and 9 and 0% in bank voles, respectively. Cysts of Taenia mustelae (9 and 27%) were the most common pathological changes in the liver. Enteritis was also rather common (14 and 34%). In field voles the prevalences of Frenkelia sp. in the brain and Sarcocystis sp. in leg muscles were low (both 6%). Bordetella bronchiseptica was commonly (31%) isolated from field vole lungs and Listeria monocytogenes from the intestines (34%). Salmonella spp. could not be found. The dynamics and abundance of inflammations in the lungs and intestines, as well as B. bronchiseptica isolations from the lungs, indicate that obvious epidemics took place in declining vole populations. Of the Luhanka subsample of 16 field voles brought to the laboratory in April, one died of listeriosis, two of Bordetella, and five died for unknown reasons. Even if small mustelids are the driving force in microtine cycles, it is possible that diseases also contribute to the decline.

Salmonella enteritidis phage types 1 and 4: pheno- and genotypic epidemiology of recent outbreaks in Finland.

In the 1990s, Salmonella enterica subsp. enterica serovar Enteritidis has caused 15 outbreaks in Finland; 12 of them were caused by phage type 1 (PT1) and PT4. Thus far, there has been no clear evidence as to the source of these Salmonella Enteritidis PT1 and PT4 strains, so it was necessary to try to characterize them further. Salmonella Enteritidis PT1 (n = 57) and PT4 (n = 43) isolates from different sources were analyzed by genomic pulsed-field gel electrophoresis (PFGE), plasmid profiling, and antimicrobial resistance testing to investigate the distribution of their subtypes in Finland. It was also hoped that this investigation would help in identifying the sources of the infections, especially the sources of the outbreaks caused by PT1 and PT4 in the 1990s. The results showed that both PFGE and plasmid profiling, but not antimicrobial susceptibility testing, were capable of differentiating isolates of Salmonella Enteritidis PT1 and PT4. By genotypic methods, it was possible to divide both PT1 and PT4 isolates into 12 subtypes. It could also be shown that all PT1 outbreak isolates were identical and, at least with this collection of isolates, that the outbreaks did not originate from the Baltic countries or from Russia, where this phage type predominates. It was also established that the outbreaks caused by PT4 all had different origins. Valuable information for future investigations was gained on the distribution of molecular subtypes of strains that originated from the tourist resorts that are popular among Finns and of strains that were isolated from livestock.

The first Salmonella enteritidis phage type 1 infection of a commercial layer flock in Finland.

The first Salmonella Enteritidis phage type (PT) 1 infection in a commercial layer flock of 2700 birds in Finland occurred in 1995. All the birds were ordered to be killed, the eggs to be destroyed and access to the layer house was denied in order to prevent spread of the infection. Ninety one commercial layers, 61 replacement pullets and 1062 eggs were collected for the analyses. The total infection level of the flock was 8%, concentrated on the 2 older age groups. S. Enteritidis PT1 was isolated from livers (5%), ovaries (2%) and from caeca (3%), of which 2 positive samples were detected with pre-enrichment and 3 without pre-enrichment by cultivation Rambach agar. Eight % of 105 pooled egg samples were positive, of which 2 were detected only from contents and 3 only from shells indicating both oviductal and faecal contamination routes of eggs. The results support the use of the extended sampling procedure in poultry flocks suspected of human food-borne Salmonella outbreaks of invasive serotypes, including not only faecal but also environmental, organ, blood and/or egg samples.

In vitro susceptibility of Francisella tularensis to fluoroquinolones and treatment of tularemia with norfloxacin and ciprofloxacin.

The in vitro susceptibility of ten strains of Francisella tularensis to four fluoroquinolones (ciprofloxacin, norfloxacin, ofloxacin and pefloxacin) was investigated by determining the MBCs of these quinolones. The results were as follows (mean +/- SE): ciprofloxacin 0.13 +/- 0.03 mg/l, norfloxacin 0.24 +/- 0.07 mg/l, ofloxacin 2.16 +/- 0.78 mg/l and pefloxacin 0.51 +/- 0.50 mg/l. These concentrations can be achieved in clinical practice. In addition, four tularemia patients were treated with an oral regimen of 750 mg ciprofloxacin b.i.d. and one patient with norfloxacin 400 mg b.i.d. The fever experienced by these volunteers vanished within a couple of days and they were able to resume normal work one week after receiving the antibiotics without any relapses later. These in vitro and in vivo results show that orally administered fluoroquinolones are promising antimicrobial agents for the treatment of human tularemia.

Fat globule membrane of sow milk as a target for adhesion of K88-positive Escherichia coli.

Membrane adhesion of K88-positive Escherichia coli was studied on intestinal brush-border membranes on 237 Finnish Landrace pigs. Forty-one per cent of the brush-border membrane preparations aggregated E. coli (positive adhesion). Similar dualism of adherence/nonadherence was observed on sow milk fat globule membranes. Washed milk fat globules (washed cream) can be used as a convenient source of material for adhesion studies. Bacterial adherence on to milk fat globules is evident as agglutination of the globules (dark-field microscopy). By this procedure the sows can be typed according to their receptor phenotype. This simple principle of fat globule agglutination due to receptors for K88-positive E. coli might be complicated by SigA-mediated bacterial adherence. Fat globule membranes were shown to contain SigA, which may act as a mediator of bacterial adherence onto fat globules. The significance of this adhesive property of milk fat globule might be to provide alternative receptors for E. coli thus preventing bacterial adhesion on to gastro-intestinal epithelium of the offspring. Sow milk fat globules can be used for typing E. coli for membrane adhesiveness. The adhesiveness of the strains showed a good correlation with the presence of the K88 antigen, as well as the hydrophobicity of the bacterial strain as determined by an association on Phenyl-Sepharose beads.