Bjørn P. Berdal

Pneumonia - a Clinical or Radiographic Diagnosis? Etiology and Clinical Features of Lower Respiratory Tract Infection in Adults in General Practice

Etiology and clinical manifestations have been studied in 153 adult patients with lower respiratory tract infection, and the results are presented according to clinical and radiographic diagnosis. Laboratory investigations revealed that bacterial infection, mycoplasma and chlamydia included, occurred as often in 22 patients whose clinical diagnoses of pneumonia were not evident radiographically, as in 20 patients with radiographic pneumonia. In the latter group significantly higher values of erythrocyte sedimentation rate and C-reactive protein were demonstrated. The most common pathogen was influenzavirus A, followed by respiratory syncytial virus, Streptococcus pneumoniae, and Mycoplasma pneumoniae. Chlamydia pneumoniae infection was found in 3 patients with radiographic pneumonia. The study supports the traditional view that patients with a positive chest radiograph as a rule present more serious manifestations of lower respiratory tract pathology than patients with a normal radiograph. However, as only 1/9 patients with pneumococcal infection and 2/7 with mycoplasmal infection had radiographic evidence of pneumonia, radiography alone did not seem to offer sufficient information for selecting patients for antibacterial therapy.

Field detection of Francisella tularensis.

A field investigation was undertaken following an outbreak of water-borne tularemia in Northern Norway. Francisella tularensis bacterial cellular components were analysed by rapid immunochromatography (RI)-testing, enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). Water from 1 reservoir, fed from a rapid stream, tested negative. From another reservoir, 2 of a chain of 3 wells tested negative. The third well, at the end of the chain, contained lemming (Lemmus lemmus) carcasses and gave ample proof of F. tularensis contamination. We concluded that the origin of the outbreak was dead, infective lemming carcasses in the water sources. For the various sampling materials, the RI-test proved itself particularly handy and versatile, compared with the ELISA and the PCR.A field investigation was undertaken following an outbreak of water-borne tularemia in Northern Norway. Francisella tularensis bacterial cellular components were analysed by rapid immunochromatography (RI)-testing, enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). Water from 1 reservoir, fed from a rapid stream, tested negative. From another reservoir, 2 of a chain of 3 wells tested negative. The third well, at the end of the chain, contained lemming (Lemmus lemmus) carcasses and gave ample proof of F. tularensis contamination. We concluded that the origin of the outbreak was dead, infective lemming carcasses in the water sources. For the various sampling materials, the RI-test proved itself particularly handy and versatile, compared with the ELISA and the PCR.

Spread of Subclinical Chlamydia pneumoniae Infection in a Closed Community

Chlamydia pneumoniae infections may spread subclinically. The present investigation took place in a military setting. Sera drawn when the conscripts had entered their military service 2 months previously had been kept frozen and were available. In a camp with 500 people, 35 (7%) developed clinical symptoms of pneumonia. The infection was serologically verified with C. pneumoniae-specific micro-immunofluorescence technique. Of 40 healthy controls, 21 turned out to fulfil the serological criteria of infection, thus, representing subclinical cases. These 21 cases, when extrapolated to the whole camp, equalled a rate of 49% which, added to the 7% of pneumonic cases, gave a total infection rate of 56%. Pre-existing IgG antibodies were demonstrated in 10% of the pneumonic cases, 48% of the subclinical cases, and 89% of the non-infected, healthy controls. Without the access to pre-epidemic sera permitting us to establish 4-fold titre rises, the spread of subclinical C. pneumoniae infection would have been noted at 5%, and not 49% as here demonstrated.

Susceptibility pattern of Scandinavian Francisella tularensis isolates with regard to oral and parenteral antimicrobial agents

Some recently introduced antimicrobial agents have only been incompletely evaluated for use in Francisella tularensis infections. The present study evaluated the susceptibility pattern of Scandinavian human, rodent, and hare F. tularensis isolates with respect to a selection of traditional as well as recently introduced antimicrobial agents. All strains were resistant to the following β‐lactams: penicillin, cephalexin, cefuroxime, ceftazidime, aztreonam, imipenem, and meropenem with minimal inhibitory concentrations > 32 mg/1. Against macrolides, a mixed susceptibility/resistance pattern appeared. All strains were susceptible to gentamicin, chloramphenicol, doxycycline, and four quinolones. Since the quinolones showed the lowest MIC values, and in addition give a good intracellular penetration, we conclude that future drugs to consider against tularemia should definitely include this group of antibiotics. The outpatient mode of antibiotic treatment is especially relevant as the Scandinavian variant of F. tularensis infection is nonlethal, usually pustuloglandular, and not septicemic. Therefore, oral drugs must be sought, and the quinolone group also satisfies this requirement.

Measles Antibodies and Herd Immunity in 20- and 40-year-Old Norwegians

The introduction of a measles vaccination programme in Norway in 1969 using one dose of vaccine, and since 1983 two doses, was followed by a substantial decrease in the incidence of the disease. Since 1992, the annual incidence has been less than 20 cases. Small clusters and outbreaks have occasionally been observed among military personnel and unvaccinated children. This paper describes a seroepidemiological investigation of the level of immunity among 1,188 military conscripts, aged 18-28 years (mean 20.7) compared with 695 healthy 40-year-olds. The conscripts had been offered measles vaccine in infancy, in some cases also at 12-13 years of age, but they had also been exposed to wild measles virus, since the virus continued to circulate many years after the vaccination had started. The measles immunity in this group is considered to indicate the immunity level among the first 5 cohorts offered measles vaccine in Norway. The 40-year-olds had grown up in a community with no measles vaccination. Their level of immunity gives an indication of the level finally obtained when there are no vaccinations, and thus of the level that would induce herd immunity against measles in the Norwegian population. The aims of the vaccination programme must be to obtain a corresponding immunity. The results of the investigation show that the percentages with measles antibodies in the respective groups were 92.3 and 98.1. The observation of measles outbreaks among young Norwegian conscripts, as well as reports from several countries on outbreaks in university and college settings with levels of seropositivity of even more than 95%, indicate that the seropositivity in the 20-year-old group may be too low to afford protection, especially when this group is living under close conditions. Consideration should be given to the need for an intensification of the existing vaccination programme to ensure that the protection level needed for herd immunity is reached.

Vesicular stomatitis virus infection enhances invasiveness of Salmonella typhimurium

When mouse fibroblast L‐929 cells were pre‐infected with vesicular stomatitis virus, an enhancement of invasiveness by Salmonella typhimurium was observed. The effect was more pronounced when higher virus doses were used. Short‐time (5 h) pre‐incubation with virus caused a moderate enhancement of invasiveness. When virus pre‐incubation time was increased to 8 h or 13 h, a further enhancement was observed. Results obtained after pre‐incubation with UV inactivated virus were similar to that achieved by the short‐time pre‐incubation with the corresponding viable virus preparation. This indicates (i) an early phase of virus infection, when virus causes enhancement of invasiveness that is not dependent on viral nucleic acid induced metabolism, and (ii) a later phase, when virus‐induced metabolism is necessary for the enhancement. When virus and bacteria were given concomitantly to infant mice, lethality was increased compared to groups that only received virus or bacteria. The data indicate that vesicular stomatitis virus aggravates infection with a facultatively intracellular bacterium, partly by enhancing the invasiveness of the bacteria.

Rapid identification of Legionella pneumophila zinc metalloprotease using chromogenic detection

Strains of Legionella spp. produce extracellular proteases that can be detected using synthetic chromogenic peptides. Chromogenic tri‐ and tetrapeptides show a high degree of sensitivity, specificity and reagent stability when linked to para‐nitroaniline (pNA). For example, SucOMe‐Arg‐Pro‐Tyr · pNa (S‐2586) is specifically hydrolysed by proteases of Legionella pneumophila and some other Legionella species. A paper disc method to sample protease directly from agar plates has been used to evaluate chromogenic peptides as reagents for diagnostic purposes. Strains of Legionella spp., Pseudomonas spp. and Enterobacteriaceae were examined, together with a recombinant Escherichia coli strain containing the cloned 38 kDa zinc metalloprotease from L. pneumophila. S‐2586 was hydrolysed by 282 out of 283 L. pneumophila strains, and by the recombinant E. coli. Two of the six strains representing other Legionella species, and 22 of the 50 strains from the Pseudomonas group were also positive. No reaction was seen with any of the Enterobacteriaceae strains. Although there was functional homology between proteases from several bacterial groups, the high prevalence of S 2586‐hydrolysing proteases within L. pneumophila indicates a potential usefulness for phenotypic identification.

Research articleField investigations of tularemia in Norway

In Norway, tularemia is a common disease in small rodent and hare populations, where large outbreaks can be observed. In humans, the yearly number of cases is low, usually less than ten, with peaks up to 44 recorded in recent years. Serological investigations on hunters and healthy school children nevertheless indicate, with up to 4.7% positivity in the latter group, that Francisella tularensis low-grade infection is widespread. F. tularensis in co-culture with amoebae, e.g. Achantamoeba castellanii, may grow after internalization and kill the amoeba. As with Legionella, Francisella virulence may be enhanced after protozoan ingestion. This suggests a mechanism that can explain the pattern of dissemination and infection in our region.

Legionella antibodies in human and animal populations in Kenya

Using a microagglutination method, domestic and wild animal sera, together with human patient and healthy blood donor sera, have been analysed for titres against various Legionella species, comprising fourteen different serogroups. Generally, the level of moderately elevated titres, i.e. ≥ 64, was low for all the aforementioned serum groups. Within the domesticated animals, cattle, pigs and dogs presented a much lower prevalence in Kenya than found elsewhere, whereas it was the other way round for goats. Human sera, either from patients or from healthy donors, did not react against L. pneumophila serogroups 1, 6, or 3, which in that sequence are the most common L. pneumophila serogroups in Europe, and in other geographic areas where legionellosis is common. High titres of ≥ 256 against L. pneumophila serogroup 6 (two cattle) or against L. bozemanii strain Mi‐15 (two cattle, one dog) indicate that although the epidemiological picture may be different from other parts of the world, Legionella infections exist in Kenya as well.

Pseudomonas Aeruginosa extracellular toxicity in infant mice and the protective effect of antitoxin A

The toxin A‐content of crude extracellular preparations from Pseudomonas aeruginosa has been measured by ELISA. Using infant mice as test animal, the toxicity of these preparations was evaluated. The LD 50 in infant mice was determined at 80 ng of purified toxin A in saline. With ten μl of rabbit antitoxin A serum given together with purified toxin, the LD 50 increased to 2,500 ng. Generally there was no correlation between the LD 50 of the extracellular preparations, their quantity of toxin A as measured by ELISA, and the protective effect of antitoxin A.