Search

Background: During the last few years the application of Western immunoblotting in the study of human infection by Rickettsia conorii has led to the development of a new method of serologic diagnosis of the Mediterranean exanthematous fever., Methods: The pattern of reactivity of serum samples sequentially obtained in the course of infection versus R. conorii antigens (Malish 7 strain) purified in discontinued density gradient and separated by SDS-PAGE was analyzed by Western immunoblotting., Results: The presence of typical profiles of rickettsial infection similar to those observed in the common forms of presentation of the Mediterranean exanthematous fever was demonstrated in a case of accidental infection transmitted via aerosol and followed by an incomplete clinical picture after the early administration of specific antibiotic therapy and in a patient with signs and symptoms characteristic of Mediterranean exanthematous fever in whom the results of indirect immunofluorescence tests were repeatedly negative., Conclusions: Western immunoblotting may be a specially useful technique as a complementary procedure in the laboratory to guide in the diagnosis of Mediterranean exanthematous fever in special situations.

The antigenic reactivity in Western immunoblotting assay of individual Rickettsia conorii components with sera of healthy people living in Salamanca Province, an endemic zone of Mediterranean spotted fever, is evaluated. Polypeptides of molecular weights 100 kDa (92.7%), 135 kDa (75.6%), 160 kDa (70.7%) and 115 kDa (48.8%) were recognized by a higher proportion of sera with indirect immunofluorescent antibody test titers > or = 1:80. Reaction with apparent rickettsial lipopolysaccharide was found in 15 (36.6%) of these samples. The involvement of different rickettsial strains, atypical routes of inoculation, varying content of the inoculum, and host factors may be determinants of the clinical expression of the spotted fever group rickettsial infection in people who produce antibodies reactive with Rickettsia conorii antigens.

The reactivity of antigenic components of Rickettsia conorii with sequentially obtained sera from 20 adult Spanish patients with Mediterranean spotted fever was analyzed by Western blot. The major rickettsial antigens reacting with the serum samples corresponded to molecular weights of 135 and 115 kDa. These antigens constantly exhibited higher staining intensity than the other antigens, and reacted with 100% and 86.7%, respectively, of acute sera and with 100% of convalescent phase samples. Rickettsial lipopolysaccharide antigens reacted with 94.7% of sera collected in the fourth and fifth week after onset of symptoms. Other major antigens reactive in the blots had molecular sizes of 160, 100, 90 and 60 kDa, and a relatively frequent humoral immune response was also seen to antigens of 80, 73 and 55 kDa.

A comparison was made of the results obtained with ciprofloxacin (750 mg/12 h) and doxycycline (100 mg/12 h), both administered p.o. for one week, in 34 and 36 patients respectively with Mediterranean spotted fever. Apyrexia was achieved after 50.1 +/- 34.2 h (mean +/- SD) of antibiotic therapy in the group of patients treated with ciprofloxacin and in 55.2 +/- 23.3 h in the group treated with doxycycline (no significant statistical differences). Resolution of the remaining signs and symptoms of the disease was achieved faster with ciprofloxacin. Both therapeutic regimens were effective and safe. Although more expensive than doxycycline, ciprofloxacin is a bactericidal compound which is better tolerated and has a lower risk of toxicity and of development of resistance. It can be considered, together with doxycycline, as an antibiotic of first choice in the treatment of Mediterranean spotted fever.

Prominent degrees of hyponatremia are detected in the severe forms of Mediterranean spotted fever and the intensity of this abnormality parallels the severity of the infectious process. In order to determine the incidence, degree and evolution of hyponatremia in 110 patients with Mediterranean spotted fever and to explore the feasible renal mechanism that could lead to this phenomenon, serum and urinary osmolality and levels of urea, creatinine and electrolytes were measured in samples obtained at selected points (up to the fifth week) in the course of the disease, and parameters of renal function were calculated. Mean serum sodium levels of 135.6 +/- 5.5 mEq/l were detected during the acute phase of the infection. At this point, 42 patients (38.2%) had sodium concentrations less than or equal to 135 mEq/l. After recovery, mean serum sodium values were 142.5 +/- 2.5. The analysis of the parameters of renal function indirectly rules out an inappropriate antidiuretic hormone secretion or renal failure as the cause of hyponatremia. As tubular incompetence to reabsorb sodium is also rejected in these patients, a shifting of sodium to the interstitial or intracellular space may account for the phenomenon.

In eight patients with Mediterranean spotted fever we evaluated the yield of the direct immunofluorescence technique against rickettsial antigens for the early laboratory diagnosis of the disease. Frozen sections of biopsy specimens of the initial lesion (tache noire) taken on the admission day were processed by a fluorescent conjugate reactive against Rickettsia conorii. In seven cases, coccobacillary formations consistent with rickettsiae were observed in the studied specimens. The results were negative in the controls and in three of six samples of exanthema elements obtained from six simultaneously studied patients with Mediterranean spotted fever. Our data demonstrate the diagnostic value of direct immunofluorescence applied on the tache noire. This technique is particularly useful in the initial stages of the disease, before the clinical and serological features have completely developed.

Gastrointestinal (GI) hemorrhage is not a common complication of Mediterranean spotted fever (MSF). We describe three MSF cases with upper digestive tract bleeding in patients from Salamanca (Spain) and the results of the histologic studies performed in two of them. Besides the classical clinical triad of the disease (fever, rash and lesion at the site of tick bite, 'tache noire'), these patients presented purpuric rash and hypoalbuminemia, previously identified in severe forms of the disease. The hemorrhagic complication occurred late in the course of the MSF (between 13 and 20 days after the onset of fever) and was the consequence of multiple acute superficial erosions of the gastric mucosa. The histologic substrate of these lesions was identified as a vasculitic process - characteristically lymphohistiocytic - affecting the small vessels of the gastric wall. Rickettsial vascular injury at this level of the digestive tract is histologically similar to that observed in other organs in patients with MSF and may manifest clinically as digestive tract bleeding.

Mediterranean spotted fever is a spotted fever group rickettsiosis caused by Rickettsia conorii. The fever has a recognized incidence in large geographic areas, and its presence in Salamanca Province (Spain) has been well documented since 1981. This work presents the results of the centralized prospective survey carried out in this area and was designed to study the epidemiological behavior of the disease and the prevalence of antibodies against R. conorii among animals and healthy human population. In 110 patients with confirmed diagnosis by an immunofluorescent antibody test we have observed a bimodal temporal curve of incidence of Mediterranean spotted fever in our zone and their predominant origin in villages under 2000 inhabitants. The serosurvey in a statistically representative sample of the human population of Salamanca shows a rate of 73.5% of reactive sera and percentages as high as 82% in samples from small villages. The seroepidemiological study of 300 animals reveals a widespread response to rickettsial antigens throughout the province. Immunofluorescent antibody titers of greater than or equal to 1:40 are present in 93% of dogs and high rates and titers are detected in other domestic mammals, suggesting their feasible epidemiological role in Mediterranean spotted fever.

The authors studied the incidence, type and systemic relationship of the retinal findings observed by ophthalmoscopy in Mediterranean spotted fever (MSF) in a consecutive series of 34 cases. It is found that retinal vasculitis either arterial and/or, more frequently, venous is present in 55.9% of the cases. Branch vein retinal thrombosis appeared as complication of such small vessel vasculitis in 1 case. Although frequent, the retinal findings were asymptomatic in all cases but the retinal vein thrombosis one, and were not significatively related to or were predicted by other systemic parameters of severity of the disease. Because of its frequency, retinal vasculitis might be considered as an important clinical sign of MSF in endemic areas.

Several studies have previously suggested the possible role of a T lymphocyte suppressor population in infections by species of the genus Rickettsia. In 15 patients with Mediterranean spotted fever (MSF), we quantified, during the acute and convalescent phases of the disease, the peripheral blood lymphocyte populations using monoclonal antibodies that recognize CD3+, CD4+, CD8+, CD38+ and CD20+ cells. In three cases a reversal in the normal ratio of T lymphocyte helper-inducer/suppressor-cytotoxic subsets was detected lasting, in two of them, up to the fifth week of the disease. This disturbance was always weak and lacked clinical significance.

A 77-year-old woman from rural Spain had a febrile summertime disease develop with rash, eschar, and pulmonary, abdominal, and neurologic signs and symptoms. Mediterranean spotted fever (MSF) was diagnosed late in the course, and antirickettsial treatment was given only during the last 30 hours of life. Clinical manifestations of severe disseminated vascular injury included thrombocytopenia, hypoalbuminemia, edema of the lungs and legs, and severe prerenal azotemia. The diagnosis was documented by specific serology. Necropsy revealed vascular injury with perivascular lymphohistiocytic infiltrates suggestive of rickettsiosis in the central nervous system, lung, heart, kidneys, esophagus, stomach, colon, pancreas, spleen, and thyroid. Gastric hemorrhage and acute pneumonia contributed to the patient's death on day 18 of illness. Antimicrobial treatment and host defenses apparently reduced rickettsiae to an undetectable quantity. MSF has increased in incidence in the Mediterranean basin and has been reported in travelers returning to the United States.