In Saint-Petersburg city, with a population of more than 4.5 million, around 30% of cases of acute intestinal infections have been etiologically verified (1). The incidence of some infections is still quite high (1, 2). For example, the incidence of shigellosis, considered to be an indicator of social problems, remains far higher in Saint-Petersburg (58.1 per 100 000 inhabitants in 2002) than in the Nordic countries (Finland 1.6, Sweden 4.2, Norway 2.9, Denmark 2.6 and Iceland 0 per 100 000 inhabitants in 2002) (3-5).
In recent years, Shigella flexneri has been the dominating cause of shigellosis in Saint-Petersburg (1, 6). The agent is known to cause severe disease and to be the main cause of deaths from acute intestinal infection (1, 6-10). In general, during the recent decade, adult patients have developed the more severe disease course (7-9). In some lethal cases, morphological and histological patterns attributable to shigellosis, such as multifocal and widely spread damage of colon and intestines were the basis for changing the clinical diagnosis to shigellosis even though laboratory tests were negative (7, 9, 11).
Rotaviral diarrhoeal disease, known to affect such vulnerable population groups as children under 2 years old and immunocompromised people (15, 16), is of increasing public health concern in Saint-Petersburg. This is due to a growing incidence rate (16.3, 25.5, and 28.0 per 100 000 inhabitants in 2000, 2001, and 2002, respectively) and the occurrence of several outbreaks among adults as well as children (2, 12).
The objective of the study was to describe the disease severity and etiological agents of acute shigellosis and rotavirus infection among hospitalised adult cases in Saint-Petersburg.
Materials and Methods
In accordance with the standard case definition set in state statistical documents, the following cases are registered as shigellosis in the Russian Federation: a) all laboratory confirmed cases (culture and/or serologically positive), and b) culture negative cases provided they show either clinical patterns attributable to shigellosis (intoxication syndrome in combination with typical dominating syndrome of distal colitis), or morphological and histological patterns attributable to shigellosis in case of lethal outcome.
Cases of acute intestinal infections caused by other bacterial and viral agents (Salmonella; Campylobacter, E. coli, Yersinia, enteroviruses, rotavirus and pathogens causing food poisoning) should be registered only when laboratory confirmed. Cases with negative laboratory results (except clinically and/or morphologically defined shigellosis) are registered as “non-verified acute intestinal infections” with syndrome based diagnosis.
Cases of acute intestinal infections are registered by all physicians in the city out-patient clinics and hospitals according to the above mentioned case definitions (2). The City Centre for Epidemiological Surveillance in Saint-Petersburg, directly subordinated to the Ministry of Public Health and Social Welfare, receives all notifications of infectious diseases.
In 2002-3, 2730 cases of shigellosis were treated in Botkin Hospital (1). We reviewed case records from 259 patients admitted to Botkin Hospital in 2002-2003. The cases were distributed in three groups:
- Group 1 were 118 non-lethal cases of shigellosis admitted during seven months of 2002-2003. We selected only cases whose shigella isolates had been examined for antimicrobial resistance (a procedure that for capacity reasons had been performed only in those seven months).
- Group 2 were all the cases of confirmed rotavirus infection admitted in 2002-3, a total of 70 patients.
- Group 3 consisted of 71 lethal cases of severe acute intestinal infection admitted to the hospital during 11 months of 2002.
88% of the non-lethal shigellosis cases (Group 1) were caused by Shigella flexneri and 12% by Shigella sonnei (table 1).
Table 1. Charachteristics of three groups of adult patients hospitalized in 2002-2003 with acute intestinal infections
In 84% of the cases with confirmed rotavirus infection (Group 2), no other causal agent was found. In 16% of the cases, rotavirus was detected in combination with salmonella and shigella (9% and 7%, respectively). Around 10% of the patients with confirmed rotavirus infection developed gastroenteritis, 56% gastroenterocolitis and 34% enterocolitis. In general, 87% of the cases with only rotavirus detected developed the colitis syndrome.
More than one third (26 cases) of the 71 lethal cases of acute intestinal infection were caused by Shigella flexneri 2a (14 cases) and 3a (9 cases) as the most common types (table 2).
Table 2. Diagnosis (causative organism) in 71 lethal cases of acute intestinal infections in Botkin Hospital, Saint Petersburg, 2002
In 38% of the cases, culture-negative clinically diagnosed shigellosis was confirmed by finding morphological and histological patterns attributable to shigellosis. Other cases with negative laboratory results (a quarter of the total number of lethal cases) did not demonstrate morphological and histological patterns typically attributable to shigellosis, and were diagnosed as “non-verified acute enterocolitis” based on autopsy.
In more than one third of the lethal cases (34%), the patient died within the first 24 hours after hospitalization. Quite a large number of Group 3 patients (20.9%) had been admitted to the hospital late in the disease course (later than the 14th illness day).
The spectrum of morphological patterns varied: ulcerative colitis and enteritis in 62% and 25% of cases respectively, hemorrhagic colitis (41%) and enteritis (more than 50%), phlegmonous inflammation signs in colon and intestine (9% and 7% respectively) and even necrotic colitis in one case.
A history of long-term alcohol consumption was revealed in approximately one third of Group 1 cases and in 76% of Group 3 cases. A wide spectrum of concomitant diseases (cardiovascular, gastrointestinal, alimentary disorders and others) was documented, most frequently in lethal cases.
Shigella flexneri is a major cause of hospitalisations and deaths from acute intestinal infections in Saint-Petersburg. This is in agreement with similar data obtained by other researchers (1, 6). Yuschuk and Pokrovskiy describe Shigella flexneri as dominating among cases hospitalised in 1994-1997 as well (9, 14). It seems that underlying diseases and alcoholism are risk factors for the disease. Other researchers have also revealed that concomitant disease and chronic alcohol intoxication are often present in severe cases of acute intestinal infection (8, 10, 13, 14, 17).
In Saint-Petersburg, the availability and quality of rotavirus diagnostics is improving year by year. This can likely contribute to an increase in the reported incidence of rotavirus infections. We found a somewhat higher proportion of colitis syndrome among our rotavirus patients than other researchers have found (13, 16).
Signs of haemocolitis were documented in the majority of the lethal cases, in more than half of the cases with non-lethal shigellosis, and in almost every third case with rotaviral monoinfection. The reason for the presence of haemocolitis in rotavirus infection needs to be studied more thoroughly and analyzed with respect to the patients’ concomitant diseases and past medical histories. The data obtained suggests that in some cases with rotavirus detected, the microbiological method, known to be much more dependent on many factors (antimicrobial preparation taken before sample examination, any pitfalls in operating procedure fulfilment and so on) could have failed due to many reasons. Mixed infection may have been under-diagnosed. Furthermore, the cases had not been examined for campylobacteriosis.
Such important points as sampling, sample delivery to the laboratory and sample storage, as well as timeliness in laboratory examination, prescribing, examination for other possible agents seem to be of particular importance to increase the effectiveness of microbiological diagnostics of acute intestinal infections in Saint-Petersburg. Improved microbiological diagnostics may subsequently lead to timely and adequate disease treatment.
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