M. Fantasia

Salmonella enteritidis in Italy

During the period 1982-1992 the percentages of Salmonella enteritidis isolations in Italy have increased from 2.4 to 57.1% from human beings and from 0.5 to 22.8% from food. Seven hundred and fifty-seven isolates, 702 from man and 55 from food, were characterized. Phage type 4 accounted for the 76.8% of these isolates. The majority of strains were sensitive to the antibiotics tested; only 18 (2.4%) showed resistance to three or more antibiotics by nine different patterns.

Foodborne outbreaks caused by salmonella in Italy, 1991–4

This report summarizes studies on 1699 foodborne outbreaks, in Italy, reported to the Istituto Superior di Sanità (ISS) (the National Institute of Health of Italy, Rome) during the period 1991-4. The most frequently reported foodborne outbreaks were caused by salmonellae (81%), in particular by Salmonella enteritidis and non-serotyped group D salmonella (34% and 33% of the total salmonella outbreaks, respectively). A vehicle was implicated in 69% of the salmonella outbreaks; eggs were implicated in 77% of the outbreaks for which a vehicle was identified or suspected. Salmonella strains isolated in 54 outbreaks were studied for phenotypic and genotypic characteristics. The isolates belonged to S. enteritidis (50 outbreaks), S. typhimurium (three outbreaks) and S. hadar (one outbreak). In the S. enteritidis outbreaks, phage type 4 was most frequently isolated (64.8%), followed by phage type 1 (14.8%). The virulence plasmid of 38 megadaltons was found in many different phage types of S. enteritidis.

Conventional and molecular approaches to isolates of Salmonella hadar from sporadic and epidemic cases.

In September 1994 an outbreak of gastroenteritis occurred in 437 people who had consumed lunch in the canteen of a factory in Central Italy. Salmonella sp. was isolated from stools of 99 patients and in 73 of them Salmonella hadar was identified. This is the first outbreak caused by this serotype described in Italy. In order to examine the genotypic basis of the epidemic strains, molecular typing was applied to sporadic strains isolated before and after the outbreak episode. For this purpose phage type, resistance to antibiotics, DNA plasmid profile and sites of insertion of the mobile element of IS200 were determined. The epidemic strains were genetically distinct from the non‐epidemic isolates; they were shown to be phage type 26, harbouring four small plasmids, were resistant to nalidixic acid and showed a unique characteristic IS200 fingerprint. The typing methods used in this study allowed the identification and discrimination of the outbreak strains from related isolates. They can thus be considered as a tool for epidemiological purposes. In addition we should point out the emerging resistance to nalidixic acid, largely used in veterinary medicine, in Salm. hadar.

Italian experience in Salmonella enteritidis 1978–1988: characterization of isolates from food and man

Salmonella enteritidis accounted for 5.45% of the 118.685 Salmonella isolates from man and for 2.65% of the 3.315 Salmonella isolates from food in Italy in the eleven year period 1978 to 1988. In the years 1978-1982 no S. enteritidis strain was isolated from eggs and poultry; in the years 1983-1988 the 53% of S. enteritidis isolates from food were from eggs and poultry. In 1989 S. enteritidis accounted for 744 isolates from man and 22 from food of which 80% were from eggs and poultry (partial data). In that year 18 outbreaks caused by S. enteritidis were reported to the National Centre of Enteric Pathogens in Rome. Characteristics of 81 S. enteritidis isolates were examined of which 27 were from sporadic cases involving humans and 40 from outbreaks in humans; 14 isolates were from food, all but one connected with the outbreaks. All the isolates studied were sensitive to the antibiotics tested; plasmid profile analysis showed a predominant profile pattern in both epidemic and non-epidemic strains; lysine decarboxylase was present in all the strains tested. Although in at least three epidemics a common supplier of eggs was proved, the source was not identified. Unfortunately it was not possible to determine the phage type of isolates because of the unavailability of specific phages.

Egg-related Salmonella enteritidis, Italy, 1991.

In recent years, Salmonella enteritidis has become an increasingly important public health problem in Italy. In some parts of the country, the fraction of total human salmonella isolates accounted for by S. enteritidis has risen from 3-4% in the mid-1980s to more than 30% in 1990. Between 1990 and 1991, the number of reported S. enteritidis outbreaks increased more than sixfold. The 33 outbreaks reported in 1991 occurred in seven contiguous regions in northern and central Italy and were clustered in time between June and October: in the majority, products containing raw or undercooked shell eggs were implicated. Five of the egg-related outbreaks that occurred within a 30 kilometre radius over a 7-week period were investigated in detail. A phage type 1 strain containing a 38.9 MDa plasmid appeared responsible for three of the outbreaks, while in the remaining two a phage type 4 strain, also with a 38.9 MDa plasmid was isolated. Efforts are being made to enhance epidemiological surveillance and laboratory evaluation, and the use of pasteurized eggs has been recommended for high-risk populations.

Results of the three-year surveillance by the Italian SALM-NET System: Human isolates of Salmonella serotypes

Within the wide framework of the European Community Human Salmonella Surveillance Project (SALM-NET), the data on the most commonly isolated serotypes in Italy from January 1994 to December 1996 are reported. The total data included in the Italian SALM-NET data base account for 34,412 Salmonella isolates. In the list of the most frequent isolates, S. enteritidis ranked always first in the years 1994, 1995 and 1996 with 5435 (43.4%), 4589 (37.1%) and 4044 (42.4%), respectively, over the total number of Salmonella isolates. This serotype is followed by S. typhimurium in the list of the top ten isolates, with 2236 (17.9%), 2831 (22.9%) and 2239 (23.5%). The other serotypes included in this list accounted for a much lower number and percentages ranging from 505 isolates of S. derby (4.0%) to 99 isolates of S. brandenburg (0.8%).

Serotype and phage type distribution of salmonellas from human and non-human sources in Italy in the period 1973–1995

According to the data collected at the Rome-based National Reference Centre for Enterobacteria, 266,547 Salmonella strains isolated from human sources (226,513) and from non human sources(40,034) were characterised in Italy during the period 1973–1995. The serotype of all isolates, and the antibiotype and phage type of selected isolates were determined. Human-source isolations grew from 4372 in 1973 to 12,310 in 1995; non-human source isolations, from 339 in 1973 to 3459 in 1995. Salm.Typhimurium ranked first in the list of the most common serotypes isolated from both sources in the period 1973–1988 except in the years 1975 and 1976 when it was overtaken by Salm. Wien. Since 1983 Salm. Enteritidis has been among the top ten isolates from animals, and ranked first in the list of isolates from humans in 1988 and from non human sources in 1991. During the last years the number of multidrug-resistant strains, mostly belonging to phage types 104 and 193 of Salm. Typhimurium has been rising. Salmonella strains have also been isolated from numerous extraintestinal infections, almost exclusively caused by Salm. Enteritidis and Typhimurium.

The antibiotic resistance patterns of Salmonella Typhi isolates in Italy, 1980-96

In this paper we report the distribution of Salmonella Typhi isolates in Italy and their resistance patterns to antibiotics. The data were collected by the Italian SALM-NET surveillance system in a pilot retrospective study of the period 1980-96. Data on drug-resistance were available for 82 isolates out of 176 S. Typhi isolated in Italy. Of these 82 isolates, 32 (39%) were resistant or intermediate to 1 or more antibiotics. Eight isolates were resistant and 7 intermediate to streptomycin; 4 isolates were resistant to ampicillin alone or in association with other antibiotics; only 2 strains (1 isolated in Lombardia in 1993 and the other 1 in Lazio in 1994) were resistant to chloramphenicol, and 2 (isolated in Sardegna and Piemonte in 1995 and 1996, respectively) showed intermediate resistance to chloramphenicol. The strains showing resistance to 3 or more antibiotics were very scarce: 1 (with 5 complete resistances) was isolated in Lazio in 1994, and another 1 (with complete resistance to 10 antibiotics and intermediate resistance to 2 antibiotics) was isolated in Molise in 1988. In conclusion, besides the routine activities to control typhoid fever, an accurate and continuous surveillance is necessary in order to quickly identify multidrug-resistant (MDR) S. Typhi strains and prevent their spread, even though their level, in our country, is still quite low.

Epidemiological markers of Salmonella typhimurium isolates in Rome

The phage type, antimicrobial resistance pattern, colicinogenic activity and DNA plasmid content of 172 strains of Salmonella typhimurium isolated in Rome from 1984 to 1986 were determined; 142 isolates were from patients with enteritis, 30 were from asymptomatic subjects. Most of the phage types identified were isolated during 2 or 3 of the study years; others, e.g., PT141, PT 204c and PT 194 were isolated during 1 year only, and only the last of these was isolated in large numbers. Phage typing proved most valuable in identifying epidemiologically related strains; DNA plasmid analysis was most useful in characterising further cultures of the same phage type, especially those isolated during suspected epidemics.

R-plasmids in Salmonella isolates from sporadic cases of gastroenteritis.

Five-hundred and twenty seven strains of Salmonella isolated from different patients admitted to hospitals in Rome from 1982 to 1985 were screened for their resistance to antimicrobial drugs.Sixty-one strains (11.6%) were found to be resistant to two or more antibiotics; the most frequent resistances were to sulfathiazole, streptomycin, tetracycline, chloramphenicol and ampicillin. Of the thirty-eight strains showing resistance to three or more antibiotics, 17 were able to transfer their resistance to E. coli K 12.The isolates were heterogeneous in plasmid population: only few strains harbored a sole plasmid, most harbored many plasmids ranging between 20 and 120 megadaltons in weight. Most strains were found to carry a conjugative plasmid of incompatibility group Inc H of 100–120 megadaltons and Inc I α of 60–70 megadaltons.