Successful control of an outbreak of colonization by Klebsiella pneumoniae carbapenemase-producing K. pneumoniae sequence type 258 in a neonatal intensive care unit, Italy

This article reports an outbreak of colonization by Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp) sequence type (ST) 258 in a neonatal intensive care unit (NICU) in Palermo, Italy. KPC-Kp ST258 was detected by an active surveillance culture programme. Between 18th September and 14th November 2012, KPC-Kp was isolated from 10 out of 54 neonates admitted in the outbreak period. No cases of infection were recorded. Male sex was associated with colonization, whereas administration of ampicillin- sulbactam plus gentamicin was protective. Infection control interventions interrupted the spread of KPC-Kp without the need to close the NICU to new admissions.

Ongoing spread of colistin-resistant Klebsiella pneumoniae in different wards of an acute general hospital, Italy, June to December 2011

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Ongoing spread of colistin-resistant Klebsiella pneumoniae in different wards of an acute general hospital, Italy, June to December 2011

We describe polyclonal spread of colistin-resistant Klebsiella pneumoniae in an acute general hospital in Italy. Between June and December 2011, 58 colistin-resistant K. pneumoniae isolates were recovered from 28 patients admitted to different wards, but mainly in the intensive care units. All isolates were tested for drug susceptibility and the presence of beta-lactamase (bla) genes. Clonality was investigated by repetitive extragenic palindromic (rep)-PCR and multilocus sequence typing (MLST). Fifty-two isolates had minimum inhibitory concentrations (MICs) for colistin of 6-128 mg/L, carried bla(KPC3) and were attributed to sequence type ST258. The remaining six isolates were susceptible to carbapenems, exhibited MICs for colistin of 3-32 mg/L, and belonged to two different types, ST15 and ST273. Rep-PCR included all isolates in three clusters, one containing all ST258 KPC-3-producing isolates and two containing ST15 and ST273 isolates.Cross-transmission containment measures and intensification of staff and environmental hygiene could not stop the outbreak. Selective pressure and horizontal transmission probably contributed to emergence and spread of three different strains of colistin-resistant K. pneumoniae in the hospital. Strict implementation of the above measures and a wider awareness of the antimicrobial resistance threat are crucial to preserve the last therapeutic options of the multidrug-resistant Gram-negative infections.

Cluster of cases of Salmonella enterica serotype Rissen infection in a general hospital, Italy, 2007

In 2007, three strains of Salmonella enterica serotype Rissen (S. Rissen) were isolated in the laboratory of diagnostic microbiology of the General Hospital of Prato, Tuscany, Italy, over a 1 month and half interval of time. The first isolate was recovered on January 26 from an outpatient with enteritis. Then, two strains were isolated on February 16 and March 11 respectively, from central venous catheters of patients who were being hospitalized in two departments of the Hospital. An epidemiologically linked cluster of cases of salmonellosis was suspected. The three strains were submitted to single enzyme-amplified fragment length polymorphism (SE-AFLP) and XbaI macrorestriction and pulsed-field gel electrophoresis (PFGE) that yielded undistinguishable profiles. Epidemiological investigations failed to identify a common source of infection within the Hospital. Moreover, the third patient had been exclusively total parenteral nutrition fed since his admission with a stomach cancer diagnosis. The first patient had a community-acquired infection, but the source of her illness was uncertain. Twenty-five further isolates identified in the years 2004-2007 in the same geographical area showed distinctly different PFGE and SE-AFLP patterns. The three patients seemed to represent a cluster of epidemiologically unrelated cases caused by a previously never recognized S. Rissen strain. Rapid subtyping of isolates is essential in the early investigation of potential outbreaks, but synthesis of conventional and molecular epidemiological investigation and availability of surveillance data is often critical to prevent the initiation of time-consuming, expensive and ineffective further investigations and control interventions.

A food borne outbreak of Salmonella enterica serotype Brandenburg as a hint to compare human, animal and food isolates identified in the years 2005-2009 in Italy

INTRODUCTION

There are only a few reported cases of Salmonella enterica serotype Brandenburg foodborne outbreaks in the literature. In Italy Brandenburg is consistently present among the top ten serotypes from human source, but at low prevalences.

MATERIALS AND METHODS

Fifty-five S. Brandenburg isolates from human, animal, environmental and food sources, including twelve isolates from a foodborne outbreak, were genotyped by Pulsed-Field Gel Electrophoresis (PFGE).

RESULTS AND DISCUSSION

Eight pulsogroups and 19 pulsotypes were detected, with a unique pulsotype being attributed to the outbreak strains. Molecular subtyping can reliably complement the epidemiological investigations. Moreover, mapping molecular types of Salmonella isolates from human and non-human source may greatly contribute to risk assessment, by tracking possible animal sources, so improving cost-effectiveness of the prevention and control strategies.

A novel VIM-type metallo-beta-lactamase (VIM-14) in a Pseudomonas aeruginosa clinical isolate from a neonatal intensive care unit

A Pseudomonas aeruginosa highly resistant to carbapenems was isolated in a neonatal intensive care unit in Palermo, Italy. The strain was found to carry a novel VIM-type enzyme, classified as VIM-14. The novel enzyme differs from VIM-4 in a G31S mutation. VIM-14 was harboured in a class 1 integron with a new organization. The integron carried the genes aac7, blaVIM-14, blaOXA-20 and aac4 in that order.

Antibiotic Resistance of Gram Negatives isolates from loggerhead sea turtles (Caretta caretta) in the central Mediterranean Sea

Previous studies on fish and marine mammals support the hypothesis that marine species harbor antibiotic resistance and therefore may serve as reservoirs for antibiotic-resistance genetic determinants. The aim of this study was to assess the resistance to antimicrobial agents of Gram negative strains isolated from loggerhead sea turtles (Carettacaretta). Oral and cloacal swabs from 19 live-stranded loggerhead sea turtles, with hooks fixed into the gut, were analyzed. The antimicrobial resistance of the isolates to 31 antibiotics was assessed using the disk-diffusion method. Conventional biochemical tests identified Citrobacter spp., Proteus spp., Enterobacter spp., Escherichia spp., Providencia spp., Morganella spp., Pantoea spp., Pseudomonas spp. and Shewanella spp. Highest prevalences of resistance was detected to carbenicillin (100%), cephalothin (92.6%), oxytetracycline (81.3%) and amoxicillin (77.8%). The isolates showing resistance to the widest range of antibiotics were identified as Citrobacterfreundii, Proteusvulgaris, Providenciarettgeri and Pseudomonasaeruginosa. In this study, antibiotic resistant bacteria reflect marine contamination by polluted effluents and C.caretta is considered a bioindicator which can be used as a monitor for pollution.

Use of pulsed-field gel electrophoresis for comparison of similar but distinguishable isolates of Shigella sonnei collected in Ireland and Italy

Comparison of pulsed-field gel electrophoresis patterns (generated with XbaI and BlnI) of Shigella sonnei isolates from Ireland and Italy suggests that two possibly distantly related lineages are present in both countries. Smaller, more closely related groups, including isolates from Ireland and Italy, were also noted. These groups raise the possibility that the dissemination of clonal groups of S. sonnei may have occurred in recent years.

Tonometers and infectious risk: myth or reality? Efficacy of different disinfection regimens on tonometer tips

PURPOSE

To evaluate the adequacy of common disinfection regimens for disposable tonometer tips and assess if disinfection of reusable prisms or the use of disposable tips is preferable.

METHODS

We used disposable tonometer tips, using the same material and tip diameter of standard Goldmann tonometer prism. Strains of Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilisand Candida albicanswere tested according to the European standard guidelines for disinfectants test. Antimicrobial effectiveness of the following disinfection practices has been assessed: dry wipe, Minuten wipes (Alpro), soaking in 3% hydrogen peroxide, 0.5% benzalkonium chloride, and 0.5% Pantasept for 1, 5, and 15 min. All tests have been performed three times and all conditions tested in duplicate.

RESULTS

Dry wiping and 1 min soak in 3% hydrogen peroxide were ineffective on all microrganisms. Minuten wipes, 1 min soak in 0.5% benzalkonium chloride or 3% hydrogen peroxide were ineffective on B. subtilis. 0.5% Pantasept soak was effective in 1 min for all microrganisms tested, whereas 3% hydrogen peroxide and 0.5% benzalkonium chloride soaks were effective when performed for at least 5 min. B. subtiliswas the most resistant organism to disinfectant regimes at 1 min time.

CONCLUSIONS

Results of our study demonstrate a relative disinfection efficacy for the different evaluated regimens, provided that correct exposure times are adopted for the chosen disinfectants, a condition difficult to ensure in a busy clinic setting. We conclude that disposable prism tonometry provides a safe alternative to Goldmann tonometry.

Pheno-Genotyping of Salmonella enterica Serotype Enteritidis Isolates Identified in Sicily During a Reemergence Period

After an upward trend paralleling that occurring in most European countries, including Italy, since October 2002 Salmonella enterica serotype Enteritidis (S. Enteritidis) has again gained the first position among outbreak and sporadic human isolates of Salmonella in Sicily. Because phage typing of S. Enteritidis has many technical and epidemiological limitations and molecular methods have proved to be poorly discriminative for this organism, multiple typing, using phage typing together with pulsed field gel electrophoresis (PFGE) and plasmid profiling on a sample of fifty human and poultry isolates identified during the period October 2002 to May 2003 in Sicily, was chosen as the most valuable strategy to explore key features of this new epidemic wave. Although the limited number of strains imposes a cautious interpretation of the results, an apparently increasing phage type heterogeneity has emerged with rise in PT6 as the more striking event. While PFGE has confirmed the findings by other authors about the close genetic homogeneity between PT4 and PT6, plasmid profiling has provided discriminative patterns for PT6 strains. Combined phenotypic and genotypic profiles are necessary for epidemiological studies and public health investigations on S. enteritidis.

[Tuberculin test: proposal for a pre-test risk assessment questionnaire and a standardized evaluation]

Relevance of latent infection in the epidemiology of tuberculosis (TB) is expected to increase in many developed countries. Indeed, many demographic, social and public health changes could contribute to the expansion of groups or communities at significantly higher risk than the general population for infection to Mycobacterium tuberculosis or progression from latent to active disease. Tuberculin skin testing (TB), the gold standard for diagnosis of M. tuberculosis infection, is imperfect and prone to false positive and negative results, unless strictly targeted and carefully standardized for reliable performance and interpretation. This paper proposes a pre-test risk assessment questionnaire and standardized criteria for evaluation of TB test according to international guidelines.

Clonal circulation of Salmonella enterica serotype Heidelberg in Italy?

Phenotypic and genetic characteristics of 21 strains of Salmonella serotype Heidelberg isolated in the years 1999 - 2003 from different sources in Italy were studied. Susceptibility patterns, plasmid analysis, and PFGE were used as epidemiological markers. Although non-homogeneous drug resistance patterns and plasmid profiles had been detected, PFGE patterns suggest the hypothesis of a nationwide clonal spread of this serotype associated with poultry.

Dispersal of methicillin resistant Staphylococcus aureus (MRSA) in a burn intensive care unit

Methicillin resistant Staphylococcus aureus (MRSA) is a pathogen of special concern in intensive care units (ICUs). The burn units are a very susceptible habitat to colonization and infection events by this organism. In this paper isolation of MRSA from a sepsis case and from samples of the care unit air is described, along with simultaneous circulation of two clones of MRSA. Some peculiar epidemiological features of MRSA in burn intensive care wards are confirmed.

Drug resistances in salmonella isolates from animal foods, italy 1998-2000

We investigated the distribution of serotypes and patterns of drug resistance of 206 strains of salmonella isolated in southern Italy in the years 1998-2000 from raw food of animal origin, faeces of food animals and animal feed. To improve knowledge of mobile genetic elements carrying the resistance genes, some molecular features were also investigated within isolates resistant to three or more antibiotics. A high proportion of isolates, 52.2% and 37.7%, respectively, belonging to both Typhimurium and other serotypes of animal origin, proved to be multidrug resistant. The DT104 complex specific multidrug pattern of resistance was quite infrequent among isolates other than Typhimurium, but resistances to nalidixic acid and kanamycin were more frequent within these last ones (36.9% vs. 11.4% and 56.5% vs. 2.2%, respectively). Class I integrons were detected in isolates of Typhimurium and seven different serotypes. The relevance of food animal environment as a drug resistance reservoir and animal food as a potential resistance gene vehicle between the farm and human ecological niches is confirmed by our findings.

Evaluation of recovery methods to detect faecal streptococci in polluted waters

AIMS

This paper compares the faecal streptococci count on 25 samples of polluted waters obtained with three techniques: most probable number (MPN), membrane filtration (MF) and pour plate (PP) methods. Although the PP method is a simple technique, familiar to water bacteriologists, it is not recommended in the international methods.

METHODS AND RESULTS

For the MPN method, azide dextrose broth and ethyl violet azide broth were employed. For the MF technique, Millipore filters were placed onto azide maltose agar (KF agar), while for the PP method, 1 ml of a decimal water dilution was added to (Kennel Faecal) KF medium. Regression analysis and Friedman's ANOVA were performed to determine the relationship between faecal streptococci counts obtained with the three techniques. Statistical analysis of the results showed that the MPN, MF and PP techniques were equally valid with respect to faecal streptococci enumeration in polluted waters.

CONCLUSION

Since the PP method was found to be as good as the other techniques, it may be preferred in polluted waters. It is more economical in terms of both time and materials than the MPN count, and it is as accurate as the MF count.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study indicates that the PP method, although not recommended internationally, is a reliable alternative to MF and MPN.

Genetic diversity of Mycobacterium tuberculosis in Sicily based on spoligotyping and variable number of tandem DNA repeats and comparison with a spoligotyping database for population-based analysis

In a previous study, we proposed to associate spoligotyping and typing with the variable number of tandem DNA repeats (VNTR) as an alternative strategy to IS6110-restriction fragment length polymorphism (RFLP) for molecular epidemiological studies on tuberculosis. The aim of the present study was to further evaluate this PCR-based typing strategy and to describe the population structure of Mycobacterium tuberculosis in another insular setting, Sicily. A collection of 106 DNA samples from M. tuberculosis patient isolates was characterized by spoligotyping and VNTR typing. All isolates were independently genotyped by the standard IS6110-RFLP method, and clustering results between the three methods were compared. The totals for the clustered isolates were, respectively, 15, 60, and 82% by IS6110-RFLP, spoligotyping, and VNTR typing. The most frequent spoligotype included type 42 that missed spacers 21 to 24 and spacers 33 to 36 and derived types 33, 213, and 273 that, together represented as much as 26% of all isolates, whereas the Haarlem clade of strains (types 47 and 50, VNTR allele 32333) accounted for 9% of the total strains. The combination of spoligotyping and VNTR typing results reduced the number of clusters to 43% but remained superior to the level of IS6110-RFLP clustering (ca. 15%). All but one IS6110-defined cluster were identified by the combination of spoligotyping and VNTR clustering results, whereas 9 of 15 spoligotyping-defined clusters could be further subdivided by IS6110-RFLP. Reinterpretation of previous IS6110-RFLP results in the light of spoligotyping-VNTR typing results allowed us to detect an additional cluster that was previously missed. Although less discriminative than IS6110-RFLP, our results suggest that the use of the combination of spoligotyping and VNTR typing is a good screening strategy for detecting epidemiological links for the study of tuberculosis epidemiology at the molecular level.

Presence of class I integrons in multidrug-resistant, low-prevalence Salmonella serotypes, Italy

In 1997 to 1999, we detected class I integrons in multidrug-resistant isolates of Salmonella enterica serovars Anatum, Blockley, Brandenburg, Bredeney, Derby, Heidelberg, Livingstone, Newport, Ohio, Panama, Paratyphi B, Saintpaul, Sandiego, and Stanley.

Endemic presence of Salmonella enterica serotype Cerro in southern Italy

Molecular typing of salmonella strains isolated between 1997 and 1999 in southern Italy and carried out by the Southern Italy Centre for Enteric Pathogens, has shown a high frequency of Salmonella enterica serotype Cerro. This serotype is extremely rare i

Surveillance of multidrug-resistant strains of Salmonella enterica serotype Typhimurium in southern Italy in the years 1992-1997

Spread of multidrug-resistant strains of Salmonella enterica serotype Typhimurium (S. typhimurium) is increasingly reported worldwide. The presence of a pattern of resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline (ACSSuT), in some cases associated to trimethoprim and infrequently to quinolones, is of particular concern. This resistance pattern appears to be chromosomally encoded and, in most epidemiological studies, closely related to definitive type 104 (DT104). In southern Italy multidrug-resistant isolates of S. typhimurium had been identified since 1980, but only during 1992 S. typhimurium strains with chromosomally encoded drug resistance were first isolated from domestic animals. One hundred fifty-five isolates--52.5% of the multidrug-resistant strains identified in the years 1992-1997--were submitted to phage typing and plasmid profile analysis. Ribotyping was also performed in comparison with a random sample of 150 strains susceptible or resistant to three or less antibiotics identified in the same interval of time. Four ribotypes (RTs)--1, 5, 8, and 48--included approximately 90% of the multiresistant strains, RT8 accounting for 61.2%. Phage type (PT) 193 is the most prevalent phage type. Phage typing and ribotyping suggest that few bacterial clones are involved in spread of multidrug-resistant S. typhimurium strains in southern Italy.

Antimicrobial resistance in Salmonella enteritidis, southern Italy, 1990-1998

During 1990 to 1998, we identified multidrug-resistant isolates of Salmonella Enteritidis in southern Italy. Plasmids containing class I integrons and codifying for synthesis of extended- spectrum beta-lactamases were detected. Active surveillance for resistance to antimicrobial agents is needed to guard against the possible spread of resistant clones.

Epidemiological study of tuberculosis in Palermo, Italy: IS6110 fingerprinting of Mycobacterium tuberculosis strains isolated in the years 1994-1998

In some industrialized countries reemergence of tuberculosis has been recorded. Most cases are thought to be caused by reactivation of infections that had been acquired many years before, but in some geographical areas up to 40% of diagnosed infections have been estimated to be newly acquired, based on the results of molecular epidemiological methods. Restriction fragment length polymorphism of the insertion sequence IS6110 of Mycobacterium tuberculosis has been widely used to evaluate epidemiological patterns of transmission in various communities. We have used IS6110 fingerprinting to analyze 101 strains which were isolated between June 1994 and June 1998 from 95 inhabitants of the province of Palermo, Italy, an area with an endemic rate for tuberculosis ranging between 5.1 and 8.0 per 100,000 persons in the last 5 years. 89 different patterns have been obtained, 87.4% of the patients were infected by presumably unrelated isolates. Six microepidemics were also recognized. These data suggest that reactivation largely exceeds recent infection.

Outbreak of Salmonella enteritis bongori 48:z35:- in Sicily

Salmonella bongori 48:z 35 :- was first isolated from a lizard in Chad in 1966 and was classified as a biochemically atypical strain of the subgenus I of Kauffmann. Successively, some additional strains with different antigenic formulas but similar bioche

Detection of Salmonella spp. in food by a rapid PCR-hybridization procedure

A rapid and sensitive PCR-hybridization procedure for detection of Salmonella serovars in food samples was developed. This method is based on three subsequent steps: (1) extraction of nucleic acids from a 2 ml aliquot of the pre-enrichment medium used for the conventional culture method after 6 h of incubation at 37 degrees C; (2) amplification with primers selected from the sequences of invE and invA genes; (3) Southern blot and hybridization with a biotin labeled oligonucleotide probe. The entire procedure requires 30 h. The PCR-hybridization assay was able to detect as little as 50 fg of purified chromosomal DNA of S. typhimurium and 0.2 cfu g-1 of an artificially contaminated food sample. Of 245 food samples analyzed by culture and PCR-hybridization, 20 were positive by both methods and 16 were positive by PCR-hybridization only. None of the 209 PCR-negative samples tested positive by culture. The sensitivity, specificity, alpha and beta error values of the results of the PCR-hybridization procedure, compared with those of culture, were 100, 92.9, 0 and 7.1%, respectively. These results indicate that a short pre-enrichment and PCR-hybridization could be used as a screening test for the detection of Salmonella in food samples.

A community-based outbreak of Salmonella enterica serotype Typhimurium associated with salami consumption in Northern Italy

An outbreak of Salmonella enterica serotype Typhimurium belonging to phage type (PT) 193 occurred in autumn 1995 and involved 83 individuals in a large area of Northern Italy (Lombardy Region). Epidemiological and microbiological investigations of strains isolated from clinical and food specimens revealed that the vehicle was a batch of salami, produced on 4 September 1995 by a local firm. The outbreak was contained when the batch was withdrawn from sale. Insufficient ripening of the salami had allowed the salmonella to survive, emphasizing the need to define criteria for the ripening process of foods such as salami.

A foodborne outbreak of Salmonella enteritidis vehicled by duck and hen eggs in southern Italy

A foodborne outbreak of Salmonella enteritidis PT4 is described. This microrganism was detected in a home-made dessert, in the duck and hen eggs used for its preparation and in faecal samples of six persons involved in the outbreak. PCR ribotyping revealed that all the strains shared a profile of S. enteritidis never previously identified in southern Italy and quite different from that of the strains simultaneously isolated in the same geographic area. The possible identification of a clonal variant of S. enteritidis PT4 host-adapted to duck is hypothesized.

Epidemiological analysis of strains of Salmonella enterica serotype Enteritidis from foodborne outbreaks occurring in Italy, 1980-1994

Polymerase chain reaction (PCR-) ribotyping was performed on 243 strains of Salmonella enterica serotype Enteritidis isolated during the years 1980-1994 from 58 foodborne outbreaks occurring in different regions of Italy. The majority (37) of the outbreaks were attributed to phage type (PT) 4, followed by PT1 (seven outbreaks); the latter was identified in 1993 in Italy in epidemic strains of Enteritidis. In eight cases more than one phage type was recognised from a single event. Nine PCR-ribotypes (PCR-RTs) were detected, with a strong prevalence of PCR-RTs f7 and e5 (23 and 21 outbreaks, respectively). In two instances two distinct PCR-RTs were identified within strains from a single outbreak. All but one of the PT1 outbreaks were caused by PCR-RT f7, whereas PT4 outbreaks could be subdivided into six subsets. Clustering of isolates was consistent with data obtained from epidemiological investigations. PCR-ribotyping proved to be an effective and reliable tool for subtyping isolates of Enteritidis belonging to the most frequent phage types. Nevertheless, in terms of laboratory expertise and lack of inter-laboratory standardisation, this typing technique is best suited for reference laboratories.

Epidemiology of Salmonella enterica serotype Enteritidis infections in southern Italy during the years 1980-1994

Increased frequency of identification of Salmonella enterica serotype Enteritidis as a causative agent of sporadic and epidemic cases of infection in humans, along with isolation in many parts of the world of strains belonging in a large proportion to a few phage types, has made phage typing alone inadequate for epidemiological investigations. In southern Italy the epidemic increase in isolation of S. enterica serotype Enteritidis that has been observed since 1990 has been associated in approximately 80% of isolates with phage type 4 (PT-4), in agreement with the epidemiological observations from other European countries. We have applied polymerase chain reaction (PCR) ribotyping in association with phage typing to a sample of non-outbreak strains and to all the outbreak strains sent for identification and typing to the Southern Italy Centre for Enterobacterial Pathogens between 1980 and 1994 from hospital and public health laboratories. This technique identified 15 distinct profiles among the 405 strains examined. Whereas a single profile (PCR ribotype a1) appeared to be closely related to PT-8, and to characterize a high percentage of the strains circulating during the early non-epidemic years (1980-1985), 11 patterns were recognizable within PT-4, and 5 within PT-1. Some of these apparently emerged after 1990. This subdivision enabled attribution of the epidemic circulation of PT-4 to multiple clones of S. enterica serotype Enteritidis.

Phage types and ribotypes of Salmonella enteritidis in southern Italy

Differently from other European countries, Southern Italy was affected by a considerable increase in human infections due to Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) only after 1990. On the present investigation, two groups of S. Enteritidis strains isolated during the low-incidence period 1980-1984 and the epidemic period 1990-1993, respectively, have been submitted to phage-typing and ribotyping in order to ascertain whether the epidemic increase was determined by the spread of a foreign bacterial clone or not. Among the 150 isolates relative to the aforesaid two periods, 12 different phage types (PTs) were observed. PT4 was the most common phage type among the strains isolated in 1980-1984 (61%) as well as in those of the epidemic period 1990-1993 (72%). PT8 was the second most frequent (33%) phage type in 1980-1984. It was substituted by PT1 (19%) in the 1990-1993 period. Analysis of rDNA patterns obtained after Hinc II digestions and Escherichia coli rRNA hybridizations showed 8 different patterns, A to H. The great majority of the strains studied (140 isolates, 93%) belonged to the ribotype A, showing a similar frequency both in 1980-1984 (36 of 39, 92%) and in 19901993 (104 of 111, 94%). The predominance of PT4 and ribotype A among both preepidemic and epidemic strains is in agreement with the hypothesis that host genetic diversity decline and modern farming practices in the poultry industry have facilitated a widespread dissemination of preexisting endemic strains. This hypothesis urges to plan new strategies in preventing S. Enteritidis infections.

Epidemiological evaluation by PCR ribotyping of sporadic and outbreak-associated strains of Salmonella enterica serotype Typhimurium

Salmonella enterica serotype Typhimurium has a very large diffusion worldwide within human and non-human hosts. The simultaneous circulation in the same geographical areas of many bacterial clones requires the use of reliable, reproducible and highly discriminatory typing techniques for epidemiological studies. Molecular biological methods, such as plasmid profile analysis, restriction endonuclease digestion of plasmid and chromosomal DNA and hybridization-based procedures have proven to be useful tools for strain differentiation. More recently, detection of polymorphisms in the intergenic spacer regions of rRNA genes by polymerase chain reaction (PCR ribotyping) has been successfully applied to characterize bacterial strains. In this study, PCR ribotyping was performed on 45 epidemiologically related and unrelated strains of S. enterica serotype Typhimurium isolated in northern and southern Italy during 1992. Isolates were simultaneously characterized by traditional ribotyping. Results suggest that PCR ribotyping is a rapid, easy-to-perform and reproducible typing method able to determine relatedness among isolates of this serotype.

Epidemic dissemination of Salmonella enterica spp. enterica serovar Bovismorbificans in southern Italy in the years 1989-1991

Epidemic strains of Salmonella enterica subsp. enterica serovar Bovismorbificans isolated in southern Italy during the years 1989-1991 were submitted to a molecular epidemiological study in comparison with isolates identified in the years 1980-1988 in the same geographic area. Genomic DNA fragments obtained by digestion with BglI or Eco RI hybridized with Escherichia coli rRNA to produce three distinct, but highly related patterns. Ribotype 1, which had never been identified before 1989, was found to characterize most of the strains identified between 1989 and 1991. Such a finding supports the hypothesis of emergence and spread of a new bacterial clone associated with the increased number of human infections reported in the same years in southern Italy.

Epidemiology of Salmonella typhimurium: ribosomal DNA analysis of strains from human and animal sources

Salmonella typhimurium is the most frequently identified serovar of Salmonella in Italy. This serovar is characterized by the widespread dissemination among human and non-human sources of phenotypically and genetically well-differentiated clones. In this study 457 strains of S. typhimurium isolated in Italy in the years 1982-91 from human and animal sources were submitted to characterization by the rDNA fingerprinting technique. Application of this typing method, after digestion of chromosomal DNA with HincII endonuclease, confirmed the greatest genetic differentiation of clones of S. typhimurium, allowing reliable identification of 45 rDNA patterns linked into 9 major clusters. rDNA pattern clusters or ribotypes specific to man were not recognized, whereas some rDNA patterns were characteristically related to ducks, pigeons and pet birds. The ribotyping results for isolates from animal hosts suggest that pig and cattle are the main source of human infection.

rRNA gene restriction patterns and biotypes of Shigella sonnei

Shigella sonnei is a major agent of diarrhoeal disease in developed as well as in developing countries. Several phenotypic methods to define strain differences have been applied to this species of Shigella including, more recently, analysis of extrachromosomal and chromosomal DNA. In this study, 432 endemic and epidemic strains isolated between 1975 and 1991 in Italy, France and Switzerland were submitted to rRNA gene restriction pattern analysis, after digestion of whole-cell DNA by Hinc II, and to concomitant biotyping. Thirteen ribotypes, H1 to H13, and five biotypes, a, d, e, f, g, were detected. Ninety-five percent of the sporadic strains were assigned to ribotypes H1 to H4, which could be subtyped, except for H4, in different biotypes. Strains from each of seven different outbreaks had indistinguishable ribotype-biotype patterns. In contrast, 65 strains, isolated in Sicily in 1980 over an extended period of apparently epidemic increase of isolations and which had previously been considered to be a single bacterial clone on the basis of resistance pattern and phage type, were found to belong to two different and scarcely related ribotypes. Ribotyping and biochemical subtyping appear to be a useful epidemiological tool in studies on the circulation and distribution of strains of S. sonnei.

The changing pattern of human immunodeficiency virus type 1 infection in intravenous drug users. Results of a six-year seroprevalence study in Palermo, Italy

A cross-sectional seroepidemiologic study was carried out between 1985 and 1990 in 1,567 heterosexual intravenous drug users who had been seen at the AIDS Regional Reference Center in Palermo, Italy, to evaluate the rate of human immunodeficiency virus type 1 (HIV-1) seroprevalence in this group and its long-term trend. Sixty serum samples collected from drug users in 1980 and 1983, before the founding of the Center (1985), were tested as well. Some demographic and behavioral risk factors were studied in a subgroup of intravenous drug users enrolled in 1985, 1987, and 1990 for their possible association with HIV-1. These factors were also studied in relation to hepatitis B virus infection, since both viruses share the same modes of spread. These drug users had a higher prevalence of markers for hepatitis B virus than of HIV-1 antibodies, and the prevalence rates in sera collected declined over time for both infections. The presence of both antibodies to HIV-1 and markers for hepatitis B virus was independently associated with the age of the drug user, the duration of drug use, and the year of serum collection. Antibodies to HIV-1 were observed more frequently in females than in males. No relation was found between education or employment status and the presence of HIV-1 antibodies or hepatitis B virus markers. Although new HIV-1 infections still occur, the decline in seroprevalence observed at the end of the 1980s might be related to modifications in social behavior among newer drug users, partial exhaustion of the susceptible population, and increasing risk awareness in more experienced users.

rDNA fingerprinting as a tool in epidemiological analysis of Salmonella typhi infections

Characterization of 169 strains of Salmonella typhi of phage types C1, C4, D1 and D9 isolated in 1975-88 was carried out by rDNA gene restriction pattern analysis. Twenty-four isolates had been recovered during four large waterbone outbreaks in the last 20 years in Sicily; 145 strains, isolated from apparently sporadic cases of infection in Southern Italy in the same period of time, were also examined. Application of rRNA-DNA hybridization technique after digestion of chromosomal DNA with Cla I showed the identity of patterns of the epidemic strains of phage types C1 and D1, confirming attribution of the outbreaks to single bacterial clones. Patterns of the two available strains of lysotype D9 were slightly different, whilst the 12 epidemic strains of phage type C4 could be assigned to two distinct patterns scarcely related to each other and, consequently, to two different clones. A considerable heterogeneity was detected among all apparently sporadic isolates of the four phage types under study. This fingerprinting method appears a reliable tool to complement phage typing in characterizing isolates of S. typhi. In particular, epidemiological features of spread of this salmonella serovar in areas, where simultaneous circulation of indigenous and imported strains occurs, can be elucidated.

Reemergence of Shigella dysenteriae type 2 in Sicily: an epidemiological evaluation

Three strains of Shigella dysenteriae type 2 were isolated from a small household outbreak which occurred in Palermo, Sicily, during summer 1990. Two isolates were recovered from hospitalized patients and one from an asymptomatic carrier. The infection could not be associated with travel to foreign countries or contact with travellers returned from abroad. Since 1953 S. dysenteriae has been never isolated in Southern Italy. The isolates from dysentery cases were susceptible to antibiotics and carried a plasmid of 120 MDa associated with a small cryptic plasmid; in contrast, the strain isolated from the healthy carrier contained an additional plasmid of approximately 40 MDa, which codified for resistance to ampicillin, streptomycin, sulfamethoxazole and trimethoprim. All strains showed some atypical biochemical properties, but their rRNA-DNA patterns of hybridization were closely similar to that of the reference strains of type 2 and easily distinguishable from those of the other types of non-Shiga bacillus reference strains. Epidemiological isolation features of these strains suggest a possible circulation of this Shigella species in Sicily. Genetic characterization of these strains may be useful for surveillance of infections by this organism.