Outbreak of Salmonella enteritidis phage type 1B associated with frozen pre-cooked chicken cubes, Finland 2012.

In August to October 2012, a nationwide outbreak of Salmonella enteritidis phase type (PT) 1B with 53 cases occurred in Finland. Hypothesis generating interviews pointed toward ready-to-eat chicken salad from a Finnish company and at the same time Estonian authorities informed of a S. enteritidis PT 1B outbreak linked to chicken wrap prepared at an Estonian restaurant. We found that chicken salad was associated with the infection (odds ratio (OR) 16·1, 95% confidence interval (CI) 1·7-148·7 for consumption and OR 17·5. 95% CI 4·0-76·0 for purchase). The frozen pre-cooked chicken cubes used in Finnish salad and in Estonian wraps were traced back to a production plant in China. Great Britain made two Rapid Alert Systems for Food and Feed notifications on chicken cubes imported to the UK from the same Chinese production plant. Microbiological investigation confirmed that the patient isolates in Estonia and in Finland were indistinguishable from the strains isolated from chicken cubes in Estonia and in the UK. We recommend that despite certificates for tested Salmonella, food items should be analyzed when Salmonella contamination in outbreak investigations is suspected. In outbreak investigations, electronically implemented case-case study saves time, effort, and money compared with case-control study.

Severe Outbreak of Sorbitol-Fermenting Escherichia coli O157 via Unpasteurized Milk and Farm Visits, Finland 2012.

Shiga toxin-producing, sorbitol-fermenting Escherichia coli O157 (SF O157) has emerged as a cause of severe human illness. Despite frequent human findings, its transmission routes and reservoirs remain largely unknown. Foodborne transmission and reservoir in cattle have been suspected, but with limited supporting evidence. This study describes the outbreak of SF O157 that occurred in Finland in 2012. The outbreak originated from a recreational farm selling unpasteurized milk, as revealed by epidemiologic and microbiological investigations, and involved six hospitalized children and two asymptomatic adults with culture-confirmed infection. An identical strain of SF O157 was isolated from patients, cattle and the farm environment, and epidemiologic analysis suggested unpasteurized milk as the vehicle of transmission. This study reports the first milkborne outbreak of SF O157, provides supporting evidence of cattle as a reservoir and highlights the health risks related to the consumption of unpasteurized milk.

Outbreak of hospital-acquired gastroenteritis and invasive infection caused by Listeria monocytogenes, Finland, 2012.

During one week in July 2012, two patients from the same ward at the municipal hospital in Vaasa, Finland, were diagnosed with septicaemia caused by Listeria monocytogenes. An outbreak investigation revealed eight concomitant cases of febrile gastroenteritis caused by L. monocytogenes on the same ward. Median age of the cases was 82 years and median incubation time for listerial gastroenteritis was 21 h (range 9-107). An additional 10 cases of invasive listeriosis caused by the same outbreak strain were identified across the whole country during the summer of 2012. Environmental investigation at the affected municipal hospital ward revealed ready-sliced meat jelly as the suspected source of the infection. During inspection of the meat jelly production plant, one pooled sample taken from a floor drain and a trolley wheel in the food processing environment was positive for the outbreak strain of L. monocytogenes. After the producer stopped the production of meat jelly, no further cases of listeriosis with the outbreak strain were identified via nationwide surveillance.

Multinational outbreak of Salmonella Enteritidis infection during an international youth ice hockey competition in Riga, Latvia, preliminary report, March and April 2015.

A multinational outbreak of salmonellosis linked to the Riga Cup 2015 junior ice-hockey competition was detected by the Finnish health authorities in mid-April and immediately notified at the European Union level. This prompted an international outbreak investigation supported by the European Centre for Disease Prevention and Control. As of 8 May 2015, seven countries have reported 214 confirmed and suspected cases, among which 122 from Finland. The search for the source of the outbreak is ongoing.

Outbreak analysis and typing of MRSA isolates by automated repetitive-sequence-based PCR in a region with multiple strain types causing epidemics.

The usefulness and performance of repetitive-sequence-based polymerase chain reaction (rep-PCR), the DiversiLab system, in the epidemiological surveillance for methicillin-resistant Staphylococcus aureus (MRSA) strain typing was assessed. MRSA isolates from five distinct outbreaks with precise epidemiological data (n = 69) and from the culture collection of well-characterized MRSA strains (n = 132) consisting of 35 spa and 23 pulsed-field gel electrophoresis (PFGE) types were analyzed. The typing results of the DiversiLab system in outbreak analysis were compared to the spa and PFGE typing methods. The DiversiLab system proved to be a reliable tool for the rapid first-line typing of MRSA isolates, showing a good reliability in distinguishing MRSA strains in an area where several MRSA types were causing epidemics. This, however, required that the automatic clustering was combined with manual interpretation using the pattern overlay function when the strain types showing high similarity were clustered together. All outbreaks were distinguished with the DiversiLab system and the PFGE method, but not with the spa typing method. The overall discriminatory power of the DiversiLab system in differentiating diverse MRSA strains proved to be good. We also demonstrated that, in addition to the genetic relatedness analysis of MRSA strains, it is important to obtain accurate epidemiological information in order to perform reliable epidemiological surveillance studies.

Rapid confirmation of suspected methicillin-resistant Staphylococcus aureus colonies on chromogenic agars by a new commercial PCR assay, the GenomEra MRSA/SA Diagnose.

A new automated closed tube PCR assay, the GenomEra(™) MRSA/SA Diagnose (Abacus Diagnostica Oy, Finland) was evaluated for rapid confirmation of methicillin-resistant Staphylococcus aureus (MRSA) from cultured screening specimens. The ability of the assay to detect genotypically different MRSA strains was studied with a collection of 304 MRSA isolates covering 68 spa types. The specificity was investigated with a collection of 146 non-MRSA staphylococcus isolates. The usefulness of the assay for clinical purposes was assessed by a sequential combination of MRSA screening culture and confirmation of the colonies with the GenomEra MRSA/SA Diagnose assay. A total of 145 suspected MRSA colonies on chromogenic plates were analyzed this way. All MRSA isolates from the culture collection and from the clinical screening specimens were confirmed as MRSA with the GenomEra MRSA/SA Diagnose assay and none of the non-MRSA staphylococci caused false-positive results, which indicates both sensitivity and specificity of 100%. The combination of GenomEra MRSA/SA Diagnose with preceding culture on selective MRSA agar permitted MRSA confirmation within 24 h. This practice offers a reliable and quick detection of MRSA that is also suitable in areas where several strain types cause epidemics.

Evaluation of the TPX MRSA assay for the detection of methicillin-resistant Staphylococcus aureus.

The aim of this study was to evaluate a new type of assay for the phenotypic detection of methicillin-resistant Staphylococcus aureus (MRSA). The assay is based on a point-of-care compatible two-photon excitation fluorescence detection technology (TPX). A collection of 243 epidemic MRSA isolates was tested in addition to 138 sporadic MRSA and 101 negative control strains. The assay proved to be both sensitive (97.9%) and specific (94.1%) in the identification of MRSA, with adequate positive (98.4%) and negative (92.2%) predictive values. The time required for obtaining a positive test result was less than 14 h for 99.0% of the MRSA true-positive samples. After a test run, the selectively enriched reaction mixtures may be recovered and further studied by molecular or standard phenotypic methods. The main benefits of the TPX methodology include a simple assay procedure, low reagent consumption, and a high-throughput capacity.

Adapting spa typing for national laboratory-based surveillance of methicillin-resistant Staphylococcus aureus.

Laboratory-based surveillance of methicillin-resistant Staphylococcus aureus (MRSA) monitors the baseline occurrence of different genotypes and identifies strains and transmission chains responsible for outbreaks. The consequences of substituting pulsed-field gel electrophoresis (PFGE) with spa typing as a first-line typing method were analyzed by typing 589 strains isolated between 1997 and 2006, with a focus on both short- and long-term correspondence between the PFGE and spa typing results. The study, covering these ten years, included all Finnish MRSA blood isolates and representatives of the two most prevalent MRSA strains (PFGE types FIN-4 and FIN-16) in Finland. In addition, all sporadic isolates from 2006 were included. spa typing was more expensive but approximately four times faster to perform than PFGE. Nearly 90% of FIN-4 and FIN-16 isolates showed consistent spa types, t172 and t067, respectively. spa typing predicted the PFGE result of the blood isolates by a Wallace coefficient of 0.9009, recognized internationally successful strains (t041, t067) to be common also in Finland, and identified a separate cluster of isolates, also related in time and place among the FIN-4 strains. Additional typing by another method was needed to provide adequate discrimination or to characterize isolates with a newly recognized spa type in Finland.

Evaluation of a commercial MRSA assay when multiple MRSA strains are causing epidemics.

Rapid and reliable diagnostic methods are needed to control methicillin-resistant Staphylococcus aureus (MRSA) transmission. We studied the BD GeneOhm MRSA Assay which is based on one specific amplification product at the junction of the right extremity sequence of the staphylococcal cassette chromosome mec (SCCmec) and the chromosomal sequence of orfX of S. aureus. The test was applied on 95 clinical isolates in Finland: 83% were positive. The isolates giving negative results represented several pulsed-field gel electrophoresis (PFGE) types and harboured SCCmec types IV, V, VI or were new types with different combinations of ccr genes.

Molecular characterization of methicillin-resistant Staphylococcus epidermidis strains from bacteraemic patients.

In order to study the clonality of clinical methicillin-resistant Staphylococcus epidermidis (MRSE) strains and their staphylococcal cassette chromosome mec (SCCmec) elements, 60 isolates of MRSE from bacteraemic patients in three units of the Helsinki University Hospital, Finland were selected, covering the periods 1990-1993 and 1997-1998. The MRSE strains were analysed by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing and SCCmec typing. Eleven PFGE types (FIN-SE-1-11) with sequence type ST2 (clonal complex 2; CC2) were identified. The previously established methicillin-resistant Staphylococcus aureus SCCmec criteria were applied to name the MRSE SCCmec complexes, and it was found that 7% of the isolates carried SCCmec type IA (ccrA1, class B), whereas the majority (93%) yielded six non-typeable SCCmec PCR patterns (P1-P6). Within each SCCmec PCR pattern, two ccr recombinase genes (ccrA2 and ccrA3) and two mec gene complexes (class A and class B) were detected. In addition, the ccrC gene was associated with three of the six patterns. In conclusion, the MRSE strains were genetically related to each other (ST2) but their SCCmec complexes were unique combinations of elements previously recognized among SCCmec types III and IV.

Clonality of epidemic methicillin-resistant Staphylococcus aureus strains in Finland as defined by several molecular methods.

In Finland, the incidence of methicillin-resistant Staphylococcus aureus (MRSA) strains has increased ten fold within the last decade. In order to follow the changing epidemiology of MRSA, accurate typing of S. aureus strains is important. The purpose of this study was to reanalyse 44 previously recognised Finnish epidemic MRSA strains (EMRSA) by several molecular typing methods and to revise their nomenclature. The 44 EMRSA strains were grouped into 26 pulsed-field gel electrophoresis (PFGE) clusters, 20 multi locus sequence typing (MLST) sequence types (ST) belonging to 12 clonal complexes (CC) of which CC8 was the most prevalent, and 27 spa types belonging to four clonal complexes. The staphylococcal cassette chromosome mec (SCCmec) type IV was predominant, and 48% of the strains were nonmultiresistant to antibiotics. The discriminatory power of PFGE clusters, MLST, and spa typing was high. The overall concordance values of typing methods differed when assessed by two different methods. Adjusted Rand coefficient provided fairly low correlations for all comparisons. However, spa type was able to efficiently predict types and clonal complexes of most of the other methods with high probability (> or =80%).

Panton-Valentine leukocidin genes and staphylococcal chromosomal cassette mec types amongst Finnish community-acquired methicillin-resistant Staphylococcus aureus strains, 1997-1999.

Methicillin-resistant Staphylococcus aureus (MRSA) strains from Finland covering years 1997-1999 were studied for the presence of Panton-Valentine leukocidin (PVL) gene loci, and the clinically well-defined community-acquired MRSA (CA-MRSA) strains (n = 108) also for staphylococcal chromosomal cassette mec (SCCmec) and multilocus sequence types (MLST). Only a minority (12%) of the CA-MRSA strains contained the PVL gene loci and possessed genotypes formerly described as typical to CA-MRSA strains. The majority of these strains were heterogenous by MLST and pulsed-field gel electrophoresis (PFGE) analysis but, however, harboured the SCCmec cassette type IV. In conclusion, it seems doubtful to consider only molecular characteristics such as the presence of PVL genes as definite markers for CA-MRSA strains.

Comparison of genotypes of methicillin-resistant and methicillin-sensitive Staphylococcus aureus in Finland.

The frequency of horizontal transfer of the staphylococcal cassette chromosome mec to methicillin-susceptible Staphylococcus aureus is unknown. In order to gain more information regarding this frequency in Finland, the genotypes of 299 clinical methicillin-sensitive Staphylococcus aureus isolates were compared to representatives of 24 epidemic methicillin-resistant Staphylococcus aureus genotypes. Sixty-eight percent of the methicillin-sensitive isolates had a genotype similar to eight of the epidemic methicillin-resistant strains. The remaining isolates (32%) showed 22 different genotypes. The results indicate that, in Finland, several methicillin-sensitive Staphylococcus aureus genotypes may have acquired the staphylococcal cassette chromosome mec.

Bacterial genotype affects the manifestation and persistence of bovine Staphylococcus aureus intramammary infection.

Two-hundred seventeen Staphylococcus aureus isolates from 116 dairy cows with intramammary infections were analyzed by pulsed-field gel electrophoresis to study the association between symptom severity, persistence of infection, and bacterial genotype. Among five main genotypes infecting 90% of the cows, one was associated with severe clinical symptoms but reduced persistence.

Changing epidemiology of methicillin-resistant Staphylococcus aureus in Finland.

Data on methicillin-resistant Staphylococcus aureus (MRSA) cases notified to the National Infectious Disease Register (NIDR) and antibiotic resistance profiles of MRSA isolates sent to the national reference laboratory between 1997 and 2002 were analysed. In addition, the diagnostic methods used for MRSA identification in Finnish microbiology laboratories, the number of MRSA screening specimens studied, and the MRSA situation in long-term care facilities in 2001 were reviewed. MRSA cases notified to the NIDR rose from 120 in 1997 to 597 in 2002 (from 2.3 to 11.5 cases per 100,000 population). The increase was greatest in elderly people and outside Helsinki metropolitan area, in the districts where the proportion of non-multiresistant strains was most prominent. The National Committee for Clinical Laboratory Standard's guidelines for the oxacillin disk diffusion test were followed, except for the incubation temperature and time, which may have hindered detection of some MRSA strains. There was a wide geographic variation in the rates of MRSA, but this was not related to screening activity. MRSA isolates from long-term facilities accounted for more than half of the notifications to the NIDR in 2001.

Recognition of two groups of methicillin-resistant Staphylococcus aureus strains based on epidemiology, antimicrobial susceptibility, hypervariable-region type, and ribotype in Finland.

Epidemiological evidence suggests that some methicillin-resistant Staphylococcus aureus (MRSA) strains are more prone to dissemination than others. We studied 72 MRSA strains, collected through nationwide MRSA surveillance in 1992 through 1999 and known to be either (i) sporadic, (ii) local outbreak strains spread within one hospital, or (iii) epidemic strains spread among hospitals, by antimicrobial susceptibility testing, hybridization of the mec hypervariable region (HVR), and ribotyping. Our results show that two main groups can be identified among these strains. The first group includes mainly nonepidemic, nonmultiresistant MRSA strains showing a specific mec HVR hybridization pattern, A, in combination with a variety of ribotypes. The other group includes multiresistant strains with mec HVR hybridization pattern B or C in association with closely related ribotype a or b. Sixty-four percent (9 of 14) of Finnish epidemic MRSA strains belong to the latter group. These findings support the existence of differences in epidemic potential among MRSA strains.

Eradication of methicillin-resistant Staphylococcus aureus from a health center ward and associated nursing home.

BACKGROUND: Long-term health care facilities have been recognized as reservoirs of multiresistant bacterial strains, especially methicillin-resistant Staphylococcus aureus (MRSA). Efforts to control MRSA in this setting usually have been only partially effective. We describe herein the eradication of epidemic MRSA from a Finnish health care center ward and affiliated nursing home. METHODS: The methods to control MRSA included (1) contact isolation precautions, (2) screening for asymptomatic carriage, (3) eradication of carriage, and (4) education of staff on hygienic measures. The first 6 patients with MRSA-positive findings were referred without delay to the Infectious Diseases Unit of the adjacent university hospital for eradication treatment. Later, an isolation unit of 6 rooms was founded in the health care center, where the MRSA-colonized patients were nursed as a separate cohort until they, in succession, were referred to the Infectious Diseases Unit for decolonization. RESULTS: From May 20 through August 17, 1993, the epidemic MRSA strain was isolated from 8 long-term patients on the 40-bed ward of the health care center, 4 of the 59 residents of the nursing home, and 1 member of the staff. Eradication of carriage was successful in all except 1 patient with dementia, who was nursed in contact isolation in the health care center until his death 21 months later. CONCLUSIONS: It is possible to eradicate MRSA from a long-term health care facility even after 13 cases by applying strict control measures. Our experience may be valuable in the future decision-making process for control of new and more challenging multiresistant bacteria, eg, vancomycin-resistant strains of MRSA.

Molecular epidemiology of methicillin-resistant Staphylococcus aureus in Finland.

This study reports the recent trends in the occurrence of methicillin-resistant Staphylococcus aureus in Finland, with special focus on characterization of the strains linked to interhospital epidemics and local outbreaks. Between 1981 and 1997, the annual number of methicillin-resistant Staphylococcus aureus isolations ranged from 89 to 272. Of all blood isolates of Staphylococcus aureus reported to the National Infectious Disease Register during the period 1995-97 (n = 2049), only six were resistant to methicillin. Between 1992 and 1997, typing analysis by various methods (i.e., antibiogram, phage typing, ribotyping, and pulsed-field gel electrophoresis) identified 18 different strains capable of causing intrahospital outbreaks or interhospital epidemics. These 18 strains were separated into 13 different ribotypes and 14 major pulsed-field gel electrophoresis types. Multiresistance was investigated as a possible marker for epidemicity. Eight of the ten interhospitally spread strains were multiresistant compared to only three of the eight intrahospitally spread outbreak strains. More than one-third of the epidemic and local outbreak strains were suspected to be of foreign origin. The majority (6 of 10) of the epidemics were localized in southern and western Finland, and the largest epidemic, which occurred in the Helsinki metropolitan area, involved over 200 persons. Thus far, the epidemics have remained primarily intracity problems, and only two strains have become endemic.

vanA and vanB incorporate into an endemic ampicillin-resistant vancomycin-sensitive Enterococcus faecium strain: effect on interpretation of clonality.

Clonal spread and horizontal transfer in the spread of vancomycin resistance genes were investigated. Multiplex PCR, pulsed-field gel electrophoresis (PFGE), hybridization of enterococcal plasmids with the vanA and vanB probes, and sequencing of a fragment of vanB were used in the analysis. Before May 1996, 12 vancomycin-resistant Enterococcus faecium (VRE) isolates were found in Finland. Between May 1996 and October 1997, 156 VRE isolates were found in the Helsinki area. Between December 1997 and April 1998, fecal samples from 359 patients were cultured for VRE. One new case of colonization with VRE was found. During the outbreak period, 88% (137 of 155) of the VRE isolates belonged to two strains (VRE types I and II), as determined by PFGE. Each VRE type I isolate possessed vanB, and five isolates also had vanA. Of the 34 VRE type II isolates, 27 possessed vanA and 7 possessed vanB. Fifteen of 21 (71%) ampicillin-resistant, vancomycin-sensitive E. faecium (VSE) isolates found during and after the outbreak period in one ward were also of type II. Two VSE type II isolates were found in the hospital before the outbreak in 1995. By PFGE, the three groups (vanA, vanB, or no van gene) of type II shared the same band differences with the main type of VRE type II with vanA. None of the differences was specific to or determinative for any of the groups. Our material suggests that vanA and vanB incorporate into an endemic ampicillin-resistant VSE strain.