Andreas Baumgartner

Mycobacterium avium subspecies paratuberculosis and Crohn's disease: a systematic review and meta-analysis

This systematic review assesses the evidence for an association between Mycobacterium avium subspecies paratuberculosis (MAP) and Crohns disease. We analysed 28 case-control studies comparing MAP in patients with Crohns disease with individuals free of inflammatory bowel disease (IBD) or patients with ulcerative colitis. Compared with individuals free of IBD, the pooled odds ratio (OR) from studies using PCR in tissue samples was 7.01 (95% CI 3.95-12.4) and was 1.72 (1.02-2.90) in studies using ELISA in serum. ORs were similar for comparisons with ulcerative colitis patients (PCR, 4.13 [1.57-10.9]; ELISA, 1.88 [1.26-2.81]). The association of MAP with Crohns disease seems to be specific, but its role in the aetiology of Crohns disease remains to be defined.

Norwalk-Like Virus Sequences in Mineral Waters: One-Year Monitoring of Three Brands

ABSTRACT In a recent study, RNA with nucleotide sequeces specific for “Norwalk-like viruses” (NLV) was detected in 11 different brands of European mineral waters. To clarify this finding, a 1-year monitoring study was conducted. Samples of three European brands of mineral water without gas were monitored weekly by reverse transcriptase PCR using generic and genogroup-specific oligonucleotides. Additional analyses were performed to investigate a possible correlation between NLV sequence contamination and mineral water lot numbers, the long-term stability (persistence) of NLV sequences in mineral water, and the level of contamination. NLV sequences were detected in 53 of 159 samples analyzed (33%) and belonged entirely to genogroup II. Although all NLV strains identified were closely related, three mineral water brand-specific clusters could be identified for both primer systems by sequencing. Analyses of second samples from lots previously shown to be positive for NLV sequences gave corresponding results in 45 of 53 cases (85%) (within a six-pack). NLV persistence was tested by analyzing 10 positive samples after 6 and 12 months of storage in darkness at room temperature. After 6 months, all samples remained positive; after 12 months, 9 of 10 samples were still positive for NLV sequences. No NLV sequences could be detected by analysis of 0.1-liter aliquots of 53 samples shown to be positive by testing of 1-liter volumes. Based on this fact and a test sensitivity of approximately 10 viral units, levels of contamination in positive mineral water samples were estimated to be in the range of 10 to 100 genomic equivalents per liter.

Detection and frequency of Cronobacter spp. (Enterobacter sakazakii) in different categories of ready-to-eat foods other than infant formula.

Two hundred sixty eight samples of ready-to-eat foods from retail shops were screened for the presence of Cronobacter by selective enrichment followed by plating on three chromogenic agars (ESIA, ESPM and DFI). Cronobacter was isolated from 14/23 samples of sprouts and fresh herbs/salads (60.9%), 7/26 samples of spices and dried herbs (26.9%) and 3/42 confectionery samples (7.1%). In cases where repeat samples were available, foods positive for Cronobacter were retested twice. In total, 54 Cronobacter isolates from 24 foods were recovered and genetic fingerprint patterns generated using PFGE. Identical PFGE-profiles were generated for Cronobacter isolates from five samples of two confectionery products obtained from a particular bakery shop over a period of 11 months. This may indicate a persistent contamination of the production site. For all other isolates, no clustering by phylogenetic analysis of PFGE-profiles was observed, indicating the sporadic nature of Cronobacter in ready-to-eat foods. Enterobacterial counts varied from a maximum value of 2.9 x 10(7) CFU/g (in dill) to a minimum value of <10 CFU/g (in confectionery and dried herbs/spices). There was no correlation between Enterobacterial count and the presence of Cronobacter. Cronobacter may be regularly imported into private households via ready-to-eat foods.

Virus-Contaminated Oysters: a Three-Month Monitoring of Oysters Imported to Switzerland

ABSTRACT Molluscan shellfish are known to be carriers of viral and bacterial pathogens. The consumption of raw oysters has been repeatedly linked to outbreaks of viral gastroenteritis and hepatitis A. Switzerland imports over 300 tons of oysters per year, 95% of which originate in France. To assess the level of viral contamination, a 3-month monitoring study was conducted. Therefore, the sensitivities of several previously described methods for virus concentration were compared, and one protocol was finally chosen by using dissected digestive tissues. Eighty-seven samples consisting of five oysters each were analyzed for Norwalk-like viruses (NLVs), enteroviruses, and hepatitis A viruses from November 2001 to February 2002. The oysters were exported by 31 French, three Dutch, and two Irish suppliers. Eight oyster samples from six French suppliers were positive for NLVs, and four samples from four French suppliers were positive for enteroviruses; two of the latter samples were positive for both viral agents. No hepatitis A viruses were detected. The sequences of NLV and enterovirus amplicons showed a great variety of strains, especially for the NLVs (strains similar to Bristol, Hawaii, Mexico, and Melksham agent). The data obtained indicated that imported oysters might be a source of NLV infection in Switzerland. However, further studies are needed to determine the quantitative significance of the risk factor within the overall epidemiology of NLVs.

Genotyping of human and porcine Yersinia enterocolitica, Yersinia intermedia, and Yersinia bercovieri strains from Switzerland by amplified fragment length polymorphism analysis

ABSTRACT In this study, 231 strains of Yersinia enterocolitica, 25 strains of Y. intermedia, and 10 strains of Y. bercovieri from human and porcine sources (including reference strains) were analyzed using amplified fragment length polymorphism (AFLP), a whole-genome fingerprinting method for subtyping bacterial isolates. AFLP typing distinguished the different Yersinia species examined. Representatives of Y. enterocolitica biotypes 1A, 1B, 2, 3, and 4 belonged to biotype-related AFLP clusters and were clearly distinguished from each other. Y. enterocolitica biotypes 2, 3, and 4 appeared to be more closely related to each other (83% similarity) than to biotypes 1A (11%) and 1B (47%). Biotype 1A strains exhibited the greatest genetic heterogeneity of the biotypes studied. The biotype 1A genotypes were distributed among four major clusters, each containing strains from both human and porcine sources, confirming the zoonotic potential of this organism. The AFLP technique is a valuable genotypic method for identification and typing of Y. enterocolitica and other Yersinia spp.

Further Evidence for Staphylococcal Food Poisoning Outbreaks Caused by egc-Encoded Enterotoxins

Staphylococcal food poisoning represents the most prevalent foodborne intoxication worldwide. It is caused by oral intake of enterotoxins preformed by Staphylococcus aureus in food. The relevance of newly described enterotoxins in outbreaks of staphylococcal food poisoning is controversially discussed. Although the staphylococcal enterotoxins SEG, SEI, SEM, SEN, and SEO elicit emesis in a monkey feeding assay, there has been no conclusive proof of their emetic activity in humans. In this study, we provide further evidence suggesting that one of these enterotoxins or a combination of SEG, SEI, SEM, SEN, and SEO cause staphylococcal food poisoning. We investigated two outbreaks registered with the Swiss Federal Office of Public Health, in which only Staphylococcus aureus strains harboring the egc cluster, including seg, sei, sem, sen, and seo linked to typical signs of staphylococcal food poisoning were isolated. The outbreaks were caused by consumption of raw goat cheese and semi-hard goat cheese, and were linked to strains assigned to CC45 (agr type I) and CC9 (agr type II), respectively. These outbreaks provide further evidence that newly-described staphylococcal enterotoxins are likely to cause staphylococcal food poisoning in humans.

Rapid detection of total and viable Legionella pneumophila in tap water by immunomagnetic separation, double fluorescent staining and flow cytometry

We developed a rapid detection method for Legionella pneumophila (Lp) by filtration, immunomagnetic separation, double fluorescent staining, and flow cytometry (IMS‐FCM method). The method requires 120 min and can discriminate ‘viable’ and ‘membrane‐damaged’ cells. The recovery is over 85% of spiked Lp SG 1 cells in 1 l of tap water and detection limits are around 50 and 15 cells per litre for total and viable Lp, respectively. The method was compared using water samples from house installations in a blind study with three environmental laboratories performing the ISO 11731 plating method. In 53% of the water samples from different taps and showers significantly higher concentrations of Lp were detected by flow cytometry. No correlation to the plate culture method was found. Since also ‘viable but not culturable’ (VNBC) cells are detected by our method, this result was expected. The IMS‐FCM method is limited by the specificity of the used antibodies; in the presented case they target Lp serogroups 1–12. This and the fact that no Lp‐containing amoebae are detected may explain why in 21% of all samples higher counts were observed using the plate culture method. Though the IMS‐FCM method is not yet fit to completely displace the established plating method (ISO 11731) for routine Lp monitoring, it has major advantages to plating and can quickly provide important insights into the ecology of this pathogen in water distribution systems.

Bacteriological Quality of Drinking Water from Dispensers (Coolers) and Possible Control Measures

Three water dispensers (coolers) were bacteriologically monitored over a period of 3 months to evaluate their hygienic status. For this purpose, 174 samples of chilled and unchilled water were analyzed for levels of mesophilic aerobic bacteria and the presence of Escherichia coli and enterococci in 100-ml samples, and the presence of Pseudomonas aeruginosa in 10- and 100-ml samples. Additionally, 12 samples from 20-liter plastic bottles of spring water used to supply the coolers and 36 samples of 12 different brands of noncarbonated bottled mineral water were similarly analyzed. Water from the coolers yielded aerobic plate counts of 3 to 5 log CFU/ml with a geometric mean of 3.86 log CFU/ml, whereas water from the 20-liter bottles had a mean aerobic plate count of 3.3 log CFU/ml. Aerobic plate counts for noncarbonated mineral waters were generally lower (13 samples, < 10 CFU/ml; 6 samples, 10 to 10(2) CFU/ml; 13 samples, 10(2) to 10(3) CFU/ml; 3 samples, 10(3) to 10(4) CFU/ ml; 1 sample, 2 x 10(4) CFU/ml). Although occasional professional cleaning of the coolers did not affect the aerobic plate count, P. aeruginosa was successfully eliminated 2 weeks after cleaning, with only one cooler becoming recolonized. Neither E. coli nor enterococci was found in any of the water samples tested. However, P. aeruginosa was identified in three (25%) of twelve 100-ml samples from 20-liter bottles of spring water; a similar frequency of 24.1% was seen for water samples from coolers. Overall, 35 (21.6%) of 162 water samples (10 ml) from coolers also yielded P. aeruginosa, suggesting potential growth of P. aeruginosa in the dispensers. Pulsed-field gel electrophoresis typing and antibiotic susceptibility testing found 19 P. aeruginosa isolates from the coolers and bottles to be identical, indicating that a single strain originated from the bottled water rather than the surroundings of the coolers. Because P. aeruginosa can cause serious nosocomial infections, its spread should be strictly controlled in institutions caring for vulnerable people such as hospitals and nursing homes. Consequently, in keeping with legal requirement for bottled spring and mineral water in Switzerland, it is also advisable that P. aeruginosa be absent in 100-ml samples of cooler water.

Antimicrobial Resistance of Escherichia coli, Enterococci, Pseudomonas aeruginosa, and Staphylococcus aureus from Raw Fish and Seafood Imported into Switzerland

A total of 44 samples of salmon, pangasius (shark catfish), shrimps, and oysters were tested for the presence of Escherichia coli, enterococci, Pseudomonas aeruginosa, and Staphylococcus aureus, which are indicator organisms commonly used in programs to monitor antibiotic resistance. The isolated bacterial strains, confirmed by matrix-assisted laser desorption ionization time-of-flight mass spectroscopy, were tested against a panel of 29 antimicrobial agents to obtain MICs. Across the four sample types, Enterococcus faecalis (59%) was most common, followed by E. coli (55%), P. aeruginosa (27%), and S. aureus (9%). All bacterial species were resistant to some antibiotics. The highest rates of resistance were in E. faecalis to tetracycline (16%), in E. coli to ciprofloxacin (22%), and in S. aureus to penicillin (56%). Antibiotic resistance was found among all sample types, but salmon and oysters were less burdened than were shrimps and pangasius. Multidrug-resistant (MDR) strains were exclusively found in shrimps and pangasius: 17% of pangasius samples (MDR E. coli and S. aureus) and 64% of shrimps (MDR E. coli, E. faecalis, and S. aureus). Two of these MDR E. coli isolates from shrimps (one from an organic sample) were resistant to seven antimicrobial agents. Based on these findings, E. coli in pangasius, shrimps, and oysters, E. faecalis in pangasius, shrimps, and salmon, and P. aeruginosa in pangasius and shrimps are potential candidates for programs monitoring antimicrobial resistance. Enrichment methods for the detection of MDR bacteria of special public health concern, such as methicillin-resistant S. aureus and E. coli producing extended-spectrum β-lactamases and carbapenemases, should be implemented.

Novel Bacteroides host strains for detection of human- and animal-specific bacteriophages in water

Bacteriophages active against specific Bacteroides host strains were shown to be suitable for detection of human faecal pollution. However, the practical application of this finding is limited because some specific host strains were restricted to certain geographic regions. In this study, novel Bacteroides host strains were isolated that discriminate human and animal faecal pollution in Switzerland. Two strains specific for bacteriophages present in human faecal contamination and three strains specific for bacteriophages indicating animal faecal contamination were evaluated. Bacteriophages infecting human strains were exclusively found in human wastewater, whereas animal strains detected bacteriophages only in animal waste. The newly isolated host strains could be used to determine the source of surface and spring water faecal contamination in field situations. Applying the newly isolated host Bacteroides thetaiotaomicron ARABA 84 for detection of bacteriophages allowed the detection of human faecal contamination in spring water.