Growth of methicillin-resistant Staphylococcus aureus during raw milk soft cheese-production and the inhibitory effect of starter cultures.

The consumption of raw milk or raw milk products might be a potential risk factor for the transmission of methicillin-resistant Staphylococcus aureus (MRSA). Therefore, we studied MRSA growth during raw milk soft cheese-production. Furthermore, we investigated the inhibitory effect of four starter cultures (Lactococcus lactis, Lacticaseibacillus rhamnosus, Lactiplantibacillus plantarum, Lactobacillus helveticus) on the growth of MRSA in a spot-agar-assay and in raw milk co-culture following a cheesemaking temperature profile. During the initial phases of raw milk cheese-production, MRSA counts increased by 2 log units. In the ripening phase, MRSA counts only dropped slightly and remained high up to the end of the storage. Comparable MRSA counts were found in the rind and core and strain-specific differences in survival were observed. In the spot-agar-assay, all four starter cultures showed strong or intermediate inhibition of MRSA growth. In contrast, in raw milk, only Lactococcus lactis strongly inhibited MRSA, whereas all other starter cultures only had minor inhibitory effects on MRSA growth. Our results indicate that MRSA follow a similar growth pattern as described for other S. aureus during raw milk soft cheese-production and illustrate the potential use of appropriate starter cultures to inhibit MRSA growth during the production of raw milk cheese.

The occurrence of methicillin-resistant non-aureus staphylococci in samples from cows, young stock, and the environment on German dairy farms.

This study aimed to determine the occurrence of methicillin-resistant (MR) non-aureus staphylococci (NAS) on 20 preselected German dairy farms. Farms were selected based on the detection of methicillin-resistant Staphylococcus aureus (MRSA) during previous diagnostic investigations. Bacterial culture of presumptive MR-NAS was based on a 2-step enrichment method that has been recommended for MRSA detection. Quarter milk samples (QMS), bulk tank milk, swab samples from young stock, and environmental samples were collected for bacterial culture. Methicillin-resistant NAS were detected on all study farms. The MR-NAS positive test rate was 3.3% (77/2,347) in QMS, 42.1% (8/19) in bulk tank milk, 29.1% (59/203) in nasal swabs from milk-fed calves, 18.3% (35/191) in postweaning calves, and 7.3% (14/191) in nasal swabs from prefresh heifers. In the environment, MR-NAS were detected in dust samples on 25% (5/20) of the dairy farms as well as in teat liners and suckers from automatic calf feeders. The geometric mean somatic cell count in QMS affected by MR-NAS (183,000 cells/mL) was slightly higher compared with all QMS (114,000 cells/mL). Nine MR-NAS species were identified; Staph. sciuri, Staph. lentus, Staph. fleurettii, Staph. epidermidis, and Staph. haemolyticus were the most common species. In addition, 170 NAS isolates were identified that showed reduced cefoxitin susceptibility (4 mg/L) but did not harbor the mecA or mecC genes. On some farms, similar mobile genetic elements were detected in MR-NAS and MRSA. It was suggested that resistance genes may be transferred between NAS and Staph. aureus on the respective farms.

The occurrence and distribution of livestock-associated methicillin-resistant Staphylococcus aureus ST398 on German dairy farms.

The objective of this study was to investigate the occurrence and distribution of methicillin-resistant Staphylococcus aureus (MRSA) on 20 German dairy farms. Farms were selected based on previous MRSA reports from phenotypic susceptibility testing of mastitis pathogens. Samples were collected from predefined groups of cows, young stock, farm personnel, and the environment. A high MRSA-positive test rate was detected in swab samples from milk-fed calves (22.7%; 46/203). In postweaning calves, the MRSA-positive test rate was 9.1% (17/187). From prefresh heifers, both nasal swabs and udder cleft swabs were collected if possible. Including both sample types, the MRSA-positive test rate in prefresh heifers was 13.0% (26/200). The positive test rate was 8.9% (17/191) in nasal swabs and 6.5% (11/170) in udder cleft swabs. In quarter milk samples (QMS), the MRSA-positive test rate was 2.9% (67/2347), and on cow level, 7.9% (47/597) of the dairy cows were affected. Among all cows included in this study, the geometric mean of somatic cell counts was higher in QMS that carried MRSA (345,000 cells/mL) in comparison to all QMS (114,000 cells/mL). No differences in parity or the affected mammary quarter position on the udder were observed among the 47 infected cows. Methicillin-resistant S. aureus was also detected in boot swab samples (dust), teat liners, and in suckers from automatic calf feeders. All isolates belonged to livestock-associated sequence type 398 and most common staphylococcal protein A (spa)-types were t011 and t034. Most isolates harbored the staphylococcal cassette chromosome mec (SCCmec)-type V, with the exception of some isolates with SCCmec-type IVa on 1 farm. Similar MRSA genotypes in samples from humans and dairy cows underline the possible zoonotic and reverse-zoonotic transmission of livestock-associated MRSA strains from dairy farms. Similar MRSA genotypes in pig and cattle barns were detected on only 1 of 5 farms that kept both cattle and pigs. Similar MRSA spa-types were detected in samples from different sources (dairy cows, young stock, environment, and humans), suggesting a possible contagious transmission on some of the farms. Sporadically, up to 3 different MRSA spa-types were detected in QMS from the respective farms. On MRSA-affected farms, improper milking hygiene procedures and elevated bulk-tank milk somatic cell counts (>250,000 cells/mL) were observed. The occurrence of livestock-associated MRSA ST398 in different samples from dairy farms, and especially in young calves, should be considered for future MRSA-monitoring programs and biosecurity guidelines.

Detection and quantification of methicillin-resistant Staphylococcus aureus in fresh broiler meat at retail in Germany.

The aim of this study was to detect, to quantify and to characterize MRSA in broiler meat samples with skin. Furthermore, we compared an isolation method using a second selective enrichment step (method A) with a simpler method omitting this step (method B). For quantification we used a direct plating method on selective agar plates and a "Most probable number" (MPN) technique for estimation of low numbers of MRSA. Presumptive MRSA colonies were confirmed by MALDI-TOF and by PCR. After confirmation the isolated MRSA were characterized by spa-typing and, if necessary, by multi-locus sequence typing. Method B detected more MRSA-positive samples (16.7%, n = 215) than method A (12.1%). However, method B also produced more false positive results (28.4%).The highest estimated number of MRSA in fresh broiler meat with skin was 1100 MPN/g, but in most positive samples (80.1%) the estimated numbers of MRSA were lower than 10 MPN/g. Thus, the numbers of MRSA in the samples were too low to detect using the spread plate technique. Ten different spa-types were identified. Six of these with 69% of the isolates were assigned to the clonal complex CC398 (t034; t011; t2576; t571; t5452; t1457). Spa-types t1430, t13177 and t899 can be assigned to CC9. Spa-type t304 was identified as MLST-type ST6. In conclusion, we provide quantitative data on low level contamination of fresh broiler meat with MRSA. Most isolated MRSA were from livestock associated spa-types. Omitting the second enrichment step was associated with an increase in sensitivity but lower specificity of the cultural method.

[The EHEC O104:H4 outbreak in Germany 2011 - lessons learned?!]. / Der EHEC O104:H4 Ausbruch 2011 in Deutschland - Lektion gelernt?!

The EHEC O104:H4 outbreak 2011 in Germany provided numerous insights into the recognition and control of such epidemic situations. Food-borne outbreaks and their related dynamics may lead to a critical burden of disease and an eventual capacity overload of the medical care system. Possible difficulties in the microbiological diagnostics of new or significantly altered infectious agents may result in a delayed detection of the outbreak as well as the launching of interventional measures. Besides an early notification of the local public health office by the affected institutions, in which a complete electronic procedure and additional sentinel or surveillance instruments (e. g., in emergency departments of hospitals) may be of great help, an interdisciplinary cooperation of the local public health and food safety agencies is the key to an effective outbreak control. Corresponding organizations on the state and federal level should support the investigation process by microbiological diagnostics and advanced epidemiological analysis as well as examination of the food chains. Finally, successful crisis communication relies on "speaking with one voice" (not necessarily one person). Immediate, transparent, appropriate and honest information of the general public concerning the reasons, consequences and (counter-) measures of a crisis are the best means to keep the trust of the population and to counteract the otherwise inevitable speculations.

The proof of the pudding is in the eating: an outbreak of emetic syndrome after a kindergarten excursion, Berlin, Germany, December 2007.

An outbreak of food poisoning (emetic syndrome) occurred in three kindergartens (A, B and C) in Berlin, Germany, on 3 December 2007 after an excursion during which food was served. We conducted a retrospective cohort study among the kindergarten children and personnel who participated in the trip. The overall attack rate among the 155 participants was 30%. It was 31% among the 137 children (aged two to six years) and 17% among adults (n=18). The consumption of rice pudding was significantly associated with disease. Among those who ate rice pudding, the attack rate was 36%, compared with 0% for non-eaters (relative risk: infinite, p<0.001, aetiological fraction: 100%), but differed significantly between kindergartens A (43%), B (61%) and C (3%), probably because groups were served from different pots. Bacillus cereus sensu stricto was identified from one vomit sample. The clinical and epidemiological characteristics suggest that B. cereus emetic toxin (cereulide) was the causative agent, although it could not be proven in the single vomit isolate. Inadequate food handling most probably led to the outbreak. Single-portion ready-to-eat rice pudding was recommended for subsequent excursions and no further cases of food poisoning occurred.

Outbreak of Salmonella Montevideo associated with a dietary food supplement flagged in the Rapid Alert System for Food and Feed (RASFF) in Germany, 2010.

In March 2010 the Rapid Alert System for Food and Feed (RASFF) was used to inform about Salmonella Montevideo in a herbal food supplement, formulated in capsules, distributed under a Dutch label in Germany. Simultaneous to the first RASFF notice, in the last two weeks of March 2010 an unusual number of 15 infections with S. Montevideo was notified within the electronic reporting system for infectious diseases at the Robert Koch Institute. Adult women (median age: 43, range: 1-90 years) were mainly affected. An outbreak was suspected and the food supplement hypothesised to be its vehicle. Cases were notified from six federal states throughout Germany, which required efficient coordination of information and activities. A case-control study (n=55) among adult women showed an association between consumption of the specific food supplement and the disease (odds ratio (OR): 27.5, 95% confidence interval (CI): 3.1-infinity, p-value=0.002). Restricting the case-control study to the period when the outbreak peaked (between 29 March and 11 April 2010) resulted in an OR of 43.5 (95% CI: 4.8-infinity, p-value=0.001). Trace-back of the supplement's main ingredient, hemp seed flour, and subsequent microbiological testing by pulsed-field gel electrophoresis supported its likely role in transmission. This outbreak investigation illustrates that information from RASFF may aid in hypothesis generation in outbreak investigations, though likely late in the outbreak.