Tips from the journals of the American Society for Microbiology

Different Packaging Conditions May Effect Spoilage of Refrigerated Beef

Researchers from Italy have found that different packaging methods utilizing air, oxygen and carbon dioxide can have an impact on the microbial spoilage of refrigerated beef. They report their findings in the July 2006 issue of the journal Applied and Environmental Microbiology.

Recognized as one of the most perishable foods, beef spoilage is commonly attributed to high water content and abundance of surface nutrients. Oxidation and color change are two obvious physical changes that occur when meat goes bad, however the growth of potentially harmful microorganisms has prompted researchers to examine new packaging methods to minimize microbial spoilage.

In the study beef was contained using three different methods of modified-atmosphere packaging (MAP) and stored at 5 degrees Celsius for fourteen days. The first method consisted of air (MAP1), the second of 60% oxygen and 40% carbon dioxide (MAP2), and the third of 20% oxygen and 40% carbon dioxide (MAP3). While stored, the beef was monitored for viable counts of Pseudomonas, Enterobacteriaceae, Brochothrix thermosphacta, and lactic acid bacteria as well as headspace gas composition, weight loss, and color change. During the first seven days, packaging method MAP2 was shown to offer the best protection, maintaining acceptable microbial loads and color change. Spoilage did occur between seven and fourteen days and although many different genera and species were identified some were found more frequently and appeared to vary according to packaging conditions. Rahnella aquatilis, Rahnella spp., Pseudomonas spp., and Carnobacterium divergens were prominent in the air packaging method, Pseudomonas spp. and Lactobacillus sakei were found in packaging high in oxygen content, and finally Rahnella spp. and L. sakei were the main species identified during storage high in carbon dioxide.

"As far as we know, this is the first study to report the changes of spoilage-related microbial flora during storage of fresh meat," say the researchers. "The assessment of microbial species diversity occurring in meat during storage and the study of the response and adaptability of the species to different antimicrobial conditions will be fundamental for improving and implementing packaging systems aimed a prolonging the shelf life of meat products."

(D. Ercolini, F. Russo, E. Torrieri, P. Masi, F. Villani. 2006. Changes in the spoilage-related microbiota of beef during refrigerated storage under different packaging conditions. Applied and Environmental Microbiology, 72. 7: 4663-4617.)

New Self Test Found to be Effective at Cervical Screening

A new user-friendly self-sampling device has accurately detected the human papillomavirus (HPV) in cervical cells collected by women at home and may increase cervical cancer screenings overall say researchers from The Netherlands. Their findings appear in the July 2006 issue of the Journal of Clinical Microbiology.

Human papillomavirus is believed to be on of the main causes of cervical cancer in women. Treatment of cervical cancer in its early stages is considered to be fairly easy and void of any major side effects, however current compliance rates for cervical screenings are not optimal. Records show that annually 30% of woman in The Netherlands, as well as the United Kingdom and the U.S., invited to participate in cervical screening programs do not attend and as a result half of the cervical cancer cases diagnosed are within this same group. A recent study polled more than 2,500 of the women who would not participate in screening programs and found that almost 30% of them actively responded when offered the option of a self-sampling method.

In the study women who had previously had a positive cervical smear test for HPV as well as healthy volunteers took a self-obtained sample at home and then visited a gynecologist where another sample was taken using an endocervical brush. Both samples were then processed using the high-risk human papillomavirus (hrHPV) test and self-obtained samples were shown to be equally sensitive in detecting high-grade cervical intraepithelial neoplasia as those collected from the endocervical brush.

"In conclusion, self-obtained samples taken by this novel device are highly representative of the hrHPV status of the cervix," say the researchers. "In combination with hrHPV testing, the use of this device may have implications for increasing the attendance rate for cervical cancer screening."

(A.A.T.P. Brink, C.J.L.M. Meijer, M.A.H.M. Wiegerinck, T.E. Nieboer, R.F.P.M. Kruitwagen, F. Van Kemenade, N.F. Daalmeijer, A.T. Hesselink, J. Berkhof, P.J.F. Snijders. 2006. High concordance of results of testing for human papillomavirus in cervicovaginal samples collected by two methods, with comparison of a novel self-sampling device to a conventional endocervical brush. Journal of Clinical Microbiology, 44. 7: 2518-2523.)

Waterfowl May Contaminate Drinking Water with Bacteria Harmful to Humans

Waterfowl have the potential to contaminate drinking water with opportunistic parasites say researchers from the U.S. and abroad. Their findings appear in the July 2006 issue of the journal Applied and Environmental Microbiology.

Microsporidia are opportunistic pathogens that commonly infect immunocompromised and immunosuppressed people through zoonotic and environmental transmission. However, because specific transmission routes are still unknown, spore identification, removal, and inactivation in drinking water are challenging, and human infections are hard to treat. Preliminary studies offer considerable evidence indicating drinking water as a source of human microsporidiosis, but nothing conclusive has been proven.

In the study researchers examined feces from 570 free-ranging, captive, and livestock birds for microsporidian spores known to infect humans, mainly Encephalitozoon hellum and Encephalitozoon intestinalis. Out of eleven avian species found to shed E. hellum and E. intestinalis, eight were aquatic. Microsporidial infections were significantly higher in waterfowl than any other bird and their fecal droppings contained more spores.

"Our findings demonstrate that waterborne microsporidian spores of species that infect people can originate from common waterfowl, which usually occur in large numbers and have unlimited access to surface waters, including waters used for production of drinking water," say the researchers.

(A. Slodkowicz-Kowalska, T.K. Graczyk, L. Tamang, S. Jedrzejewski, A. Nowosad, P. Zduniak, P. Solarczyk, A.S. Girouard, A.C. Majewska. 2006. Microsporidian species known to infect humans are present in aquatic birds: implications for transmission via water? Applied and Environmental, 72. 7: 4540-4544.)

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Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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