Mary Ellen Sanders, Ph.D.

Dairy & Food Culture Technologies

Consulting in the science of probiotics

Publications by Mary Ellen Sanders, Ph.D.

1.       Sanders ME, Merenstein DJ, Ouwehand AC, Reid G, Salminen S, Cabana MD, Paraskevakos G, Leyer G. Probiotic Use in At-Risk Populations. Accepted, J Amer Pharmacy Assoc.

2.       Sanders ME. 2016. Probiotics and microbiota composition. BMC Medicine. 14:82. DOI: 10.1186/s12916-016-0629-z

3.       Merenstein DJ, et al. Safety of Bifidobacterium animalis subsp. lactis (B. lactis) strain BB-12-supplemented yogurt in healthy children.  Gut Microbes. 2015;6(1):66-77.

4.       Hill C, Scott K, Klaenhammer TR, Quigley E, Sanders ME. 2016. Commentary: Probiotic nomenclature matters. Gut Microbes 7(1):1-2.

5.       Sanders ME, Shane AL, Merenstein DJ. Advancing human probiotic research in the United States: challenges and strategies. Gut Microbes 2016 Mar 10:1-4.

6.       Hutkins RW, Krumbeck JA, Bindels LB, Cani PD, Fahey G, Goh YH, Hamaker B, Martens EC, Mills DA, Rastall RA, Vaughan E, Sanders ME. Prebiotics: why definitions matter. Current Opinion in Biotechnology 2016, 37:1–7.

2.       Glanville J, King S, Hill C, Guarner F, Sanders ME. Use of systematic review and meta-analysis to evaluate evidence for health claims on probiotic foods in the European Union. Nutrition Journal. 2015, 14:16.

3.       Merenstein DJ,  Tan TP, Solano-Aguilar G, Molokin A, Smith KH, Roberts RF, Shara NM, Mete M, Sanders ME. Safety of Bifidobacterium animalis subsp. lactis (B. lactis) strain BB-12-supplemented yogurt in healthy adults on antibiotics: a phase 1 safety study. Gut Microbes 6(1):66-77.

4.       Ebner S, Smug LN, Kneifel W, Salminen SJ, Sanders ME. 2014. Probiotics in dietary guidelines and clinical recommendations outside the European Union. World J Gastroenterol. 20(43): 16095-16100.

5.       Hill C, Guarner F, Reid G, Gibson GR, Merenstein DJ, Pot B, Morelli L, Canani RB, Flint, HJ, Salminen S, Calder PC, Sanders ME. 2014. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nature Rev Gastroenterol Hepatol. 11, 506–514.

6.       Sanders ME, Lenoir-Wijnkoop I, Salminen S, Merenstein DJ, Gibson GR, Petschow BW, Nieuwdorp M, Tancredi D, Cifelli C, Jacques P, Pot B. Probiotics and Prebiotics: Prospects for Public Health and Nutritional Recommendations. Ann N Y Acad Sci. 2014 Feb;1309(1):19-29.

7.       King S, Glanville J, Sanders ME, Fitzgerald A, Varley D. 2014. The Effectiveness of Probiotics on Length of Illness in Healthy Children and Adults who Develop Common Acute Respiratory Infectious Conditions: A Systematic Review and Meta-Analysis. Br J Nutr. 112(1):41-54.

8.       Sanders ME, Klaenhammer TR, Ouwehand AC, Marco ML, Johansen E, Pot B, Leyer G, Tennilä J, Ross RP, Franz C, Heimbach JT, Salminen S, Pridmore RD, Charbonneau D, Call E, Pagé N, Lenoir-Wijnkoop I. 2014. Effects of genetic, processing, or product formulation changes on efficacy and safety of probiotics. Ann N Y Acad Sci. 1309(1):1-18.

9.       Smug L, Salminen S, Sanders ME, Ebner S. 2014. Yoghurt and probiotic bacteria in dietary guidelines of the member states of the European Union. Beneficial Microbes 5(1):61-66.

10.   Hecht GA, Blaser MJ, Gordon J, Kaplan L, Knight R, Laine L, Peek R, Sanders ME, Sartor B, Wu G, Yang V. 2013. What's the Value of an FDA IND for Fecal Microbiota Transplantation in Clostridium difficile Infection? Clin Gastroenterol Hepatol. 12(2):289-91.

11.   Petschow B. Dore J, Hibberd P, Dinan T, Reid G, Blaser M, Cani PD, Degnan FH, Foster J, Gibson G, Hutton J, Klaenhammer TR, Ley R, Nieuwdorp M, Pot B, Relman D, Serazin A, Sanders ME. Probiotics, prebiotics, and the host microbiome: the science of translation. Annals NY Acad Sci. Dec;1306(1):1-17.  

12.   Hill C and Sanders ME. 2013. Rethinking “probiotics”. Gut Microbes. 4(4):269-270.

13.   Sanders ME, Guarner F, Guerrant R, Holt PR, Quigley EMM, Sartor RB, Sherman PM, Mayer E. 2013. An update on the use and investigation of probiotics in health and disease. Gut 62(5):787-96.

14.   Sanders, ME. 2012. Probiotics for the healthy consumer. Functional Food Reviews 4(4): 144-151.

15.   Bäckhed F, Fraser C, Ringel Y, Sanders ME, Sartor RB, Sherman PM, Versalovic J, Young V, Finlay BB. 2012. Defining a healthy human gut microbiome:  Current concepts, future directions, and clinical applications. Cell Host Microbe 12(5):611-22.

16.   Donovan SM, Schneeman B, Gibson GR, Sanders ME. Establishing and evaluating health claims for probiotics. Adv Nutr. 2012 Sep 1;3(5):723-5.

17.   Guarner F, Khan AG, Garisch J, Eliakim R, Gangl A, Thomson A, Krabshuis J, Lemair T, Kaufmann P, de Paula JA, Fedorak R, Shanahan F, Sanders ME, Szajewska H, Ramakrishna BS, Karakan T, Kim N. World Gastroenterology Organisation Global Guidelines: probiotics and prebiotics October 2011. J Clin Gastroenterol. 2012 Jul;46(6):468-81.

18.   Floch MH, Walker WA, Madsen K, Sanders ME, Macfarlane GT, Flint HJ, Dieleman LA, Ringel Y, Guandalini S, Kelly CP, Brandt LJ. 2011. Recommendations for probiotic use – 2011 update. J Clin Gastroenterol. 45 Suppl:S168-71.

19.   Sanders ME. Impact of probiotics on colonizing microbiota of the gut. 2011. J Clin Gastroenterol. 45 Suppl:S115-9.

20.   Wallace TC, Guarner F, Madsen K, Cabana MD, Gibson G, Hentges E, Sanders ME. 2011. Human gut microbiota and its relationship to health and disease. Nutr Rev. 69(7):392-403.

21.   Guarner F, Sanders ME, Gibson G, Klaenhammer T, Cabana M, Scott K, Reid G, Delzenne NM, Fahey G, Hill C. 2011. Probiotic and prebiotic claims in Europe: seeking a clear roadmap. Brit J Nutr. 106(11):1765-7.

22.   Sanders ME, Heimbach JT, Pot B, Tancredi D, Lenoir-Wijnkoop I, Lähteenmäki-Uutela A, Gueimonde M, Bañares S. 2011. Health claims substantiation for probiotic and prebiotic products. Gut Microbes 2:1-7.

23.   Merenstein D, Gonzalez J, Young AG, Roberts RF, Sanders ME, Petterson S. 2011. Study to investigate the potential of probiotics in children attending school. Eur J Clin Nutr. 65(4):447-53.

24.   Sanders, ME, Levy DD. 2011. The science and regulations of probiotic food and supplement product labeling. Annals New York Acad Sci; 1219 S1, E1–E23.

25.   Sanders, M.E. 2011. Substantiating health benefit claims for probiotics in the United States. In, Health Claims and Probiotics, W. Kneifel, S. Salminen, Eds. Blackwell Wiley, Oxford UK.

26.   Klein M, Sanders ME, Duong T, Young HA. 2010. Probiotics: From Bench to Market. Annals New York Acad Sci. Vol. 1212 S1, pages E1-E14.

27.   Sanders ME. 2010. International Scientific Association for Probiotics and Prebiotics 2010 Meeting Report. Functional Food Reviews 2:131-140.

28.   Shane, AL, Cabana, MD, Vidry, S., Merenstein, D, Hummelen, R, Ellis, CL, Heimbach, JH, Hempel, S, Lynch, SV, Sanders, ME, Tancredi, DJ. 2010. Guide to designing, conducting, publishing and communicating results of clinical studies involving probiotic applications in human participants. Gut Microbes 1(4): 1-10. 

29.   Merenstein, D., Smith K., Scriven, M., Roberts, R., Sanders, M.E., Petterson, S. 2010. The study to investigate the potential benefits of probiotics in yogurt, a patient-oriented, double-blind, cluster-randomised, placebo-controlled, clinical trial. Eur. J. Clin Nut. 64(7):685-91.

30.   Merenstein D., Murphy, M., Fokar, A., Hernandez, R., Park, H., Nsouli H., Sanders, M.E., Davis B., Niborski V., Tondu F., Shara N. 2010. Use of a fermented dairy probiotic drink containing Lactobacillus casei (DN-114 001) to decrease the rate of illness in kids: the DRINK study. A patient-Oriented, Double-Blind, Cluster-Randomized, Placebo-Controlled, Clinical Trial. European J. Clin Nutr. 64(7):669-77.

31.   Sanders, M.E., Merenstein, D.J. Use of probiotic yogurts in health and disease. 2010. In, Probiotics: Clinical Guide, M. Floch, A. Kim, Eds., Slack Inc., pp. 95-120.

32.   Sanders M.E., Akkermans LMA., Haller D, Hammerman C, Heimbach J, Huys G, Levy D, Mack D, Phothirath P, Constable A, Solano-Aguilar G, Vaughan E. 2010. Assessment of probiotic safety for human use. Gut Microbes 1 (3):1-22.

33.   Sanders, M.E., Marco, M. 2010. Food formats for effective delivery of probiotics. Ann. Rev. Food Sci. Technol. 1:65–85.

34.   Quigley, E.M.M. and Sanders, M.E. 2009. Probiotic Foods for Gastrointestinal Health. Gastroenterology & Endoscopy News Special Edition. October;7:27-33.

35.   Sanders, M.E. 2009. How do we know when something called “probiotic” is really a probiotic? A guideline for consumers and healthcare professionals. Functional Food Rev 1:3-12.

36.   Engelbrektson A, Korzenik JR, Pittler A, Sanders ME, Klaenhammer TR, Leyer G, Kitts CL. 2009. Probiotics to minimize the disruption of faecal microbiota in healthy subjects undergoing antibiotic therapy. J Med Microbiol 58:663-70.

37.   Sanders, M.E. 2008. Clinical use of probiotics: what physicians need to know. Am Fam Physician. 78(9):1026.

38.   Reid G, Gibson G, Sanders ME, Guarner F, Versalovic J; International Scientific Association for Probiotics and Prebiotics. Probiotic prophylaxis in predicted severe acute pancreatitis. Lancet. 2008 Jul 12;372(9633):112-3.

39.   Mercenier A, Lenior-Wijnkoop I, Sanders ME. 2008. Physiological and functional properties of probiotics. Bulletin of the International Dairy Federation 429/2008.

40.   Sanders ME. 2008. Use of probiotics and yogurts in maintenance of health. J Clin Gastroenterol. 42 Suppl 2:S71-S74.

41.   Floch M, Walker WA, Guandalini S, Hibberd P, Gorbach S, Surawicz C, Sanders ME, Garcia-Tsao G, Quigley E, Isolauri E, Fedorak R, Dieleman L. 2008. Recommendations for Probiotic Use-2008. J Clin Gastroenterol. 42 Suppl 2:S104-S108.

42.   Douglas L and Sanders ME. 2008. Probiotics and prebiotics in dietetic practice. J Amer Dietetics Assoc. 108:510-521.

43.   Sanders, M.E. Probiotics: Definition, Source, Selection and Uses. 2008. Clin Infect Dis. 46(S2):S58-S61.

44.   Hoffman FA, Heimbach JT, Sanders ME, Hibberd PL. Executive summary: scientific and regulatory challenges of development of probiotics as foods and drugs. Clin Infect Dis. 2008 Feb 1;46 Suppl 2:S53-7.

45.   Lenoir-Wijnkoop I, Sanders, M.E., Van Loo, J., Rayes, N., Timmerman, H., Sherman, P. Cabana, M., Corthier, G., Charbonneau, D., Vaneechoutte, M., Caglar, E., Wolvers, D., Manneck, I. 2007. Probiotic and prebiotic influence beyond the intestinal tract. Nutr Rev. 65:469-489.

46.   Sanders M.E., Gibson G.R., Gill H. and Guarner F. 2007. Probiotics: their potential to impact human health. Council for Agricultural Science and Technology (CAST), Issue Paper 36, CAST, Ames, Iowa.

47.   Sanders, ME. 2007. Probiotics: strains matter. Functional Food and Nutraceuticals. June, pages 34-41.

48.   Sanders ME, Hamilton-Miller, J, Reid G, Gibson G. 2007. A non-viable preparation of L. acidophilus is not a probiotic. Clin Infect. Dis. 44:886.

49.   Sanders, M.E. and Gibson, G.R. Probiotics & Prebiotics. Touch Briefings, US Gastroenterology Review 2006, pages 205-209.

50.   Sanders, M.E. 2006. Summary of probiotic activities of Bifidobacterium lactisHN019. J. Clin Gastroenterol. 40:776-83.

51.   Engelbrektson A.L., Korzenik J. R., Sanders M.E., Clement B. C., Leyer G., Klaenhammer T. R. and Kitts C. L. 2006. Analysis of treatment effects on the microbial ecology of the human intestine. FEMS Microbial Ecology 57(2):239-50.

52.   Sanders, M.E. 2005. Objectives and activities of the International Scientific Association for Probiotics and Prebiotics. In, Cesare Schiavi (Ed.) Probiotics, Biotherapeutics & Health. Mofin Alce, Novara, Italy, p. 206-216.

53.   Sanders, M.E. 2005. 10 myths about probiotics. Prepared Foods, July, p. 67-73.

54.   Sanders, M.E., Guarner, F., Mills, D., Pot, B., Rafter, J., Rastall, R., Reid, G., Ringel, Y., Rowland, I., Saarela, M. and Tuohy, K. 2005. Selected Topics in Probiotics and Prebiotics: Meeting Report for the 2004 International Scientific Association for Probiotics and Prebiotics. Cur Iss Intestinal Microbiol. 6: 55-68.

55.   Sanders, M.E. and J. Korzenik. 2005. The potential impact of probiotics and prebiotics on gastrointestinal and immune health of combat soldiers. Proceedings of Meeting on Optimization of Nutrient Composition for Assault Rations, Sponsored by the Committee on Military Nutrition Research, Food and Nutrition Board, Institute of Medicine, The National Academies Press, Washington DC, p. 341-361.

56.   Rastall, R. A., Gibson, G. R., Gill, H.S., Guarner, F., Klaenhammer, T. R., Pot, B., Reid, G., Rowland, I. R., and Sanders, M. E. 2005. Modulation of the microbial ecology of the human colon by probiotics, prebiotics and synbiotics to enhance human health: An overview of enabling science and potential applications. FEMS Microbiol. Ecol. 52(2):145-152.

57.   Tompkins TA, Sanders ME. 2004. Good intentions, poor study design. Can Fam Physician. 50:1499-500.

58.   Reid G, Guarner F, Gibson G, Tompkins T, Gill H, Rowland I, Rastall B, Pot B, Sanders ME; International Scientific Association for Probiotics and Prebiotics. 2004. Discussion on toll-like receptor 9 signaling mediates the anti-inflammatory effects of probiotics in murine experimental colitis. Gastroenterology. 127(1):366-7.

59.   Sanders, M.E. and J. Heimbach.2004. Functional foods in the USA: emphasis on probiotic-containing foods. Food Science and Technology Bulletin - Functional Foods 1(8) 1–10.

60.   Sanders, M.E., T. Tompkins, J. Heimbach, S. Kolida. 2004. Weight of evidence needed to substantiate a health effect for probiotics and prebiotics: scientific and regulatory considerations in Canada, EU, and U.S. Eur J Nutr. 44(5): 303-310.

61.   Yeung, P. S. M., M. E. Sanders, C. L. Kitts, R. Cano, P. S. Tong. 2004. Application of genomic and phenotypic analyses to commercial probiotic strain identity and relatedness. J. Appl. Microbiol. 97:1095-1104.

62.   Reid, G, M. E. Sanders, H. R. Gaskins, G. Gibson, A. Mercenier, R. Rastall, M. Roberfroid, I. Rowland, C. Cherbut, and T. R. Klaenhammer. 2003. New scientific paradigms for probiotics and prebiotics. J. Clin. Gastroenterol. 37:105-118.

63.   Sanders, M. E., L. Morelli and T. Tompkins. 2003. Sporeformers as human probiotics: Bacillus, Sporolactobacillus and Brevibacillus. Comp. Rev. Food Sci. Food Safety. 2:101-110.

64.   Sanders, M. E. 2003. Probiotics: considerations for human health. Nutr. Rev. 61:91-99.

65.   Sanders, M. E. 2002. Probiotics: State of the art in the USA. Microecol. Therapy 29:1-5.

66.   Sanders, M. E. 2002. Market and regulatory challenges for functional dairy foods: communicating health benefits. Bulletin of the International Dairy Federation 375:17-19.

67.   Yeung, P. S. M., M. E. Sanders, C. L. Kitts, R. Cano and P. S. Tong. 2002. Species-specific identification of commercial probiotic strains. J. Dairy Sci. 85:1039-1051.

68.   Sanders, M. E., L. Morelli and S. Bush. 2001. “Lactobacillus sporogenes” is not a Lactobacillus probiotic. ASM News 67:385-386.

69.   Yeung, P. S. M. and M. E. Sanders. 2001. Probiotic Products: Considerations in Development and Labeling. Food Technology International 2001:37-41.

70.   Kaplan, C. W., J. C. Astaire, M. E. Sanders, B. S. Reddy and C. L. Kitts. 2001. Terminal restriction fragment pattern analysis of changing bacterial assemblages in rat feces during ingestion of Lactobacillus acidophilus NCFM®. Appl. Environ. Microbiol. 67:1935-1939.

71.   Sanders, M. E. and T. R. Klaenhammer. 2001. The scientific basis of Lactobacillus acidophilus NCFM® functionality as a probiotic. J. Dairy Sci. 84:319-331.

72.   Sanders, M. E. 2000. Dairy products. In J. Lederberg (Ed.) Encyclopedia of Microbiology, Second Edition, Academic Press, Orlando, FL. Vol. 2, p. 1-8.

73.   Sanders, M.E. 2000. Considerations for use of probiotic bacteria to modulate human health. J. Nutr. 130:384S-390S.

74.   Sanders, M. E. 1999. Proboitics. Food Technology 53:67-77.

75.   Sanders, M. E. and J. Huis in’t Veld. 1999. Bringing a probiotic-containing functional food to the market: microbiological, product, regulatory and labeling issues. Antonie van Leeuwenhoek 76:293-315.

76.   Sanders, M. E. 1999. Capitalizing on probiotics and their potential as healthful food ingredients. California Dairy Dispatch 6:1-3.

77.   Rao, C. V., M. E. Sanders, C. Indranie, B. Simi and B. S. Reddy. 1999. Prevention of colon carcinogenesis by the probiotic Lactobacillus acidophilus-NCFM® in rats. Intern. J. Oncol. 14:939-944.

78.   Sanders, M. E. 1998. Development of Consumer Probiotics for the U.S. Market. Brit. J. Nutr. 80, Suppl. 2:S213-218.

79.   Sanders, M. E. 1998. Overview of functional foods: emphasis on probiotic bacteria. Intern. Dairy J. 8:341-347.

80.   Sanders, M. E. 1996. Probiotic cultures and human health. In Germfree Life and Its Ramifications, K. Hashimoto, et al. (eds.), XII ISG Publishing Committee, Shiozawa, Japan.

81.   Sanders, M. E., D. C. Walker, K. M. Walker, K. Aoyama, and T. R. Klaenhammer. 1996. Performance of commercial cultures in fluid milk applications. J. Dairy Sci. 79:943-955.

82.   Sanders, M. E. 1995. Lactic acid bacteria and human health. In R. Fuller, P. Heidt, V. Rusch and D. van der Waaij (Eds.) Probiotics: Prospects of Use in Opportunistic Infections, Institute for Microbiology and Biochemistry, Herborn, Germany, p. 126-140.

83.   Sanders, M. E. 1995. Lactococci. In Y. H. Hui and G. G. Khachatourians (Eds.) Food Biotechnology: Microorganisms, VCH Publishers, Inc., New York, p. 645-664.

84.   Sanders, M. E. Lactic acid bacteria as promoters of human health. 1994. In I. Goldberg (Ed.) Functional Foods. Chapman and Hall, New York, p. 294-322.

85.   Sanders, M. E. 1994. How healthful is yogurt? Healthline 13:8.

86.   Sanders, M. E. 1993. Healthful attributes of microbes in yogurt. Contemporary Nutrition. Volume 18, No. 5.

87.   Sanders, M. E. 1993. Summary of conclusions from a consensus panel of experts on health attributes of lactic cultures: significance to fluid milk products containing cultures. J. Dairy Sci. 76:1819-1828.

88.   Sanders, M. E. 1993. Bacteriophages in industrial fermentations. In R. G. Webster and A. Granoff (Eds.) Encyclopedia of Virology, Academic Press.

89.   Sanders, M. E. 1993. Effect of consumption of lactic cultures on human health. Adv. Food Nutr. Res. 37:67-130.

90.   Sanders, M. E., B. Wasserman, and E. A. Foegeding. 1993. Research needs in biotechnology. Food Technol. 47:18S-21S.

91.   Sanders, M. E. 1992. Dairy products. In J. Lederberg (Ed.) Encyclopedia of Microbiology, Academic Press, Orlando, FL. Vol. 2, p. 1-8.

92.   Sanders, M. E. 1991. Genetic approaches for the improvement of strains for Italian cheese manufacture: a review. J. Dairy Sci. 74:3647.

93.   Sanders, M. E., J. K. Kondo, and D. L. Willrett. 1991. Lactic acid bacteria applications. In I. Goldberg and R. Williams (Eds.) Biotechnologically Derived Ingredients For Food Products, Van Nostrand Reinhold, New York, p. 433-459.

94.   Sanders, M. E. 1991. Mixed cultures in dairy fermentations. In E. Johnson and G. Zeikus (Eds.) Mixed Cultures in Biotechnology, McGraw-Hill, New York, NY. p.105-133.

95.   Sanders, M. E. and J. W. Shultz. 1990. Cloning of phage resistance genes from Lactococcus lactis ssp. cremoris KH. J. Dairy Sci. 73:2044-2053.

96.   Sanders, M. E., 1988. Phage resistance in lactic acid bacteria. Biochimie 70: 411-421.

97.   Sanders, M. E. and J. W. Shultz. 1987. Method for cloning in the lactic acid bacteria. European Patent Application. 88118362.8.

98.   Sanders, M. E. and M. A. Nicholson. 1987. A method for genetic transformation of non-protoplasted Streptococcus lactis. Appl. Environ. Microbiol. 53:1730-1736.

99.   Sanders, M. E. 1987. Bacteriophages of Industrial Importance. In S. M. Goyal, C. P. Gerba and G. Bitton (Eds.) Phage Ecology, John Wiley and Sons, Inc. p.211-244.

100.            Sanders, M. E., P. J. Leonhard, W. D. Sing, and T. R. Klaenhammer. 1986. A conjugal strategy for construction of fast acid-producing, phage resistant lactic streptococci for use in dairy fermentations. Appl. Environ. Microbiol. 52:1001-1007.

101.            Sanders, M. E. and T. R. Klaenhammer. 1984. Phage resistance in a phage-insensitive strain of Streptococcus lactis: temperature-dependent phage development and host-controlled phage replication. Appl. Environ. Microbiol. 47:979-985.

102.            Sanders, M. E. 1983. Mechanisms and plasmid linkage of bacteriophage resistance in group N streptococci. Ph. D. thesis, North Carolina State University, Raleigh.

103.            Sanders, M. E. and T. R. Klaenhammer. 1983. Characterization of phage sensitive mutants from a phage-insensitive strain of Streptococcus lactis: evidence for a plasmid determinant that prevents phage adsorption. Appl. Environ. Microbiol. 46:1125-1133.

104.            Sanders, M. E. and T. R. Klaenhammer. 1981. Evidence for plasmid linkage of restriction and modification in Streptococcus cremoris KH. Appl. Environ. Microbiol. 42:944-950.

105.            Sanders, M. E. and T. R. Klaenhammer. 1980. Restriction and modification in group N streptococci: effect of heat on development of modified lytic bacteriophage. Appl. Environ. Microbiol. 40:500-506.