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The Microbiome in Autism Spectrum Disorder

Approaches to studying and manipulating the enteric microbiome to improve autism symptoms

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Article: 26878 | Received 03 Dec 2014, Accepted 06 Apr 2015, Published online: 07 May 2015

References

  • Williams BL , Hornig M , Buie T , Bauman ML , Cho Paik M , Wick I , etal. Impaired carbohydrate digestion and transport and mucosal dysbiosis in the intestines of children with autism and gastrointestinal disturbances. PLoS One. 2011; 6: e24585.
  • Wang L , Christophersen CT , Sorich MJ , Gerber JP , Angley MT , Conlon MA . Increased abundance of Sutterella spp. and Ruminococcus torques in feces of children with autism spectrum disorder. Mol Autism. 2013; 4: 42.
  • Wang L , Conlon MA , Christophersen CT , Sorich MJ , Angley MT . Gastrointestinal microbiota and metabolite biomarkers in children with autism spectrum disorders. Biomark Med. 2014; 8: 331–44.
  • Kang DW , Park JG , Ilhan ZE , Wallstrom G , Labaer J , Adams JB , etal. Reduced incidence of Prevotella and other fermenters in intestinal microflora of autistic children. PLoS One. 2013; 8: e68322.
  • Claus SP , Ellero SL , Berger B , Krause L , Bruttin A , Molina J , etal. Colonization-induced host-gut microbial metabolic interaction. MBio. 2011; 2: e00271–10.
  • Holmes E , Li JV , Marchesi JR , Nicholson JK . Gut microbiota composition and activity in relation to host metabolic phenotype and disease risk. Cell Metab. 2012; 16: 559–64.
  • Nicholson JK , Holmes E , Kinross J , Burcelin R , Gibson G , Jia W , etal. Host-gut microbiota metabolic interactions. Science. 2012; 336: 1262–7.
  • Shenderov BA , Midtvedt T . Epigenomic programing: a future way to health?. Microb Ecol Health Dis. 2014; 25 24145, doi: http://dx.doi.org/10.3402/mehd.v25.24145 .
  • Alenghat T . Epigenomics and the microbiota. Toxicol Pathol. 2015; 43: 101–6.
  • Borre YE , Moloney RD , Clarke G , Dinan TG , Cryan JF . The impact of microbiota on brain and behavior: mechanisms & therapeutic potential. Adv Exp Med Biol. 2014; 817: 373–403.
  • Borre YE , O'Keeffe GW , Clarke G , Stanton C , Dinan TG , Cryan JF . Microbiota and neurodevelopmental windows: implications for brain disorders. Trends Mol Med. 2014; 20: 509–18.
  • Macfabe DF . Short-chain fatty acid fermentation products of the gut microbiome: implications in autism spectrum disorders. Microb Ecol Health Dis. 2012; 23 19260, doi: http://dx.doi.org/10.3402/mehd.v23i0.19260 .
  • Diaz Heijtz R , Wang S , Anuar F , Qian Y , Bjorkholm B , Samuelsson A , etal. Normal gut microbiota modulates brain development and behavior. Proc Natl Acad Sci USA. 2011; 108: 3047–52.
  • Krajmalnik-Brown R , Lozupone C , Kang DW , Adams JB . Gut bacteria in children with autism spectrum disorders: challenges and promise of studying how a complex community influences a complex disease. Microb Ecol Health Dis. 2015; 26 26914, doi: http://dx.doi.org/10.3402/mehd.v26.26914 .
  • Macfabe D . Autism: metabolism, mitochondria, and the microbiome. Glob Adv Health Med. 2013; 2: 52–66.
  • Frye RE , Melnyk S , Macfabe DF . Unique acyl-carnitine profiles are potential biomarkers for acquired mitochondrial disease in autism spectrum disorder. Transl Psychiatry. 2013; 3: e220.
  • Foley KA , MacFabe DF , Kavaliers M , Ossenkopp KP . Sexually dimorphic effects of prenatal exposure to lipopolysaccharide, and prenatal and postnatal exposure to propionic acid, on acoustic startle response and prepulse inhibition in adolescent rats: relevance to autism spectrum disorders. Behav Brain Res. 2015; 278: 244–56.
  • Foley KA , MacFabe DF , Vaz A , Ossenkopp KP , Kavaliers M . Sexually dimorphic effects of prenatal exposure to propionic acid and lipopolysaccharide on social behavior in neonatal, adolescent, and adult rats: implications for autism spectrum disorders. Int J Dev Neurosci. 2014; 39: 68–78.
  • Foley KA , Ossenkopp KP , Kavaliers M , Macfabe DF . Pre- and neonatal exposure to lipopolysaccharide or the enteric metabolite, propionic acid, alters development and behavior in adolescent rats in a sexually dimorphic manner. PLoS One. 2014; 9: e87072.
  • Nankova BB , Agarwal R , MacFabe DF , La Gamma EF . Enteric bacterial metabolites propionic and butyric acid modulate gene expression, including CREB-dependent catecholaminergic neurotransmission, in PC12 cells–possible relevance to autism spectrum disorders. PLoS One. 2014; 9: e103740.
  • Troyb E , Orinstein A , Tyson K , Eigsti IM , Naigles L , Fein D . Restricted and repetitive behaviors in individuals with a history of ASDs who have achieved optimal outcomes. J Autism Dev Disord. 2014; 44: 3168–84.
  • Troyb E , Rosenthal M , Eigsti IM , Kelley E , Tyson K , Orinstein A , etal. Executive functioning in individuals with a history of ASDs who have achieved optimal outcomes. Child Neuropsychol. 2014; 20: 378–97.
  • Tyson K , Kelley E , Fein D , Orinstein A , Troyb E , Barton M , etal. Language and verbal memory in individuals with a history of autism spectrum disorders who have achieved optimal outcomes. J Autism Dev Disord. 2014; 44: 648–63.
  • Niehus R , Lord C . Early medical history of children with autism spectrum disorders. J Dev Behav Pediatr. 2006; 27: S120–7.
  • Atladottir HO , Henriksen TB , Schendel DE , Parner ET . Autism after infection, febrile episodes, and antibiotic use during pregnancy: an exploratory study. Pediatrics. 2012; 130: e1447–54.
  • Fallon J . Could one of the most widely prescribed antibiotics amoxicillin/clavulanate “augmentin” be a risk factor for autism?. Med Hypotheses. 2005; 64: 312–15.
  • Mezzelani A , Landini M , Facchiano F , Raggi ME , Villa L , Molteni M , etal. Environment, dysbiosis, immunity and sex-specific susceptibility: a translational hypothesis for regressive autism pathogenesis. Nutr Neurosci. 2015; 18: 145–61.
  • Mellon AF , Deshpande SA , Mathers JC , Bartlett K . Effect of oral antibiotics on intestinal production of propionic acid. Arch Dis Child. 2000; 82: 169–72.
  • Finegold SM . Therapy and epidemiology of autism–clostridial spores as key elements. Med Hypotheses. 2008; 70: 508–11.
  • Finegold SM . State of the art; microbiology in health and disease. Intestinal bacterial flora in autism. Anaerobe. 2011; 17: 367–8.
  • Sandler RH , Finegold SM , Bolte ER , Buchanan CP , Maxwell AP , Vaisanen ML , etal. Short-term benefit from oral vancomycin treatment of regressive-onset autism. J Child Neurol. 2000; 15: 429–35.
  • Frye RE , Rose S , Slattery J , MacFabe DF . Gastrointestinal dysfunction in autism spectrum disorder: the role of the mitochondria and the enteric microbiome. Microb Ecol Health Dis. 2015; 26 27458, doi: http://dx.doi.org/10.3402/mehd.v26.27458 .
  • Bilbo SD , Nevison CD , Parker W . A model for the induction of autism in the ecosystem of the human body: the anatomy of a modern pandemic?. Microb Ecol Health Dis. 2015; 26 26253, doi: http://dx.doi.org/10.3402/mehd.v26.26253 .
  • Kuhn M , Grave S , Bransfield R , Harris S . Long term antibiotic therapy may be an effective treatment for children co-morbid with Lyme disease and autism spectrum disorder. Med Hypotheses. 2012; 78: 606–15.
  • Kuhn M , Bransfield R . Divergent opinions of proper Lyme disease diagnosis and implications for children co-morbid with autism spectrum disorder. Med Hypotheses. 2014; 83: 321–5.
  • Manev R , Manev H . Aminoglycoside antibiotics and autism: a speculative hypothesis. BMC Psychiatry. 2001; 1: 5.
  • Adams JB , Johansen LJ , Powell LD , Quig D , Rubin RA . Gastrointestinal flora and gastrointestinal status in children with autism–comparisons to typical children and correlation with autism severity. BMC Gastroenterol. 2011; 11: 22.
  • Edelson SM . Parent ratings of behavioral effects of biomedical treatments. Autism Research Institute Newsletter .
  • Vrieze A , de Groot PF , Kootte RS , Knaapen M , van Nood E , Nieuwdorp M . Fecal transplant: a safe and sustainable clinical therapy for restoring intestinal microbial balance in human disease?. Best Pract Res Clin Gastroenterol. 2013; 27: 127–37.
  • Aroniadis OC , Brandt LJ . Fecal microbiota transplantation: past, present and future. Curr Opin Gastroenterol. 2013; 29: 79–84.
  • Alang N , Kelly CR . Weight gain after fecal microbiota transplantation. Clin Infect Dis. 2015; 2: 1–2.
  • Toh MC , Allen-Vercoe E . The human gut microbiota with reference to autism spectrum disorder: considering the whole as more than a sum of its parts. Microb Ecol Health Dis. 2015; 26 26309, doi: http://dx.doi.org/10.3402/mehd.v26.26309 .
  • Elliott DE , Weinstock JV . Helminth-host immunological interactions: prevention and control of immune-mediated diseases. Ann N Y Acad Sci. 2012; 1247: 83–96.
  • Parker W . The “hygiene hypothesis” for allergic disease is a misnomer. BMJ. 2014; 348: g5267.
  • Siniscalco D , Antonucci N . Possible use of Trichuris suis ova in autism spectrum disorders therapy. Med Hypotheses. 2013; 81: 1–4.
  • Gilbert JA , Krajmalnik-Brown R , Porazinska DL , Weiss SJ , Knight R . Toward effective probiotics for autism and other neurodevelopmental disorders. Cell. 2013; 155: 1446–8.
  • Hsiao EY , McBride SW , Hsien S , Sharon G , Hyde ER , McCue T , etal. Microbiota modulate behavioral and physiological abnormalities associated with neurodevelopmental disorders. Cell. 2013; 155: 1451–63.
  • Karunasena E , McMahon KW , Kurkure PC , Brashears MM . A comparison of cell mediators and serum cytokines transcript expression between male and female mice infected with Mycobacterium avium subspecies paratuberculosis and/or consuming probiotics. Pathog Dis. 2014; 72: 104–10.
  • Shida K , Nomoto K . Probiotics as efficient immunopotentiators: translational role in cancer prevention. Indian J Med Res. 2013; 138: 808–14.
  • Toral M , Gomez-Guzman M , Jimenez R , Romero M , Sanchez M , Utrilla MP , etal. The probiotic Lactobacillus coryniformis CECT5711 reduces the vascular pro-oxidant and pro-inflammatory status in obese mice. Clin Sci (Lond). 2014; 127: 33–45.
  • Adams CM . Patient report: autism spectrum disorder treated with camel milk. Glob Adv Health Med. 2013; 2: 78–80.
  • Al-Ayadhi LY , Elamin NE . Camel milk as a potential therapy as an antioxidant in autism spectrum disorder (ASD). Evid Based Complement Alternat Med. 2013; 2013: 602834.
  • Bashir S , Al-Ayadhi LY . Effect of camel milk on thymus and activation-regulated chemokine in autistic children: double-blind study. Pediatr Res. 2014; 75: 559–63.
  • Ramaekers VT , Rothenberg SP , Sequeira JM , Opladen T , Blau N , Quadros EV , etal. Autoantibodies to folate receptors in the cerebral folate deficiency syndrome. N Engl J Med. 2005; 352: 1985–91.
  • Frye RE , Sequeira JM , Quadros EV , James SJ , Rossignol DA . Cerebral folate receptor autoantibodies in autism spectrum disorder. Mol Psychiatry. 2013; 18: 369–81.
  • Suez J , Korem T , Zeevi D , Zilberman-Schapira G , Thaiss CA , Maza O , etal. Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature. 2014; 514: 181–6.
  • Palmnas MS , Cowan TE , Bomhof MR , Su J , Reimer RA , Vogel HJ , etal. Low-dose aspartame consumption differentially affects gut microbiota-host metabolic interactions in the diet-induced obese rat. PLoS One. 2014; 9: e109841.
  • Elder JH , Shankar M , Shuster J , Theriaque D , Burns S , Sherrill L . The gluten-free, casein-free diet in autism: results of a preliminary double blind clinical trial. J Autism Dev Disord. 2006; 36: 413–20.
  • Knivsberg AM , Reichelt KL , Hoien T , Nodland M . A randomised, controlled study of dietary intervention in autistic syndromes. Nutr Neurosci. 2002; 5: 251–61.
  • Whiteley P , Haracopos D , Knivsberg AM , Reichelt KL , Parlar S , Jacobsen J , etal. The ScanBrit randomised, controlled, single-blind study of a gluten- and casein-free dietary intervention for children with autism spectrum disorders. Nutr Neurosci. 2010; 13: 87–100.
  • Kossoff EH , Wang HS . Dietary therapies for epilepsy. Biomed J. 2013; 36: 2–8.
  • Frye RE , Rossignol D , Casanova MF , Brown GL , Martin V , Edelson S , etal. A review of traditional and novel treatments for seizures in autism spectrum disorder: findings from a systematic review and expert panel. Front Public Health. 2013; 1: 31.
  • Chan SS , Luben R , van Schaik F , Oldenburg B , Bueno-de-Mesquita HB , Hallmans G , etal. Carbohydrate intake in the etiology of Crohn's disease and ulcerative colitis. Inflamm Bowel Dis. 2014; 20: 2013–21.
  • Flint HJ , Duncan SH , Scott KP , Louis P . Links between diet, gut microbiota composition and gut metabolism. Proc Nutr Soc. 2015; 74: 13–22.
  • Kau AL , Ahern PP , Griffin NW , Goodman AL , Gordon JI . Human nutrition, the gut microbiome and the immune system. Nature. 2011; 474: 327–36.
  • Brudnak MA , Rimland B , Kerry RE , Dailey M , Taylor R , Stayton B , etal. Enzyme-based therapy for autism spectrum disorders – is it worth another look?. Med Hypotheses. 2002; 58: 422–8.
  • Munasinghe SA , Oliff C , Finn J , Wray JA . Digestive enzyme supplementation for autism spectrum disorders: a double-blind randomized controlled trial. J Autism Dev Disord. 2010; 40: 1131–8.
  • Amato KR , Leigh SR , Kent A , Mackie RI , Yeoman CJ , Stumpf RM , etal. The role of gut microbes in satisfying the nutritional demands of adult and juvenile wild, black howler monkeys (Alouatta pigra). Am J Phys Anthropol. 2014; 155: 652–64.
  • Koeth RA , Wang Z , Levison BS , Buffa JA , Org E , Sheehy BT , etal. Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis. Nat Med. 2013; 19: 576–85.
  • Adams JB , Audhya T , McDonough-Means S , Rubin RA , Quig D , Geis E , etal. Nutritional and metabolic status of children with autism vs. neurotypical children, and the association with autism severity. Nutr Metab (Lond). 2011; 8: 34.
  • Adams JB , Audhya T , McDonough-Means S , Rubin RA , Quig D , Geis E , etal. Effect of a vitamin/mineral supplement on children and adults with autism. BMC Pediatr. 2011; 11: 111.
  • Finegold SM , Molitoris D , Song Y , Liu C , Vaisanen ML , Bolte E , etal. Gastrointestinal microflora studies in late-onset autism. Clin Infect Dis. 2002; 35: S6–16.
  • Thurm A , Manwaring SS , Luckenbaugh DA , Lord C , Swedo SE . Patterns of skill attainment and loss in young children with autism. Dev Psychopathol. 2014; 26: 203–14.
  • Kushki A , Brian J , Dupuis A , Anagnostou E . Functional autonomic nervous system profile in children with autism spectrum disorder. Mol Autism. 2014; 5: 39.
  • Nuske HJ , Vivanti G , Hudry K , Dissanayake C . Pupillometry reveals reduced unconscious emotional reactivity in autism. Biol Psychol. 2014; 101: 24–35.
  • Eilam-Stock T , Xu P , Cao M , Gu X , Van Dam NT , Anagnostou E , etal. Abnormal autonomic and associated brain activities during rest in autism spectrum disorder. Brain. 2014; 137: 153–71.
  • Scahill L , Dimitropoulos A , McDougle CJ , Aman MG , Feurer ID , McCracken JT , etal. Children's Yale-Brown obsessive compulsive scale in autism spectrum disorder: component structure and correlates of symptom checklist. J Am Acad Child Adolesc Psychiatry. 2014; 53: 97–107.e1.
  • Erickson CA , Veenstra-Vanderweele JM , Melmed RD , McCracken JT , Ginsberg LD , Sikich L , etal. STX209 (arbaclofen) for autism spectrum disorders: an 8-week open-label study. J Autism Dev Disord. 2014; 44: 958–64.
  • Butter E , Mulick J . The Ohio autism clinical impressions scale (OACIS). 2006; Columbus, OH: Children's Research Institute.
  • Psychopharmacology TORUoP. OSU autism rating scale—DSM-IV (OARS-4). 2005; Columbus, OH: Children's Research Institute.
  • Choque Olsson N , Bolte S . Brief report: “Quick and (not so) dirty” assessment of change in autism: cross-cultural reliability of the developmental disabilities CGAS and the OSU autism CGI. J Autism Dev Disord. 2014; 44: 1773–8.
  • Wink LK , Early M , Schaefer T , Pottenger A , Horn P , McDougle CJ , etal. Body mass index change in autism spectrum disorders: comparison of treatment with risperidone and aripiprazole. J Child Adol Psychopharm. 2014; 24: 78–82.
  • Singh K , Connors SL , Macklin EA , Smith KD , Fahey JW , Talalay P , etal. Sulforaphane treatment of autism spectrum disorder (ASD). Proc Natl Acad Sci U S A. 2014; 111: 15550–5.
  • Arnold LE , Aman MG , Hollway J , Hurt E , Bates B , Li X , etal. Placebo-controlled pilot trial of mecamylamine for treatment of autism spectrum disorders. J Child Adol Psychopharmacol. 2012; 22: 198–205.
  • Cohen IL , Gardner JM , Karmel BZ , Kim SY . Rating scale measures are associated with Noldus EthoVision-XT video tracking of behaviors of children on the autism spectrum. Mol Autism. 2014; 5: 15.
  • Papagiannopoulou EA , Chitty KM , Hermens DF , Hickie IB , Lagopoulos J . A systematic review and meta-analysis of eye-tracking studies in children with autism spectrum disorders. Soc Neurosci. 2014; 9: 610–32.
  • Fawkes DB , Malow BA , Weiss SK , Reynolds AM , Loh A , Adkins KW , etal. Conducting actigraphy research in children with neurodevelopmental disorders-a practical approach. Behav Sleep Med. 2014; 12: 1–16.
  • Rossignol DA , Frye RE . Melatonin in autism spectrum disorders: a systematic review and meta-analysis. Dev Med Child Neurol. 2011; 53: 783–92.
  • Johnson CR , Turner KS , Foldes EL , Malow BA , Wiggs L . Comparison of sleep questionnaires in the assessment of sleep disturbances in children with autism spectrum disorders. Sleep Med. 2012; 13: 795–801.
  • Schneider CK , Melmed RD , Barstow LE , Enriquez FJ , Ranger-Moore J , Ostrem JA . Oral human immunoglobulin for children with autism and gastrointestinal dysfunction: a prospective, open-label study. J Autism Dev Disord. 2006; 36: 1053–64.
  • Caplan A , Walker L , Rasquin A . Development and preliminary validation of the questionnaire on pediatric gastrointestinal symptoms to assess functional gastrointestinal disorders in children and adolescents. J Pediatr Gastroenterol Nutr. 2005; 41: 296–304.
  • Dimenas E , Glise H , Hallerback B , Hernqvist H , Svedlund J , Wiklund I . Quality of life in patients with upper gastrointestinal symptoms. An improved evaluation of treatment regimens?. Scand J Gastroenterol. 1993; 28: 681–7.
  • Thiass CA , Zeevi D , Levy M , Zilberman-Schapira G , Suez J , Tengeler AC , etal. Transkingdom control of microbiota diurnal oscillations promotes metabolic homeostasis. Cell. 2014; 159: 514–29.
  • Langille MG , Zaneveld J , Caporaso JG , McDonald D , Knights D , Reyes JA , etal. Predictive functional profiling of microbial communities using 16S rRNA marker gene sequences. Nat Biotechnol. 2013; 31: 814–21.
  • Shaw W . Increased urinary excretion of a 3-(3-hydroxyphenyl)-3-hydroxypropionic acid (HPHPA), an abnormal phenylalanine metabolite of Clostridia spp. in the gastrointestinal tract, in urine samples from patients with autism and schizophrenia. Nutr Neurosci. 2010; 13: 135–43.
  • Persico AM , Napolioni V . Urinary p-cresol in autism spectrum disorder. Neurotoxicol Teratol. 2013; 36: 82–90.
  • Altieri L , Neri C , Sacco R , Curatolo P , Benvenuto A , Muratori F , etal. Urinary p-cresol is elevated in small children with severe autism spectrum disorder. Biomarkers. 2011; 16: 252–60.
  • Aw W , Fukuda S . Toward the comprehensive understanding of the gut ecosystem via metabolomics-based integrated omics approach. Semin Immunopathol. 2014; 37: 5–16.
  • Rosser EC , Oleinika K , Tonon S , Doyle R , Bosma A , Carter NA , etal. Regulatory B cells are induced by gut microbiota-driven interleukin-1beta and interleukin-6 production. Nat Med. 2014; 20: 1334–9.
  • Mortha A , Chudnovskiy A , Hashimoto D , Bogunovic M , Spencer SP , Belkaid Y , etal. Microbiota-dependent crosstalk between macrophages and ILC3 promotes intestinal homeostasis. Science. 2014; 343: 1249288.
  • Sustr V , Stingl U , Brune A . Microprofiles of oxygen, redox potential, and pH, and microbial fermentation products in the highly alkaline gut of the saprophagous larva of Penthetria holosericea (Diptera: Bibionidae). J Insect Physiol. 2014; 67: 64–9.
  • Jones RM , Luo L , Ardita CS , Richardson AN , Kwon YM , Mercante JW , etal. Symbiotic lactobacilli stimulate gut epithelial proliferation via Nox-mediated generation of reactive oxygen species. Embo J. 2013; 32: 3017–28.
  • Neish AS . Redox signaling mediated by the gut microbiota. Free Radic Res. 2013; 47: 950–7.
  • Tan J , McKenzie C , Potamitis M , Thorburn AN , Mackay CR , Macia L . The role of short-chain fatty acids in health and disease. Adv Immunol. 2014; 121: 91–119.
  • Bauerl C , Collado MC , Zuniga M , Blas E , Perez Martinez G . Changes in cecal microbiota and mucosal gene expression revealed new aspects of epizootic rabbit enteropathy. PLoS One. 2014; 9: e105707.
  • Theriot CM , Koenigsknecht MJ , Carlson PE , Hatton Jr., GE , Nelson AM , Li B , etal. Antibiotic-induced shifts in the mouse gut microbiome and metabolome increase susceptibility to Clostridium difficile infection. Nat Commun. 2014; 5: 3114.
  • Perez-Cobas AE , Artacho A , Knecht H , Ferrus ML , Friedrichs A , Ott SJ , etal. Differential effects of antibiotic therapy on the structure and function of human gut microbiota. PLoS One. 2013; 8: e80201.
  • Perez-Cobas AE , Gosalbes MJ , Friedrichs A , Knecht H , Artacho A , Eismann K , etal. Gut microbiota disturbance during antibiotic therapy: a multi-omic approach. Gut. 2013; 62: 1591–601.
  • Fouhy F , Guinane CM , Hussey S , Wall R , Ryan CA , Dempsey EM , etal. High-throughput sequencing reveals the incomplete, short-term recovery of infant gut microbiota following parenteral antibiotic treatment with ampicillin and gentamicin. Antimicrob Agents Chemother. 2012; 56: 5811–20.
  • Dethlefsen L , Relman DA . Incomplete recovery and individualized responses of the human distal gut microbiota to repeated antibiotic perturbation. Proc Natl Acad Sci USA. 2011; 108: 4554–61.