title: Method for Bacterial Growth and Ammonia Production and Effect of Inhibitory Substances in Disposable Absorbent Hygiene Products.
abstract: OBJECTIVE
  The purpose of this study was to evaluate a pragmatic laboratory method to provide a technique for developing incontinence products better able to reduce malodor when used in the clinical setting.
  
  
  METHODS
  Bacterial growth and bacterially formed ammonia in disposable absorbent incontinence products was measured by adding synthetic urine inoculated with bacteria to test samples cut from the crotch area of the product. The inhibitory effect's of low pH (4.5 and 4.9) and 3 antimicrobial substances-chlorhexidine, polyhexamethylene biguanide (PHMB), and thymol-at 2 concentrations each, were studied.
  
  
  RESULTS
  From the initial inocula of 3.3 log colony-forming units per milliliter (cfu/mL) at baseline, the bacterial growth of the references increased to 5.0 to 6.0 log cfu/mL at 6 hours for Escherichia coli, Proteus mirabilis, and Enterococcus faecalis. At 12 hours there was a further increase to 7.0 to 8.9 log cfu/mL. Adjusting the pH of the superabsorbent in the incontinence product from 6.0 to pH 4.5 and pH 4.9 significantly (P < .05) inhibited the bacterial growth rates, in most cases, both at 6 and 12 hours. The effect was most pronounced at pH 4.5. Chlorhexidine had significant (P < .05) inhibitory effect on E. coli and E. faecalis, and at 12 hours also on P. mirabilis. For PHMB and thymol the results varied. At 6 hours, the ammonia concentration in the references (pH 6.0) was 200 to 300 ppm and it was 1500 to 1600 ppm at 8 hours. At pH 4.5, no or little ammonia production was measured at 6 and 8 hours. At pH 4.9, there was a significant reduction (P < .01). Chlorhexidine and PHMB exerted a significant (P < .01 or P < .001) inhibitory effect on ammonia production at both concentrations and at 6 and 8 hours. Thymol 0.003% and 0.03% showed inhibitory effect at both 6 hours (P < .01 or P < .001) and at 8 hours (P < .05 or P < .001).
  
  
  CONCLUSIONS
  The method described in this study can be used to compare the ability of various disposable absorbent products to inhibit bacterial growth and ammonia production. This technique, we describe, provides a pragmatic method for assessing the odor-inhibiting capacity of specific incontinence products.
authors.affiliation: Ulla Forsgren-Brusk, MSc, SCA Hygiene Products AB, Gothenburg, Sweden. Birgitta Yhlen, BSc, SCA Hygiene Products AB, Gothenburg, Sweden. Marie Blomqvist, BSc, SP Technical Research Institute, Food and Bioscience, Gothenburg, Sweden. Peter Larsson, MD, PhD, Department of Infectious Diseases, Institute of Biomedicine, University of Gothenburg and Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Ulla
authors.initials: U
authors.lastname: Forsgren-Brusk
authors.forename: Birgitta
authors.initials: B
authors.lastname: Yhlen
authors.forename: Marie
authors.initials: M
authors.lastname: Blomqvist
authors.forename: Peter
authors.initials: P
authors.lastname: Larsson
mesh_terms: D041342:Absorbent Pads / Q000382:microbiology / Q000592:standards*; D000641:Ammonia / Q000032:analysis / Q000378:metabolism*; D000890:Anti-Infective Agents / Q000494:pharmacology / Q000627:therapeutic use; D001419:Bacteria / Q000187:drug effects / Q000254:growth & development*; D002710:Chlorhexidine / Q000494:pharmacology / Q000627:therapeutic use; D004926:Escherichia coli / Q000254:growth & development / Q000472:pathogenicity; D006801:Humans; D006920:Hygiene / Q000592:standards; D009812:Odorants / Q000517:prevention & control*; D011513:Proteus mirabilis / Q000254:growth & development / Q000472:pathogenicity; D013943:Thymol / Q000494:pharmacology / Q000627:therapeutic use; D014549:Urinary Incontinence / Q000628:therapy*; D014556:Urine / Q000382:microbiology
chemical_list: D000890:Anti-Infective Agents; D013943:Thymol; D000641:Ammonia; D002710:Chlorhexidine