The following info might be useful: It is believed that formalin given time will kill any microorganisms that are present in tissue and that formalin will inactivate tuberculosis.
Vardaxis et al (J Clin Pathol 1997;50:429-433) were quite rightly concerned with the disinfection of bacterial endospores. Endospores can survive the most adverse chemical and physical environments and can cause such diseases as tetanus, anthrax, gas gangrene and botulism. They used autoclave spore containing test strips and fixed them in various fixatives such as 10% neutral buffered formalin, ethanol in various concentrations (70% & 50%) and two commercial non-formalin fixatives (Kryofix & Spuitfix). Fixation times varied from 24 hours to 14 days. They found that 10% formalin killed all microbes within 24 hours, where as only one non-formalin fixative (Spuitfix) killed the spores and this was only after 7 days fixation. Microwave fixation also did not kill the spores. These workers did note that spore strips do not behave like tissue and that tissue may have a protective effect on pathogens. Cleary et al (J Clin Pathol 2005;58:22-25) studied the antimicrobial effects of UMFix, an alcohol based tissue fixative, on various microorganisms. The UMFix solution was compared with 10% neutral buffered formalin. After a short exposure, UMFix rapidly killed vegetative bacteria, yeasts, moulds, and viruses. Bacterial spores were resistant to killing by UMFix. All organisms were killed by the 10% neutral buffered formalin preparation. They concluded that UMFix was microbicidal for vegetative bacteria, yeasts, and aspergillus species after a short exposure, although it was not active against spore forming bacillus species. The methanol content of the fixative was responsible for the killing effect of this fixative. No killing was seen when polyethylene glycol was used alone. Kappel et al (HUM PATHOL 27:1361--1364, 1996) attempted to grow TB from formalin fixed lung tissue that had previously been shown to be positive by sputum culture. They were unable to culture TB from these tissues. Gerston et al (HUM PATHOL 35:571-575.2004) in South Africa analysed 138 formalin fixed lungs with histological evidence of AFB and were able to culture TB from 12 of these cases (one of these cases had been fixed for 80 days before being tested). Gerston et al suggest that there is a risk of contracting tuberculosis from tissue that has been fixed in formalin, if aerosols or accidental inoculation should occur. Trimming and sectioning wax blocks are of concern but no studies have been done yet. Of concern to histotechnolgists are: 1. Tissue with Inflammation-induced Encapsulation may protect bugs from formalin. 2. Formalin dilutes as it penetrates tissue. 3. Formalin substitutes may not be germicidal. Regards Tony Henwood JP, MSc, BAppSc, GradDipSysAnalys, CT(ASC) Laboratory Manager & Senior Scientist Tel: 612 9845 3306 Fax: 612 9845 3318 the children's hospital at westmead Cnr Hawkesbury Road and Hainsworth Street, Westmead Locked Bag 4001, Westmead NSW 2145, AUSTRALIA -----Original Message----- From: histonet-boun...@lists.utsouthwestern.edu [mailto:histonet-boun...@lists.utsouthwestern.edu] On Behalf Of Weaver, Colin Sent: Saturday, 24 July 2010 2:15 AM To: histonet@lists.utsouthwestern.edu Subject: [Histonet] Formalin substitutes Hi everyone - does anyone know how effective these formalin substitutes are at killing microorgansms9esp HG3) in the tissue fixed? I know that Finefix states that because of the alcohol content being over 70% that it is effective against many micro-organisms but info seems scarce on the others Thanks and have a nice weekend Colin Weaver Histology lab manager VLA Thirsk North Yorkshire UK </pre><br>Veterinary Laboratories Agency (VLA)<br><br>This email and any attachments is intended for the named<br>recipient only.<br>If you have received it in error you have no authority to use,<br>disclose, store or copy any of its contents and you should destroy<br>it and inform the sender. 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