[Histonet] Formalin substitutes

Tue Jul 27 02:24:07 CDT 2010

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-bounces <@t> lists.utsouthwestern.edu
[mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Weaver,
Colin
Sent: Saturday, 24 July 2010 2:15 AM
To: histonet <@t> 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

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