SMTL Newsletter, Volume 2, No 1, June 2000

Maggots and the battle against MRSA.

Staphylococcus aureus is a Gram positive bacterium that exists as a skin commensal in a significant proportion of the population. Despite its ubiquitous nature, it is a recognised potential pathogen with the ability to cause a wide range of infections from localised skin eruptions to life-threatening conditions such as bacteraemia, endocarditis and pneumonia.

An important feature of the bacterium is its ability to develop resistance to commonly used antibiotics and antiseptics. These resistant strains are known as MRSA (methicillin-resistant Staphylococcus aureus).

The virulence or pathogenicity of some strains of MRSA may not be very different from those of methicillin sensitive Staphylococcus aureus (MSSA) but when infections do occur, they can be more difficult to control and result in increased mortality.

MRSA like MSSA can be isolated from wounds that are apparently healing normally. Whilst it is unlikely that any attempt would be made to eliminate MSSA in this situation, a more aggressive approach may be adopted with MRSA because of the potential risk that simple colonisation may progress into a hard-to-treat clinical infection.

If active treatment to eradicate MRSA from a wound is considered appropriate, mupirocin is generally selected as the agent of choice. For minor skin lesions, mupirocin is applied in a polyethylene glycol base (Bactroban), but this should not be used on larger wounds because of potential problems of nephrotoxicity caused by the polyethylene glycol. Mupirocin in a paraffin base (Bactroban Nasal) is usually recommended for this purpose but prolonged application should be avoided because of the possibility of inducing mupirocin resistant strains of MRSA. The normal recommended dose is 3-4 applications per day for 5-10 days. Once daily application is unlikely to be effective. The requirement to apply an ointment to a wound several times a day does not fit well with normal wound management practice, which is generally to apply a dressing system that may remain undisturbed for several days.

From time to time patients present with wounds containing MRSA that have failed to respond to mupirocin. This may be due to the nature of the wound, inappropriate use of the treatment, or the existence or development of resistance. In these situations alternative forms of therapy are required to eradicate the organism and facilitate healing.

One technique that has been used successfully is the application of maggots, sterile larvae of the common greenbottle Lucilia sericata.

Five consecutive patients with different types of wounds infected with MRSA that had failed to respond to conventional therapy were treated with sterile maggots. In every instance the maggots cleansed the wounds, eliminated the MRSA, and allowed healing to commence in an average of 4 days (7,3,6,2,2).

The use of maggots in this way provides healthcare professionals with an additional weapon in the fight against this and other pathogenic organisms regardless of whether the wound contains necrotic material. It also means that the usage of valuable treatments like mupirocin and other antibiotics can be reduced or reserved for other applications.

For further information on MRSA and the use of maggots in the treatment of infected wounds see 'Maggots and MRSA: An Ancient Solution to a Modern Problem' a book published by SMTL price £5.00.

S. Thomas

SMTL picture to tour the World.

A photograph of a leg wound from the article in World Wide Wounds on larval therapy for an infected insect bite is to be used in a human body exhibit (for 10 to 14 year-olds) that will travel internationally for five years.

Rob Lunde (Curator of ``Science World'' in Vancouver) wrote to SMTL in October, asking for permission to use the image.

The exhibition is called Grossology: The Impolite Science of the Human Body. It's based on a series of best-selling "Grossology" books by Sylvia Branzei. The books and exhibition, designed for children ages 9 to 13, deal with how and why we produce things like poop, vomit, gas, burps, snot, boogers, pee, pimples, blisters,warts, scabs, etc. in language and terms children use. One of the exhibits features a large 3-D fibreglass model of human skin that children can climb on. The picture of the wound from the SMTL website is on the graphics panel for the climbing skin. The image of the wound is covered by a cloth bandage that the visitor lifts to see the image of the wound.

Grossology opened on Feb 4, 2000 in Vancouver (until April 30) and is currently booked for the next five years to museums and science centres in North America and Asia. It will probably also visit the UK and the rest of Europe. 

P. Phillips

Papers, Standards and Circulars

SAB on conductive gel pads.

Safety Action Bulletin NAW SAB (99)40, ``Conductive gel pads for defibrilation or cardioversion'', informs users not to rely on a the gel pad/paddles to monitor the patients heart rhythm after defibrillation or cardioversion.

Because there may be a significant delay (3-4 minutes) for the ECG trace to return, critical shock monitoring should be undertaken via leads or other independent means.

P. Phillips

Hazard Notice on Mediteck Products.

Hazard Notice MDA HN2000(03) (April 2000), ``MEDITECK LTD PRODUCTS : WITHDRAWAL FROM USE'', states that the following products from Mediteck Ltd should be withdrawn from use as their sterility and safety cannot be guaranteed:

  • Sterile Dressing Pack, Drug Tariff Specification No. 10
  • Latex examination gloves
  • Crepe Bandages
  • Gauze Swab BP
  • Absorbent Cotton Wool BP

The Hazard Notice is available on the MDA website at:

P. Phillips

Safety Notice on Gas Cylinders and fire risks.

MDA Safety Notice MDA SN 2000(07) (April 2000) notes that there is a serious risk of fire if substances such as dirt, oil, grease or hand creams contaminate connections between medical devices and medical gas cylinders. This applies to cylinders containing: oxygen, nitrous oxide, oxygen/nitrous oxide (Entonox), oxygen/carbon dioxide and oxygen/helium mixtures.

Apparently, the MDA has recently received two reports of fire occurring on the opening of oxygen cylinders. The critical factor on investigation was the presence of contaminants such as hand cream, grease and oil.

The notice includes a number of action points that should be covered in training users who use or handle gas cylinders. The Safety Notice is available on the MDA website at:

P. Phillips

Introduction to Trocars, Low temperature sterilisation.

Volume 5, numbers 2 and 3 of ``ECRI Health Technology Monitor'' has an interesting article on trocars and laparoscopic procedures, including the dangers of trocar insertion. The authors also discuss the usefulness of shielded versus nonshielded trocars. Although the FDA state that they ``are unaware of any data ... showing that these shielded trocars provide any additional protection from injury to bowel, blood vessels or other organs'', the ECRI believe that proper use of shielded trocars for primary insertions (in laparoscopies) may help reduce the number of trocar injuries.

Volume 5, numbers 10 and 11 have a useful paper entitled ``Low-Temperature Sterilisation: An Overview''. The paper considers the pros and cons of various methods, including Ethylene Oxide, Gas plasma and Liquid chemical germicides (LCG). It concludes that gas plasma technology offers a number of advantages over EtO, including faster turnaround times and safety.

ECRI can be contacted in the UK on 01707-871511, Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

P. Phillips

Luer lock syringes and syringe drivers

The Pharmaceutical Journal (May 20, 2000, p 772) carried a letter from Alder Hey children's hospital noting that they had experienced problems relating to residual solution left in syringes when used with Graseby and IVAC syringe drivers. Luer-slip syringes infused all of the solution, but luer-lock syringes were left with residual volumes of between 0.2ml and 0.6ml. Their main concern is that low-volume infusions given to neonates using this method could result in an underdose of up to 25%.

The authors of the letter recommend that pharmacists check the practice relating to the use of syringes and syringe drivers in their own trusts.

P. Phillips

Checks and tests for newly delivered medical devices.

MDA DB9801, Supplement 1, was issued in December 1999. The document outlines a methodology to help choose appropriate pre-first-use checks and tests for newly-delivered products. Table 1 in the document covers the key issues to be addressed for different categories of medical device, from sterile and non-sterile bulk products, such as gloves, catheters, syringes and dressings to complex electrically powered devices, such as infusion pumps. The rest of the document contains modules and forms to enable you to put the required checks into action.

The document is a supplement to DB 9801 ``Medical Device and Equipment Management for Hospital and Community-based Organisations''.

P. Phillips

Glove protein standard now published.

EN 455 Part 3 (Medical glove for single use - Part 3: Requirements and testing for biological evaluation) has now been published. The standard covers test methods for determining protein content and endotoxin load.

Purchasing gloves low in protein is an essential step in preventing the sensitisation of staff and patients to latex proteins, and SMTL are now working to this latest version of the standard for all protein determinations carried out for the Welsh Contracts and for commercial organisations.

P. Phillips

Chest Drains - No More Kebabs!

Traditionally, if it was necessary to drain air, blood or effusion from the pleural space, a small skin incision was made in the chest wall following local anaesthesia, and a plastic tube drain mounted on a sharp trochar was pushed into the pleural cavity. The trochar was then removed, and the tube connected to an underwater seal drain. In both experienced and inexperienced hands the consequences of using the sharp stiff trochar could be disastrous. Not only could the lung be pierced if the disease process had made the visceral pleura adherent to the parietal pleura, but accidental spearing of the liver, spleen, heart or mediastinum were all reported.

In the 1980s, the Advanced Trauma Life Support Course which started in the USA, but is now taught in the UK and almost all round the world, advocated and taught the safer technique of the ``mini-thoracotomy'' approach to chest drainage. With the skin anaesthetised, a small incision is made, and artery forceps are used to bluntly dissect down to the pleura. The pleura reached, the closed, blunt forceps are 'popped' through the pleura above a rib, and replaced by a gloved finger, which sweeps inside the pleural cavity checking for, and separating, any adhesions. The tube drain is then inserted directly, guided by the gloved finger now pulled out from the pleural cavity, but resting on the rib and 'pointing' at the entry hole into the pleural space. The trochar is not used at all.

This technique has been taught now for more than 10 years and its safety has led to its widespread use in all specialities from Emergency Medicine and Intensive Care to General Medicine and Surgery and Paediatrics.

It is now possible to buy chest drainage tubes without the trochar as manufacturing companies have responded to this widely accepted technique. Many Trusts have gone over to only ordering the trochar-less tube drains, which still come in the full range of sizes and this is a move to be encouraged. Hopefully, the days of the ``kebab stick'' are over!

Eileen Williams,

Consultant Anaesthetist and ATLS Instructor

Glan Clwyd Hospital,


Latex and nitrile gloves superior to Vinyl

An article in the October 1999 issue of the American Journal of Infection Control (AJIC, October 1999, Volume 27, Number 5) has shown substantial differences between Latex/Nitrile gloves and Vinyl.

The authors carried out testing on 4 brands of latex, 2 brands of nitrile and 4 brands of vinyl glove.

The gloves were tested for pinholes ``out of the box'', and except for 1 brand of vinyl glove with a 12% failure rate, there was little difference between the rest. However, after being subjected to ``simulated usage'' conditions (attaching and removing a capped needle to a luer-lock syringe 30 times, connecting and disconnecting a luer-lock syringe to IV tubing 8 times, manipulating a stopcock 8 times and wrapping, taping and unwrapping a blunt object 2 times) the vinyl gloves were found to have failure rates of 26-61% for the non-stretch vinyl, and 12-20% for the stretch vinyl. In contrast, the latex gloves had a 0-4% failure rate and the nitrile a 1-3% failure rate.

The authors conclude that the barrier properties of vinyl are compromised more frequently than those of latex or nitrile, and that vinyl is only appropriate for non-rigorous, low-risk procedures of short duration, whereas latex or nitrile are the materials of choice for high-risk situations, including exposure to blood-borne pathogens.

P. Phillips

Alginate dressings in surgery and wound debridement.

Large quantities of alginate dressings are used each year for the treatment of exuding wounds such as leg ulcers, pressures sores and infected surgical wounds. Originally these were presented in the form of a loose fleece formed primarily from fibres of calcium alginate. More recently dressings have been developed in which the fibres have been entangled to form a product with more cohesive structure to increase the strength of the fabric when soaked with exudate or blood. Some products also contain a significant proportion of sodium alginate to improve the gelling properties of the dressing in use, and other dressings made from freeze dried alginate have also been produced.

Once in contact with an exuding wound, an ion exchange reaction that takes place between the calcium ions in the dressing and sodium ions in serum or wound fluid. When a significant proportion of the calcium ions present on the fibre have been replaced by sodium, the fibre swells and partially dissolves forming a gel-like mass although the degree of swelling is determined principally by the chemical composition of the alginate as determined by its botanical source.

Although it is recognised that differences between the various brands of dressings may influence their handling characteristics - particularly when wet, it is generally assumed that these differences are of limited relevance to the performance of the dressings clinically or at a cellular level. There is some evidence to suggest, however, that these assumptions may not be correct and that alginates may influence wound healing in a number of ways not yet fully understood.

This review of the literature encompassing the history, origin, structure, chemistry and clinical applications of alginates and alginate dressings has revealed that despite their widespread use, they have been the subject of very few well controlled clinical studies. There is fairly convincing evidence, however, that they do offer advantages over more traditional dressings for at least some clinical indications. It has also become obvious that there is a general lack of understanding on the part of some clinicians and others concerning the importance of the secondary dressing system that must be used in conjunction with alginate dressings.

Careful examination of the design and outcomes of the published studies suggests that the choice of  both the primary alginate dressing and the secondary dressing can play a major role  in determining treatment outcomes.

This article is a summary of a literature review that came second in the 1999 Journal of Wound Care Awards. The complete review has been published in three parts in the JOWC, Volume 9, Nos 2, 3 and 4.


Contract Information

Vygon Lectrocaths

Users of the Vygon Lectrocath should be aware that both single and double-wrapped versions are available on the current Welsh Contract. Advice from Dr Peter Jones (Consultant Anaesthetist, UHW and chairman of the Mid and South East Wales Commodity Advisory Group) is that the double wrapped catheter should be the preferred version for use by scrub teams.

P. Phillips

Nitrile gloves on contract.

Due to overwhelming interest in the use of nitrile gloves for latex-allergic staff, Welsh Health Supplies have now awarded a contract for the Bodyguard Medisavers nitrile glove. The glove was tested at SMTL, and found to fully comply with EN 455 parts 1 and 2. The gloves are available on contract, but are not presently available from the Bridgend and Denbigh stores.

P. Phillips

Hudson to change their distributors.

Hudson have announced their intention to change the distributor of their range of respiratory care products (including the AquaPak humidification system). Previously available via Henleys in the UK, it appears that they are going to be using HM&S from July 2000.

R. Flanagan

Welsh Health Supplies


We are looking for a snappier title than ``SMTL News'' - if you have a good idea, please email one of the editors (details below).


The Medical
Disposables and
Dressings Newsletter
Vol. 2 No. 1
June 2000
Published by:
The Surgical Materials
Testing Laboratory

Edited by:
Dr Stephen Thomas
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
Peter Phillips
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

Contact Information
Tel: 01656-752820
Fax: 01656-752830
Princess of Wales Hospital
Coity Road
CF31 1RQ
©2000 by SMTL.
All rights reserved. No permission necessary to copy, reprint and distribute unaltered within the NHS as required.

This file is also available from

Joomla Templates: by JoomlaShack