Issue 9 / 18 March 2013

SURGICAL masks, currently available for between 14 and 50 cents each, are a low-cost, convenient solution to the risk of iatrogenic septic arthritis, says a leading infection prevention specialist.

However, Associate Professor Allen Cheng, deputy head of infection prevention at The Alfred Hospital in Melbourne, said the question was where to draw the line on wearing a mask, particularly in very low-risk procedures such as vaccinations.

Professor Cheng was commenting on a case report in this week’s issue of the MJA about a prosthetic shoulder infection which may have been caused by an intra-articular injection performed by a proceduralist not wearing a mask. (1)

Dr Nicholas Coatsworth, microbiology registrar at Royal North Shore Hospital in Sydney, and coauthors detailed the case of a 72-year-old man with a prosthetic right shoulder joint who presented with fever, a warm, swollen shoulder joint, pain on passive movement of the joint and an elevated C-reactive protein level less than 24 hours after receiving an injection into the joint of 8 mL of radiographic contrast before a computed tomography (CT) arthrogram of his shoulder.

After aspiration of the joint, culture yielded light growth of Streptococcus mitis group 1, the authors wrote. The proceduralist — who used aseptic technique for the injection, but did not wear a mask — provided an oropharyngeal swab and several organisms were cultured from it, including multiple viridans Streptococcus species.

Pulsed-field gel electrophoresis was performed on the samples, and the authors found that “the patient’s organism and a strain of the S. mitis recovered from the proceduralist’s throat showed indistinguishable fragment patterns”.

“This strongly suggested droplet transmission of the proceduralist’s oral flora onto the needle or skin, with subsequent inoculation into the shoulder joint”, they wrote.

“This is the first published instance of molecular epidemiology technique showing probable transmission of oral flora from a proceduralist to the joint of a patient, resulting in iatrogenic septic arthritis.

The man had joint failure 6 months after the acute presentation, confirmed on arthrogram and by arthroscopy, and underwent a full revision of the right shoulder prosthesis. “The procedure was uncomplicated, and the patient remains well with no signs of recurrent infection”, the authors wrote.

Professor Cheng said the case study raised an issue that had largely been invisible.

“I suspect there are more cases like this one happening than we know about”, he said.

“These were questions we learned a long time ago, about aseptic technique. Increasingly it’s being recognised that it is the little things that we do [in preventing infection] — or don’t do — that can add up to a bit of risk.”

Professor Cheng said that while surgical masks were a cheap and convenient way of reducing the risk of iatrogenic infection, it was a question of how far to push the use of surgical masks.

“There is a point where the risk of transmission is so low — giving vaccinations for example — but where do you draw that line?” he said. “Is it giving steroid injections? Or epidurals?

“The spectrum of risk is small enough that you can really only make recommendations about wearing surgical masks. The risk is not great enough to legislate.

“There’s still a little bit of an open question — it’s never completely clear that the organism that caused the infection [in this case] came from the mouth of the proceduralist — but it would make sense to use surgical masks in that situation, particularly as the cost of using them is so low”, Professor Cheng said.

– Cate Swannell

1. MJA 2013; 198: 285-286

Posted 18 March 2013

3 thoughts on “Cheap way to cut infection risk

  1. EyeDoc says:

    This story is not new or surprising to Eye Docs, but we are all in such silos now that not much information transfer occurs. A pity.

    Intravitreal injections were rare even five years ago but now are very common, to treat many retinal vascular conditions. (tens of) Thousands of injections are given per year in Australia and it was realised early on that it would be far more cost effective to do these in the office, not in a theatre. To define safety and risk for office injections there have been many large trials and these have found that
    – eyelid speculum,
    – iodine prep and
    – MASKS
    are independently associated with lower endophthalmitis rates. Interestingly, sterile drapes and postop antibiotic drops are not…

    I think that these studies may well translate to any procedure that involves needle entry, certainly they point to areas that should be considered by other practitioners.

  2. Matthias Maiwald says:

    I agree with Allen Cheng on the importance of maintaining good aseptic procedures, and also that it is a question of where to draw the line. Just to recapitulate, we have a special situation here: the pathogenetic mechanisms are that there is an artificial joint where the natural local defence mechanisms have been inactivated by the presence of prosthetic material, a large amount (8 ml) of fluid is injected, and therefore very small numbers of inoculated bacteria can cause infections. This is anecdotally also a problem in corticosteroid injections, where the local defence is diminished by the steroid (again, a clear pathogenetic mechanism). However, some advocates of evidence-based medicine that I have encountered would dismiss such basic patient safety measures as wearing masks while doing procedures and performing skin antisepsis as “not being supported by evidence” because there have been no clinical trials that studied them.

  3. Kevin B Orr says:

    Perhaps the best and simplist protection against infection when giving injections or aspirating would be to ban talking during the procedure!

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