Glove Powder Increases Staphylococcus aureus Abscess Rate in a Rat Model

Methods

Female Sprague-Dawley rats between 200 and 250 g were housed in the Veterans Affairs Medical Center under guidelines provided by the Institutional Animal Care and Use Committee, including supervision by a veterinarian with training in laboratory animal science. Variable doses of MSSA in concentrations of 0, 10², 10³, 10⁴, and 10⁵ colony forming units (cfu).mL and concentrations of starch powder of 0, 10, 50, and 100 mg/mL were injected into the subcutaneous tissue of the dorsum of the rats. We used MSSA because this organism is responsible for approximately 40% to 50% of postoperative surgical site infections and for the practical reason that use of the methicillin-resistant S. aureus would have required a biohazard safety level unavailable in our laboratory. The bacteria was prepared by inoculating in broth under agitation at 35°C for 12 h. The subsequent broth was then diluted to a 0.5-McFarlane standard corresponding to 10⁸ organisms/mL. It was then diluted in a 1-mL aliquot containing 10² through 10⁵ cfu. Glove powder from Roquette America, Inc. (Keokuk, IO) was sterilized using dry heat at 450°F for 3 h and was added to the bacteria aliquots of 0, 10, 50, and 100 mg/mL. Control animals received sterile saline injection with no bacteria or starch, with bacteria only, and with starch only.

Separate inocula were placed in each of the flanks of the rats. The injection site was prepared by shaving the hair and cleaning with chlorhexidine scrub. The 1-mL aliquot was then injected under the dermis of the rat. This model was chosen over introduction of bacteria into an incision or by encapsulation because it minimized possible experimental variability caused by distribution of the inoculum, additional foreign body presence (e.g., sutures), or dissolution of a capsule. The animal was then returned to its cage and observed in a recovery room for any postoperative complications. Animals were observed daily and euthanized if exhibiting any outward signs of abscess such as fluctuance, ulceration, or distress. Animals were harvested 10 days after inoculation. Injection sites were examined for signs of abscess, including erythema and presence of pus. Injection sites were cultured for S. aureus. The primary endpoint was gross abscess formation verified according to culture. Data were analyzed to determine whether the presence of starch powder decreased the number of bacteria needed to produce gross abscess and to determine the number of starch granules required to be present for any particular inoculum to cause infection. We used Systat (Systat Software, Inc., Chicago, IL) to conduct a chi-square test to calculate odds ratios (ORs) for the likelihood of glove powder to cause abscesses.

Results

No abscesses formed in our control animals (sterile inoculum) (Table 1). Increasing bacteria concentrations and increasing amounts of starch powder led to more-frequent abscess formation. The abscesses were readily detected using physical examination 10 days post inoculation, and on section had a purulent center. Abscesses measured approximately 1 cm in diameter. Refractile bodies typical of starch granules were identified on hematoxylin and eosin–stained sections of selected abscesses. A higher concentration of starch (100 mg/mL) decreased the necessary inoculum of bacteria that produced abscess from 10⁴ to 10² cfu/mL. The presence of starch, regardless of concentration, increased the likelihood of abscess formation in the presence of bacteria (OR = 1.8, 95% confidence interval = 1.06, 2.57).

Discussion

Research on surgical glove powder and surgical site infection has been sparse. Other effects of glove powder are better known, including its ability to encourage adhesions [3]. Residual starch powder has been found to lead to postoperative scarring reactions in patients and to produce inflammatory responses in the eyes, pericardium, peritoneum, and pleural surfaces, as well as the meninges [4]. Other research has shown that surgical glove powder not only promotes adhesion formation, but also facilitates tumor cell adhesion and growth in an animal model [5]. Although “clean” incisions are commonly considered to be sterile, approximately 30% of hernia wounds cultured intraoperatively contained bacteria [6].

The presence of a foreign body in a surgical incision has long been known to reduce the inoculum of bacteria required to produce infection. Perioperative antimicrobials are used whenever a medical prosthetic or device is implanted in a patient to reduce the likelihood of infection [7]. Jaffrey and Nade showed in a pilot study that abscess rate increased when a small amount of glove powder (2 mg) was added to 10³ cfu of MSSA. ² We confirmed the earlier findings and extended the study to include glove concentrations from 5 to 100 mg/mL and S. aureus concentrations 10² to 10⁵ cfu/mL. Our results suggest that increasing the amount of glove powder leads to more-frequent abscess formation and reduces the inoculum of bacteria required to produce an abscess. Because most contaminated operations in practice will have perioperative antibiotic prophylaxis, it is likely that the use of antibiotics would increase the number of organisms required to produce an abscess or perhaps eliminate abscess formation.

The majority of glove powder remains on the inside of the gloves, although amounts can be released during removal and when gloves are torn or punctured. Powdered gloves are limited to 15 mg/dm² with a typical surgical glove having 10 dm². Review of gloves manufactured in 2001 showed a range of 30 to 513 mg per glove for surgeons' gloves. Of the gloves tested, only 55.7% met the new maximum powder guidelines [8]. It is difficult to estimate the exact amount of glove powder that is released into an incision, especially with the variability in size and the practice of changing gloves during surgery, thereby introducing additional powder. According to our data, the existence of more than 10 mg/mL of glove powder may affect the rate of abscess formation.

Conclusion

Surgical glove powder reduces the inoculum of bacteria required to produce an abscess and increases the likelihood of abscess formation in Sprague-Dawley rats. Higher concentration of glove powder leads to more-frequent abscess formation. Reducing glove powder contamination would lead to less-frequent abscess formation.