Commentary:    The diagnostic imaging of osteomyelitis (bone infection) can require the combination of diverse imaging techniques for an accurate diagnosis and clinical staging .(1)   Conventional radiography should always be the first imaging modality to start with, as it provides an overview of the anatomy and the pathologic conditions of the bone and soft tissues of the region of interest.  However, since the specificity of plain x-rays for detection is higher than its sensitivity, other, more reliable methods of imaging are necessary.(2 – 4)   Ultra-sonography is most useful in the diagnosis of fluid collections, periosteal involvement, and surrounding soft tissue abnormalities and may provide guidance for diagnostic or therapeutic aspiration, drainage and/or tissue biopsy. Computed tomography (CT) scans can be a useful method to detect early osseous erosion and to document the presence of sequestra, cloacae, foreign bodies, or gas formation; nevertheless, they are generally is less sensitive than other modalities for the detection of osteomyelitis.(3)   Magnetic resonance imaging (MRI) is the most sensitive and most specific imaging modality for the detection of infection in bone (Sens /Spec = 82%-100%/ 75%-95%), provides superb anatomic detail and gives more accurate information of the extent of the infectious process in bone and soft tissue.(3 -5)    Although nuclear medicine imaging (technetium-99 bone scans and Indium-111 white blood cell scans) is particularly sensitive in identifying multifocal osseous involvement, they are rather nonspecific.(6)   

Since no one study is able to definitively confirm the presence of absence of infection, cross-sectional imaging modalities such as CT and MR scanning are now considered the gold standard in diagnosing osteomyelitis, giving excellent anatomic delineation of the infected area and the surrounding soft tissue envelope.   In our protocols, all methods of used, selectively: (7) plain radiographs  to reveal internal hardware, axial alignment, fracture patterns and instability; nuclear scans  to correlate  cellular activity with radiographic change and assess for  poly-osseous disease;  CT scans to delineate sequestra, cloacae, bone volumes, and the extent of fracture healing (union vs non-union);  MRI and PET/CT scans to define the zone of injury/inflammation, disclose skip-lesions and highlight necrotic foci.   

Bibliography:  (1) Haas DW, McAndrew MP. Bacterial osteomyelitis in adults: evolving considerations in diagnosis and treatment. Am J Med, l996; 101:550-561.  (2)  Pineda C, Espinosa R, Pena A. Radiographic imaging in osteomyelitis: the role of plain radiography, computed tomography, ultrasonography, magnetic resonance imaging, and scintigraphy.   Semin Plast Surg, 2009 May; 23(2):80-9.  (3) Termaat MF, Raijmakers PG, Scholtein HJ et al. The accuracy of diagnostic imaging for the assessment of chronic osteomyelitis: a systemic review and meta-analysis. J Bone Joint Surg Am, 2005; 87:2464-2471.  (4) Mahnken AH, Bucker A, Adam G, Gunther RW. MRI of osteomyelitis: sensitivity and specificity of STIR sequences in comparison with contrast-enhanced T1 spin echo sequences. RöFo, 2000; 172” 1016-1019.  (5) Littenerg B, Mushlin AL. Technetium bone scanning in the diagnosis of osteomyelitis: a meta-analysis of test performance. J Gen Intern Med, l992; 7:158-163.  (6) Cierny III, G., Pennick, JJ, Mader, JT, A Clinical Staging System for Adult Osteomyelitis, J. Clinical Orthopaedics and Related Research, Number 414, pp 7-24, September 2003 .  (7)  Cierny G, DiPasquale D. Adult Osteomyelitis. Chapter 16 in Orthopaedic Knowledge Update : Musculoskeletal Infection. Amer. Acad. Orthop. Surg, Rosemont, IL, 2009. pp 135-155.

Article review:   Bhavan KP, Marschall J, Olsen MA, et al:  The Epidemiology of hematogenous vertebral osteomyelitis: a cohort study in a tertiary care hospital.  BMC Infectious Diseases, 2010: 10: 158doi: 10.1186/1471-2334-10-158  (Published 7-7-2010).

Dr. Cierny’s comments:  this article describes the epidemiology and early management of hematogenous vertebral osteomyelitis (anatomic types I and IV) in 70 patients over a 2-year period at Barnes Hospital in Missouri (a retrospective, cohort review).  A microbiological diagnosis was made in only two-thirds the cases.  S. aureus was the most common causative organism.

Results – The mean age was 59.7 years with 54% male. Predisposing factors included: B-hosts with diabetes (43%) or renal insufficiency (24%); in the 30 days prior to admission, an indwelling catheter (30%), bacteremia (19%) or skin/soft tissue infection (17%).  Back pain was the most common symptom (87%), followed by weakness (56%) and fever (46%); seven patients presented with paraplegia.  48% had a normal WBC but 95-98% had either an elevated ESR or CRP. 

The lumbar spine was the most common anatomic location (47%): thoracic (29%); cervical (24%).  Among the 46 (66%) patients with a microbiological diagnosis, the most common organisms were MSSA (33%) and MRSA (22%).  Among the 44 (63%) patients who had a diagnostic biopsy, open biopsy was more likely to result in pathogen recovery [14 (93%) of 15 with open biopsy vs. 14 (48%) of 29 with needle biopsy; p=0.003].   Surgery was required during the initial hospitalization in 23% of patients: decompression laminectomy 14%), laminectomy /fusion (7%) and corporectomy (1%).  Treatment outcomes were not included.  

PREVENTING HOSPITAL ACQUIRED INFECTIONS:   The translation of basic epidemiologic evidence into successful prevention has led to several successes in hospital-acquired infection prevention research over the past decade.  First is the use of alcohol-based hand rubs in clinical practice.

I.  Hand Hygiene:  Before the past decade, the major method of decontamination of the hands was the use of soap and water. The limitations of this procedure included the time it took to do, the number of sinks and the location of sinks in the hospital defined the optimal adherence to policy, and repeat use of detergents can be very irritating to the skin.

In 2002, the Centers for Disease Control and Prevention [CDC] through the Healthcare and Infection Control Practices Advisory Committee firmly established alcohol-based hand rubs at the center of hand hygiene practices, recommending them for routine decontamination of hands in all clinical situations except when the hands are visibly soiled.    Application of the rub takes seconds, the compounds are non-irritating and the dispensers are small, inexpensive and accessible wherever needed.  By 2008 84% of all US hospitals surveyed indicated that they had adopted alcohol-based hand rub and number of studies have shown dramatic increases in adherence to hand hygiene.  - Mody L, et al; Adoption of Alcohol-Based Handrub by United States Hospitals: a National Survey. Infect Control Hosp Epidemiol., 2008; 29:1177-1180.

II. Central Line catheter infections:  In the 2000s, there were 2 separate reports of large collaborative regional demonstration projects that focused on improved implementation of existing recommendations to prevent central line-associated blood stream infections (CLABSI) among patients in intensive care units (ICUs), first in southwestern Pennsylvania (2005) and then in Michigan (2006). Both studies demonstrated ~70% reductions in CLABSI rates across a wide variety of facility and ICU types, suggesting that the preventable fraction of these infections was perhaps much larger than we had originally thought.  The protocol was a 5-step process:  1) hand hygiene by the person inserting the device.  2) maximal barrier precautions.  3) chlorhexidine gluconate for antisepsis applied to the site of the insertion.  4) avoidance of femoral central line insertion.  5) removal of the central line as soon as possible /when no longer needed.

The results of these 2 studies have changed expectations of CLABSI prevention programs. The earlier single-center reports were viewed by many as somehow aberrant, the result of special circumstances and/or resources that could exist only in those particular, reporting facilities. These regional studies demonstrated that better implementation of existing recommendations can have a major impact across a wide spectrum of hospital settings —– dramatic success was possible, and not just under special circumstances.

III. DECOLONIZATION OF PATIENTS: Another innovative advance is the role of “source control” in preventing infection, particularly with the use of chlorhexidine bathing of patients. Based on data suggesting that colonization of a patient’s skin is an important source of spread for epidemiologic imported bacteria, it was hypothesized that daily bathing with a skin antiseptic (chlorhexidine gluconate) would decrease the burden of the patient’s skin contamination, indirectly decrease contamination in the environment, decrease transmission by healthcare worker, and play a role in decreased transmission of resistant pathogens and the incidence of both surgical site infections and CLABSI.  Today, data strongly suggest that daily chlorhexidine bathing can significantly reduce contamination of the patient’s skin, the environment, and healthcare workers’ hands, and an impact on methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococcus (VRE) acquisition has been documented.  - Barta R, Cooper BS, Whitely C, Patel AK, Wyncoll D, Edgeworth JD.  Efficacy and limitation of a chlorhexidine-based decolonization strategy in preventing transmission of methicillin-resistant Staphylococcus aureus in an intensive care unit. Clin Infect Dis. 2010;50:210-217.

Discussion: One area of controversy is the role of active surveillance, or what the value is of actively screening patients for MRSA.  . Most of the studies done in the past were typically small, single-institution studies, and often with quasi-experimental, pre- vs post- design. The results from those studies leave the conclusions open to interpretation and raise the issues of potential confounding or bias. With that said, even more rigorously done, recent studies have come to different conclusions.   Clearly, more work needs to be done.  - Harbarth S, Fankhauser C, Schrenzel J, et al. Universal screening for methicillin-resistant Staphylococcus aureus at hospital admission and nosocomial infection in surgical patients. JAMA. 2008;299:1149-1157. CONCLUSION: A universal, rapid MRSA admission screening strategy did not reduce nosocomial MRSA infection in a surgical department with endemic MRSA prevalence but relatively low rates of MRSA infection. – Robicsek A, Beaumont JL, Paule SM, et al. Universal surveillance for methicillin-resistant Staphylococcus aureus in 3 affiliated hospitals. Ann Intern Med. 2008;148:409-418.  CONCLUSION: The introduction of universal admission surveillance for MRSA was associated with a large reduction in MRSA disease during admission and 30 days after discharge.

IV. Catheter-Associated Urinary Tract Infections:  Wald and colleagues  looked at catheter-associated UTIs [urinary tract infections] — morbidity and mortality associated with the device.  There is good evidence that getting the catheter out by postoperative day 2 makes a real difference. – Wald HL, Ma A, Bratzler DW, Kramer AM. Indwelling urinary catheter use in the postoperative period: analysis of the national surgical infection prevention project data. Arch Surg. 2008;143:551-557.

IF YOU HAVE DIABETES, A JOINT REPLACEMENT OR ARTHRITIS…. YOU’RE AT INCREASED  RISK FOR A BONE INFECTION?  George Cierny, MD, and Doreen DiPasquale, MD; *BottomLine Health, 2010; Vol 24(3), pp9-11

* Bottom Line/Health interviewed George Cierny, MD, and Doreen DiPasquale, MD, physician-partners at REOrthopaedics in San Diego.  Dr. Cierny is an international lecturer in orthopedic surgery who has published more than 100 scien­tific papers and/or book chapters in the field of musculoskeletal pathology and infection. Dr.Di­Pasquale, an orthopedic-trauma surgeon, is former resi­dency program director at George Washington University in Washington, DC, and National Na­val Medical Center in Bethesda, Maryland.

—————- When most people think of bone problems, broken bones and osteoporosis (re­duced bone density and strength) come to mind. But our bones also can be the site of infections that can sometimes go unrecognized for months or even years. This is especially the case if the only symptoms of bone infection (a condition known as osteo­myelitis) are ones that are commonly mis­taken for common health problems, such as ordinary back pain or fa­tigue. What you need to know…

ARE YOU AT RISK? Older adults (age 70 and older), people with diabetes or arthritis and anyone with a weakened immune sys­tem (due to chronic disease, such as cancer, for example) are among those at greatest risk for osteo­myelitis.   Anyone who has an artificial joint (such as a total hip replacement or total knee replacement) or metal implants attached to a bone also is at increased risk for osteomyelitis and should discuss the use of anti­biotics before any type of surgery, including routine dental and oral surgery. Bacteria in the mouth can enter the bloodstream and cause a bone infection.

TYPES OF BONE INFECTIONS: Before the advent of joint-­replacement surgery, most bone in­fections were caused by injuries that expose the bone to bacteria in the en­vironment (such as those caused by a car accident) or a broken bone…or an infection elsewhere in the body, such as pneumonia or a urinary tract infection, that spreads to the bone through the bloodstream. Now: About half the cases of osteo­myelitis are complications of surgery in which large metal implants are used to stabilize or replace bones and joints (such as in the hip or knee).   

Osteomyelitis is divided into three main categories, depending on the origin of the infection… Blood-born osteomyelitis occurs when bacteria that originate else­where in the body migrate to and in­fect bone. People with osteoarthritis or rheumatoid arthritis are prone to blood-borne infections in their af­fected joints due to injury to cells in the lining of the joints that normally prevent bacteria from entering the bloodstream. Contiguous-focus osteomyelitis oc­curs when organisms— usually bacte­ria, but at times fungal species —infect bone tissue. These cases usually occur in people with diabetes, who will often de­velop pressure sores on the soles of their feet or ­buttocks due to poor cir­culation and impaired immunity.   Post-traumatic osteomyelitis: Trau­ma or surgery to a bone and/or sur­rounding tissue can open the area to bacteria and other microbes. The use of prosthetic joints, surgical screws, pins or plates also makes it easier for bacteria to enter and in­fect the bone.  Important: any of the three types of bone infections described above can lead to chronic osteomyelitis, an initially low-grade infection that can persist for months or even years with few or no symptoms. Eventu­ally it gets severe enough to liter­ally destroy bone. Left untreated, the affected bone may have to be amputated.

DIFFICULT TO DIAGNOSE – When osteomyelitis first develops (acute osteomyelitis), the symptoms —such as pain, swelling and tender­ness—are usually the same as those caused by other infections. If the initial infection is subtle (low-grade) or doesn’t resolve completely with treatment, it can result in chronic osteomyelitis. In this case, you may have no symptoms or symp-toms that are not specific.  For example, some one who has had surgery might blame discomfort on delayed recovery, not realizing what they have a bone infection.  A surprising finding: When we stud­ied the histories of more than 2,000 osteomyelitis patients, we found that most of those with chronic infections had relatively little pain from the in­fection itself. About 28% of those who required surgery for infection had normal white blood cell counts—suggesting that, over time, the body adjusts to lingering infections.  If a doctor suspects that you may have osteomyelitis because of chron­ic pain…swelling…possibly fever…fatigue…or other symptoms, he/she will usually order special laboratory tests that detect the formation of an­tibodies and/or cellular signaling compounds. If the results indicate the presence of infection, he/she may then order an X-ray, a magnetic reso­nance imaging (MRI) scan or a nuclear scan(bone scan). These and other imaging tests can readily detect damaged­ bone tissue and re­veal the presence of infection.

BEST TREATMENT OPTIONS   About 60% to 70% of people with acute osteomyelitis can be cured with antibiotics (or anti­fungal agents, if a fungal infection is present) if treat­ment begins early enough to prevent the infection from becoming chronic. In these cases, patients exhibit symp­toms…test positive for infection…and readily respond to drug treatments. Most patients can be cured with a four- to six-week course of antibiotics. Fungal infections are more resistant to treatment—antifungal drugs may be needed for several months.

For chronic osteomyelitis, surgical debridement (the removal of dam­aged tissue and bone using such in­struments as a scalpel, dental burrs and/or chisels) usually is necessary. Reasons: dam­aged bone can lose its blood supply, die and remain in the body without living cells or circu­lation. Such “dead bone” is invulnerable to the effects of antibiotics and provides safe haven to organisms attached to its surface.  To address this, the surgeon, after debridement, may insert a slow-release antibiotic depot (antibiotic beads) that release antibiotic for up to a month. This approach can increase drug concentrations up to 100 times more than oral antibiotic therapy and help to eliminate the sequestered microorganisms.   Using these and other innovations, the REOrthopaedics  center in Southern California now posts an overall success rate of 95%.    Nevertheless,  up to 6% of patients who are otherwise healthy may require a second or even a third operation to completely cure the infec­tion;  and, iIn patients suffering from diabetes or oth­er disorders affecting wound healing (compromised hosts) , the percentage may be as high as 25%.    To improve your chances of a full recovery from chronic osteomyeli­tis following treatment: eat well, maintain healthy blood sugar levels, stay active after treat­ment (to promote blood circulation, prevent blood clots and help main­tain an appetite) and don’t use to­bacco products.

_{Copyright © 2009 by Boardroom Inc., 281 Tresser Blvd., Stamford, Connecticut 06901-3229.                          www.BottomLineSecrets.com}

How does malnutrition affect outcomes of patients with musculoskeletal infection?”     Good nutrition is essential for normal wound healing and host defense against infection.  A lack of proteins, fats, vitamins and minerals creates a welcome environment for invading bacteria:  1) decreased production of new blood vessels to heal wounds, potentiate antimicrobial effectiveness and thereby prevent infection; 2) lack of proteins to seal and heal wounds, stop bleeding and kill bacteria (antibodies against bacteria and viruses);  3) impotent white blood cells (natural  killer cells ) to destroy invaders.   In our protocols and staging system, patients with obesity and/or mal-nutrition are considered B-hosts with co-morbidities affecting wound healing and treatment outcomes.

 How can I be obese and still be malnourished?  Concomitant  obesity and malnutrition can offend occur if the obesity is linked to: 1)  the consumption of empty calories in a diet of processed, fast  foods lacking minerals and containing additives to prolong shelf life; 2) bariatric patients following bariatric surgery where absorption is altered; 3) dietary deficiencies in folate, selenium, zinc and vitamins A, B-12, B-1, C, D and E.  Obesity, for these purposes, is defined as a Mean Body Index (BMI) > 40.   Our treatment center has introduced many innovations in treatment that have improved outcomes for all B-hosts.

How do you diagnose mal-nutrition?  Common measurements of nutritional status include: laboratory tests (serum albumin, transferring, pre-albumin and total lymphocyte count); body measurements such as BMI, tricps skin fold thickness (fat reserves) and a  mid-humeral circumference (protein reserves).  

Can I still be operated if I am malnourished?  In order to prevent post-operative wound complications (healing) and infection (SSI), surgery is often delayed until a mal-nourished patient can first be restored to good health and nutrition.  However, in the case of a serious infection or tumor, when a delay of surgery cannot be advised, alternative and sometimes more circuitous methods must be employed to reach a similar goal (TREATMENT OUTCOMES: slide #4).  

BLOOD TESTS TO DIAGNOSE OSTEOMYELITIS / BONE and SOFT TISSUE  INFECTIONS - 

The Erythrocyte Sedimentation Rate (ESR):   When inflammation is present in the body, proteins are produced by the liver and the immune system under many abnormal conditions, such as an infection, an autoimmune disease, and/or cancer.  The increased presence of these proteins will cause red blood cells to stick together in solution (whole blood) and, therefore, settle out of solution more slowly than when these proteins are absent or in lower concentrations.   The Erythrocyte Sedimentation Rate (ESR) is, therefore, a non-specific test to indicate thickening of the blood due and can be used to rule in or rule out disease processes that, when present, stimulate production of these proteins (see below discussion of acute phase proteins).   Since there are many possible causes of an elevated sedimentation rate, this blood test is done with other tests to confirm a diagnosis such as a chronic osteomyelitis.  Once a sed rate (ESR) blood test is conducted, the course of a disease or the effectiveness of treatment can be monitored.

C-reactive protein (CRP): CRP is believed to play another important role in innate immunity, as an early defense system against infection.  It is a protein found in the blood, the levels of which rise in response to inflammation due to trauma, infection or serious illnesses; it is an “acute-phase protein” synthesized by the liver.  It is not related to C-peptide or protein C.   A rise in C-RP is due to a rise in the plasma concentration of IL-6(see below), which is produced predominantly by macrophages and fat cells.   CRP binds to microbes and is thought to enhance the process of phagocytosis (cellular ingestion/digestion) of bacteria by macrophages.  

When signaled, the CRP level rises above normal limits within 6 hours, and peaks at 48 hours.  Thereafter, its level is determined by the rate of production (and hence the severity of the precipitating cause).  Measuring and charting C-reactive protein values can prove useful in determining the presence of disease, disease progress and/or the effectiveness of various treatments.

Acute-phase proteins:  a class of proteins whose plasma concentrations increase (positive acute-phase proteins) or decrease (negative acute-phase proteins) in response to inflammation. This response is called the acute-phase reaction (also called acute-phase response).  In response to injury, local inflammatory cells (neutrophils, granulocytes and macrophages) secrete a number of cytokines; cytokines are chemical signals between cells that have an effect on other cells, the most most notable of which are the interleukins IL-1, IL-6 and IL-8 and tumor-necrosis factor alpha (TNF- α).   

Interleukin-6 (IL-6) is both a pro-inflammatory and anti-inflammatory cytokine.  It is secreted by T-cells and macrophages to stimulate immune response to trauma, especially burns or other tissue damage leading to inflammation. IL-6 has been shown to be required for resistance against certain bacteria (i.e.; Streptococcus pneumoniae).  IL-6, one of the most important mediators of fever and of the acute phase response, can be secreted in response to specific microbial molecules referred to as pathogen associated molecular patterns (PAMPs).  These PAMPs bind to highly important group of detection molecules of the innate immune system called pattern recognition receptors (PRRs) which signal cascades giving rise to inflammatory cytokine production.

 At our Osteomyelitis Treatment Center in Sand Diego, CA we use the ESR, CRP and IL-6 blood tests in the diagnosis of bone and soft tissue infections as well as in the follow up following treatment results and peri-prosthetic total joint infections.

The Fate of the Unexpected Positive Intraoperative Cultures After Revision Total Knee Arthroplasty.  Robert L. Barrack,  Ajay Aggarwal,  R. Stephen J. Burnett,  John C. Clohisy,  Elie Ghanem,  Peter Sharkey and Javad Parvizi.  Washington University & Barnes-Jewish Hosp., St. Louis, MO;  Thomas Jefferson University & Rothman Inst,  Philadelphia, PA.  Journal of Arthroplasty, 2007; 22(6) pp94-99.

-Of a consecutive series of 692 revision total knees at 3 centers, intra-operative cultures were unexpectedly found to be positive in 41cases (5.9%). Of the 41, 29 (71%) cases had a single positive intra-operative culture and were determined to be a probable false positive based on absence of any other evidence of infection, of which 5 were treated with extended course of intravenous antibiotics after hospital discharge and the remaining 24 received no further treatment. None of these 24 patients manifested any sign of infection at follow-up, averaging 46 months (range, 24-74 months): Staph. epi (46%); enterococcus (11%); Staph. aureus (14%); Strep (9%); Corynebact. (7%); Diptheroids(7%); Prop. Acne(4%). Twelve patients were determined to have probable type 1 peri-prosthetic infection, 11 of which were treated with a course of antibiotics: Staph. epi.(50%); Enterococcus 29%; Staph. aureus 7%; MRSE (7%); Strep(7%).   Two (18%) of these patients became re-infected within one year.  CONCLUSION: A single positive intra-operative culture after revision total knee arthroplasty does not mandate further treatment in the absence of any other signs of infection.  DR. CIERNY’S COMMENTS: THIS ARTICLE EMPHASIZES TWO VERY IMPORTANT POINTS WHEN SENDING WOUND  CULTURES: 1) ALWAYS SEND MORE THAN ONE SPECIMEN WHEN CULTURING A WOUND. —–  FALSE POSITIVE CULTURES DO OCCUR;  2) BIOPSY WHAT YOU CULTURE AND CULTURE WHAT YOU BIOPSY.  A  POSITIVE CULTURE +  TISSUE WITH NO EVIDENCE OF ACUTE INFLAMMATION = A FALSE POSITIVE CULTURE.  IF, HOWEVER, THERE IS A POSITIVE CULTURE WITH POSITIVE HISTOLOGY IN AN UNEXPECTED SCENARIO FOLLOWING IMPLANTATION OF HARDWARE (SEE PROTOCOL),  AT THE VERY LEAST WE WOULD RECOMMEND OPEN IRRIGATION/DEBRIDEMENT OFTHE WOUND, SYSTEMIC ANTIBIOTICS AND ANTIBIOTIC-DEPOT FILLING OF THE ADJACENT DEAD SPACE. 

Time-related Concordance Between Swab and Biopsy Samples in the Microbiological Assessment of Burn Wounds  Ebrahim Salehifar, PharmD; Ghasemali Khorasani, MD; Shahram Ala, PharmD.  Mazandaran University of Medical Sciences; Emam Square, Valliasr Blvard; Sari, Mazandaran.   Wounds, VOLUME: 21Mar 01 2009.

-The aim of this study was to investigate the concordance between swab and tissue biopsy samples in terms of microbiological isolates and their time-related changes. A total of 156 samples (78 swab and 78 biopsy) were collected from 39 cases of partial- or full-thickness burns and compared at days 7 and 14 after admission regarding the type of microorganisms and their time-related changes. Pseudomonas aeruginosa and Citrobacter freundii were the two most common microorganisms found by both sampling methods. While the majority of swab and biopsy samples were concordant in day 7, the rate of concordance in day 14 was less than day 7—87.1% versus 66.6%, respectively. After comparing the ratio of P aeruginosa and C freundii in positive swab and biopsy cultures on days 7 and 14, unlike the swab samples, the biopsy samples yielded similar results both times (75% P aeruginosa and 25% C freundii, respectively).      DR. CIERNY’S COMMENTS:  THE RESULTS OF THIS STUDY SUGGEST THAT TISSUE SWABS ARE SUFFICIENT FOR WOUND MONITORING ONLY DURING THE ACUTE-PHASE OF AN  INFECTION.  BY THE SECOND WEEK, THE MAJORITY OF THE PATHOGENS ARE SESSILE (WITHIN THE BIOFILM COLONY) AND NO LONGER FREE-SWIMMING (PLANKTONIC) OR AMENABLE TO GROWTH IN STANDARD CULTURE MEDIA.   IN THIS STUDY, AS IN OTHERS DEALING WITH BIOFILM INFECTIONS, DEEP TISSUE SPECIMENS WERE REQUIRED TO HARVEST ENOUGH PLANKTONIC (CULTURABLE) ORGANISMS TO YIELD POSITIVE RESULTS.  HOWEVER,  EVEN THEN, 20-40% OF OUR CULTURES WILL  STILL COME UP  “NO GROWTH”  UNTIL WE DEVELOP METHODS TO FREEING OR INTICE SESSILE ORGANISMS BACK TO  PLANKTONIC PHENOTYPES.