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Use of bacterial cultures in open wound fractures

A prospective cohort study

Hasan, Obada; Rahim Khan, Hamza A; Mustafa, Syed F; Muhammad, Zehra A; Ahmad, Tashfeen

doi: 10.4103/ijssr.ijssr_20_17
Original Article
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Introduction: Open fractures are a big challenge for surgeons to treat due to wound contamination leading to infection is a well established complication. To overcome this complication, prophylactic antibiotic therapy is routinely recommended for open fractures.

Methods: A single center, prospective cohort study was conducted on patients at a tertiary care academic center to assess surgical site infection following fixation of upper and lower limb open fractures. In this study, we aimed to identify the utility of postdebridement cultures for predicting postoperative wound infection with the identification of association between the incidence of infection and factors such as age, gender, fracture site, cause of injury, and the time between injury and presentation at hospital.

Results: Postdebridement cultures of 46 patients were collected, of which 28.3% showed microbial growth. During the hospital stay, three patients developed clinically deep wound infection. Postdebridement culture growth was not significantly associated with the development of clinical infection within the hospital stay (P = 0.188). Out of 43 remaining patients, 11 patients develop wound infection on follow up. Four out of 11 had positive growth on initial cultures.

Conclusion: In this study, we evaluated that postdebridement wound cultures were not useful in predicting wound infection in the postoperative period.

Methods: A single center, prospective cohort study was conducted on patients at a tertiary care academic center to assess surgical site infection following fixation of upper and lower limb open fractures. In this study, we aimed to identify the utility of postdebridement cultures for predicting postoperative wound infection with the identification of association between the incidence of infection and factors such as age, gender, fracture site, cause of injury, and the time between injury and presentation at hospital.

Results: Postdebridement cultures of 46 patients were collected, of which 28.3% showed microbial growth. During the hospital stay, three patients developed clinically deep wound infection. Postdebridement culture growth was not significantly associated with the development of clinical infection within the hospital stay (P = 0.188). Out of 43 remaining patients, 11 patients develop wound infection on follow up. Four out of 11 had positive growth on initial cultures.

Conclusion: In this study, we evaluated that postdebridement wound cultures were not useful in predicting wound infection in the postoperative period.

Results: Postdebridement cultures of 46 patients were collected, of which 28.3% showed microbial growth. During the hospital stay, three patients developed clinically deep wound infection. Postdebridement culture growth was not significantly associated with the development of clinical infection within the hospital stay (P = 0.188). Out of 43 remaining patients, 11 patients develop wound infection on follow up. Four out of 11 had positive growth on initial cultures.

Conclusion: In this study, we evaluated that postdebridement wound cultures were not useful in predicting wound infection in the postoperative period.

Conclusion: In this study, we evaluated that postdebridement wound cultures were not useful in predicting wound infection in the postoperative period.

Department of Surgery, Section of Orthopaedics, Aga Khan University Hospital, Karachi, Pakistan

Medical College, Aga Khan University Hospital, Karachi, Pakistan

Medical College, Aga Khan University Hospital, Karachi, Pakistan

Department of Surgery, Section of Orthopaedics, Aga Khan University Hospital, Karachi, Pakistan

Department of Surgery, Section of Orthopaedics, Aga Khan University Hospital, Karachi, Pakistan

Address for correspondence:Hamza Rahim Khan, Medical College, Aga Khan University Hospital, Karachi, Pakistan hamza_saeedahmed@hotmail.com

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Introduction

An open fracture refers to an injury in which there is a break in the overlying skin and soft tissue, resulting in exposure of the fractured bone to the external environment. An estimated 3.5–6 million fractures occur each year in the US, and about 150,000 of these are open fractures. 1 , 2 Another study done at Scotland reported an open fracture incidence rate of 3,070,000/year. 3 Given the higher population density in Pakistan, the incidence may even be higher than those reported by studies in other regions.

Open fractures have always been difficult to treat, and infection is a well-established complication since the bone and soft tissue become exposed to external environment, increasing the likelihood of microbial contamination. 4 The treatment strategy varies according to the type of fracture and severity of the injury, but the basic principles of management include aggressive irrigation of open wounds, early surgical debridement, broad-spectrum antimicrobial prophylaxis, and fixation of fracture. The classification that is most widely used for open fractures is the Gustilo and Anderson classification which groups open fractures into three major grades in order of increasing severity by taking into consideration the energy of the fracture, extent of contamination, and the degree of soft-tissue damage. 5 Type I infections have 0%–2% risk of infection, Type II infections have a 2%–12% risk, and Type III infections have the highest risk of 10%–50%. 6 , 7

Patzakis et al. in his landmark study demonstrated a significant reduction in the incidence of infection with the use of prophylactic parenteral antibiotics in open wound fractures. 8 Antibiotics are now routinely administered as part of the trauma management protocol for open fractures. It is recommended to start antibiotic therapy early as administration beyond 3 h has been shown to have an increased risk of infection. 9 The choice of antibiotic depends on the severity of fracture: Type I and II injuries most commonly grow Staphylococcus aureus 6 , 8 and more severe Type III injuries predominantly grow Gram-negative aerobes. 7 , 10 Treatment guidelines support early antibiotic coverage of Gram-positive organisms in all grades of fractures with a single agent such as second-generation cephalosporin and addition of a Gram-negative agent such as gentamicin for Grade III fracture. 11

Sixty percent of open fractures are contaminated with bacteria at the time of injury. 5 , 12 The utility of sequential culture and sensitivity studies for predicting infection has been studied. Lingaraj et al. demonstrated that organisms grown in predebridement cultures did not correlate with postoperative wound infection. 13 Lee showed that postdebridement cultures could predict infection in only 42% of the cases. 11 However, another study by D'Souza et al. showed that both pre-and post-debridement cultures play a role in predicting postoperative infection. 14

The development of infection has been attributed to various factors. The timing of operative debridement is recommended to be no >6 h since the onset of injury to minimize the infection risk. 15 , 16 However, recent studies have demonstrated no significant decrease in infection with early debridement. 17 , 18 , 19 Zumsteg et al. in a recent study demonstrated that the severity of fracture according to Gustilo classification was most strongly associated with the development of infection and neither early debridement within 6 h nor early administration of antibiotics significantly reduced infection in upper limb fractures. 20

Naeemullah et al. demonstrated in his study in Pakistan that incidence of infection increased with severity of injury and with the time between injury and surgical debridement. 21 A review of literature showed that the association of postdebridement cultures with the incidence of infection has not been studied in our setting.

It was hypothesized that postdebridement cultures are helpful in predicting postoperative wound infection. Therefore, we aim to identify the utility of postdebridement cultures for predicting postoperative wound infection. We also aim to identify the association between development of infection and factors such as age, gender, fracture site, cause of injury, and the time between injury and presentation at hospital.

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Materials and Methods

We conducted a single-center, prospective cohort study on a single group of patients at a tertiary care academic center to assess surgical site infection following fixation of an open fracture. Protocol was developed before study start-up and is available from corresponding author on request.

Institutional Ethics Committee approval was obtained beforehand with reference numbers 3193-SUR-ERC-14 and 3194-PED-ERC-14. Study was registered at Research Registry with UIN 3466 and 3467 for lower limb fractures and upper limb fractures, respectively. Prospective data from our institutions' orthopedic trauma registry were acquired by research associate. From January 2015 to December 2016, 59 patients were selected with the aim of recruiting all eligible patients who visit our hospital. Inclusion criteria were all patients presenting to the emergency department (ED) that had an open fracture of the limb, recorded in the orthopedic trauma registry, and postdebridement cultures done by treating surgeons and residents. Patients who already had wound debridement done before presentation were excluded from the study. Final sample size was 46 after excluding patients with incomplete data or not fulfilling criteria.

Data on gender, age, location of fracture, etiology of fracture, Gustilo classification, duration between injury and arrival at ED, development of clinical infection after debridement, and follow-up assessment were taken from the registry. We retrospectively collected information from the institution's electronic database on the empiric antibiotic therapy given, Gram staining, and culture and sensitivity reports of samples sent postdebridement.

All fractures were assessed for severity using the Gustilo and Anderson classification. Patients were started on empiric antibiotic therapy within 1 h of presentation in the emergency room (ER) after initial management including tetanus prophylaxis, resuscitation, and stabilization of pulmonary and cardiovascular functions according to institutional protocol. The choice of antibiotics was as per the ED physician's discretion and not an institutional policy. Patients underwent wound debridement and fracture stabilization within 24 h of presentation by trained orthopedic surgeons who had a minimum prior experience of 5 years in performing this procedure. In the operating room, samples were sent for Gram staining and culture and sensitivity after debridement was done using the standard procedure under strict aseptic conditions. Antibiotic therapy was modified based on the sensitivity reports. Repeat cultures were done where signs of clinical infection were noted and patients were switched to appropriate antibiotics based on the culture and sensitivity reports. The microbial flora cultured in the postdebridement samples and the samples sent after infection signs noted were compared.

Clinical infection was defined according to the Centers for Disease Control and Prevention criteria 22 which divides infections into superficial and deep based on the extent of skin and tissue involvement. The factors considered for the diagnosis of infection include the presence of local or systemic signs of inflammatory response including fever, local erythema, warmth, purulent discharge, or the invasion of sterile host tissue, leading to necrosis irrespective of whether the bacterial cultures were positive or negative.

Patients who met these criteria within hospital stay and 2 weeks, 6 weeks, or 3 months after surgical debridement were considered to have clinical infection. Hence, all patients were followed up for a period of at least 3 months after the initial debridement. At the time of follow-up visits, patients and records were evaluated by a research associate who has more than 3-year experience in data collection and data management at Orthopedic Surgery Department. All results were cross-checked by two doctors and the principal investigator. The time durations were calculated as follows: the time of the injury was inquired from the patient, family, or the emergency medical personnel. The time of the patients' arrival at ED was recorded from the hospital's electronic database. Follow-up time intervals were calculated from the registry.

The primary outcome measure was to assess the role of postdebridement culture in predicting clinical infection. The secondary outcome measures were to look for possible association of clinical infection with age, gender, location of fracture, cause of injury, Gustilo classification, and the duration between injury and presentation to the ER. We also described the common microbes cultured from open fracture wounds in our institute and the commonly used agents for empiric therapy in such patients.

Statistical analysis was performed using SPSS 21 software (IBM Corp, Armonk, NY, USA). Descriptive statistical measures such as mean, median, mode, and standard deviation (SD) were calculated for each variable. Fischer's exact test was performed to calculate the statistical significance between different variables. Furthermore, this work has been reported in line with the Strengthening the Reporting of Cohort Studies in surgery criteria. 23

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Results

A total of 59 open fracture patients recruited within which forty patients have a history of road traffic accident, ten have firearm injury, three have injury due to fall, two patients have blast, and two have machine injury, whereas one patient has blunt trauma and one has injury due to firecrackers. None of the patients refused to participate in the study and given consent. Out of 59 patients, due to 8 patients lost to follow-up and some missing data of five patients such as time of injury, 46 patients were included in the study Figure 1.

Figure 1

Figure 1

Out of the 46 patients, 36 were males and 10 were females. Mean age of the patients was 35.5 years (SD 13.1). Nineteen of the fractures were of upper limb and 27 of lower limb. The median time from the occurrence of injury to the presentation at the ER was 230 min. The most common type of trauma causing the fracture in included patients was road traffic accidents (71.7%) followed by firearm injuries (17.4%). Gustillio Grade 3a (30.4%) and 3c (28.3%) were the highest Table 1.{Table 1}

All the 46 patients had samples sent for cultures postdebridement, of which 13 (28.3%) showed microbial growth. A total of three patients developed clinical infection during the hospital stay. All of these had a deep infection of the wound. Out of these three patients, only one had positive results on Gram staining. Two of these three patients with clinical infection showed growth on postdebridement. Both had growth of two organisms, one of which was S. aureus. Postdebridement culture growth was not significantly associated with the development of clinical infection within the hospital stay (P = 0.188) Table 2.{Table 2}

The postdebridement cultures that were positive grew Staphylococcal species (4), Enterobacter species (4), Pseudomonas (2), Klebsiella (2), and Acinetobacter (2) among others. Samples from five patients grew more than one organism Table 3.{Table 3}

Repeat cultures sent after infection developed in the three patients showed polymicrobial growth in the two patients who initially had positive culture growth and unimicrobial in the one patient who had negative culture growth initially. No significant correlation was observed between organisms grown on the cultures done initially and those done after infection was suspected. Culture from one of the patients grew methicillin-resistant S. aureus, and for this patient, infection persisted for 3 months. For the remaining three patients, infection resolved within 6 weeks of debridement with adequate antibiotic therapy tailored to the culture and sensitivity reports. The most frequently used antibiotics were clindamycin, ciprofloxacin, and augmentin, often in combination.

Of the 43 patients who did not develop in-hospital infection, 11 patients did develop clinically significant infection on follow-up. Four patients had an infection on 2-week follow-up, five patients on 6-week follow-up, and two patients on 3-month follow-up. Out of these 11 patients, four had positive growth on initial cultures; however, repeat cultures done after infection was suspected did not match the initial results.

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Discussion

Open fractures are a major cause of morbidity and mortality following traumatic injuries. One of the major complications of open fracture is the development of clinical infection. Despite improvements in management, infection still remains a significant problem. 6 , 7 Our study showed that infection occurred in a total of 14 patients during the 3-month period. During the immediate postoperative period, three patients (6.5%) developed signs of clinical infection. The prevalence of wound infection in literature has been reported from 4.5% to 6% 9 , 13 after surgical debridement and use of prophylactic parenteral antibiotics.

The role of wound cultures for predicting wound infection has remained controversial. Our study showed that postdebridement wound cultures were not useful in predicting wound infection in the postoperative period. The organisms grown on these cultures did not correlate with those grown on samples taken after the development of clinical infection. Multiple studies have negated the use of initial wound cultures in predicting infection. 13 , 24 However, D'Souza et al. showed that both pre- and post-debridement cultures provide significant information for predicting infection with predebridement samples being more sensitive and postdebridement samples being more specific. Another study reported that postdebridement cultures are of more prognostic value and advocated against the routine use of predebridement cultures. 11

The lack of correlation between cultures and subsequent infection may be due to a sampling error. Open fracture wounds are often contaminated with multiple microorganisms and inadequate sampling, particularly from larger wounds may particularly favor the selection of some organisms. Moreover, surgical debridement and irrigation may change the local wound ecology to favor certain organisms. Despite strict antiseptic measures, nosocomial contamination can be a possible explanation for appearance of new organisms in cultures that did not grow initially.

It is well established that the timely surgical debridement and administering of antibiotics reduce the development of infection. After Patzakis et al. demonstrated the role of antibiotics in his study, 8 they are routinely administered. Current guidelines recommend the use of a first-generation cephalosporin (or a similar agent active against Gram-positive organisms) for Grade I and II fractures; for Grade III fractures, a broad-spectrum agent such as piperacillin/tazobactam is recommended. 25 Some authors advocate the use of combination therapy for Grade III fractures such as cefazolin plus an aminoglycoside to cover both Gram positives and negatives. 9 However, the choice of empiric antibiotic in our hospital is largely based on physicians' clinical judgment rather than following a definite protocol. The variation in antibiotic regimen may be based on other factors such as availability and previous treatment in other centers before presentation to our ED. The definitive reasons for this variation are beyond the scope of this study.

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Conclusion

Our study showed that postdebridement wound cultures were not useful in predicting wound infection in the postoperative period. Further studies should be carried out to study the usefulness of pre- and post-debridement cultures as these are routinely done in many centers.

Strengths

Our study questions the common clinical practice of sending postdebridement cultures to predict wound infections. The evidence for this practice is conflicting, and it has not been adequately studied in our setting.

Limitations

The sample size of our study was relatively small to derive strong associations. We could not compare predebridement cultures as they are not routinely performed in our hospital. The lack of standardized empiric antibiotic protocol is also a potential limitation of this study. Further research, including randomized clinical trials, should be done to study the usefulness of both pre- and post-debridement cultures to establish firm guidelines.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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    Keywords:

    Culture; fracture; infection; open; wound

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