The Effects of Early Antibiotic Administration on Bacterial Culture Growth From Hand Abscesses

Preoperative Antibiotics Influence Culture Yield in the Treatment of Hand, Wrist, and Forearm Infections

When treating upper-extremity infections, clinicians frequently must decide whether to initiate antibiotics or delay them with the goal of optimizing culture yield at the time of surgical debridement. The purpose of this study was to determine whether the administration of preoperative antibiotics affects intraoperative culture yield and whether there is a "safe" interval prior to culture acquisition within which antibiotics can be administered without affecting culture yield.

Methods

We conducted a retrospective review of 470 consecutive patients who underwent debridement for a presumed acute infection of the hand, wrist, or forearm at a single tertiary care center between January 2015 and May 2020. Data including patient demographics, mechanism of infection and affected body part(s), and details of antibiotic administration, including type and timing with respect to culture acquisition, were collected.

Results

Three hundred and forty-one patients (73%) received preoperative antibiotics prior to debridement and culture acquisition. The rate of positive cultures among patients who received preoperative antibiotics was 81% compared with 95% among patients who did not receive preoperative antibiotics (p < 0.01; odds ratio, 4.73). Even a single dose of antibiotics imparted a significantly increased risk of obtaining negative intraoperative cultures, and an incremental increase in the likelihood of obtaining negative cultures was seen with each preoperative dose given up to 7 doses. We did not identify a "safe" interval of time between antibiotic administration and culture acquisition such that culture yield was not affected.

Conclusions

Patients who received preoperative antibiotics for the treatment of upper-extremity infections were approximately 5 times more likely to have negative cultures at the time of debridement than those who did not receive preoperative antibiotics. This effect persisted regardless of the number of doses given or the interval between antibiotic administration and culture acquisition.

Level of Evidence

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

[Hand Infections - A Review Article]

This review article addresses the incidence, types, and causes of hand infections, as well as risk factors and differential diagnosis.

Utility of Common Biomarkers for Diagnosing Infection in Nonunion

OBJECTIVES

To evaluate the diagnostic utility of leukocyte count (WBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) for distinguishing between septic and aseptic nonunions.

DESIGN

A single-gate (cohort) design was used, using 1 set of eligibility criteria applied to a consecutive sample of nonunions.

SETTING

Private quaternary referral center.

PATIENTS/PARTICIPANTS

Inclusion criteria were consecutive patients (≥18 years) with a nonunion requiring surgery that allowed for direct or medullary canal tissue sampling from the nonunion site. The cohort included 204 subjects with 211 nonunions.

INTERVENTION

Blood samples were drawn for laboratory analysis of WBC, ESR, and CRP before surgery.

MAIN OUTCOME MEASUREMENTS

The reference standard used to define infection was the fracture-related infection confirmatory criteria. Measures of diagnostic accuracy were calculated. To assess the additional diagnostic gain of each index lab test while simultaneously considering the others, logistic regression models were fit.

RESULTS

The prevalence of infection was 19% (40 of 211 nonunion sites). The positive likelihood ratios (95% confidence interval) for WBC, ESR, and CRP were 1.07 (0.38-3.02), 1.27 (0.88-1.82) and 1.57 (0.94-2.60), respectively. Multivariable modeling adjusted for the effect of preoperative antibiotics showed that WBC (P = 0.42), ESR (P = 0.48), and CRP (P = 0.23) were not significant predictors of infection.

CONCLUSIONS

In this consecutive sample of 211 nonunions in whom standard clinical practice would be to obtain index lab tests, our findings showed that WBC, ESR, and CRP were not significant predictors of infection.

LEVEL OF EVIDENCE

Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

The molluscum contagiosum BOTE sign-Infected or inflamed?

BACKGROUND

Molluscum contagiosum (MC) is a common skin infection in the pediatric age group. The infection is self-limited and manifests as discrete, umbilicated skin-colored papules on any skin surface of the body. At times, complications such as local dermatitis and swelling, erythema, and pus formation may appear. These signs of inflammation are commonly presumed to represent bacterial infection.

METHODS

This multicenter study was a retrospective analysis of data collected on all patients diagnosed with inflamed lesions secondary to MC and treated at the Hadassah Medical Centers and Shaare Zedek Medical Center in Jerusalem, Israel, from 1/1/2008 to 1/07/2018. Characteristics of children with positive cultures were compared to those with negative cultures and those with contaminants.

RESULTS

A total of 56 cases were reviewed; the mean age at presentation was 4.6 years. Fever was reported in 12.5%, and 62.5% received systemic antibiotics because of their inflamed MC prior to admission. Fifty-five percent had sterile cultures or cultures growing only contaminants. Only seven had positive cultures with the common cutaneous pathogens. No statistical difference was observed between the patients with pathogenic isolates and patients with sterile or non-pathogenic cultures in terms of demographics, lesion characteristics, inflammatory markers, or length of hospitalization.

CONCLUSION

The findings suggest that most cases of suspected MC-related secondary infection can be attributed to inflammation rather than to bacterial infection. However, in some cases, true bacterial infection should be suspected and treated accordingly.

Acute Deep Infections of the Upper Extremity: The Utility of Obtaining Atypical Cultures in the Presence of Purulence

PURPOSE

In the setting of acute deep upper extremity infections, evidence is lacking to guide the decision whether to send atypical cultures (fungal and acid-fast-bacillus [AFB]) during surgical debridement, especially in the presence of purulent fluid that is commonly observed with typical bacterial infections. Our purpose was to determine the frequency of positive atypical cultures and the frequency with which they alter treatment, and identify factors associated with positive atypical cultures.

METHODS

We retrospectively identified 100 adult patients undergoing surgical debridement of acute deep infections of the upper extremity in which fungal and/or AFB cultures were sent. Necrotizing and superficial infections were excluded. Descriptive statistics were used to describe patient characteristics, infection diagnoses, number of cultures sent with corresponding rates of positivity, and treatments. Cohorts with positive and negative atypical cultures were compared with bivariate analysis for all collected variables.

RESULTS

One or more immunocompromising comorbidities were present in 46% of patients. Diagnoses included soft tissue abscess (46%), suppurative flexor tenosynovitis (22%), septic arthritis (21%), osteomyelitis (9%), and septic bursitis (2%). Aerobic bacterial, anaerobic bacterial, fungal, and AFB cultures were sent in 100%, 99%, 94%, and 82% of patients, respectively. Corresponding rates of positivity were 74%, 34.3%, 5.3%, and 2.4%, respectively. Atypical cultures were positive for 7% of patients and 2.9% of all atypical tests sent. Antibiotic treatment was influenced by atypical culture data for 4% of patients. For patients with positive atypical cultures, purulence was observed during surgery in 86% of cases. Bivariate analysis demonstrated symptom duration greater than 7 days as potentially associated with atypical culture positivity.

CONCLUSIONS

Intraoperative purulence at the time of surgical intervention should not deter the surgeon from obtaining atypical cultures. As expected, atypical cultures are infrequently positive given the rarity of associated diseases. Symptoms greater than 7 days may predict a higher incidence of atypical culture positivity for patients being treated surgically within 30 days of initial symptom onset.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic IV.