Clinical characteristics and therapeutic outcomes of hematogenous vertebral osteomyelitis caused by methicillin-resistant Staphylococcus aureus

A case of recurrent osteomyelitis due to retained micro-catheter after cerebral angiography

Infections associated with healthcare manipulations, particularly bloodstream infections stemming from catheters and medical devices, significantly heighten the probability of vertebral osteomyelitis. The diagnosis of infective endocarditis (IE) frequently overlaps with vertebral osteomyelitis (VO). In cases where individuals are suspected of having hematogenous vertebral osteomyelitis and have an intravascular catheter or device, it is recommended to undertake blood culture collection. We present a case of a 39-year-old male with a history of interventional AVM embolization and cerebral angiography, experiencing recurrent vertebral osteomyelitis. No definitive source of infection had been found, and transthoracic echocardiography (TTE) yielded negative results for IE. In Trans Esophageal Echocardiography (TEE), a retained micro-catheter extending from the aortic arch to the inguinal artery was discovered. Although we cannot definitively attribute the source of the osteomyelitis to the retained micro-catheter, no episodes of infection have been reported ever since. This case underscores the need to enhance our approaches and guidelines related to operating protocols in the surgical setting. Improving these guidelines can prevent similar occurrences in the future, emphasizing the importance of continuous improvement in healthcare practices.

Predictive Factors of Cloxacillin Susceptibility in Primary Bacterial Spinal Infection

STUDY DESIGN

Prognostic study.

OBJECTIVES

The objective of this study is to identify predictive factors for cloxacillin susceptibility in spinal infections.

METHODS

A retrospective analysis was conducted using data from January 1, 1997, to December 31, 2021. The study included patients presenting with back pain and either a positive bacterial culture from the spine or radiological evidence of spinal infection (spondylodiscitis and/or epidural abscess) along with positive bacterial blood culture.

RESULTS

Among 171 patients (127 males, 44 females), 53.2% had Staphylococcus isolates, with 40.4% showing cloxacillin resistance. Lower globulin levels (<33.5 g/L), recent hospitalization within 90 days, and residence in an old age home predicted gram-positive bacteria with cloxacillin resistance and gram-negative bacteria as causative organisms (P<.05). The 30-day and 1-year all-cause mortality rates were 0% and 8.2%, respectively. Higher red cell distribution width (RDW >16.1%) and Charlson comorbidity index (CCI) scores predicted 1-year all-cause mortality (P<.05). Intensive care unit admission was required for 9.9% of patients.

CONCLUSIONS

This study identified predictive factors for spinal infection by gram-positive bacteria with cloxacillin resistance and gram-negative bacteria. Patients with lower globulin levels (<33.5 g/L), recent hospitalization within 90 days, or residency in an old age home upon admission should avoid standalone cloxacillin therapy and consider antibiotics with gram-negative coverage. Higher RDW (>16.1%) and CCI scores were associated with increased 1-year all-cause mortality. These findings contribute to treatment decision-making and improving patient outcomes in spinal infections.

Risk Factors and Outcomes of Hematogenous Vertebral Osteomyelitis in Patients With Staphylococcus aureus Bacteremia

BACKGROUND

Hematogenous vertebral osteomyelitis (HVOM) is an incompletely understood complication of Staphylococcus aureus bacteremia (SAB).

METHODS

Eligible SAB patients with and without HVOM were prospectively enrolled from 1995 through 2019 at Duke University Health System. HVOM was diagnosed either radiographically or microbiologically. Multivariable logistic regression analysis was performed to identify clinical and microbial factors associated with HVOM risk. All bloodstream S. aureus isolates were genotyped using spa typing.

RESULTS

Of 3165 cases of SAB, 127 (4.0%) developed HVOM. Patients who experienced HVOM were more likely to have community-acquired SAB (30.7% vs 16.7%, P < .001), have a longer time to diagnosis of SAB (median, 5 days; interquartile range [IQR], 2-10.5 vs median, 2 days; IQR, 0-4; P < .001), and to exhibit persistent bacteremia (48.8% vs 20.6%, P < .001). A significant number of HVOM patients developed infective endocarditis (26% vs 15.2%, P = .002). Overall, 26.2% (n = 33) of SAB patients with HVOM underwent surgical intervention. Methicillin resistance (46.6% vs 41.7%, P = .318) and bacterial genotype were not associated with the development of HVOM. At the 12-month follow-up, 22% of patients with HVOM had died. Of the surviving patients, 20.4% remained on antibiotic therapy, and 29.6% had recurrence of either HVOM or SAB.

CONCLUSIONS

Among patients with SAB, HVOM risk was associated with clinical factors and not bacterial genotype. Despite being a rare complication of SAB, patients with HVOM had high all-cause mortality rates and healthcare resource requirements up to 1 year after their HVOM diagnosis. Close clinical monitoring is indicated in this vulnerable population.

The Epidemiology of Spondylodiscitis in Germany: A Descriptive Report of Incidence Rates, Pathogens, In-Hospital Mortality, and Hospital Stays between 2010 and 2020

BACKGROUND

Spondylodiscitis can lead to significant morbidity and mortality. Understanding its up-to-date epidemiological characteristics and trends is important to improve patient care.

METHODS

This study analyzed trends in the incidence rate of spondylodiscitis cases in Germany between 2010 and 2020, as well as the pathogens, in-hospital mortality rate, and length of hospital stay. Data were obtained from the Federal Statistical Office and the Institute for the Hospital Remuneration System database. The ICD-10 codes "M46.2-", "M46.3-" and "M46.4-" were evaluated.

RESULTS

The incidence rate of spondylodiscitis increased to 14.4/100,000 inhabitants, with 59.6% cases occurring in patients 70 years or older and affecting mainly the lumbar spine (56.2%). Absolute case numbers increased from 6886 by 41.6% to 9753 in 2020 (IIR = 1.39, 95% CI 0.62-3.08). Staphylococci and Escherichia coli were the most coded pathogens. The proportion of resistant pathogens was 12.9%. In-hospital mortality rates increased to a maximum of 64.7/1000 patients in 2020, intensive care unit treatment was documented in 2697 (27.7%) cases, and the length of stay per case was 22.3 days.

CONCLUSION

The sharply increasing incidence and in-hospital mortality rate of spondylodiscitis highlights the need for patient-centered therapy to improve patient outcomes, especially in the geriatric, frail population, which is prone to infectious diseases.

Distribution of Underlying Causative Organisms, Patient Age, and Survival in Spontaneous spondylodiscitis with Special Focus on Elderly Patients

BACKGROUND AND OBJECTIVE

 spondylodiscitis is becoming a more frequently encountered diagnosis in our clinical practice. Multimorbid and especially older patients build up a relevant portion of cases. The goal of our study was to evaluate our clinical data and to reveal specifics concerning elderly patients with spontaneous spondylodiscitis.

PATIENTS AND METHODS

 We retrospectively analyzed clinical data for the years from 2012 to 2014. The search was conducted on the basis of the International Classification of Diseases, 10th Revision (ICD-10) diagnoses for spondylodiscitis. Postoperative infections were not included in this study. All cases were evaluated in terms of infectious agents (in blood culture and/or computerized tomography [CT]-guided or surgical biopsy), age, and overall survival.

RESULTS

 Fifty-one patients with spontaneous spondylodiscitis were identified. The most frequent pathogen was methicillin-sensitive Staphylococcus aureus (MSSA; n = 21; 41.17%). Escherichia coli and S. epidermidis were each found in four patients each (7.84%). Methicillin-resistant S. aureus (MRSA), Pseudomonas aeruginosa, and S. hominis were found in three cases (5.88%). Other bacteria were found in one case (each 1.96 %). In 12 cases, there was no bacteria growth (23.53%). One of these patients revealed to have a tuberculosis infection, diagnosed after the study period (in 2015). Two-thirds of the patients were ≥65 years old (n = 34). All three patients with MRSA were >65 years old. Three of seven patients <50 years had IV drug abuse (42.86%). In these patients, rather rare infectious agents for spondylodiscitis were found (P. aeruginosa, S. hominis, Citrobacter). Mortality was 7.84% (n = 4). All of these patients were ≥67 years old, three of four (75%) were ≥75 years old.

CONCLUSION

 Our study of spontaneous spondylodiscitis showed a stronger representation of older patients (>65 years). Lethal outcome exclusively concerned the older age group. S. aureus was the most frequent pathogen as shown previously. MRSA infections might be more common in the older age group. Rare causative organisms mainly occurred in patients with iv drug abuse. Further evaluation through randomized multicenter studies focusing on the different subgroups and comorbidities in larger populations and correlation with appropriate treatment options is necessary.

Minimally Invasive Spine Stabilization for Pyogenic Spondylodiscitis: A 23-Case Series and Review of Literature

Background and Objectives: The incidence of pyogenic spondylodiscitis has been increasing due to the aging of the population. Although surgical treatment is performed for refractory pyogenic spondylodiscitis, surgical invasiveness should be considered. Recent minimally invasive spine stabilization (MISt) using percutaneous pedicle screw (PPS) can be a less invasive approach. The purpose of this study was to evaluate surgical results and clinical outcomes after MISt with PPS for pyogenic spondylodiscitis. Materials and Methods: Clinical data of patients who underwent MISt with PPS for pyogenic spondylitis were analyzed. Results: Twenty-three patients (18 male, 5 female, mean age 67.0 years) were retrospectively enrolled. The mean follow-up period was 15.9 months after surgery. The causative organism was identified in 16 cases (69.6%). A mean number of fixed vertebrae was 4.1, and the estimated blood loss was 145.0 mL. MISt with PPS was successfully performed in 19 of 23 patients (82.6%). Four cases (17.4%) required additional anterior debridement and autologous iliac bone graft placement. CRP levels had become negative at an average of 28.4 days after surgery. There was no major perioperative complication and no screw or rod breakages during follow-up. Conclusions: MISt with PPS would be a less invasive approach for pyogenic spondylodiscitis in elderly or immunocompromised patients.

Influence of microbiological diagnosis on the clinical course of spondylodiscitis

PURPOSE

This study sought to recognize differences in clinical disease manifestations of spondylodiscitis depending on the causative bacterial species.

METHODS

We performed an evaluation of all spondylodiscitis cases in our clinic from 2013-2018. 211 patients were included, in whom a causative bacterial pathogen was identified in 80.6% (170/211). We collected the following data; disease complications, comorbidities, laboratory parameters, abscess occurrence, localization of the infection (cervical, thoracic, lumbar, disseminated), length of hospital stay and 30-day mortality rates depending on the causative bacterial species. Differences between bacterial detection in blood culture and intraoperative samples were also recorded.

RESULTS

The detection rate of bacterial pathogens through intraoperative sampling was 66.3% and could be increased by the results of the blood cultures to a total of 80.6% (n = 170/211). S. aureus was the most frequently detected pathogen in blood culture and intraoperative specimens and and was isolated in a higher percentage cervically than in other locations of the spine. Bacteremic S. aureus infections were associated with an increased mortality (31.4% vs. overall mortality of 13.7%, p = 0.001), more frequently developing complications, such as shock, pneumonia, and myocardial infarction. Comorbidities, abscesses, length of stay, sex, and laboratory parameters all showed no differences depending on the bacterial species.

CONCLUSION

Blood culture significantly improved the diagnostic yield, thus underscoring the need for a structured diagnostic approach. MSSA spondylodiscitis was associated with increased mortality and a higher incidence of complications.

Vertebral osteomyelitis in patients with Staphylococcus aureus bloodstream infection: Evaluation of risk factors for treatment failure

OBJECTIVES

Staphylococcus aureus is the most common cause of pyogenic vertebral osteomyelitis (VO). Studies indicate that S. aureus VO results in poor outcome. We aimed to investigate risk factors for treatment failure in patients with Staphylococcus aureus bloodstream infection (SAB) and VO.

METHODS

We conducted a post hoc-analysis of data from a German bi-center prospective SAB cohort (2006-2014). Patients were followed-up for one year. Primary outcome was treatment failure defined as relapse and/or death within one year.

RESULTS

A total of 1069 patients with SAB were analyzed, with 92 VO patients. In addition to antibiotic treatment, surgery was performed in 60/92 patients. Treatment failed in 44/92 patients (death, n = 42; relapse, n = 2). Multivariable analysis revealed higher age (HR 1.04 [per year], 95%CI 1.01-1.07), Charlson comorbidity index (HR 1.20, 95%CI 1.06-1.36), presence of neurologic deficits (HR 2.53, 95%CI 1.15-5.53) and local abscess formation (HR 3.35, 95%CI 1.39-8.04) as independent risk factors for treatment failure. In contrast, surgery seemed to be associated with a favourable outcome (HR 0.45 (95%CI 0.20-0.997)).

CONCLUSION

SAB patients with VO exhibit a high treatment failure rate. Red flags are older age, comorbidities, neurologic deficits and local abscess formation. Whether these patients benefit from intensified treatment (e.g. radical surgery, prolongation of antibiotics) should be investigated further.

De novo methicillin-resistant Staphylococcus aureus vs. methicillin-sensitive Staphylococcus aureus infections of the spine, similar clinical outcome, despite more severe presentation in surgical patients

Vertebral osteomyelitis (VO) is a severe infection of the vertebral body and the adjacent disc space, where Staphylococcus aureus is most commonly isolated. The objective of this retrospective study was to determine risk factors for and compare outcome differences between de novo methicillin-resistant Staphylococcus aureus (MRSA) VO and methicillin-sensitive Staphylococcus aureus (MSSA) VO. A retrospective cohort study was performed by review of the electronic medical records of 4541 consecutive spine surgery patients. Among these 37 underwent surgical treatment of de novo MRSA and MSSA spinal infections. Patient demographics, pre- and postoperative neurological status (ASIA impairment score), surgical treatment, inflammatory laboratory values, nutritional status, comorbidities, antibiotics, hospital stay, ICU stay, reoperation, readmission, and complications were collected. A minimum follow-up (FU) of 12 months was required. Among the 37 patients with de novo VO, 19 were MRSA and 18 were MSSA. Mean age was 52.4 and 52.9 years in the MRSA and MSSA groups, respectively. Neurological deficits were found in 53% of patients with MRSA infection and in 17% of the patients with MSSA infection, which was statistically significant (p < 0.05). Chronic renal insufficiency and malnutrition were found to be significant risk factors for MRSA VO. Preoperative albumin was significantly lower in the MRSA group (p < 0.05). Patients suffering from spinal infection with chronic renal insufficiency and malnutrition should be watched more carefully for MRSA. The MRSA group did not show a significant difference with regard to final clinical outcome despite more severe presentation.

The effectiveness of a percutaneous endoscopic approach in a patient with psoas and epidural abscess accompanied by pyogenic spondylitis: a case report

Background

Psoas or epidural abscesses are often accompanied by pyogenic spondylitis and require drainage. Posterolateral percutaneous endoscopic techniques are usually used for hernia discectomy, but this approach is also useful in some cases of psoas or lumbar ventral epidural abscess. We here report a case of psoas and epidural abscesses accompanied by pyogenic spondylitis that was successfully treated by percutaneous endoscopic drainage.

Case presentation

Our patient was a 57-year-old Japanese woman who had been receiving chemotherapy for inflammatory breast cancer and who became unable to walk due to lower back and left leg pain. She was transported as an emergency to another hospital. Magnetic resonance imaging revealed psoas and epidural abscesses accompanied by pyogenic spondylitis, and methicillin-resistant Staphylococcus aureus was detected in a blood culture. Drainage of the psoas abscess was performed under echo guidance, but was not effective, and she was transferred to our institution. We performed percutaneous endoscopic drainage for the psoas and epidural abscesses. Immediate pain relief was achieved and the inflammatory reaction subsided after 8 weeks of antibiotic therapy with daptomycin.

Conclusions

Percutaneous endoscopy allowed us to approach the psoas and epidural abscesses directly, enabling the immediate drainage of the abscesses with less burden on the patient.

Selection of an appropriate empiric antibiotic regimen in hematogenous vertebral osteomyelitis

Background

Empiric antibiotic therapy for suspected hematogenous vertebral osteomyelitis (HVO) should be initiated immediately in seriously ill patients and may be required in those with negative microbiological results. The aim of this study was to inform the appropriate selection of empiric antibiotic regimens for the treatment of suspected HVO by analyzing antimicrobial susceptibility of isolated bacteria from microbiologically proven HVO.

Method

We conducted a retrospective chart review of adult patients with microbiologically proven HVO in five tertiary-care hospitals over a 7-year period. The appropriateness of empiric antibiotic regimens was assessed based on the antibiotic susceptibility profiles of isolated bacteria.

Results

In total, 358 cases of microbiologically proven HVO were identified. The main causative pathogens identified were methicillin-susceptible Staphylococcus aureus (33.5%), followed by methicillin-resistant S. aureus (MRSA) (24.9%), Enterobacteriaceae (19.3%), and Streptococcus species (11.7%). Extended spectrum β-lactamase (ESBL)-producing Enterobacteriaceae and anaerobes accounted for only 1.7% and 1.4%, respectively, of the causative pathogens. Overall, 73.5% of isolated pathogens were susceptible to levofloxacin plus rifampicin, 71.2% to levofloxacin plus clindamycin, and 64.5% to amoxicillin-clavulanate plus ciprofloxacin. The susceptibility to these oral combinations was lower in cases of healthcare-associated HVO (52.6%, 49.6%, and 37.6%, respectively) than in cases of community-acquired HVO (85.8%, 84.0%, and 80.4%, respectively). Vancomycin combined with ciprofloxacin, ceftriaxone, ceftazidime, or cefepime was similarly appropriate (susceptibility rates of 93.0%, 94.1%, 95.8%, and 95.8%, respectively).

Conclusions

Based on our susceptibility data, vancomycin combined with a broad-spectrum cephalosporin or fluoroquinolone may be appropriate for empiric treatment of HVO. Fluoroquinolone-based oral combinations may be not appropriate due to frequent resistance to these agents, especially in cases of healthcare-associated HVO.

Short- versus long-course antibiotics in osteomyelitis: A systematic review and meta-analysis

Current practice of long-term antibiotic use in patients with osteomyelitis is controversial. Recent studies showed short-term antibiotic use to be non-inferior to long-term use, but the results of these studies have been inconsistent. In this review, the PubMed and Embase databases were searched from inception through to June 2018 for randomised controlled trials (RCTs), cohort studies or case-control studies comparing two different durations of antibiotic use. Short antibiotic courses were defined as antibiotics administered for a shorter period than the recommended 4-6 weeks. A random-effects model was used to calculate summary odds ratios (ORs) of treatment failure in patients treated with short-course antibiotics compared with long-course antibiotics. A total of 15 articles (5 RCTs and 10 observational studies) and 3598 patients were included. The overall OR of treatment failure in patients receiving short-course antibiotics was 1.50 [95% confidence interval (CI) 0.97-2.34]. Subgroup analysis revealed that a short course of antibiotic treatment was associated with an increased treatment failure rate in vertebral osteomyelitis (OR = 2.06, 95% CI 1.18-3.57) while having a similar rate to a long antibiotic course in acute osteomyelitis of childhood (OR = 1.86, 95% CI 0.75-4.64). Meta-regression found a higher proportion of Staphylococcus aureus infection was related to a higher risk of treatment failure in patients with vertebral osteomyelitis (Coef. = 4.996; P = 0.032). Short-course antibiotics are safe and effective in children with acute osteomyelitis. Long-course antibiotics may still be preferred in vertebral osteomyelitis, especially in patients with S. aureus infection.

Clinical Characteristics and Outcomes of Patients with Culture-Negative Pyogenic Spondylitis according to Empiric Glycopeptide Use

Background

The optimal choice of antibiotics is challenging in culture-negative pyogenic spondylitis (PS). The empiric use of glycopeptides is suggested depending on various risk factors, although clinical data are sparse. This study aimed to analyze the clinical characteristics and outcomes of patients with culture-negative PS and evaluate the effect of empiric glycopeptide use on clinical outcomes in these patients.

Materials and Methods

Data on the characteristics, treatment, and outcomes of 175 patients diagnosed with PS were retrospectively obtained from the electronic database of a tertiary referral hospital from 2009 to 2016. Patients with negative culture results were grouped by the duration of glycopeptide treatment: glycopeptide therapy <28 days (Group A) and glycopeptide therapy ≥28 days (Group B).

Results

Of 89 patients with negative culture results, 78 were included in the analysis (Group A, n = 66; Group B, n = 12). The mean age of patients with negative culture results was 65.5 years, and 52.6% were male. The median follow-up duration was 573 (interquartile range [IQR], 83 – 1,037) days. The duration of intravenous glycopeptide therapy was 0.0 (IQR, 0.0 – 0.0) days and 55.5 (IQR, 37.0 – 75.7) days for Groups A and B, respectively. Patients who used glycopeptide longer empirically (Group B) had more commonly undergone a previous spinal procedure, including surgery (P = 0.024). The length of hospitalization, erythrocyte sedimentation rate, and C-reactive protein level were significantly higher in Group B compared with those in Group A (P <0.001, P <0.001, and P = 0.006, respectively). Regarding treatment modalities, patients in Group B underwent surgery more frequently (P = 0.017). The duration of parenteral antibiotic treatment was longer in Group B (P <0.001). Recurrence was noted in 7 patients (9.0%), and the recurrence rate was not significantly different between the 2 groups (Group A, 5/66 [7.6%]; Group B, 2/12 [16.7%]; P = 0.293).

Conclusion

The recurrence rate among patients with culture-negative PS was not different based on the duration of empiric glycopeptide use. However, considering the small sample size and heterogeneity of our study population, we suggest that it is reasonable to administer glycopeptide antibiotics in these patients depending on clinical risk factors. Further large-scale prospective studies are needed to obtain more evidence for appropriate antibiotic treatment.

Therapeutic outcome of spinal implant infections caused by Staphylococcus aureus: A retrospective observational study

Spinal implant infection is a rare but significant complication of spinal fusion surgery, and the most common pathogen is Staphylococcus aureus. It is difficult to treat due to this pathogen's biofilm-forming ability and antibiotic resistance. We evaluated the therapeutic outcome of treatments for S aureus spinal implant infections. We retrospectively reviewed all patients with S aureus spinal implant infections at 11 tertiary-care hospitals over a 9-year period. Parameters predictive of treatment failure and recurrence were analyzed by Cox regression. Of the 102 patients with infections, 76 (75%) were caused by methicillin-resistant S aureus (MRSA) and 51 (50%) were late-onset infections. In all, 83 (81%) patients were managed by debridement, antibiotics, and implant retention (DAIR) and 19 (19%) had their implants removed. The median duration of all antibiotic therapies was 52 days. During a median follow-up period of 32 months, treatment failure occurred in 37 (36%) cases. The median time to treatment failure was 113 days, being <1 year in 30 (81%) patients. DAIR (adjusted hazard ratio [aHR], 6.27; P = .01) and MRSA infection (aHR, 4.07; P = .009) were independently associated with treatment failure. Rifampin-based combination treatments exhibited independent protective effects on recurrence (aHR, 0.23; P = .02). In conclusion, among patients with S aureus spinal implant infections, MRSA and DAIR were independent risk factors for treatment failure, and these risk factors were present in the majority of patients. In this difficult-to-treat population, the overall treatment failure rate was 36%; rifampin may improve the outcomes of patients with S aureus spinal implant infections.

Epidemiology and Outcomes of Infectious Spondylodiscitis in Hemodialysis Patients

STUDY DESIGN

A retrospective study of patients who were hospitalized for infectious spondylodiscitis over a 13-year period.

OBJECTIVE

To elucidate the epidemiology and prognostic factors of infectious spondylodiscitis in hemodialysis (HD) patients and to identify the impact of HD on infectious spondylodiscitis.

SUMMARY OF BACKGROUND DATA

Only a few case studies of infectious spondylodiscitis in HD patients can be found in the literature. Reports of prognostic factors are limited and patients' outcomes have not been well described.

METHODS

The cases of 1402 patients who were hospitalized for infectious spondylodiscitis over a 13-year period were retrospectively reviewed. Of these, 102 patients on maintenance HD were enrolled in this study. Cox proportional hazard model was used to evaluate the risk factors of mortality and recurrence.

RESULTS

The 102 enrolled patients had an average age 63.3 ± 11.2 years old and male-to-female ratio of 1:1.04. Back pain was present in 75.5% of patients and the most commonly infected site was the lumbosacral spine. Infection associated with vascular access was identified in 31.4% of patients. The prevalence of dialysis via central venous catheters was higher than prevalent HD patients. Methicillin-resistant Staphylococcus aureus was the most common pathogen, followed coagulase-negative staphylococci. The patients' in-hospital survival rate was 82.4%; their vascular access survival rate was 75.5%; their 1-year survival rate was 78.4%, and their 1-year recurrence rate was 20.2%. Congestive heart failure was associated with an increased 1-year mortality. Other variables exhibited no significant relationship with patients' in-hospital mortality, 1-year mortality or recurrence.

CONCLUSION

The characteristics and outcomes of infectious spondylodiscitis in HD patients were elucidated. Most of the demographic and clinical variables, evaluated upon admission, did not predict mortality or recurrence.

LEVEL OF EVIDENCE

3.

Diagnostics and antibiotic therapy for spondylodiscitis

Purpose. Spondylodiscitis as a rare disease has increased in recent years; there are only a few recommendations regarding the diagnostics and treatment. The objective of this retrospective study was to characterise these patients and identify factors for a favourable healing process - with an emphasis on antibiotic therapy.Methodology. Findings/treatment regimens for all patients with spondylodiscitis treated at a tertiary care hospital in 2012/2013 were recorded. The patients were classified into two groups, depending on the healing process.Results. Fifty-seven patients met the clinical/radiological criteria for spondylodiscitis. The main symptom was massive back pain, combined with a moderate CRP elevation (median 96 mg l^-1), and occasionally fever (39 %). CT-guided aspiration - in addition to blood cultures - improved the detection rate for the causative pathogen from 49 to 82 %. Thirty patients had a favourable clinical course; 25 had an unfavourable clinical course (prolonged clinical course, recurrence, death). Pathogen-specific antibiotic therapy had a decisive effect on the clinical course: initial high-dose intravenous therapy for at least 14 days was associated significantly more often with a favourable clinical course (90 vs 30 % after 24 months, P<0.001). Fourteen days after the start of treatment, marked pain reduction and a CRP reduction of at least 50 % were good prognostic parameters and markers of effective antibiotic therapy.Conclusion. Pathogen detection and establishment of an optimal antibiotic regimen are cornerstones of successful conservative therapy for spondylodiscitis. Targeted initial intravenous therapy for at least 14 days with a bactericidal antibiotic leads to a better clinical course.

Clinical characteristics, treatments, and outcomes of hematogenous pyogenic vertebral osteomyelitis, 12-year experience from a tertiary hospital in central Taiwan

BACKGROUND

In Taiwan, studies about hematogenous pyogenic vertebral osteomyelitis (HPVO) are limited. We conducted a retrospective study to evaluate the clinical presentations, treatment, and outcomes of patients with the diagnosis of HPVO.

METHOD

This 12.5-year retrospective study included patients with a diagnosis of HPVO. Medical records of all HPVO patients were thoroughly reviewed and their clinical data were analyzed by the SPSS software.

RESULT

414 HPVO cases were included and the mean age was 61.6 ± 13.4 years. The mean duration of symptoms was 29 ± 35.3 days and pain over the affected site was reported by most patients (86.0%). Gram-positive bacteria, especially Staphylococcus aureus (162/399 = 40.6%), were the main HPVO pathogens. Escherichia coli (42/399 = 10.5%) was the most common gram-negative isolate. Surgery was performed in 68.8% of cases and the mean duration of total antibiotic treatment was 104.7 ± 77.7 days. All-cause mortality and recurrence rates were 6.3% and 18.8%, respectively. In multivariate analysis, polymicrobial infection (OR: 4.154, 95% CI: 1.039-16.604, p = 0.044), multiple vertebral body involvement (OR: 2.202, 95% CI: 1.088-4.457, p = 0.028), abscess formation treated with antibiotics alone (OR: 2.912, 95% CI: 1.064-7.966, p = 0.037), and the duration of antimicrobial treatment less than 4 weeks (OR: 3.737, 95% CI: 1.195-11.683, p = 0.023) were associated with HPVO recurrence.

CONCLUSION

In Taiwan, HPVO mainly affected the elderly and S. aureus remained the most common HPVO pathogen. In patients with risk factors associated with HPVO recurrence, a longer duration (≥6 weeks) of antimicrobial therapy is suggested.

Pyogenic Vertebral Osteomyelitis: Clinical Features, Diagnosis, and Treatment

Pyogenic vertebral osteomyelitis (PVO) may result in neurological deficits and sequelae, so early diagnosis and appropriate treatment are critical. Many previous studies on PVO exist, but our paper has aimed to comprehensively summarize the clinical aspects of PVO. Through review of the vast literature on the clinical research of PVO an overview of the clinical characteristics, diagnostic methods, treatment and prognosis is provided.

[Spondylodiscitis : Current strategies for diagnosis and treatment]

Spondylodiscitis is a severe infectious disease of the intervertebral discs and of the adjacent parts of the vertebral bodies, culminating in destruction of the mobile segment. It is accompanied by a mortality rate of approximately 15%. Severe courses of the disease can also lead to abscess formation and dispersal of sepsis. Malpositioning of the axis organ and deficits in neurological function up to paraplegia are also possible complications. Timely diagnostics and targeted therapy contribute to minimizing the risk of significant health disorders. This review article gives a summary of important algorithms in the diagnostics and treatment and discusses them against the background of currently available literature. According to the current state of knowledge the surgical treatment of spondylodiscitis provides many advantages and is therefore the method choice, even if a conservative approach can be successful in selected cases. The endpoints of treatment are cleansing of the infection with normalization of laboratory parameters of inflammation and the osseous fusion of the mobile segment.

Comparison of gram-negative and gram-positive hematogenous pyogenic spondylodiscitis: clinical characteristics and outcomes of treatment

Background

To the best of our knowledge, no study has compared gram-negative bacillary hematogenous pyogenic spondylodiscitis (GNB-HPS) with gram-positive coccal hematogenous pyogenic spondylodiscitis (GPC-HPS) regarding their clinical characteristics and outcomes.

Methods

From January 2003 to January 2013, 54 patients who underwent combined antibiotic and surgical therapy in the treatment of hematogenous pyogenic spondylodiscitis were included.

Results

Compared with 37 GPC-HPS patients, the 17 GNB-HPS patients were more often found to be older individuals, a history of cancer, and a previous history of symptomatic urinary tract infection. They also had a less incidence of epidural abscess formation compared with GPC-HPS patients from findings on magnetic resonance imaging (MRI). Constitutional symptoms were the primary reasons for initial physician visits in GNB-HPS patients whereas pain in the affected spinal region was the most common manifestation in GPC-HPS patients at initial visit. The clinical outcomes of GNB-HPS patients under combined surgical and antibiotic treatment were not different from those of GPC-HPS patients. In multivariate analysis, independent predicting risk factors for GNB-HPS included a malignant history and constitutional symptoms and that for GPC-HPS was epidural abscess.

Conclusions

The clinical manifestations and MRI presentations of GNB-HPS were distinguishable from those of GPC-HPS.

Reduced ability to work both before and after infectious spondylodiscitis in working-age patients

BACKGROUND

As little is known about the ability to work in patients with infectious spondylodiscitis, we compared the relation between the workforce before infection with that of a reference population and described the patients' ability to work after infection including predictors of return to work (RTW).

METHODS

We identified all patients aged 20-57 years treated for infectious spondylodiscitis January 1994-May 2009 at hospitals in Funen County, Denmark. The work status of each week from 2 years before until 2 years after index date was compared with that of a reference population. Time to RTW was described using cumulative incidence curves and univariate cause-specific Cox-regression analyses (hazard ratios - HRs).

RESULTS

Of 112 identified patients, 8 (7%) died within the first year and 48 (43%) were part of the workforce 1 year before index. Through the entire observation period, the patients had lower affiliation to the workforce compared with the reference population. During the observation period, the proportion of patients on permanent disability pension increased from 24% to 38% and the proportion of self-supporters decreased from 58% to 33%. Seventy-three per cent of the patients being part of the workforce 1 year before index returned to the workforce within the 2 year follow-up. Main predictor of RTW was being part of the workforce 1 year before index (HR = 7.8; CI: 2.4-25.3).

CONCLUSIONS

Patients with infectious spondylodiscitis were less likely to be part of the workforce before infection compared with a reference population and infection further lowered their ability to RTW.

Infectious Discitis and Spondylodiscitis in Children

In children, infectious discitis (D) and infectious spondylodiscitis (SD) are rare diseases that can cause significant clinical problems, including spinal deformities and segmental instabilities. Moreover, when the infection spreads into the spinal channel, D and SD can cause devastating neurologic complications. Early diagnosis and treatment may reduce these risks. The main aim of this paper is to discuss recent concepts regarding the epidemiology, microbiology, clinical presentation, diagnosis, and treatment of pediatric D and SD. It is highlighted that particular attention must be paid to the identification of the causative infectious agent and its sensitivity to antibiotics, remembering that traditional culture frequently leads to negative results and modern molecular methods can significantly increase the detection rate. Several different bacterial pathogens can cause D and SD, and, in some cases, particularly those due to Staphylococcus aureus, Kingella kingae, Mycobacterium tuberculosis, Brucella spp., the appropriate choice of drug is critical to achieve cure.

Vertebral osteomyelitis in adults: an update

INTRODUCTION

The incidence of vertebral osteomyelitis is increasing, attributed to an ageing population with inherent co-morbidities and improved case ascertainment.

SOURCES OF DATA

References were retrieved from the PubMed database using the terms 'vertebral osteomyelitis' and 'spondylodiscitis' between January 1, 2009 and April 30, 2014 published in English as checked in May 2014 (>1000 abstracts checked).

AREAS OF AGREEMENT

Blood cultures and whole spine imaging with magnetic resonance imaging are essential investigations. Thorough debridement is the mainstay of surgical management, although placing metalwork in active infection is becoming increasingly common.

AREAS OF CONTROVERSY

The extent of pursuing spinal biopsies to determine aetiology, antimicrobial choices and duration, monitoring the response to treatment, and surgical techniques and timing all vary widely in clinical practice with heterogeneous studies limiting comparisons. Surgery, rather than conservative approaches, is being proposed as the default management choice, because it can, in carefully selected patients, offer faster reduction in pain scores and improved quality of life.

AREAS TIMELY FOR DEVELOPING RESEARCH

Further studies are needed to define the most effective technique for spinal biopsies to maximize determining aetiology. High-quality trials are required to provide an evidence base for both the medical and surgical management of vertebral osteomyelitis, including challenging medical management as the default option.

Neurologic Complications, Reoperation, and Clinical Outcomes After Surgery for Vertebral Osteomyelitis

STUDY DESIGN

A consecutive retrospective cohort study from 2008 to 2013 at a single tertiary-care institution was conducted.

OBJECTIVE

The aim of the study was to characterize recovery from pain and neurologic deficit after surgery for vertebral osteomyelitis (VO), and identify incidence of postoperative adverse events.

SUMMARY OF BACKGROUND DATA

A minority of patients with VO require surgery. Although prior studies have characterized outcomes after medical management, the morbidity after surgery is poorly defined.

METHODS

The primary outcome was change from baseline in a Modified McCormick Scale (MMS, 1-5 scale), whereas secondary outcomes included reoperation and change in self-reported pain Visual Analog Scale (VAS, 0-10 scale). MMS and VAS were collected throughout the postoperative course as surrogates for neurologic function and degree of pain. Intraoperative, short-term postoperative (<30 d), and long-term neurologic complications were recorded. New-onset neurologic deficits in the postoperative period were considered neurologic complications.

RESULTS

Fifty patients were included; a majority (52%) presented with a neurologic deficit. The median length of follow-up was 18 months. A statistically significant improvement in MMS was observed by 12 months postoperatively, whereas an improvement in VAS was observed by 3 months. The mean improvement in MMS at last follow-up was 0.35, whereas the mean improvement in VAS was 3.40. One quarter of patients required reoperation. At 24 months postoperatively, 10% died, 26% underwent reoperation, 42% experienced a neurologic complication, and 60% experienced at least one of these 3 adverse events.

CONCLUSION

This is the first study to investigate neurologic complications, reoperation, and pain in a longitudinal manner after surgery for VO. We observed statistically significant improvements in MMS and VAS in the postoperative period. Despite these improvements, the 24-month incidence of overall adverse events was 60%. Patients and clinicians should be aware of the clinical improvement but high incidence of adverse events after surgical management of VO.

LEVEL OF EVIDENCE

4.

Vertebral Osteomyelitis and Septic Arthritis Associated With Staphylococcus hyicus in a Juvenile Peregrine Falcon ( Falco peregrinus )

A 6-week-old, parent-reared peregrine falcon ( Falco peregrinus ) was presented with spastic hypertonus of its hind limbs of unknown origin and duration. Radiologic examination revealed smooth periosteal reactions ventrally at thoracic vertebrae 5 to 7. Contrast-enhanced computed tomography identified the swelling as inflammation; antibiotic, antimycotic, anti-inflammatory, and analgesic treatments were initiated, and vitamins and minerals were supplemented. Because the bird's condition did not improve after 10 days, it was euthanatized and submitted for postmortem examination. On histopathologic examination, chronic, active osteomyelitis was diagnosed in thoracic vertebrae 5 to 7, and chronic, active arthritis was present in both the right shoulder and left elbow joints. Staphylococcus hyicus was isolated from these 3 locations, as well as from lungs and liver, indicating a chronic septic staphylococcosis. Although infections with Staphylococcus species are occasional causes of vertebral osteomyelitis in juvenile poultry with active growth plates, it is only sporadically reported in raptors and companion birds. This case report is the first description of the clinical features and diagnostic and pathologic findings in a juvenile peregrine falcon with hematogenous osteomyelitis and arthritis associated with septicemia caused by S hyicus.

Outcome of conservative and surgical treatment of pyogenic spondylodiscitis: a systematic literature review

BACKGROUND

Spondylodiscitis is a spinal infection affecting primarily the intervertebral disk and the adjacent vertebral bodies. Currently many aspects of the treatment of pyogenic spondylodiscitis are still a matter of debate.

PURPOSE

The aim of this study was to review the currently available literature systematically to determine the outcome of patients with pyogenic spondylodiscitis for conservative and surgical treatment strategies.

METHODS

A systematic electronic search of MEDLINE, EMBASE, Cochrane Collaboration, and Web of Science regarding the treatment of pyogenic spondylodiscitis was performed. Included articles were assessed on risk of bias according the Cochrane Handbook for Systematic Reviews of Interventions, and the quality of evidence and strength of recommendation was evaluated according the GRADE approach.

RESULTS

25 studies were included. Five studies had a high or moderate quality of evidence. One RCT suggest that 6 weeks of antibiotic treatment of pyogenic spondylodiscitis results in a similar outcome when compared to longer treatment duration. However, microorganism-specific studies suggest that at least 8 weeks of treatment is required for S. aureus and 8 weeks of Daptomycin for MRSA. The articles that described the outcome of surgical treatment strategies show that a large variety of surgical techniques can successfully treat spondylodiscitis. No additional long-term beneficial effect of surgical treatment could be shown in the studies comparing surgical versus antibiotic only treatment.

CONCLUSION

There is a strong level of recommendation for 6 weeks of antibiotic treatment in pyogenic spondylodiscitis although this has only been shown by one recent RCT. If surgical treatment is indicated, it has been suggested by two prospective studies with strong level of recommendation that an isolated anterior approach could result in a better clinical outcome.

Susceptibility Pattern of Microorganisms Isolated by Percutaneous Needle Biopsy in Nonbacteremic Pyogenic Vertebral Osteomyelitis

Pyogenic vertebral osteomyelitis (VO) is diagnosed according to several lines of evidence: clinical, biological, radiological, and histological. Definitive diagnosis requires the isolation of a causative pathogen or histological confirmation. The aim of our study was to describe the microorganisms isolated by percutaneous needle biopsy (PNB) and to analyze their susceptibility patterns, in order to assess the possibility of empirical combination therapy for the treatment of nonbacteremic patients without resorting to PNB. Based on a French prospective multicenter study of 351 patients with VO, we compiled clinical, biological, and radiological findings for 101 patients with microbiologically confirmed VO. Based on antibiotic susceptibility testing of PNB isolated pathogens, the suitabilities of four antibiotic combinations were analyzed: ofloxacin plus rifampin, levofloxacin plus rifampin, ciprofloxacin plus clindamycin, and ciprofloxacin plus amoxicillin-clavulanate. The main causative pathogens identified were coagulase-negative Staphylococcus spp. (26% of isolates), followed by Staphylococcus aureus (21%), Streptoccocus spp. (13%), and enterobacteria (21%). Empirical antibiotic combination therapy was effective in nearly 75% of cases, and the different combinations gave similar results, except for ofloxacin-rifampin, which was effective in only 58% of cases. A "perfect" empirical antibiotic therapy does not exist. If PNB is not possible, a combination of a fluoroquinolone with clindamycin or rifampin can be used, but the high risk of microbiological failure does not allow the exclusion of PNB. (This study has been registered with EudraCT, number 2006-000951-18, and ClinicalTrials.gov, number NCT00764114.).

Staphylococcus aureus infections: epidemiology, pathophysiology, clinical manifestations, and management

Staphylococcus aureus is a major human pathogen that causes a wide range of clinical infections. It is a leading cause of bacteremia and infective endocarditis as well as osteoarticular, skin and soft tissue, pleuropulmonary, and device-related infections. This review comprehensively covers the epidemiology, pathophysiology, clinical manifestations, and management of each of these clinical entities. The past 2 decades have witnessed two clear shifts in the epidemiology of S. aureus infections: first, a growing number of health care-associated infections, particularly seen in infective endocarditis and prosthetic device infections, and second, an epidemic of community-associated skin and soft tissue infections driven by strains with certain virulence factors and resistance to β-lactam antibiotics. In reviewing the literature to support management strategies for these clinical manifestations, we also highlight the paucity of high-quality evidence for many key clinical questions.

Antibiotic treatment for 6 weeks versus 12 weeks in patients with pyogenic vertebral osteomyelitis: an open-label, non-inferiority, randomised, controlled trial

BACKGROUND

Duration of treatment for patients with vertebral osteomyelitis is mainly based on expert recommendation rather than evidence. We aimed to establish whether 6 weeks of antibiotic treatment is non-inferior to 12 weeks in patients with pyogenic vertebral osteomyelitis.

METHODS

In this open-label, non-inferiority, randomised controlled trial, we enrolled patients aged 18 years or older with microbiologically confirmed pyogenic vertebral osteomyelitis and typical radiological features from 71 medical care centres across France. Patients were randomly assigned to either 6 weeks or 12 weeks of antibiotic treatment (physician's choice in accordance with French guidelines) by a computer-generated randomisation list of permuted blocks, stratified by centre. The primary endpoint was the proportion of patients who were classified as cured at 1 year by a masked independent validation committee, analysed by intention to treat. Non-inferiority would be declared if the proportion of cured patients assigned to 6 weeks of treatment was not less than the proportion of cured patients assigned to 12 weeks of treatment, within statistical variability, by an absolute margin of 10%. This trial is registered with EudraCT, number 2006-000951-18, and Clinical Trials.gov, number NCT00764114.

FINDINGS

Between Nov 15, 2006, and March 15, 2011, 359 patients were randomly assigned, of whom six in the 6-week group and two in the 12-week group were excluded after randomisation. 176 patients assigned to the 6-week treatment regimen and 175 to the 12-week treatment regimen were analysed by intention to treat. 160 (90·9%) of 176 patients in the 6-week group and 159 (90·9%) of 175 of those in the 12-week group met the criteria for clinical cure. The difference between the groups (0·05%, 95% CI -6·2 to 6·3) showed the non-inferiority of the 6-week regimen when compared with the 12-week regimen. 50 patients in the 6-week group and 51 in the 12-week group had adverse events, the most common being death (14 [8%] in the 6-week group vs 12 [7%] in the 12-week group), antibiotic intolerance (12 [7%] vs 9 [5%]), cardiorespiratory failure (7 [4%] vs 12 [7%]), and neurological complications (7 [4%] vs 3 [2%]).

INTERPRETATION

6 weeks of antibiotic treatment is not inferior to 12 weeks of antibiotic treatment with respect to the proportion of patients with pyogenic vertebral osteomyelitis cured at 1 year, which suggests that the standard antibiotic treatment duration for patients with this disease could be reduced to 6 weeks.

FUNDING

French Ministry of Health.

Therapeutic outcomes of hematogenous vertebral osteomyelitis with instrumented surgery

BACKGROUND

Patients with hematogenous vertebral osteomyelitis (HVO) occasionally require instrumentation for spinal stabilization. However, placing instrumentation in the setting of spinal infection raises concerns about recurrent infection due to bacteria adhering to the foreign material. In this study, we evaluated the therapeutic outcomes of patients with HVO who underwent instrumented surgery.

METHODS

We conducted a retrospective chart review of adult patients with microbiologically diagnosed HVO who underwent surgical intervention in 5 tertiary care hospitals over an 8-year period.

RESULTS

A total of 153 patients with HVO underwent surgical management for their infections. Of these 153 patients, 94 (61.4%) underwent surgical debridement alone (noninstrumented surgery) and 59 (38.6%) underwent surgical debridement and instrumentation (instrumented surgery). The median durations of antibiotic therapy were 66 and 80 days for the noninstrumentation and instrumentation groups, respectively (P = .22). Clinical outcomes were similar between the groups, including rates of infection-related death (2.1% vs 0%; P = .52), primary failure (1.1% vs 5.1%; P = .30), and recurrence (4.8% vs 6.8%; P = .72). Among the instrumentation group, there was a significant decreasing trend for recurrence according to total duration of antibiotic therapy: 22.2% (4-6 weeks), 9.1% (6-8 weeks), and 2.6% (≥ 8 weeks; P = .04). Duration of pre-instrumentation antibiotic therapy and single-stage operation (vs 2-stage operation) were not risk factors for recurrence.

CONCLUSIONS

Spinal instrumentation in patients with HVO may be safe with pathogen-directed prolonged antibiotic therapy and should not be abandoned or delayed solely because of the risk of recurrence.

Risk factors for mortality among patients with Staphylococcus aureus bacteremia: a single-centre retrospective cohort study

INTRODUCTION

Staphylococcus aureus bacteremia is associated with significant morbidity and mortality. Given the paucity of recent Canadian data, we estimated the mortality rate associated with S. aureus bacteremia in a tertiary care hospital and identified risk factors associated with mortality.

METHODS

We retrospectively reviewed the records of adults with S. aureus bacteremia admitted to a tertiary care centre in southwestern Ontario between 2008 and 2012. Cox regression analysis was used to evaluate associations between predictor variables and all-cause, in-hospital, and 90-day postdischarge mortality.

RESULTS

Of the 925 patients involved in the study, 196 (21.2%) died in hospital and 62 (6.7%) died within 90 days after discharge. Risk factors associated with in-hospital and all-cause mortality included age, sepsis (adjusted hazard ratio [adjusted HR] 1.49, 95% confidence interval [CI] 1.08-2.06, p = 0.02), admission to the intensive care unit (adjusted HR 3.78, 95% CI 2.85-5.02, p < 0.0001), hepatic failure (adjusted HR 3.36, 95% CI 1.91-5.90, p < 0.0001) and metastatic cancer (adjusted HR 2.58, 95% CI 1.77-3.75, p < 0.0001). Methicillin resistance, hepatic failure, cerebrovascular disease, chronic obstructive pulmonary disease and metastatic cancer were associated with postdischarge mortality.

INTERPRETATION

The all-cause mortality rate in our cohort was 27.9%. Identification of predictors of mortality may guide empiric therapy and provide prognostic clarity for patients with S. aureus bacteremia.

Bone and joint infection as a predictor of community-acquired methicillin-resistant Staphylococcus aureus bacteraemia: a comparative cohort study

BACKGROUND

A new clone of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA), sequence type (ST) 72-staphylococcal chromosomal cassette mec (SCCmec) type IV/IVA without the Panton-Valentine leucocidin (PVL) genes, has been the major clonal type in Korea since 2007. However, there have been no evaluations of the clinical features, risk factors and outcomes associated with CA-MRSA bacteraemia in Korea.

METHODS

Adult patients with community-acquired S. aureus bacteraemia (SAB) were enrolled between 1 January 2004 and 31 September 2012. We compared the clinical features and outcomes of CA-MRSA bacteraemia with those of community-acquired methicillin-susceptible S. aureus (CA-MSSA) bacteraemia and evaluated the risk factors for CA-MRSA infection. A microbiological study of the CA-MRSA isolates was also conducted.

RESULTS

In total, 169 patients were included, i.e. 31 (18%) patients with CA-MRSA bacteraemia and 138 (82%) patients with CA-MSSA bacteraemia. Bone and joint infection [45.2% (14/31) versus 22.5% (31/138); adjusted OR, 2.61; 95% CI, 1.09-6.21] was an independent predictor of CA-MRSA bacteraemia. There were no significant differences in relapse of bacteraemia and mortality within 12 weeks after SAB between the two groups. ST72-SCCmec type IV/IVA without the PVL genes was the most common genotype, especially among bone and joint infections (64%, 9/14) as well as among the CA-MRSA isolates (71%, 22/31).

CONCLUSIONS

CA-MRSA accounted for 18% of community-acquired SAB and was significantly associated with bone and joint infection. Our study suggests that CA-MRSA should be considered in patients with bone and joint infection and that empirical therapy against MRSA should be included.

Distribution of HIV-1 in the genomes of AIDS patients

The localization of HIV-1 proviruses in compositional DNA fractions from 27 AIDS patients during the chronic phase of the disease with depletion of CD4+ and different levels of viremia showed the following. (1) At low viremia, proviruses are predominantly localized in the GC-richest isochores, which are characterized by an open chromatin structure; this result mimics findings on HIV-1 integration in early infected cells in culture. (2) At higher viremia, an increased distribution of proviruses in GC-poor isochores (which match the GC poorness of HIV-1) was found; this suggests a selection of cells in which the 'isopycnic' localization leads to a higher expression of proviruses and, in turn, to higher viremia. (3) At the highest viremia, integrations in GC-rich isochores are often predominant again, but generally not at the same level as in (1); this may be the consequence of new integrations from the extremely abundant RNA copies.