Single Positive Culture Research Articles

Preventing early-onset group B streptococcal sepsis: is there a role for rescreening near term?

Objective: The Centers for Disease Control and Prevention 2010 guidelines recommend group B streptococcus (GBS) screening at 35–37-week gestation to identify women with positive cultures who should receive intrapartum antibiotics and notes that the predictive value of a negative culture declines after 5 weeks. However, despite the lack of evidence, current guidelines do not recommend rescreening for those screened between 35 and 37 weeks. Our objectives were to investigate the rate of conversion from negative to positive results in women rescreened after appropriate screening at 35–37-week gestation and to examine the impact of rescreening on the use of intrapartum antibiotics. Additionally, we examined cases of early-onset group B streptococcal sepsis (early-onset GBS) in term neonates.Methods: We performed a retrospective cohort study of women delivering liveborn infants 1 January, 2010–31 December, 2014 in Kaiser Permanente Northern California. Data were obtained from database extraction and chart review.Results: We identified 135,585 women with GBS screening at 35–37-week gestation; 4511 (3.3%) women were rescreened. Of the 3860 (85.6%) initially screened negative, 218 (5.6%) converted to positive. Fewer women in the discordant negative to positive group received GBS prophylaxis prior to delivery compared with women with a single positive culture (65.9 versus 92.3%, p < .001). In the discordant negative to positive group, results were available at the time of delivery in 133 of 217 subjects (61.3%). There were 18 cases of early-onset GBS at term (0.10 per 1000 livebirths); the majority of cases occurred among women with negative screening.Conclusion: Our results provide support for the current CDC recommendation against rescreening near term for those women already screened at 35–37-week gestation given the low rate of conversion from negative to positive, and the extremely low rate of early-onset GBS in the screened population.

A Single Positive Tissue Culture Increases the Risk of Rerevision of Clinically Aseptic THA: A National Register Study.

The diagnostic and prognostic value of unexpected positive intraoperative cultures remains unclear in diagnosing prosthetic joint infection (PJI) in THA revisions. Therefore, we asked: (1) What is the clinical importance of bacterial growth in intraoperative tissue cultures taken during first-time revision of a clinically aseptic THA in terms of all-cause rerevision and rerevision for PJI specifically? (2) Is there a difference in outpatient antibiotic treatment patterns that is dependent on the number of positive intraoperative cultures? This register-based study included all procedures reported to the Danish Hip Arthroplasty Register (DHR) as first-time aseptic loosening revisions performed during January 2010 to May 2016. DHR data were merged with that of the Danish Microbiology Database, which contains data from all intraoperatively obtained cultures in Denmark. Both registers have been validated and have a very high degree of completeness and very few patients are missing as a result of emigration. Revisions were grouped based on the number of unexpected positive cultures growing the same bacterial genus: zero, one, or two or more cultures. We defined a positive culture as "unexpected" if it was observed after a revision THA that had been reported to the DHR as aseptic. In Denmark, cultures are routinely obtained even in revisions coded as aseptic, and in this report, 91% (2090 of 2305) of the revision THAs coded as aseptic had cultures taken. The revisions were followed until rerevision, death, or end of the 1-year followup period. The relative risk for rerevision resulting from all causes and PJI was estimated. The Danish National Prescription Registry was reviewed for outpatient antibiotic prescription within 6 weeks of revision. We included 2305 first-time aseptic revisions. Unexpected growth was found in 282 THAs (12%), of which 170 (60%) had growth in only one culture or mixed microbial growth. Coagulase-negative Staphylococcus was the dominating bacteria in 121 revisions (71%). Rerevision was performed on 163 THAs (7%) with PJI being the indication for rerevision in 43 THAs (26%). The risk of all-cause rerevision was greater among first-time revisions with one positive culture (relative risk [RR], 1.73; 95% confidence interval [CI], 1.07-2.80; p = 0.020), but not in the two or more positive group (RR, 1.52; 95% CI, 0.82-2.80; p = 0.180) when compared with the culture-negative THAs. First-time revisions with one positive culture also had a higher risk of rerevision for PJI specifically (RR, 2.63; 95% CI, 1.16-5.96; p = 0.020), but this was not the case in the two or more positive group (RR, 2.28; 95% CI, 0.81-6.43; p = 0.120). Outpatient antibiotic prescription was more frequent after revisions with two or more positive cultures compared with culture-negative revision (50 of 112 [45%] versus 353 of 2023 [17%]; p < 0.001). This was not the case in revisions with one positive culture (36 of 170 [21%] versus 353 of 2023 [17%]; p = 0.220). First-time clinically aseptic THA revisions with unexpected growth in one biopsy culture had an increased risk for rerevision, both in terms of all-cause revision and revision for PJI. The predominant bacteria in revisions with later rerevision was coagulase-negative Staphylococcus. This emphasizes that unexpected bacterial growth with common bacteria may be clinically important, even if only one of five biopsy cultures is positive. Level III, therapeutic study.

713. Vancomycin Heteroresistance in Coagulase Negative Staphylococci (CoNS) Causing Central Line-Associated Bloodstream Infection (CLABSI) in Pediatric Patients with Leukemia

BackgroundHeteroresistance to vancomycin in Staphylococcus aureus may be associated with poor response to therapy. Although CoNS are the most important CLABSI pathogens in children with leukemia, and treatment failure is common, little is known about the frequency or clinical significance of heteroresistance. This is a retrospective study to evaluate frequency, risk factors and clinical impact of heteroresistance in CoNS CLABSI in immunocompromised children.MethodsThe study was approved by the Institutional Review Board. All patients undergoing treatment for leukemia at St. Jude Children’s Research Hospital with CoNS isolated from blood between 2010 and 2016 were eligible. The first available isolate from each blood culture episode was obtained from the clinical laboratory and tested for vancomycin heteroresistance by population analysis profiling in comparison to the hVISA strain Mu3. Clinical data were collected from the medical record for up to 9 months after the episode. Episodes with ≥2 positive cultures or a single positive culture from a single lumen CVC were classified as CLABSI. Outcomes of interest included treatment failure (death or relapse of infection) or poor response to vancomycin therapy (persistence of bacteremia ≥1 day after initiation of vancomycin or treatment failure). Logistic regression was used to test associations between heteroresistance and exposures, and cumulative incidence analyses were used to test the effect on outcomes.ResultsA total of 74 CoNS isolates were obtained from 65 participants, 39 with ALL and 26 with AML; 25/74 (33.8%) of isolates showed showed heteroresistance. The strongest identified risk factor for infection with a heteroresistant organism was number of days of vancomycin in the preceding 60 days (OR = 1.05/day; P = 0.035). In the 40 CLABSI episodes, heteroresistant isolates had a higher cumulative incidence of poor response and of treatment failure (P = 0.006 and P = 0.003, respectively).ConclusionVancomycin heteroresistance is common in CoNS causing CLABSI in children undergoing treatment for leukemia, and is associated with an increased risk of Treatment Failure. Further research should aim to validate this finding in an independent cohort and identify strategies to improve the diagnosis and treatment of these infections.Disclosures R. Hayden, Roche Molecular: Scientific Advisor, Consulting fee. Abbott Molecular: Scientific Advisor, Consulting fee. Quidel: Scientific Advisor, Consulting fee. J. Wolf, Karius Inc.: Investigator, Research support.

The 2018 Definition of Periprosthetic Hip and Knee Infection: An Evidence-Based and Validated Criteria

BackgroundThe introduction of the Musculoskeletal Infection Society (MSIS) criteria for periprosthetic joint infection (PJI) in 2011 resulted in improvements in diagnostic confidence and research collaboration. The emergence of new diagnostic tests and the lessons we have learned from the past 7 years using the MSIS definition, prompted us to develop an evidence-based and validated updated version of the criteria. MethodsThis multi-institutional study of patients undergoing revision total joint arthroplasty was conducted at 3 academic centers. For the development of the new diagnostic criteria, PJI and aseptic patient cohorts were stringently defined: PJI cases were defined using only major criteria from the MSIS definition (n = 684) and aseptic cases underwent one-stage revision for a noninfective indication and did not fail within 2 years (n = 820). Serum C-reactive protein (CRP), D-dimer, erythrocyte sedimentation rate were investigated, as well as synovial white blood cell count, polymorphonuclear percentage, leukocyte esterase, alpha-defensin, and synovial CRP. Intraoperative findings included frozen section, presence of purulence, and isolation of a pathogen by culture. A stepwise approach using random forest analysis and multivariate regression was used to generate relative weights for each diagnostic marker. Preoperative and intraoperative definitions were created based on beta coefficients. The new definition was then validated on an external cohort of 222 patients with PJI who subsequently failed with reinfection and 200 aseptic patients. The performance of the new criteria was compared to the established MSIS and the prior International Consensus Meeting definitions. ResultsTwo positive cultures or the presence of a sinus tract were considered as major criteria and diagnostic of PJI. The calculated weights of an elevated serum CRP (>1 mg/dL), D-dimer (>860 ng/mL), and erythrocyte sedimentation rate (>30 mm/h) were 2, 2, and 1 points, respectively. Furthermore, elevated synovial fluid white blood cell count (>3000 cells/μL), alpha-defensin (signal-to-cutoff ratio >1), leukocyte esterase (++), polymorphonuclear percentage (>80%), and synovial CRP (>6.9 mg/L) received 3, 3, 3, 2, and 1 points, respectively. Patients with an aggregate score of greater than or equal to 6 were considered infected, while a score between 2 and 5 required the inclusion of intraoperative findings for confirming or refuting the diagnosis. Intraoperative findings of positive histology, purulence, and single positive culture were assigned 3, 3, and 2 points, respectively. Combined with the preoperative score, a total of greater than or equal to 6 was considered infected, a score between 4 and 5 was inconclusive, and a score of 3 or less was not infected. The new criteria demonstrated a higher sensitivity of 97.7% compared to the MSIS (79.3%) and International Consensus Meeting definition (86.9%), with a similar specificity of 99.5%. ConclusionThis study offers an evidence-based definition for diagnosing hip and knee PJI, which has shown excellent performance on formal external validation.

Diagnostic accuracy of synovial fluid, blood markers, and microbiological testing in chronic knee prosthetic infections.

This retrospective study was undertaken to define cut-off values for synovial fluid (SF) leukocyte count and neutrophil percentage for differentiating aseptic failure and periprosthetic joint infection (PJI) and to evaluate the diagnostic accuracy of blood inflammatory markers, and microbiological testing according to the criteria proposed by the International Consensus Meeting (ICM) of Philadelphia. All patients who underwent revision total knee arthroplasty from January 2010 to July 2015 were included: we identified and classified 31 PJIs and 136 aseptic joints. The diagnostic performance of single test was assessed by receiver operating characteristic curve analyses. The sensitivity and specificity were calculated for each of the cut-off values and the area under the curve (AUC) was calculated. The median SF leukocyte count as well as the neutrophil percentage and inflammatory markers were significantly higher in patients with PJI than in those with aseptic failure (p<0.001). A leukocyte count of>2.8×103/μL had a sensitivity of 83.8% and a specificity of 89.7% whereas a neutrophil percentage of>72% yielded a marginally higher sensitivity of 84% and a specificity of 91%. Applying the ICM criteria we found a significant correlation between all these diagnostic measures and PJI (p<0.001) except for a single positive culture. The most accurate criterion of the ICM was the synovial neutrophil differential (AUC=0.89; 95% CI 0.81-0.97), followed by SF leukocyte count (AUC=0.86; 95% CI 0.78-0.94), increased inflammatory markers (AUC=0.85; 95% CI 0.76-0.93), and two positive periprosthetic cultures (AUC=0.84; 95% CI 0.73-0.94). The presence of sinus tract communicating with the joint and a single positive culture showed unfavourable diagnostic accuracy (AUC=0.60, 95% CI 0.47-0.72; AUC=0.49, 95% CI 0.38-0.61, respectively) CONCLUSIONS: The present study highlights the adequate ability of fluid cell count and neutrophil differential to distinguish between PJI and aseptic loosening. The clinical utility of fluid analysis in diagnosing infection can be improved by evaluation of other diagnostic criteria. Level I Diagnostic Study.

Should we treat patients with only one set of positive blood cultures for extensively drug-resistant Acinetobacter baumannii the same as multiple sets?

Acinetobacter species are not considered skin commensals and under-treatment is an overriding concern when caring for critically-ill patients who are mostly at risk of extensively drug-resistant Acinetobacter baumannii (XDRAB) infections. Hence even a single blood culture yielding XDRAB will tend to prompt intervention. However, field observations suggest that patients with single-positive blood cultures had milder disease and were more likely to be recruited in interventional studies than those with multiple-positive blood cultures, yet no distinction is made in current clinical or trial recruitment practices. To our knowledge, this is the first study to compare the clinical characteristics and outcomes of patients with single-positive versus multiple-positive blood cultures for XDRAB. In this multicenter prospective cohort study of XDRAB bacteremic patients from July 2010 to June 2015, only patients with at least two simultaneously drawn blood cultures were included. The patients were classified as having single-positive or multiple-positive blood cultures according to the number of positive blood cultures yielding XDRAB. The primary end-point was the 28-day mortality. Of a total of 155 patients enrolled, 69 had a single-positive and 86 had multiple-positive blood cultures. Leukopenia (37.2% vs. 16.2%; P = 0.004), thrombocytopenia (56.0% vs. 26.5%; P < 0.001), higher Pitt bacteremia scores (6.6 vs. 5.5, P = 0.03) and higher 28-day mortality rates (70.9% vs. 43.5%; P = 0.001) distinguished patients with multiple-positive from those with single-positive cultures. Multivariate logistic regression showed that multi-positivity independently predicted 28-day mortality (adjusted odds ratio, 2.34; 95% confidence interval (CI), 1.03–5.28; P = 0.04) and the Cox regression confirmed that multi-positivity (adjusted hazard ratio, 1.80; 95% CI, 1.13–2.85; P = 0.01) predicted rapid mortality. Patients with multiple versus single positive blood cultures yielding XDRAB had greater morbidity and mortality. Investigators and clinicians should be aware that the blood culture positivity rate impacts outcomes of XDRAB bacteremia.

What is the Diagnostic Accuracy of Aspirations Performed on Hips With Antibiotic Cement Spacers?

Periprosthetic joint infection is a serious complication after THA and commonly is treated with a two-stage revision. Antibiotic-eluting cement spacers are placed for local delivery of antibiotics. Aspirations may be performed before the second-stage reimplantation for identification of persistent infection. However, limited data exist regarding the diagnostic parameters of synovial fluid aspiration with or without saline lavage from a hip with an antibiotic-loaded cement spacer. We asked: (1) For hips with antibiotic cement spacers, does saline lavage influence the diagnostic validity of aspirations? (2) What is the diagnostic accuracy of preoperative aspirations performed on hips with antibiotic cement spacers using the Musculoskeletal Infection Society (MSIS) criteria, stratified by saline and nonlavage? (3) For hips with antibiotic spacers, what are the optimal thresholds for synovial fluid white blood cell (WBC) count and polymorphonuclear neutrophil (PMN) percentage for diagnosing infections? One hundred seventy-four hips (155 patients) with antibiotic-eluting cement spacers inserted between October 2012 and July 2015 were reviewed. Of these, 98 hips (80 patients) met the inclusion criteria and were included in the analysis (77 nonlavage, 21 saline lavage aspirations). Laboratory data from the aspiration and preoperative workup and intraoperative details were collected. Infection status of each hip procedure was determined based on a modified MSIS criteria using serologic, histologic, and intraoperative findings (sinus tract communicating with the joint at surgery or two positive intraoperative periprosthetic cultures with the same organism or two of the three following criteria: elevated erythrocyte sedimentation rate [ESR] [> 30 mm/hour] and C-reactive protein [CRP] [> 10 mg/L], a single positive intraoperative periprosthetic tissue culture, or a positive histologic analysis of periprosthetic tissue [> 5 neutrophils per high power field]). The diagnostic parameters were calculated for the MSIS criteria thresholds for synovial fluid (ie, WBC count > 3000 cells/µL and PMN percentage > 80%). Optimal thresholds were calculated for the corrected synovial WBC count and PMN percentage with a receiver operating characteristic curve. Separate analyses were performed for the hips with successful aspirations (nonlavage group) and those with saline lavage aspirations. The WBC count and PMN percentage were higher in hips with infection than in hips without infection when nonlavage aspirations were done (WBC count, 6680 cells/µL ± 6980 cells/µL vs 2001 ± 4825; mean difference, 4679; 95% CI, 923-8436; p = 0.015; PMN percentage, 83% ± 13% vs 44% ± 30%; mean difference, 39%; 95% CI, 39%-49%; p < 0.001) and the findings between infected and noninfected aspirations were not different when saline lavage aspirations were done (WBC count, 782 cells/µL ± 696 vs 307 cells/µL ± 343; mean difference, 475; 95% CI, -253 to 1203; p = 0.161; PMN percentage, 67% ± 15% vs 58% ± 28%; mean difference, 10%; 95% CI, -11% to 30%; p = 0.331). Aspirations performed without lavage yielded good diagnostic accuracy in all parameters (WBC count, 78% [95% CI, 70%-86%]; PMN percentage. 79% [95% CI, 70%-88%]; positive culture: 84% [95% CI, 81%-90%]; at least one of the above: 79% [95% CI, 70%-88%]); but in the saline lavage group, none had WBC counts above the threshold (diagnostic accuracies for WBC count, 0%; PMN percentage, 71% [95% CI, 62%-86%]; positive culture, 76% [95% CI, 76%-86%]; at least one: 71% [95% CI, 57%-91%]). Because saline lavage did not result in differences between aspirations from infected and noninfected hips, we calculated the optimal thresholds in the nonlavage group only; the optimal threshold for synovial WBC count was 1166 cells/µL and for synovial PMN the percentage was 68%, which corresponds to WBC count diagnostic accuracy of 78% (95% CI, 69%-87%) and PMN percentage accuracy of 78% (95% CI, 69%-87%). Because the MSIS criteria thresholds resulted in suboptimal sensitivities owing to a higher number of false negatives, we recommend considering lower WBC count and PMN percentage thresholds for hip-spacer aspirations. Furthermore, the WBC count and PMN percentage results from aspirations performed with saline lavage are not reliable for treatment decisions. Level III, diagnostic study.

PTH-217 Spinal infections among patients with long term central venous catheters for home parenteral nutrition: a descriptive case series

<h3>Introduction</h3> Long-term central venous catheters for home parenteral nutrition (HPN) carry a risk of recurrent bacterial colonisation and catheter related sepsis (CRS).¹Spinal infections following an episode of CRS are uncommon but may be underreported or overlooked due to the high incidence of osteoporotic fractures in this cohort.²We aimed to determine the frequency and describe cases of spinal infections in HPN patients at our institution. <h3>Method</h3> We performed a retrospective review of all spinal infections presenting in our HPN patients between January 2010 and October 2013, a cohort of approximately 270 patients. Data were extracted on basic demographics, indication for and duration of HPN, means of venous access, history of presentation and management. <h3>Results</h3> The CRS rate was 0.9 per 1000 catheter days. Six patients were identified (mean age 65 years, 5 male) with spinal infection, a rate of 0.02 per 1000 catheter days. Duration with current CVC ranged from 5 months to 2 years. All patients presented with spinal pain; 5/6 cervical, 1/6 thoracic. All patients had a normal white cell count and differential, and in only 1 case was the CRP elevated. In 4 cases an organism was isolated at the time of presentation from blood cultures taken centrally and/or peripherally – commonly staphylococcal species. All patients had contrast-enhanced magnetic resonance imaging (MRI) with features compatible with spinal infection and in two patients a repeat MRI demonstrated resolution of changes. In three patients a disc biopsy was performed yielding one negative culture, one microbiological correlation with blood cultures and a single positive culture (unknown isolate). All patients received three months of intravenous antibiotic therapy augmented with surgery or conservative management on a case-by-case basis. The CVC was removed in 4/6 patients at presentation, with salvage in the remaining two. <h3>Conclusion</h3> Spinal infections associated with long-term CVC for HPN should be considered in patients presenting with spinal pain. They are often of insidious onset and may present with normal inflammatory markers which may contribute to delayed or missed diagnoses that together with differences in the definition of CRS¹may partially explain the poor representation in the current HPN-related literature.³Gold-standard imaging is with contrast-enhanced MRI with formal biopsy decided on an individual basis. Management should involve prolonged antibiotics and liaison with microbiology and neurosurgery. Multidisciplinary discussion on CVC salvage is important especially in cases of difficult vascular access. <h3>Disclosure of interest</h3> None Declared. <h3>References</h3> Reimund JM, <i>et al.</i><i>Clin Nutr.</i>2002;21(2):33–38 Haderslev KV, <i>et al.</i><i>JPEN</i>2004;28(5):289–294 Huard G, <i>et al.</i><i>J Clin Med Res.</i>2014;6(4):272–277

Recurrence of pulmonary Mycobacterium avium complex disease due to endogenous reactivation

Introduction: An official American Thoracic Society and Infectious Disease Society of America statement has shown that patients with pulmonary Mycobacterium avium complex (MAC) disease who complete 10–12 months of negative cultures on therapy but then have either single or multiple positive MAC cultures are more likely to have reinfection with a new MAC strain. Case presentation: A 63‐year‐old woman was diagnosed with pulmonary disease caused by clarithromycin (CAM)‐susceptible MAC. Before initiating chemotherapy using a four‐drug regimen containing CAM, an investigation of the patient’s residential bathroom was conducted and one of the M. avium isolates recovered from the bathtub inlet was found to be genetically identical to sputum‐derived isolates by variable number tandem repeats analysis using M. avium tandem repeat loci (MATR‐VNTR). A second investigation of the bathroom during chemotherapy showed no M. avium isolates, and five consecutive sputum cultures were negative for 12 months until chemotherapy was discontinued. A recurrence occurred 3 months after the end of chemotherapy (at age 65 years). A third investigation of the bathroom was performed and MATR‐VNTR analysis revealed that the VNTR profile of the M. avium isolates recovered from the sputum at recurrence was identical to that of the isolates recovered from the sputum at initial diagnosis and the bathroom at the first investigation. Conclusion: The recurrence occurred due to endogenous reactivation of the initial M. avium isolate despite drug treatment for 12 months after sputum culture conversion. Further genetic analyses of MAC isolates recovered from patients and environments should be encouraged.

Diagnosis of Periprosthetic Joint Infection

Diagnosis of Periprosthetic Joint Infection

Diagnosis of Periprosthetic Joint Infection

Consensus: PJI is defined as: Two positive periprosthetic cultures with phenotypically identical organisms, or A sinus tract communicating with the joint, or Having three of the following minor criteria: -Elevated serum C-reactive protein (CRP) AND erythrocyte sedimentation rate (ESR) -Elevated synovial fluid white blood cell (WBC) count OR ++change on leukocyte esterase test strip -Elevated synovial fluid polymorphonuclear neutrophil percentage (PMN%) -Positive histological analysis of periprosthetic tissue -A single positive culture ErratumThe Journal of ArthroplastyVol. 29Issue 10PreviewIn the article “Workgroup 7: Diagnosis of Periprosthetic Joint Infection” (Zmistowski et al, Journal of Arthroplasty 29/2S:7), there is an error in the author group. The author/delegate name “Drago Lorenzo, MD” should be “Lorenzo Drago, MD”. The correct author surname is Drago. Full-Text PDF

Epidemiology and Risk Factors for Bloodstream Infections in a Home Parenteral Nutrition Program

An increasing number of patients with intestinal failure are receiving home parenteral nutrition (HPN). Associated complications include bloodstream infections (BSIs), but data on rates and risk factors for HPN-related BSIs are scarce. A retrospective review was conducted of patients enrolled in the regional HPN program between 2001 and 2008. Demographic information and data on indication for HPN, duration of PN therapy, type and date of insertion of central venous access device, and blood culture results were recorded. In total, 155 patients (165 courses of HPN) were included for a total of 45,876 catheter days. The mean patient age was 49 years, and 105 (64%) patients were female. A total of 105 organisms were cultured from 93 distinct episodes of BSIs. The rate of BSI was found to be 2.0 per 1000 catheter days, but excluding BSIs with a single positive culture of coagulase-negative staphylococcus and diphtheroid bacilli, the rate of infection was 1.4 per 1000 catheter days. Male sex and underlying malignancy were significant predictors of BSI, with hazard ratios of 1.69 (95% confidence interval [CI], 1.14-2.60; P = .009) and 2.38 (95% CI, 1.53-3.50; P < .001). In a large heterogeneous group of HPN patients, the BSI rate ranged between 1.4 and 2.0 infections per 1000 catheter days. Isolated organisms were similar to those found in hospitalized patients. Male sex and underlying malignancy were significant risk factors for BSI. These high-risk patients are likely to benefit from interventions aimed at reducing BSIs.

Epidemiologic surveillance to detect false-positive Mycobacterium tuberculosis cultures

This study was aimed to investigate the ability of potential indices from epidemiologic surveillance to detect false-positive cultures of Mycobacterium tuberculosis (MTB). All clinical specimens for mycobacterial culture from April 1 to August 31, 2010, were reviewed. Single-positive cultures without relevant clinical and pathologic information were categorized as suspected false-positive cultures. Genotyping methods were used to confirm false-positive cultures. The performance of epidemiologic surveillance indices to detect potential false-positive cultures was evaluated. A total of 14,462 specimens were sent to the laboratory and 214 batches were processed in 107 work days (average 67.6 specimens per batch, ranging from 21 to 130 specimens per batch). Seventy-one single-positive cultures were identified, among which 5 cultures of multidrug-resistant MTB in 1 batch were false-positive, confirmed by genotyping methods. Epidemiologic surveillance with statistical process control charts for single-positive cultures per day showed good performance in epidemiologic surveillance. The false-positive rate was 38.5% in the 13 potential false-positive cultures according to the statistical process control chart for single-positive cultures per day. Although the incidence of tuberculous disease is high in Taiwan, clustering of multidrug-resistant MTB in 1 batch or clustering of single-positive cultures still suggested the occurrence of false-positive MTB cultures. Therefore, epidemiologic surveillance for the clustering of single-positive cultures with the statistical process control chart could be used to monitor the occurrence of false-positive results.

Case of laboratory cross-contamination of Mycobacterium tuberculosis in the broth-based culture system

We experienced a case of laboratory cross-contamination of Mycobacterium tuberculosis on the broth based culture system. These false-positive cultures were confirmed by analysis of DNA fingerprinting, RFLP method, which showed the same pattern in three specimens with that of the first manipulated specimen in our laboratory on that day, out of 7 specimens examed. We found possible several process causing cross-contamination where mixture of the foreign body could occur in buffer or NALC-NaOH. False-positive cultures for Mycobacterium tuberculosis may lead to unnecessary, potentially toxic, costly treatment, and changing the treatment strategy. So we must critically interpret a single positive culture, especially by liquid media.

Sonication cultures of explanted components as an add‐on test to routinely conducted microbiological diagnostics improve pathogen detection

The purpose of this study was to improve the pathogen detection in prosthetic joint infections, particularly to evaluate the feasibility of the sonication culture method in the clinical routine. Explanted components of all patients with presumptive prosthetic or implant infection were sonicated separately in sterile containers to dislodge the adherent bacteria from the surfaces and cultured. The results of sonication culture were compared to the conventional tissue culture. We investigated 60 consecutive patients with loosening of the prostheses or implants Forty patients had septic and 20 aseptic loosening (24 knee prostheses, 21 hip prostheses, 6 mega-prostheses, 2 shoulder prostheses, 6 osteosynthesis, 1 spinal instrumentation). The sensitivity of sonication fluid culture was 83.3%, of single positive tissue culture was 72.2% and 61.1% when two or more cultures yielded the same microorganism. In patients receiving antibiotic therapy the sensitivity was 65.9%, 57.5%, and 42.5%, respectively. Pathogens detected in a single tissue culture as well as in sonication culture yielded a significantly higher rate of prosthetic infection than conventional tissue culture alone (p = 0.008), even in patients receiving continuous antibiotic therapy before explantation (p = 0.016). The sonication method represents an essential add-on in pathogen detection compared to conventional tissue culture.

Association between 16S-23S Internal Transcribed Spacer Sequence Groups of Mycobacterium avium Complex and Pulmonary Disease

Organisms within the Mycobacterium avium complex (MAC) may have differential virulence. We compared 33 subjects with MAC pulmonary disease to 75 subjects with a single positive culture without disease. M. avium isolates were significantly more likely to be associated with MAC pulmonary disease (odds ratio = 5.14, 95% confidence interval = 1.25 to 22.73) than M. intracellulare.

The Fate of the Unexpected Positive Intraoperative Cultures After Revision Total Knee Arthroplasty

Of a consecutive series of 692 revision total knees at 3 centers, intraoperative cultures were unexpectedly found to be positive in 41 cases (5.9%). Of the 41, 29 (71%) cases had a single positive intraoperative 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). Twelve patients were determined to have probable type 1 periprosthetic infection, 11 of which were treated with a course of antibiotics. Two of these patients became reinfected within a year. A single positive intraoperative culture after revision total knee arthroplasty does not mandate further treatment in the absence of any other signs of infection.

Infectious Complications of Central Venous Catheters Increase the Risk of Catheter-Related Thrombosis in Hematology Patients: A Prospective Study

We studied whether the risk of central venous catheter (CVC) -related thrombosis increased after an episode of CVC-related infection in patients undergoing intensive chemotherapy. Secondly, we determined whether thrombosis can be predicted or excluded by CVC lock fluid surveillance cultures. In a prospective setting, 105 consecutive patients were carefully examined for CVC-related infection and thrombosis. In all patients, microbial surveillance cultures of CVC lock fluid were taken every other day. All patients with clinical suspicion of CVC-related thrombosis underwent Doppler ultrasound or additional venography. The cumulative incidence of CVC-related infection was 24% (25 of 105 patients). Clinically manifest thrombosis occurred in 13 (12%) of 105 patients. In patients with CVC-related infection, the risk of thrombosis increased markedly in comparison to those without infection (relative risk, 17.6; 95% CI, 4.1 to 74.1). In patients having two or more positive subsequent CVC lock fluid cultures with identical micro-organisms, 71.4% developed thrombosis, as compared with 3.3% in patients with negative or a single positive culture. The risk of clinically manifest thrombosis is increased after an episode of CVC-related infection in patients undergoing intensive chemotherapy. Surveillance culturing of CVC lock fluid may be clinically useful in estimating the risk for thrombosis and the instigation of focused early intervention.

Recognition of Misdiagnosed Tuberculosis in a Bone Marrow Transplant Recipient Leads to Identification of "Pseudotuberculosis" Due to Laboratory Contamination

Allogeneic bone marrow transplant recipients are at increased risk for tuberculosis. A single positive sputum culture for M. tuberculosis in an allogeneic bone marrow transplant recipient with graft versus host disease (GVHD) resulted in misdiagnosis and unnecessary treatment. Lack of definite features of tuberculosis in this patient prompted an investigation for possible laboratory error. Six of 7 patient specimens processed concurrently and reported positive for Mycobacterium tuberculosis were determined to false positive based upon restriction fragment length polymorphism analysis, drug-susceptibility patterns, and epidemiologic review. Contamination resulted during digestion of the clinical specimens. All false-positive specimens were acid-fast stain-negative, and a single culture was positive for M. tuberculosis. Five of the six cases had risk factors for tuberculosis. Therefore, a stain-negative single culture positive for M. tuberculosis even in patients at risk for tuberculosis such as bone marrow transplant recipients should prompt physicians to contact the laboratory. This would result in detection of unsuspected laboratory error and avoid unnecessary therapy.

A systematic review of the clinical significance of pulmonary Mycobacterium kansasii isolates in HIV infection.

Guidelines recommend treating HIV-infected patients with pulmonary Mycobacterium kansasii infection only in the presence of multiple positive cultures and clinical and radiographic abnormalities. Some authors suggest a single positive culture warrants treatment. A systematic literature review was done to determine whether HIV-infected patients who had M. kansasii isolated from respiratory specimens may have an indolent infection (often referred to as colonization) not requiring treatment and to determine the utility of diagnostic criteria in distinguishing disease from indolent infection. Sixteen studies were included, with at least 573 patients: mean age 44 years; 91% male; 64% men who had sex with men; 35% injection drug users; and median CD4 lymphocyte count of 2-381 cells/microL. The median rate of indolent infection was 8%. Of the few patients who did not satisfy diagnostic criteria and were left untreated, outcomes were generally favorable. Overall, survival was longer in treated patients (mean 12 vs. 4 months). Indolent pulmonary infection with M. kansasii may exist in the setting of HIV, but published data do not provide adequate information to identify such patients. It is unclear whether unfulfilled diagnostic criteria necessarily imply the absence of disease in this context.