Consensus definitions have emerged for the discrimination between infected and uninfected prosthetic joints but diagnostic uncertainty often occurs. We examined the accuracy of orthopaedic surgeons’ assessments to diagnose the infected prosthetic hip or knee and elucidated the added value of laboratory parameters. A prospective cohort study of patients undergoing revision arthroplasty of hip or knee was conducted over a one-year period. Orthopaedic surgeons’ determinations prior to arthroplasty were recorded. A reference diagnostic standard was determined retrospectively by independent review from 3 infectious diseases physicians. Patients were followed up to 12 months. For 198 patients enrolled, 228 surgical encounters (110 knee, 118 hip) were classified by independent reviewers as 176 uninfected and 52 infected. Orthopaedic surgeons’ preoperative diagnoses of infection had high diagnostic accuracy (sensitivity 89%, specificity 99%, PPV 98%, NPV 97%). Addition of intraoperative findings and histopathology improved their diagnostic accuracy. Addition of culture and PCR results improved sensitivity of diagnostic determinations but not specificity. We provide evidence that clinical acumen has high diagnostic accuracy using routine preoperative parameters. Histopathology from intraoperative specimens would improve surgeons’ diagnostic accuracy but culture and PCR from intraoperative specimens could create greater diagnostic uncertainty. This study is critical to further our understanding of the added value, if any, of laboratory testing to support clinical decision making for the suspected infected joint and allow us to identify diagnostic gaps for emerging technologies to fill that will improve our ability to diagnose the infected prosthetic joint.
A number of exciting new technologies have emerged to detect infectious diseases with greater accuracy and provide faster times to result in hopes of improving the provision of care and patient outcomes. However, the challenge in evaluating new methods lies not in the technical performance of tests but in (1) defining the specific advantages of new methods over the present gold standards in a practicable way and (2) understanding how advanced technologies will prompt changes in medical and public health decisions. With rising costs to deliver care, enthusiasm for innovative technologies should be balanced with a comprehensive understanding of clinical and laboratory ecosystems and how such factors influence the success or failure of test implementation. Selecting bloodstream infections as an exemplar, we provide a 6-step model for test adoption that will help clinicians and laboratorians better define the value of a new technology specific to their clinical practices.
bloodstream infections; clinical utility; diagnostic tests; sepsis; test adoption
Physicians rely on blood culture to diagnose bloodstream infections (BSI) despite its limitations. As new technologies emerge for rapid BSI diagnosis, optimization of their application to patient care requires an understanding of clinicians’ perspectives on BSI diagnosis and how a rapid test would influence medical decisions.
We administered a 26-question survey to practitioners in infectious diseases/microbiology, critical care, internal medicine, and hematology/oncology services in USA and Germany about current standards in diagnosing and treating BSI and a hypothetical rapid BSI test.
Responses from 242 providers had roughly equal representation across specialties. For suspected BSI patients, 78% of practitioners would administer empiric broad spectrum antibiotics although they estimated, on average, that 31% of patients received incorrect antibiotics while awaiting blood culture results. The ability of blood culture to rule in or rule out infection was very/extremely acceptable in 67% and 36%, respectively. Given rapid test results, 60–87% of practitioners would narrow the spectrum of antimicrobial therapy depending on the microorganism detected, with significantly higher percentages when resistance determinants were also tested. Over half of respondents felt a rapid test would be very/extremely influential on clinical practice.
Limitations of blood culture were perceived as a barrier to patient care. A rapid test to diagnose BSI would impact clinical practice, but the extent of impact may be limited by prevailing attitudes and practices. Opportunities exist for interventions to influence practitioners’ behaviors in BSI management particularly with emergence of newer diagnostic tests.
“Pseudomonas andersonii” is a Gram-negative bacillus initially isolated from a granulomatous lung lesion. Novel species status has not been validated for this single strain. We report four additional cases of pulmonary granuloma involving P. andersonii and further characterize the organism. These patients had pulmonary nodules that were surgically resected and which grew P. andersonii on routine culture. Mycobacterium avium complex was concomitantly isolated in two cases, and fungal structures were identified histopathologically in two other cases. The five P. andersonii strains described to date were similar in growth characteristics, biochemical reactions, matrix-assisted laser desorption ionization–time of flight mass spectrometry protein profiles, and susceptibility to antimicrobial agents. Their 16S rRNA genes were 99.9 to 100% identical but less than 95.0% similar to those of all other known bacteria. The gyrA genes of these strains were 99.5 to 100% identical. These shared features illustrate P. andersonii as a unique and distinct bacterium and support the novel species status of the organism.
bacteria; rapid-growing mycobacteria; multilocus sequencing; Mycobacterium chelonae-abscessus complex; Mycobacterium franklinii; sinopulmonary disease; tuberculosis and other mycobacteria; United States; CME; research; Suggested citation for this article: Simmon KE; Brown-Elliott BA; Ridge PG; Durtschi JD; Mann LB; Slechta ES; et al. Mycobacterium chelonae-abscessus complex associated with sinopulmonary disease; northeastern USA. Emerg Infect Dis [serial on the Internet]. 2011 Sep [date cited]. http://dx.doi.org/10.3201/eid1709.101667
Parasitic infection is uncommon in the United States, but surveys suggest that physicians test when the presence of parasites is unlikely and fail to order appropriate testing when suspicion is high. Numerous studies confirm that immunoassays are more sensitive for Giardia and Cryptosporidium detection, but our experience was that physicians preferentially used ovum and parasite examination (O&P). We conducted a retrospective study of fecal parasite testing at a referral laboratory nationally (1997 to 2006) and during a Cryptosporidium outbreak (Utah, 2007) to correlate physician use of O&P and enzyme immunoassays (EIAs) with the yield of parasites detected. Nationally, of 170,671 episodes, 76.0% (n = 129,732) included O&P, 27.9% (n = 47,666) included Giardia EIA, and 5.7% (n = 9,754) included Cryptosporidium EIA. Most pathogens were Giardia or Cryptosporidium. More episodes were positive when EIA was performed (n = 1,860/54,483 [3.4%]) than when O&P only was performed (n = 1,667/116,188 [1.4%]; P < 0.001), and EIA was more sensitive than O&P. However, more O&P results were positive among patients with both O&P and EIA performed (2.5%) than among those with O&P only performed (1.4%; P < 0.001), suggesting that patients tested by O&P only may have been at lower risk. During the first 10 weeks of the outbreak, physicians also preferentially used O&P over EIA, but no Cryptosporidium cases were detected by O&P. We conclude that clinicians frequently use O&P testing when test performance and epidemiology support the use of immunoassays or no testing. We recommend that stool O&P be limited to patients with negative immunoassay results and persistent symptoms or individuals at increased risk for non-Giardia, non-Cryptosporidium infection. An evidence-based algorithm for the evaluation of patients with suspected intestinal parasitic infection is proposed.
Reference isolates of Mycobacterium neoaurum, Mycobacterium aurum, and the nonvalidated species “Mycobacterium lacticola” were the focus of two recent molecular taxonomic studies. On the basis of this grouping, we identified 46 clinical pigmented, rapidly growing mycobacterial isolates. By 16S rRNA gene sequencing, only two major taxa were identified: M. neoaurum and a previously uncharacterized “M. neoaurum-like” group. The M. neoaurum-like group exhibited only 99.7% identity to M. neoaurum by 16S rRNA gene sequencing and 96.5% identity to M. neoaurum by rpoB sequencing and was named M. bacteremicum. No clinical isolates of M. aurum or M. lacticola were identified. Of isolates with known sources, 4/8 (50%) of M. bacteremicum isolates and 22/34 (65%) of M. neoaurum isolates were recovered from blood, and 35% of these were known to be from patients with catheter-related sepsis. MIC and clinical data on these 46 isolates of M. neoaurum and M. bacteremicum along with a review of 16 previously reported cases of infection with the M. neoaurum-M. lacticola group demonstrated that the isolates were highly susceptible to all drugs tested except clarithromycin, and most clinical cases were successfully treated. The clarithromycin resistance suggested the presence of an inducible erm gene reported in other species of rapidly growing mycobacteria. Sequencing studies are currently required to identify these two species. Strain ATCC 25791 (originally submitted as an example of Mycobacterium aurum) is proposed to be the type strain of M. bacteremicum.
We assessed the utility of culture for Mycoplasma pneumoniae and Chlamydophila pneumoniae to diagnose respiratory tract infections. Compared to PCR and IgM serology, culture was less sensitive and had extremely low yield. Culture is not recommended for these pathogens, and this method should be eliminated from routine practice.
The 16S rRNA gene is commonly used to identify Mycobacterium spp., but alternative DNA targets can provide better resolution to the species level. We evaluated a novel system that enables simultaneous amplification, sequencing, and analysis of two different DNA targets in a single tube to identify clinical isolates of Mycobacterium spp. For 139 clinical isolates, we found that the 16S rRNA gene alone identified 67 (48%) isolates as single species, 68 (49%) isolates to the complex or group level, and 4 (3%) isolates to the genus level only. The rpoB gene alone identified 117 (84%) isolates as single species, 10 (7%) isolates to the complex or group level, and 12 (8%) isolates to the genus level only. Combining the separate analyses for sequencing of two gene targets, 119 (86%) isolates were identified as single species and 10 (7%) isolates were identified to the complex or group level. Seven (5%) isolates were identified as novel species within established groups, and 3 (2%) were identified to the genus level only. Dual-locus identification identified 110 (79%) isolates as single species and 22 (16%) isolates to the complex or group level. Six (4%) were identified as novel species within established groups, and 1 (1%) was identified to the genus level only. Identifications were more accurate when both the 16S rRNA and rpoB genes were screened, and reliance on a single gene target was suboptimal. RipSeq dual-locus software provides an accurate alternative method for laboratories using two different gene targets for microorganism identification.
Mycobacterium abscessus is resistant to multiple antibiotics, creating treatment challenges. Carbapenems are tested to increase therapeutic alternatives. We performed in vitro susceptibility testing by Etest of four carbapenems for M. abscessus isolates. Imipenem demonstrated the most in vitro activity, and testing of other carbapenems provided no additional value.
Phenotypic identification of AmpC, KPC and extended-spectrum β-lactamases (ESBLs) among members of the Enterobacteriaceae remains challenging. This study compared the Phoenix Automated Microbiology System (BD Diagnostics) with the Clinical and Laboratory Standards Institute confirmatory method to identify ESBL production among 200 Escherichia coli and Klebsiella pneumoniae clinical isolates. The Phoenix system misclassified nearly half of the isolates as ESBL-positive, requiring manual testing for confirmation. Inclusion of aztreonam±clavulanic acid (CA) and cefpodoxime±CA in the testing algorithm increased the ESBL detection rate by 6 %. Boronic acid-based screening identified 24 isolates as AmpC+, but in a subset of genotypically characterized isolates, appeared to have a high false-positivity rate. PCR screening revealed eight KPC+ isolates, all of which tested as ESBL+ or ESBL+ AmpC+ by phenotypic methods, but half were reported as carbapenem-susceptible by the Phoenix system. Overall, these results indicate that laboratories should use the Phoenix ESBL results only as an initial screen followed by confirmation with an alternative method.
Identification of viridans group streptococci (VGS) to the species level is difficult because VGS exchange genetic material. We performed multilocus DNA target sequencing to assess phylogenetic concordance of VGS for a well-defined clinical syndrome. The hierarchy of sequence data was often discordant, underscoring the importance of establishing biological relevance for finer phylogenetic distinctions.
Coagulase-negative staphylococci (CNS) are important causes of infective endocarditis (IE), but their microbiological profiles are poorly described. We performed DNA target sequencing and susceptibility testing for 91 patients with definite CNS IE who were identified from the International Collaboration on Endocarditis—Microbiology, a large, multicenter, multinational consortium. A hierarchy of gene sequences demonstrated great genetic diversity within CNS from patients with definite endocarditis that represented diverse geographic regions. In particular, rpoB sequence data demonstrated unique genetic signatures with the potential to serve as an important tool for global surveillance.
Accurate species determination for anaerobes from blood culture bottles has become increasingly important with the reemergence of anaerobic bacteremia and prevalence of multiple-drug-resistant microorganisms. Our knowledge of the taxonomical diversity of anaerobes that cause bloodstream infections is extremely limited, because identification historically has relied on conventional methods. Over a 5-year period, we profiled anaerobic bacteremia at a large tertiary care hospital with 16S rRNA gene sequencing to gain a better understanding of the taxonomical diversity of the bacteria. Of 316 isolates, 16S rRNA gene sequencing and phylogenetic analysis identified 316 (100%) to the genus or taxonomical group level and 289 (91%) to the species level. Conventional methods identified 279 (88%) to the genus level and 208 (66%) to the species level; 75 (24%) were misidentified at the species level, and 33 (10%) results were inconclusive. High intragenus variability was observed for Bacteroides and Clostridium species, and high intraspecies variability was observed for Bacteroides thetaiotaomicron and Fusobacterium nucleatum. Sequence-based identification has potential benefits in comparison to conventional methods, because it more accurately characterizes anaerobes within taxonomically related clusters and thereby may enable better correlation with specific clinical syndromes and antibiotic resistance patterns.
The rapid diagnosis of infections with Bordetella and Legionella species is important for patient management. With observed increases in direct fluorescent-antibody (DFA) testing volumes, we retrospectively compared the performance characteristics of DFA testing to those of culture and PCR. For Bordetella sp., samples were classified as positive by DFA testing (184 [3%] of 6,195 samples) and culture (150 [2%] of 6,251 samples) significantly less often than by PCR (2,557 [10%] of 26,929 samples). Of 360 samples tested by both DFA and PCR methods, 81 (16 by DFA testing and 79 by PCR) were determined to be positive for Bordetella, with a sensitivity and specificity of DFA testing of 18% and 99%, respectively. Of 1,426 samples tested by both DFA and culture methods, 48 (44 by DFA testing and 15 by culture) were determined to be positive for Bordetella, with a sensitivity and specificity of DFA testing of 73% and 98%, respectively. For Legionella sp., samples were identified as positive by DFA testing (31 [0.25%] of 12,597 samples) and culture (85 [0.6%] of 13,572 samples) significantly less often than by PCR (27 [4%] of 716 samples). Of 62 samples tested by both DFA and PCR methods, none were positive for Legionella sp. by DFA testing and 3 were positive by PCR. Of 3,923 samples tested by both DFA and culture methods, 22 (3 by DFA testing and 21 by culture) were positive for Legionella sp., with a sensitivity and specificity of DFA testing of 9.5% and 100%. Overall, DFA testing for Bordetella sp. and Legionella sp. is an insensitive method, and despite its continued popularity, clinical microbiology laboratories should not offer it when more sensitive tests like PCR are available.
Mycobacterium massiliense is a rapidly growing mycobacterium that is indistinguishable from Mycobacterium chelonae/M. abscessus by partial 16S rRNA gene sequencing. We sequenced rpoB, sodA, and hsp65 genes from isolates previously identified as being M. chelonae/M. abscessus and identified M. massiliense from isolates from two patients with invasive disease representing the first reported cases in the United States.
Mycobacterium cosmeticum; catheter infection; rapidly growing mycobacteria; letter
Most patients with herpes simplex virus (HSV) central nervous system (CNS) infection have abnormal cerebrospinal fluid (CSF) indices. Therefore, we implemented screening criteria based on CSF values and host immune status to guide testing. All CSF samples submitted for HSV PCR analysis from January 1999 through December 2004 were included in the study. Specimens from patients with human immunodeficiency virus, a history of transplants, an age of <2 years, a CSF white blood cell count of >5 cells/mm3, or a protein level of >50 mg/dl were tested upon request. All other samples were rejected and frozen. To validate our screening criteria, rejected specimens were pooled and tested retrospectively. Electronic medical records were also reviewed. A total of 1,659 HSV PCR requests from 1,458 patients were screened. Of the 1,296 specimens (78.1%) accepted for testing, 1,213 were negative, 7 were positive for HSV type 1 (HSV-1), 26 were positive for HSV-2, and 50 had unavailable results. Sixteen requests were rejected because an alternative microbiologic diagnosis had been established. Of the 347 samples rejected based on criteria, 222 (64.0%) remained available for pooled testing. No HSV-1-positive samples were identified in the rejected specimens. Two rejected specimens tested positive for HSV-2 DNA, but both met acceptance criteria which had not been communicated to the laboratory. Few patients (7.8%) with rejected specimens were treated with acyclovir, which suggests a low clinical concern for HSV encephalitis. Acceptance criteria based on CSF parameters and host immune status saved time and cost and did not miss patients with HSV CNS infection. Communication between the clinician and the laboratory is imperative for a successful screening program.
Fungal infections are increasing, particularly among immunocompromised hosts, and a rapid diagnosis is essential to initiate antifungal therapy. Often fungi cannot be identified by conventional methods and are classified as nonsporulating molds (NSM).We sequenced internal transcribed spacer regions from 50 cultures of NSM and found 16 potential pathogens that can be associated with clinical disease. In selected clinical settings, identification of NSM could prove valuable and have an immediate impact on patient management.
Laboratories often receive clinical isolates for bacterial identification that have ambiguous biochemical profiles by conventional testing. With the emergence of 16S rRNA gene sequencing as an identification tool, we evaluated the usefulness of SmartGene IDNS, a 16S rRNA sequence database and software program for microbial identification. Identification by conventional methods of a diverse group of bacterial clinical isolates was compared with gene sequences interrogated by the SmartGene and MicroSeq databases. Of 300 isolates, SmartGene identified 295 (98%) to the genus level and 262 (87%) to the species level, with 5 (2%) being inconclusive. MicroSeq identified 271 (90%) to the genus level and 223 (74%) to the species level, with 29 (10%) being inconclusive. SmartGene and MicroSeq agreed on the genus for 233 (78%) isolates and the species for 212 (71%) isolates. Conventional methods identified 291 (97%) isolates to the genus level and 208 (69%) to the species level, with 9 (3%) being inconclusive. SmartGene, MicroSeq, and conventional identifications agreed for 193 (64%) of the results. Twenty-seven microorganisms were not represented in MicroSeq, compared to only 2 not represented in SmartGene. Overall, SmartGene IDNS provides comprehensive and accurate identification of a diverse group of bacteria and has the added benefit of being a user-friendly program that can be modified to meet the unique needs of clinical laboratories.
bioterrorism; diagnostic tests; health resources; public health; laboratories; decision making; letter
The incidence of and average time to detection for Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella (HACEK) bacteria in blood cultures with standard incubation and the utility of extended incubation of blood culture bottles were reviewed at four tertiary care microbiology laboratories. HACEK organisms were isolated from 35 (<0.005%) of 59,203 positive blood cultures. None of 407 blood cultures with extended incubation grew HACEK or other bacteria. Bacteremia from HACEK bacteria is rare, and extended incubation of blood cultures to recover HACEK bacteria is unnecessary.
Recovery of Streptococcus pneumoniae from positive blood culture bottles may be difficult due to autolysis of pneumococci. Therefore, we evaluated the performance of the Binax NOW S. pneumoniae antigen test with samples from positive blood culture bottles and defined the duration of detectable pneumococcal antigen in these bottles. Use of the S. pneumoniae antigen test is an alternative method for identifying S. pneumoniae from positive blood culture bottles and may enable a diagnosis of pneumococcal bacteremia despite negative subcultures.
A new, clear-plastic nonvented aerobic FA bottle, designed to prevent breakage, has been developed for the BacT/ALERT blood culture system. We assessed the new plastic FA bottle by comparing its performance with that of the current glass FA bottle for recovery of microorganisms and time to detection of growth in blood samples obtained for culture from adult patients with suspected bloodstream infections. We conclude that the BacT/ALERT plastic and glass FA bottles are comparable for recovery of microorganisms and that the safety advantage of plastic bottles can be achieved without compromising performance.