Laboratory approaches to determining blood culture contamination rates: an ASM Laboratory Practices Subcommittee report.

Blood culture contamination (BCC) is the presence of specific commensal and environmental organisms cultivated from a single blood culture set out of a blood culture series and that do not represent true bacteremia. BCC can impact quality of care and lead to negative outcomes, unnecessary antibiotic exposure, prolonged hospital stays, and substantial costs. As part of the laboratory's quality management plan, microbiology laboratory personnel are tasked with monitoring BCC rates, preparing BCC rate reports, and providing feedback to the appropriate committees within their healthcare system. The BCC rate is calculated by the laboratory using pre-set criteria. However, pre-set criteria are not universally defined and depend on the individual institution's patient population and practices. This mini-review provides practical recommendations on elaborating BCC rate reports, the parameters to define for the pre-set criteria, how to collect and interpret the data, and additional analysis to include in a BCC report.

Considerations from the College of American Pathologists for Implementation of an Assay for SARS-CoV-2 Testing after a Change in Regulatory Status.

The U.S. Food & Drug Administration (FDA) regulates the marketing of manufacturers' in vitro diagnostic tests (IVDs), including assays for the detection of SARS-CoV-2. The U.S. government's Clinical Laboratory Improvement Amendments (CLIA) of 1988 regulates the studies that a clinical diagnostic laboratory needs to perform for an IVD before placing it into use. Until recently, the FDA has authorized the marketing of SARS-CoV-2 IVDs exclusively through the Emergency Use Authorization (EUA) pathway. The regulatory landscape continues to evolve, and IVDs will eventually be required to pass through conventional non-EUA FDA review pathways once the emergency declaration is terminated, in order to continue to be marketed as an IVD in the United States. When FDA regulatory status of an IVD changes or is anticipated to change, the laboratory should review manufacturer information and previously performed internal verification studies to determine what, if any, additional studies are needed before implementing the non-EUA version of the IVD in accordance with CLIA regulations. Herein, the College of American Pathologists' Microbiology Committee provides guidance for how to approach regulatory considerations when an IVD is converted from EUA to non-EUA status.

Microbiological Evaluation of Opened Saline Bottles for Scleral Lens Use and Hygiene Habits of Scleral Lens Patients.

SIGNIFICANCE: Scleral lenses have become a widely used treatment option for patients with irregular corneas and ocular surface disease. Successful wear entails use of a nonpreserved saline solution to fill the lens before application on the eye. PURPOSE: The purposes of this study were to evaluate solution from opened bottles of multidose preservative-free saline for microbiological growth and to better understand study participant hygiene habits while handling these bottles for scleral lens wear. METHODS: Eligible study participants in this single-center prospective study were patients who routinely used multidose preservative-free saline solution for scleral lens rinsing and filling. Study participants completed a 12-question survey regarding their scleral lens hygiene habits and donated their opened multidose preservative-free saline bottle (PuriLens Plus; The Lifestyle Company, Inc., Freehold, NJ), which was processed for bacterial and fungal cultures. RESULTS: Thirty-five participants (19 males, 16 females) with ages ranging from 6 to 81 years (mean, 47.9 years) were included. Indications for scleral lens wear included those with irregular corneas and ocular surface disease. The overall rate of microbial contamination among saline samples was 62.9% (n = 22). Twenty-one different microorganisms were identified. The survey responses did not differ significantly (P > .05) for any of the questions with regard to likelihood of positive culture. There were no significant age or sex differences between participants with positive or negative culture results. No significant differences were found between isolation of specific microorganisms and any of the survey responses. CONCLUSIONS: This study suggests that off-label multidose preservative-free saline commonly used to rinse and fill scleral lenses before application on the eye may become contaminated with microorganisms once the bottle has been opened. Eye care practitioners and scleral lens patients should be aware of these potential contaminations and prioritize lens, hand, and environmental hygiene to minimize the risk of ocular complications.

Defining the Breakpoint Duration of Staphylococcus aureus Bacteremia Predictive of Poor Outcomes.

BACKGROUND: Persistent Staphylococcus aureus bacteremia (SAB) is defined based on varying duration in literature. The primary objective was to determine the risk of poor outcomes in relation to bacteremia duration. METHODS: Multicenter, prospective, observational study of adult hospitalized patients with SAB. Medical records were reviewed for pertinent data. Patients were grouped by bacteremia duration: short (1-2 days), intermediate (3-6 days), and prolonged (≥7 days) and compared for risk factors and outcomes. RESULTS: Of 884 patients, 63% had short, 28% intermediate, and 9% prolonged bacteremia. Overall mean age was 57 years, and 70% were male. The prolonged group had the highest proportion of methicillin-resistant SAB (P < .0001). Choice of antibiotic therapy did not significantly affect bacteremia duration; however, time to source-control procedure was delayed in the prolonged and intermediate groups compared with the short group (3.5 vs 3 vs 1 day, P < .0001). Metastatic complications, length of stay, and 30-day mortality were progressively worse as bacteremia duration increased (P < .0001). Every continued day of bacteremia was associated with a relative risk of death of 1.16 (95% confidence interval, 1.10-1.22; P < .0001), with a significant increase in risk starting at 3 days as determined by receiver operating characteristic analysis. CONCLUSIONS: Optimal management of SAB should target bacterial clearance as soon as possible to minimize incremental risk of mortality with each day of positive blood culture. Delay in source control but not type of antistaphylococcal therapy was significantly associated with prolonged bacteremia and worse outcomes.

Clinical Significance of Low Serum Cryptococcal Antigen Titers by Lateral Flow Assay in Immunocompromised Patients: a Retrospective Case-Control Study.

Cryptococcus species are associated with invasive fungal infections in immunosuppressed individuals. The clinical significance of low-titer cryptococcal antigen (CrAg) by lateral flow assay is frequently uncertain. We investigated the correlation of low CrAg titers with disease in an immunocompromised patient population. Patients with first-time positive CrAg results with low serum titers (≤1:10) at two medical centers (Los Angeles, CA) from April 2014 to July 2018 were included. Age-matched controls with high (≥1:20) and negative titers were selected. We extracted medical records for pertinent clinical, radiologic, and laboratory data for cryptococcal disease. From 2,196 serum samples submitted for CrAg testing, 96 cases were included (32 each in low-titer, high-titer, and negative-titer groups). One or more immunocompromising condition was identified in 95% of patients, including HIV infection (45%), solid organ transplant (26%), and cirrhosis (22%). Pulmonary cryptococcosis was diagnosed in 9 (28%) low-titer and 8 (25%) high-titer patients (P = 1.00). Disseminated cryptococcosis occurred in 7 (22%) low-titer and 15 (47%) high-titers cases (P = 0.064). Titers ≤1:10 more frequently represented isolated antigenemia in HIV-positive than non-HIV, immunocompromised patients (P < 0.001). Follow-up testing in patients with ≤1:5 titers (n = 21) showed persistently low titers in 6 of 12 instances and increased titers in 2 cases. Twenty-seven patients with low CrAg titers were treated with antifungal therapy and 22 (81%) responded well clinically. Low-serum CrAg titers (≤1:10) correlated with cryptococcal disease in a substantial proportion of non-HIV immunocompromised patients and should prompt careful clinical workup for cryptococcal infection.

Bacteriostatic Effect of Multidose Preservative-free Buffered Saline Used in Scleral Lens Wear.

SIGNIFICANCE: Scleral lenses have become an increasingly common treatment for ocular surface disease and irregular corneas. Multidose, preservative-free saline solutions are frequently used off-label to fill scleral lenses. Because the fluid resides over the ocular surface during lens wear, contaminated solutions may increase the risk of infectious complications. PURPOSE: We sought to assess the viability of skin microorganisms and pathogens associated with keratitis once introduced into a multidose preservative-free saline (MDPFS) solution containing the bacteriostatic agent boric acid (PuriLens Plus; The Lifestyle Co., Inc., Freehold, NJ). METHODS: Eleven bacterial and one yeast isolate were each inoculated to three lots of MDPFS as well as to sterile normal saline for comparison. Microorganism concentrations were enumerated at baseline and days 1, 3, 7, 14, 21, and 28. Persistence of microorganism viability was compared between MDPFS lots and between MDPFS and normal saline for each organism. RESULTS: Duration of microorganism viability was ≥24 hours in MDPFS with no significant difference in the distribution of survival duration of microorganisms in MDPFS versus normal saline (P = .15). Candida albicans concentrations declined 14 days earlier in MDPFS, whereas concentrations of viable organisms in MDPFS remained within 1 log of baseline for the longest durations for Pseudomonas aeruginosa (7 days), Escherichia coli (14 days), and Achromobacter xylosoxidans (≥28 days). Gram-positive organism concentrations remained within 1 log of baseline for no more than 3 days. Mild lot-to-lot variation in organism concentrations was noted near the end points of viability. Bacteriostasis was demonstrated in that concentrations of all organisms remained at or below baseline levels throughout the 28-day period. CONCLUSIONS: After microbial contamination, persistence of organism viability was similar in PuriLens and normal saline. Environmental gram-negative organisms, many of which can contribute to infectious keratitis, can persist for weeks once introduced into saline solutions.

Utility of qSOFA score in identifying patients at risk for poor outcome in Staphylococcus aureus bacteremia.

BACKGROUND: The prognostic capability of the quick Sequential Organ Failure Assessment (qSOFA) bedside scoring tool is uncertain in non-ICU patients with sepsis due to bacteremia given the low number of patients previously evaluated. METHODS: We performed a retrospective cohort study of adult hospitalized patients with Staphylococcus aureus bacteremia (SAB). Medical charts were reviewed to determine qSOFA score, systemic inflammatory response syndrome (SIRS) criteria, and Pitt bacteremia score (PBS) at initial presentation; their predictive values were compared for ICU admission within 48 h, ICU stay duration > 72 h, and 30-day mortality. RESULTS: Four hundred twenty-two patients were included; 22% had qSOFA score ≥2. Overall, mean age was 56y and 75% were male. More patients with qSOFA ≥2 had altered mentation (23% vs 5%, p < 0.0001), were infected with MRSA (42% vs 30%, p = 0.03), had endocarditis or pneumonia (29% vs 15%, p = 0.0028), and bacterial persistence ≥4d (34% vs 20%, p = 0.0039) compared to qSOFA <2 patients. Predictive performance based on AUROC was better (p < 0.0001) with qSOFA than SIRS criteria for all three outcomes, but similar to PBS ≥2. qSOFA≥2 was the strongest predictor for poor outcome by multivariable analysis and showed improved specificity but lower sensitivity than SIRS ≥2. CONCLUSIONS: qSOFA is a simple 3-variable bedside tool for use at the time of sepsis presentation that is more specific than SIRS and simpler to calculate than PBS in identifying septic patients at high risk for poor outcomes later confirmed to have S. aureus bacteremia.

Clinical Impact of Laboratory Implementation of Verigene BC-GN Microarray-Based Assay for Detection of Gram-Negative Bacteria in Positive Blood Cultures.

Gram-negative bacteremia is highly fatal, and hospitalizations due to sepsis have been increasing worldwide. Molecular tests that supplement Gram stain results from positive blood cultures provide specific organism information to potentially guide therapy, but more clinical data on their real-world impact are still needed. We retrospectively reviewed cases of Gram-negative bacteremia in hospitalized patients over a 6-month period before (n = 98) and over a 6-month period after (n = 97) the implementation of a microarray-based early identification and resistance marker detection system (Verigene BC-GN; Nanosphere) while antimicrobial stewardship practices remained constant. Patient demographics, time to organism identification, time to effective antimicrobial therapy, and other key clinical parameters were compared. The two groups did not differ statistically with regard to comorbid conditions, sources of bacteremia, or numbers of intensive care unit (ICU) admissions, active use of immunosuppressive therapy, neutropenia, or bacteremia due to multidrug-resistant organisms. The BC-GN panel yielded an identification in 87% of Gram-negative cultures and was accurate in 95/97 (98%) of the cases compared to results using conventional culture. Organism identifications were achieved more quickly post-microarray implementation (mean, 10.9 h versus 37.9 h; P < 0.001). Length of ICU stay, 30-day mortality, and mortality associated with multidrug-resistant organisms were significantly lower in the postintervention group (P < 0.05). More rapid implementation of effective therapy was statistically significant for postintervention cases of extended-spectrum beta-lactamase-producing organisms (P = 0.049) but not overall (P = 0.12). The Verigene BC-GN assay is a valuable addition for the early identification of Gram-negative organisms that cause bloodstream infections and can significantly impact patient care, particularly when resistance markers are detected.

A Dysregulated Balance of Proinflammatory and Anti-Inflammatory Host Cytokine Response Early During Therapy Predicts Persistence and Mortality in Staphylococcus aureus Bacteremia.

OBJECTIVES: The contribution of individual immune response to Staphylococcus aureus bacteremia on outcome has not been well studied. The objective was to relate the host cytokine response to outcome of Staphylococcus aureus bacteremia. DESIGN: Prospective observational study. SETTING: Three U.S. university-affiliated medical centers. PATIENTS: Adult patients infected with Staphylococcus aureus bacteremia hospitalized between July 2012 and August 2014. INTERVENTIONS: Blood specimens were obtained at Staphylococcus aureus bacteremia onset and 72 hours after therapy initiation. Levels of tissue necrosis factor, interleukin-6, interleukin-8, interleukin-17A, and interleukin-10 were measured by enzyme-linked immunosorbent assay at each time point and compared between those with persistent bacteremia (≥ 4 d) and resolving bacteremia. Primary outcome was persistent bacteremia after 4 days of effective therapy. Secondary outcomes were 30-day mortality and 30-day recurrence. MEASUREMENTS AND MAIN RESULTS: A total of 196 patients were included (mean age, 59 yr); of them, 33% had methicillin-resistant Staphylococcus aureus bacteremia. Forty-seven percent of the methicillin-resistant Staphylococcus aureus strains were staphylococcal cassette chromosome mec IV. Persistent bacteremia occurred in 24% of patients (47/196); they were more likely to die than resolving bacteremia group (28% vs 5%; p < 0.001). Compared with resolving bacteremia group, persistent bacteremia patients had higher initial median levels of tissue necrosis factor (44.73 vs 21.68 pg/mL; p < 0.001), interleukin-8 (124.76 vs 47.48 pg/mL; p = 0.028), and interleukin-10 (104.31 vs 29.72 pg/mL; p < 0.001). Despite 72 hours of treatment, levels remained higher for the persistent bacteremia group than for the resolving bacteremia group (tissue necrosis factor: 26.95 vs 18.38 pg/mL, p = 0.02; interleukin-8: 70.75 vs 27.86 pg/mL, p = 0.002; interleukin-6: 67.50 vs 21.81 pg/mL, p = 0.005; and interleukin-10: 30.98 vs 12.60 pg/mL, p < 0.001). Interleukin-17A levels were similar between groups at both time points. After controlling for confounding variables by multivariate analysis, interleukin-10/tissue necrosis factor ratio at 72 hours most significantly predicted persistence (odds ratio, 2.98; 95% CI, 1.39-6.39; p = 0.005) and mortality (odds ratio, 9.87; 95% CI, 2.64-36.91; p < 0.001) at values more than 1.00 and more than 2.56, respectively. CONCLUSIONS: Sustained elevation of interleukin-10/tissue necrosis factor ratio at 72 hours suggests a dysregulated immune response and may be used to guide management to improve outcomes.

Infants 1-90 days old hospitalized with human rhinovirus infection.

BACKGROUND: Human rhinovirus (HRV) is a common cause of respiratory illness in children. The impact of HRV infection on 1- to 90-day-old infants is unclear. We hypothesized that HRV infection would be clinically similar to respiratory syncytial virus (RSV) infection in the hospitalized infants. METHODS: We conducted a retrospective study of hospitalized infants, who were 1-90 days old, with HRV or RSV within the Southern California Kaiser Permanente network over a 1-year period (August 2010 to October 2011). RESULTS: We identified 245 hospitalized infants who underwent respiratory virus testing. HRV was found in 52 infants (21%) compared to 79 infants (32%) with RSV (P = 0.008). Infants with HRV infection experienced longer hospital stays compared to those with RSV (median length of stay 4 days vs. 3 days, P = 0.009) and had fewer short hospital stays ≤3 days (P = 0.029). There was a trend in infants with HRV infection to be younger (P = 0.071) and have more fevers (P = 0.052). CONCLUSIONS: Recent advances in diagnostics allow for identification of a broad range of viral pathogens in infants. Compared to RSV, HRV was associated with longer hospital stays. Additional studies and improved, more specific testing, methods are needed to further define the effects of HRV infection in infants 1-90 days old.

tcdA As a diagnostic target in a loop-mediated amplification assay for detecting toxigenic Clostridium difficile.

BACKGROUND: The illumigene® (Meridian Bioscience, Inc., Cincinnati, OH) and GeneOhm® (BD Diagnostics, La Jolla, CA) Clostridium difficile assays target the tcdA gene and tcdB gene, respectively. We assessed the use of tcdA as the molecular target in the illumigene® C. difficile loop-mediated amplification assay in detecting a wide variety of C. difficile strains including those with tcdA deletions. METHODS: We tested 38 C. difficile strains and 108 patient stool specimens using the illumigene® assay. The GeneOhm® real-time polymerase chain reaction (PCR) assay served as the reference method. Discordant results were resolved by repeat testing, anaerobic culture, and a laboratory-developed real-time PCR targeting tcdA and tcdB. RESULTS: Both illumigene® and GeneOhm® assays detected all 37 C. difficile toxin B(+) strains representing seven toxinotypes and including four toxin A(-) B(+) isolates. No cross-reactivity with 20 other Clostridium species or toxin-negative C. difficile was observed in either assay. Among patient stool specimens, agreement was 94.4% (102/108). After discordant result resolution, agreement was 96.3% (104/108). Specimens with initially discordant results had target concentrations approaching the limit of detection for the two commercial assays. Discordance appeared unrelated to whether tcdA or tcdB was the amplification target. CONCLUSION: The tcdA 5' region used by the illumigene® assay is a practical target for toxigenic C. difficile detection.

Rapid diagnostic work-up of Streptococcus dysgalactiae endophthalmitis by a novel culture processing system.

The diagnosis of infective endophthalmitis is supported by microbiological work-up. Rapid work-up is critical to confirm clinical suspicion and appropriate antimicrobial therapy. We report the novel use of an automated liquid culture processing system (FAST system, Qvella, ON, Canada) in a vitreous fluid culture. A 59-year-old patient with post-operative endophthalmitis presented with acute right eye pain and blurred vision. Vitreous fluid collected for microbiology culture was of limited quantity and only inoculated to thioglycolate broth. The broth recovered beta-haemolytic, group G Streptococcus dysgalactiae susceptible to penicillin and vancomycin. Experimental application of the FAST system to purify the organism from broth culture yielded the same identification and susceptibility test results but 1 day sooner. Despite prompt treatment with appropriate antibiotics, including vancomycin and ceftazidime, disease progressed rapidly and required enucleation to achieve a stable therapeutic outcome. Use of automated processing of monomicrobial broth cultures has thus far focused on positive blood culture broths, but could potentially include other liquid-based cultures such as for sterile body fluids of critical nature.

The clinical significance of staphylococcus pettenkoferi: a retrospective review at a tertiary care medical center.

Staphylococcus pettenkoferi is a recently described coagulase-negative staphylococcal pathogen. We retrospectively reviewed 25 cases in which S. pettenkoferi was identified in routine cultures (12 blood, 13 other). Most were found with commensal flora and considered clinically insignificant, but its significance was uncertain in two cases from non-healing, deep foot wounds.

Direct MALDI-TOF MS and Antimicrobial Susceptibility Testing of Positive Blood Cultures Using the FASTTM System and FAST-PBC Prep Cartridges-Performance Evaluation in a Clinical Microbiology Laboratory Serving High-Risk Patients.

Bloodstream infections are a leading cause of morbidity and mortality. The rapid diagnostic testing of positive blood cultures (PBCs) shortens times to effective therapy and the de-escalation of broad-spectrum empiric therapy. This is the first study examining the Qvella FASTTM System for the rapid (~20 min) purification of microorganisms directly from PBCs using BacT/Alert® FA/FAN bottles in the bioMérieux Virtuo instrument. We compared the performance of the FASTTM System Liquid ColonyTM (LC), for immediate downstream ID and phenotypic AST, to standard workflow involving colonies obtained by overnight subculture. The LC yielded a concordant species ID by VITEK MS in 121/138 (87.7%) samples, identifying 32 different Gram-positive and Gram-negative species with 3/123 (2.6%) discordances. Compared to standard workflow, direct AST of the LC using VITEK® 2 yielded 98.4% categorical agreement and 98.0% essential agreement. Very major error, major error, and minor error rates were 1.0%, 0.0%, and 1.8%, respectively, for Gram-negative organisms; and 1.9%, 0.2%, and 1.2%, respectively, for Gram-positive organisms. The median times from positive blood culture flag to results by FASTTM System for ID and AST were 7.8 h and 15.7 h, respectively, versus 22.4 h and 36.6 h for standard workflow, respectively. In conclusion, the FASTTM System provides reliable results for direct ID and AST from PBCs with significantly decreased turnaround times.

Clostridioides difficile Toxin B PCR Cycle Threshold as a Predictor of Toxin Testing in Stool Specimens from Hospitalized Adults.

Rapid, accurate detection of Clostridioides difficile toxin may potentially be predicted by toxin B PCR cycle threshold (tcdB Ct). We investigated the validity of this approach in an inpatient adult population. Patients who tested positive by C. difficile PCR (Cepheid GeneXpert) from December 2016 to October 2020 (n = 368) at a tertiary medical center were included. All stool samples were further tested by rapid glutamate dehydrogenase (GDH)/toxin B EIA and cell cytotoxin neutralization assay (CCNA). Receiver operating characteristic curves were analyzed. The area under the curve for tcdB Ct predicting toxin result by EIA was 0.795 (95% confidence interval (CI) 0.747−0.843) and by CCNA was 0.771 (95% CI 0.720−0.822). The Youden Ct cutoff for CCNA was ≤27.8 cycles (sensitivity 65.0%, specificity 77.2%). For specimens with Ct ≤ 25.0 cycles (n = 115), CCNA toxin was positive in >90%. The negative predictive value of tcdB Ct for CCNA was no greater than 80% regardless of cutoff chosen. In summary, very low Ct values (≤25.0) could have limited value as a rapid indicator of positive toxin status by CCNA in our patient population. A broad distribution of Ct values for toxin-negative and toxin-positive specimens precluded more robust prediction. Additional data are needed before broader application of Ct values from qualitatively designed assays to clinical laboratory reporting.

Distance Between Home and the Admitting Hospital and Its Effect on Survival of Low Socioeconomic Status Population With Staphylococcus aureus Bacteremia.

OBJECTIVE: Bacteremia is the presence of bacteria in the bloodstream. The objective of this study was to determine the relationship between low socioeconomic status (SES) and the epidemiology, process of care, and outcomes of patients with Staphylococcus aureus bacteremia (SAB). METHODS: We conducted a multicenter, retrospective, cohort study that evaluated adult patients with SAB in 3 Los Angeles County hospitals from July 15, 2012, through May 31, 2018. We determined SES (low SES, intermediate SES, and high SES) for each patient and compared sociodemographic and epidemiologic characteristics, management of care received by patients with SAB (ie, process of care), and outcomes. We used a Cox proportional hazards model to determine predictors of 30-day mortality for each SES group. RESULTS: Of 915 patients included in the sample, 369 (40%) were in the low-SES group, 294 (32%) in the intermediate-SES group, and 252 (28%) in the high-SES group. Most significant predictors of 30-day mortality in the Cox proportional hazards model were admission to an intensive care unit (hazard ratio [HR] = 9.04; 95% CI, 4.26-19.14), Pitt bacteremia score ≥4 indicating critical illness (HR = 4.30; 95% CI, 2.49-7.44), having ≥3 comorbidities (HR = 2.05; 95% CI, 1.09-3.85), and advanced age (HR = 1.03; 95% CI, 1.01-1.05). Distance between home and admitting hospital affected mortality only in the low-SES group (HR = 1.02; 95% CI, 1.00-1.02). CONCLUSIONS: SES did not independently affect the outcome of SAB; however, the farther the patient's residence from the hospital, the greater the negative effect on survival in a low-SES population. Our findings underscore the need to develop multipronged, targeted public health efforts for populations that have transportation barriers to health care.

Isolation and characterization of "Pseudomonas andersonii" from four cases of pulmonary granulomas and emended species description.

"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.

Correlation of Chlamydia and Chlamydophila spp. IgG and IgM antibodies by microimmunofluorescence with antigen detection methods.

Correlation of serologic titers for Chlamydia trachomatis with other tests has been based on direct fluorescence antibody (DFA) testing and culture, but not on nucleic acid-based tests that are used for screening. We retrospectively reviewed the specificity of antibodies against C. trachomatis, Chlamydia psittaci, and Chlamydophila pneumoniae by microimmunofluorescence (MIF) when compared with DFA, culture, nucleic acid probe, and transcription-mediated amplification. Over a 6-year period, 226 cases had both MIF and one of these other methods performed for comparison. Agreement between C. trachomatis antigen or nucleic acid detection and MIF results was 87% (197/226). C. trachomatis serology had a negative predictive value of 98%, and 10.6% of cases were positive by serology and negative by antigen testing. Of the 13 patients who had a positive C. trachomatis antigen or nucleic acid test result, 9 had IgG and/or IgM titers highest against C. trachomatis, 3 had IgG titers highest against C. pneumoniae, and 1 had undetectable titers for the three chlamydial species. Twenty-five patients had positive IgG and/or IgM titers to C. trachomatis but negative antigen test results. Serologic testing can increase the sensitivity of detecting C. trachomatis infections.