Diagnostic Yield of Computed Tomography for Cancer Detection in a Tertiary Referral Population of Idiopathic Inflammatory Myositis Patients

OBJECTIVE

To inform guidance for cancer detection in patients with idiopathic inflammatory myopathy (IIM), we evaluated the diagnostic yield of computed tomography (CT) imaging for cancer screening/surveillance within distinct IIM subtypes and myositis-specific autoantibody strata.

METHODS

We conducted a single-center, retrospective cohort study in IIM patients. Overall diagnostic yield (number of cancers diagnosed/number of tests performed), percentage of false positives (number of biopsies performed not leading to cancer diagnosis/number of tests performed), and test characteristics were determined on CT of the chest and abdomen/pelvis.

RESULTS

Within the first 3 years since IIM symptom onset, a total of 9 of 1,011 (0.9%) chest CT scans and 12 of 657 (1.8%) abdomen/pelvis CT scans detected cancer. Diagnostic yields for both CT of the chest and CT of the abdomen/pelvis were highest in dermatomyositis, specifically anti-transcription intermediary factor 1γ (2.9% and 2.4% for CT of the chest and abdomen/pelvis, respectively). The highest percentage of false positives was in patients with antisynthetase syndrome (ASyS) (4.4%) and immune-mediated necrotizing myopathy (4.4%) on CT of the chest, and ASyS (3.8%) on CT of the abdomen/pelvis. Patients ages <40 years old at IIM onset had both low diagnostic yields (0% and 0.5%) and high false-positive rates (1.9% and 4.4%) for CT of the chest and abdomen/pelvis, respectively.

CONCLUSION

In a tertiary referral cohort of IIM patients, CT imaging has a wide range of diagnostic yield and frequency of false positives for contemporaneous cancer. These findings suggest that cancer detection strategies targeted according to IIM subtype, autoantibody positivity, and age may maximize cancer detection while minimizing the harms and costs of over-screening.

The yin and yang of GSM and low sexual desire

Numerous surveys have documented that sexuality and/or sexual activity is important to women at all stages of adulthood, including postmenopause. Genitourinary syndrome of menopause (GSM) and hypoactive sexual desire disorder (HSDD) are common disorders in postmenopausal women and may co-occur. Both are often undiagnosed due to a lack of knowledge of the disorder, health-care professional discomfort in discussing sexual problems or a lack of routine screening. It is incumbent upon health-care professionals to identify and differentiate these conditions in women through a biopsychosocial assessment, and may require a focused physical examination. Numerous treatments, both non-pharmacologic and pharmacologic, are available to address GSM and HSDD.

Association of Anti-CCAR1 Autoantibodies With Decreased Cancer Risk Relative to the General Population in Patients With Anti-Transcriptional Intermediary Factor 1γ-Positive Dermatomyositis

OBJECTIVE

To describe the disease specificity, clinical phenotype, and risk of cancer in dermatomyositis (DM) patients with autoantibodies against cell division cycle and apoptosis regulator protein 1 (anti-CCAR1).

METHODS

The frequency of anti-CCAR1 autoantibodies was measured by enzyme-linked immunosorbent assay in the serum of DM patients from 2 independent cohorts (Johns Hopkins and Stanford), with patients with several other rheumatic diseases and healthy controls used as comparators. Clinical features and the risk of cancer incidence relative to that in the general population were determined in anti-CCAR1-positive DM patients.

RESULTS

Anti-CCAR1 antibodies were significantly associated with anti-transcriptional intermediary factor 1γ (anti-TIF1γ) antibodies present in the serum of patients with DM: 80 (32%) of 252 anti-TIF1γ-positive DM patients versus 14 (8%) of 186 anti-TIF1γ-negative DM patients were positive for anti-CCAR1 antibodies (P < 0.001). Anti-CCAR1 antibodies were not detected in any of the 32 serum samples from healthy controls, and were present at very low frequencies in the sera of patients with other rheumatic diseases: 1 (2.3%) of 44 patients with anti-hydroxymethylglutaryl-coenzyme A reductase-positive necrotizing myopathy, 1 (2.3%) of 44 patients with inclusion body myositis, and 3 (6.5%) of 46 patients with systemic lupus erythematosus were positive for anti-CCAR1 antibodies. Upon examining data on occurrence of cancer from the onset of DM onward, the observed number of cancers diagnosed in anti-TIF-1γ-positive DM patients was significantly greater than expected in both cohorts, with a standardized incidence ratio (SIR) of 3.49 (95% confidence interval [95% CI] 2.39-4.92) in the Johns Hopkins cohort and a SIR of 4.54 (95% CI 3.04-6.52) in the Stanford cohort (each P < 0.001). DM patients who were both anti-TIF1γ positive and anti-CCAR1 positive had lower SIRs for cancer, with a SIR of 1.78 (95% CI 0.77-3.51) (P = 0.172) in the Johns Hopkins cohort and a SIR of 1.61 (95% CI 0.44-4.13) (P = 0.48) in the Stanford cohort.

CONCLUSION

Anti-CCAR1 autoantibodies are specific for anti-TIF1γ-positive DM. Their presence in anti-TIF1γ-positive patients attenuates the risk of cancer to a level comparable to that seen in the general population.

Subsets of Idiopathic Inflammatory Myositis Enriched for Contemporaneous Cancer Relative to the General Population

OBJECTIVE

This study investigates cancer risk in idiopathic inflammatory myopathy (IIM) relative to the general population.

METHODS

We conducted a single-center, retrospective cohort study of IIM patients and malignancy. Myositis-specific and -associated autoantibodies were determined by Euroimmun line blot, enzyme-linked immunosorbent assay, and immunoprecipitation. We calculated standardized prevalence ratios (SPRs) and adjusted for calendar year, age, sex, race, and ethnicity by comparing observed cancers in IIM patients versus expected cancers in the general population using the Surveillance, Epidemiology, and End Results registry.

RESULTS

Of 1,172 IIM patients, 203 (17%) patients with a cancer history were studied. Over a median follow-up of 5.2 years, the observed number of IIM patients diagnosed with cancer was increased 1.43-fold (SPR 1.43 [95% confidence interval (95% CI) 1.15-1.77]; P = 0.002). Within 3 years of IIM symptom onset, an increased SPR was observed for anti-transcription intermediary factor 1γ (anti-TIF1γ)-positive patients for ovarian and breast cancer (ovarian SPR 18.39 [95% CI 5.01-47.08], P < 0.001; breast SPR 3.84 [95% CI 1.99-6.71], P < 0.001). As expected, anti-TIF1γ positivity was associated with a significantly elevated SPR; however, only 55% (36 of 66) of all cancers within 3 years of dermatomyositis onset were observed in anti-TIF1γ-positive patients. Other myositis-specific autoantibodies, including anti-Mi-2, anti-small ubiquitin-like modifier activating enzyme (SAE), and anti-nuclear matrix protein 2 (NXP-2), accounted for 26% (17 of 66) of cancers diagnosed within 3 years of dermatomyositis onset. No cancer association, positive or negative, was observed for patients with antisynthetase, anti-melanoma differentiation-associated protein 5 (anti-MDA-5), or anti-hydroxymethylglutaryl-coenzyme A reductase (anti-HMGCR) antibodies.

CONCLUSION

In a tertiary referral center population, anti-TIF1γ was most strongly associated with breast and ovarian cancer. Patients with antisynthetase, anti-MDA-5, or anti-HMGCR antibodies had the same cancer risk as the general population.

Clinical Subgroups and Factors Associated With Progression in Patients With Inclusion Body Myositis

BACKGROUND AND OBJECTIVES

Sporadic inclusion body myositis (IBM) is the most common acquired myopathy in individuals older than 50 years. The disorder is slowly progressive, and although many therapies have been investigated, response has generally been poor. Clinical heterogeneity may influence treatment responsiveness; however, data regarding heterogeneity in IBM are limited and often conflicting. We aim to identify clinically distinct subgroups within a large IBM cohort and prognostic factors for disease progression.

METHODS

Clinical, histologic, radiologic, and electrophysiologic data were analyzed for all patients with IBM and other forms of myositis enrolled in a longitudinal cohort from The Johns Hopkins Myositis Center from 2003 to 2018. Patients with IBM were included if they met at least one of the following criteria: Griggs possible, European Neuromuscular Centre 2011 probable, or Lloyd-Greenberg data-derived criteria for IBM. Univariate, multivariate, and graphical analyses were used to identify prognostic factors in patients with IBM. Thus, linear and logistic regressions were used to adjust for potential confounding variables. The evolution of creatine kinase and muscle strength was studied using multilevel linear regression models. Nonmodifiable risk factors (sex, race, disease duration, and age at the onset of first symptoms) were used as adjusting covariates for the regression analyses.

RESULTS

Among the 335 patients meeting the inclusion criteria for IBM, 64% were male with an average age of disease onset of 58.7 years and delay to diagnosis of 5.2 years. Initial misdiagnosis (52%) and immunosuppressant treatment (42%) were common. Less than half (43%) of muscle biopsies demonstrated all 3 pathologic hallmarks: endomysial inflammation, mononuclear cell invasion, and rimmed vacuoles. Black patients had significantly weaker arm abductors, hip flexors, and knee flexors compared with non-Black patients. Female patients had stronger finger flexors and knee extensors compared with their male counterparts. Younger age (<50 years) at onset was not associated with increased weakness.

DISCUSSION

Our study demonstrates that female and Black patients have distinct clinical phenotypes and trajectories within the overarching IBM clinical phenotype. These subgroups may have different responses to therapies, which may influence the design of future clinical trials in IBM.

Current status of clinical outcome measures in inclusion body myositis: a systematised review

OBJECTIVES

Sporadic inclusion body myositis (IBM) is a debilitating idiopathic inflammatory myopathy (IIM) which affects hand function, ambulation, and swallowing. There is no approved pharmacological therapy for IBM, and there is a lack of suitable outcome measure to assess the effect of an intervention. The IBM scientific interest group under IMACS reviewed the previously used outcome measures in IBM clinical studies to lay the path for developing a core set of outcome measures in IBM.

METHODS

In this systematised review, we have extracted all outcome measures reported in IBM clinical studies to determine what measures were being used and to assess the need for optimising outcome measures in IBM.

RESULTS

We found 13 observational studies, 17 open-label clinical trials, and 15 randomised control trials (RCTs) in IBM. Six-minute walk distance, IBM-functional rating scale (IBM-FRS), quantitative muscle testing, manual muscle testing, maximal voluntary isometric contraction testing, and thigh muscle volume measured by MRI were used as primary outcome measures. Twelve different outcome measures of motor function were used in IBM clinical trials. IBM-FRS was the most used measure of functionality. Swallowing function was reported as a secondary outcome measure in only 3 RCTs.

CONCLUSIONS

There are inconsistencies in using outcome measures in clinical studies in IBM. The core set measures developed by the IMACS group for other IIMs are not directly applicable to IBM. As a result, there is an unmet need for an IBM-specific core set of measures to facilitate the evaluation of new potential therapeutics for IBM.

Gastroparesis in systemic sclerosis: a detailed analysis using whole-gut scintigraphy

OBJECTIVES

Gastroparesis is a common complication of SSc. We sought to determine the degree of overlap between gastroparesis and dysmotility in other areas of the gut, correlate our findings with gastrointestinal (GI) symptoms, and examine associations between gastroparesis and SSc features.

METHODS

Whole-gut scintigraphy was performed on SSc patients who were enrolled in the Johns Hopkins Scleroderma Cohort, for whom detailed longitudinal clinical and serologic data are collected. A subset of patients completed the University of California Los Angeles Scleroderma Clinical Trial Consortium Gastrointestinal Tract Instrument 2.0 (UCLA GIT 2.0) to quantify their GI symptoms. We examined associations between the presence and severity of gastroparesis, GI symptoms, and SSc clinical features.

RESULTS

Ninety-seven SSc patients with and without GI symptoms underwent whole-gut scintigraphy and completed the gastric emptying study. Of the 97, 34 (35%) met criteria for gastroparesis. Of the measures assessed, delayed liquid emptying captured more patients with delayed gastric transit than delayed solid emptying (74% vs 55%), and percentage liquid emptying correlated best with GIT Reflux (ρ = -0.33, P = 0.01) and Distension (ρ = -0.30, P = 0.03) scores. Of 33 patients with gastroparesis, 30 (91%) had abnormal transit in other areas of the GI tract. Higher anti-centromere protein B (CENP-B) titres correlated with slower gastric emptying (ρ = -0.26, P = 0.03), but no specific clinical features of SSc were associated with gastroparesis.

CONCLUSIONS

Gastric emptying of liquids when given alongside solids may be more sensitive and provide a more clinically relevant measure of gastroparesis in SSc than solid gastric emptying or liquid gastric emptying alone. SSc patients with gastroparesis frequently have dysmotility in other areas of the GI tract, underscoring the need for whole-gut scintigraphy to evaluate the entire gut.

Mushroom supplements triggering a flare of HMGCR immune mediated necrotising myopathy

Hydroxyl-methyl-glutaryl-Co-A reductase (HMGCR) immune mediated necrotising myopathy (IMNM) is a rare autoimmune myositis that is thought to be triggered by statins and responds to immunomodulation. We report a case of a woman in her 30s with HMGCR IMNM without a history of statin exposure who had a clear flare of her myositis after beginning mushroom supplements. Mushrooms are natural HMGCR inhibitors, and this is the first case to demonstrate a flare triggered by mushrooms in a patient with known HMGCR IMNM. This case highlights the importance of reviewing diet and supplements in patients with IMNM. It also emphasises the importance of strict statin avoidance for patients with IMNM even when the myositis is under good control.

The Effect of Mycophenolate Mofetil as First-Line Therapy on the Timing of Urine Protein-to-Creatinine Ratio Reduction in Immunosuppressant-Naive Patients With Lupus Nephritis at a Single Center

BACKGROUND/OBJECTIVES

Early response to immunosuppressive therapy predicts good renal outcome in lupus nephritis (LN). The purpose of this study was to assess the effect of mycophenolate mofetil (MMF) on the timing of urine protein-to-creatinine ratio reaching 200 mg or less after starting MMF as initial therapy for class III, IV, or V in immunosuppressant-naive patients with LN.

METHODS

Patients who had a diagnosis of biopsy-proven LN were included in this cohort study. The initial dose of MMF was 1000 mg twice daily. If no improvement, it was increased to 1500 mg twice daily after 1 month. For statistical analysis, exact binomial distribution 95% confidence intervals were calculated.

RESULTS

Nine patients were identified. There were 3 patients with class III, 3 with class IV, 1 with class III to V, 1 with class II to V, and 1 with class V lupus nephritis. The majority were African Americans (70%). At baseline, proteinuria ranged between 0.41 and 4 g, and 88% had normal estimated glomerular filtration rate. Forty-four percent of patients reached 0.28 g of proteinuria within 8 weeks of starting MMF (95% confidence interval, 14%-79%), all of which maintained the same level of response and normal estimated glomerular filtration rate at 12 months. Thirty-three percent of patients achieved the American College of Rheumatology complete response at 8 weeks.

CONCLUSIONS

This study demonstrates that only a minority of immunosuppressant-naive LN patients achieved the American College of Rheumatology complete response at 8 weeks after initiation of MMF. A rapid decline in the proteinuria to 0.28 g within the first 8 weeks of the treatment correlated strongly with achieving the same level of response at 12 months.

The Cancer Risk Profile of Systemic Lupus Erythematosus Patients

ABSTRACT

Systemic lupus erythematosus (SLE) patients have a well-established increased risk for cancer. Research from the past 2 decades has identified the specific malignancies that afflict SLE patients at disproportionate rates. Systemic lupus erythematosus patients are at heightened risk for several hematologic malignancies as well as for certain solid tumors, including lung, thyroid, and hepatobiliary cancers. They are at decreased risk for several cancers as well, including prostate and melanoma. Improved understanding of the unique cancer risk profile of SLE patients has led some professional societies to recommend specialized cancer screening and prevention measures for these patients and has enabled clinicians to better serve the SLE patient population.

The phenotype of myositis patients with anti-Ku autoantibodies

OBJECTIVES

To define the clinical features of anti-Ku-positive myositis patients and to determine the reliability of the Euroline assay to detect anti-Ku autoantibodies.

METHODS

Serum samples were screened for anti-Ku autoantibodies by Euroline and positive samples were confirmed by ELISA. The prevalence and severity of clinical features at onset and during follow-up in patients with anti-Ku-positive myositis were compared to those with dermatomyositis, immune-mediated necrotizing myopathy (IMNM), the antisynthetase syndrome (AS), inclusion body myositis (IBM), anti-U1-RNP-positive myositis, and anti-PM/Scl-positive myositis.

RESULTS

72 (2.9%) of 2475 samples were anti-Ku positive by Euroline using the manufacturer's recommended cutoff of >15. Just 17 (23.6%) of these were confirmed by ELISA and considered anti-Ku-positive for the analysis. Comparators included 169 IMNM, 168 AS, 387 IBM, 20 anti-U1-RNP-positive, and 47 anti-PM/Scl-positive patients. Muscle weakness was a presenting feature in 38% of anti-Ku-positive patients; 81% developed weakness during follow-up. Anti-Ku-positive patients had increased distal weakness compared to the non-IBM comparators. Interstitial lung disease (ILD) was present in 19% of anti-Ku-positive patients at the first visit and eventually developed in 56% of them. Throughout the course of disease, Gottron's papules and/or heliotrope rashes were less common in anti-Ku-positive patients (19%) compared to those with dermatomyositis (94%) or anti-PM/Scl-positive myositis (89%). Anti-Ku-positive patients never developed calcinosis.

CONCLUSIONS

The phenotype of anti-Ku positive myositis is distinguished by distal weakness, frequent ILD, infrequent rash, and no calcinosis. When used according to the current manufacturer's instructions, the Euroline assay has a high false-positive rate for anti-Ku autoantibodies.

Simultaneous assessment of colon motility in children with functional constipation by cine-MRI and colonic manometry: a feasibility study

BACKGROUND

Colonic manometry is the current reference standard for assessing colonic neuromuscular function in children with intractable functional constipation (FC). Recently, cine magnetic resonance imaging (cine-MRI) has been proposed as a non-invasive alternative. We compared colonic motility patterns on cine-MRI with those obtained by manometry in children, by stimulating high-amplitude propagating contractions (HAPCs) with bisacodyl under manometric control while simultaneously acquiring cine-MRI.

METHODS

After Institutional Review Board approval, adolescents with FC scheduled to undergo colonic manometry were included. A water-perfused 8-lumen catheter was used for colonic manometry recordings. After an intraluminal bisacodyl infusion, cine-MRI sequences of the descending colon were acquired for about 30 min simultaneously with colonic manometry. Manometry recordings were analysed for HAPCs. MRI images were processed with spatiotemporal motility MRI techniques. The anonymised motility results of both techniques were visually compared for the identification of HAPCs in the descending colon.

RESULTS

Data regarding six patients (three males) were analysed (median age 14 years, range 12-17). After bisacodyl infusion, three patients showed a total of eleven HAPCs with colonic manometry. Corresponding cine-MRI recorded high colonic activity during two of these HAPCs, minimal activity during seven HAPCs, while two HAPCs were not recorded. In two of three patients with absent HAPCs on manometry, colonic activity was recorded with cine-MRI.

CONCLUSIONS

Simultaneous acquisition of colonic cine-MRI and manometry in children with FC is feasible. Their motility results did not completely overlap in the identification of HAPCs. Research is needed to unravel the role of cine-MRI in this setting.

MRI in idiopathic, stable, slipped capital femoral epiphysis: evaluation of contralateral pre-slip

PURPOSE

Early diagnosis and treatment of slipped capital femoral epiphysis (SCFE) is important to prevent slip progression and avoid complications. We sought to determine if MRI findings in patients with unilateral SCFE could indicate 'pre-slip' or predict future SCFE in the contralateral hip.

METHODS

A prospective study evaluated patients with unilateral SCFE over a two-year period. MRI of the asymptomatic hip was performed within the perioperative period. Patients were followed with radiographs until a contralateral slip occurred or until physeal closure. Demographics, clinical stability, severity, posterior slope angle (PSA), modified Oxford Bone Score (mOBS) and patency of the triradiate cartilage were recorded and statistical analysis performed.

RESULTS

In all, 33 of 54 patients with unilateral SCFE were enrolled into the study. In all, 29 (87.8%) had complete follow-up. Five of the enrolled patients (15.2%) developed a sequential slip requiring in situ pinning. Six of 33 (18.2%) patients had positive MRI findings: four of which proceeded to sequential SCFE and two which did not. One sequential slip had a negative MRI. PSA predicted 1/11 sequential slips (sensitivity 9.09%, specificity 81.4%, positive predictive value (PPV) 11.1%, negative predictive value (NPV) 77.8%) and mOBS predicted 5/11 sequential slips (sensitivity 45.5%, specificity 93%, PPV 62.5%, NPV 87%). An open triradiate cartilage was present in 8/11 patients with sequential slips (sensitivity 72.7%, specificity 81.4%, PPV 50%, NPV 92.1%).

CONCLUSION

MRI findings consistent with 'pre-slip' were present in 66.7% of patients who developed a sequential SCFE. Further study on the utility/sensitivity of MRI in predicting sequential SCFE is warranted.

LEVEL OF EVIDENCE

II, diagnostic.

Fevers in Adult Lupus Patients

Variability in systemic lupus erythematosus (SLE) disease manifestations is well recognized. Lupus disease activity can range from mild to severe. Fever is a common manifestation of SLE and occurs in 36%-86% of patients. In the Modified Systemic Lupus Erythematosus Disease Activity Index (M-SLEDAI), fever is taken into account as disease activity scoring. Assessment of lupus patients with fever is an important diagnostic challenge, since the initial clinical presentation of a patient with lupus is very similar to the acute febrile phase of an infection. The attribution of fever to SLE holds only after other causes are excluded.

Cell surface hydrophobicity of colistin-susceptible vs resistant Acinetobacter baumannii determined by contact angles: methodological considerations and implications

Contact angle analysis of cell surface hydrophobicity (CSH) describes the tendency of a water droplet to spread across a lawn of filtered bacterial cells. Colistin-induced disruption of the Gram-negative outer membrane necessitates hydrophobic contacts with lipopolysaccharide (LPS). We aimed to characterize the CSH of Acinetobacter baumannii using contact angles, to provide insight into the mechanism of colistin resistance. Contact angles were analysed for five paired colistin-susceptible and resistant Ac. baumannii strains. Drainage of the water droplet through bacterial layers was demonstrated to influence results. Consequently, measurements were performed 0·66s after droplet deposition. Colistin-resistant cells exhibited lower contact angles (38·8±2·8-46·8±1·3°) compared with their paired colistin-susceptible strains (40·7±3·0-48·0±1·4°; anova; P<0·05). Contact angles increased at stationary phase (50·3±2·9-61·5±2·5° and 47·4±2·0-50·8±3·2°, susceptible and resistant, respectively, anova; P<0·05) and in response to colistin 32mgl(-1) exposure (44·5±1·5-50·6±2·8° and 43·5±2·2-48·0±2·2°, susceptible and resistant, respectively; anova; P<0·05). Analysis of complemented strains constructed with an intact lpxA gene, or empty vector, highlighted the contribution of LPS to CSH. Compositional outer-membrane variations likely account for CSH differences between Ac. baumannii phenotypes, which influence the hydrophobic colistin-bacterium interaction. Important insight into the mechanism of colistin resistance has been provided. Greater consideration of contact angle methodology is necessary to ensure accurate analyses are performed.

Classification of Leptospira genomospecies 1, 3, 4 and 5 as Leptospira alstonii sp. nov., Leptospira vanthielii sp. nov., Leptospira terpstrae sp. nov. and Leptospira yanagawae sp. nov., respectively

The genus Leptospira currently comprises 16 named species. In addition, four unnamed hybridization groups were designated Leptospira genomospecies 1, 3, 4 and 5. These groups represent valid species-level taxa, but were not assigned names in the original description by Brenner et al. [Int J Syst Bacteriol 49, 839-858 (1999)]. To rectify this situation, it is proposed that Leptospira genomospecies 1, genomospecies 3, genomospecies 4 and genomospecies 5 should be classified as Leptospira alstonii sp. nov., Leptospira vanthielii sp. nov., Leptospira terpstrae sp. nov. and Leptospira yanagawae sp. nov., respectively, with strains L. alstonii 79601(T) ( = ATCC BAA-2439(T)), L. vanthielii WaZ Holland(T) ( = ATCC 700522(T)), L. terpstrae LT 11-33(T) ( = ATCC 700639(T)) and L. yanagawae Sao Paulo(T) ( = ATCC 700523(T)) as the type strains. The type strains are also available from the culture collections of the WHO Collaborating Centres in Amsterdam, The Netherlands, and Brisbane, Australia.

Pasteurella multocida: diseases and pathogenesis

Pasteurella multocida is an enigmatic pathogen. It is remarkable both for the number and range of specific disease syndromes with which it is associated, and the wide range of host species affected. The pathogenic mechanisms involved in causing the different syndromes are, for the most part, poorly understood or completely unknown. The biochemical and serological properties of some organisms responsible for quite different syndromes appear to be similar. Thus, the molecular basis for host predilection remains unknown. The recent development of genetic manipulation systems together with the availability of multiple genome sequences should help to explain the association of particular pathological conditions with particular hosts as well as helping to elucidate pathogenic mechanisms.

Quantification of adiposity in small rodents using micro-CT

Non-invasive three-dimensional imaging of live rodents is a powerful research tool that has become critical for advances in many biomedical fields. For investigations into adipose development, obesity, or diabetes, accurate and precise techniques that quantify adiposity in vivo are critical. Because total body fat mass does not accurately predict health risks associated with the metabolic syndrome, imaging modalities should be able to stratify total adiposity into subcutaneous and visceral adiposity. Micro-computed tomography (micro-CT) acquires high-resolution images based on the physical density of the material and can readily discriminate between subcutaneous and visceral fat. Here, a micro-CT based method to image the adiposity of live rodents is described. An automated and validated algorithm to quantify the volume of discrete fat deposits from the computed tomography is available. Data indicate that scanning the abdomen provides sufficient information to estimate total body fat. Very high correlations between micro-CT determined adipose volumes and the weight of explanted fat pads demonstrate that micro-CT can accurately monitor site-specific changes in adiposity. Taken together, in vivo micro-CT is a non-invasive, highly quantitative imaging modality with greater resolution and selectivity, but potentially lower throughput, than many other methods to precisely determine total and regional adipose volumes and fat infiltration in live rodents.

Persistent hypogammaglobulinemia following mononucleosis in boys is highly suggestive of X-linked lymphoproliferative disease--report of three cases

Hypogammaglobulinemia is a common symptom in different immunodeficiencies. It is, however, not usually associated with Epstein-Barr virus (EBV) infections. The X-linked lymphoproliferative disease (XLP) on the other hand shows immunological changes in response to the EBV. Here we report three previously healthy boys, all of which developed persistent hypogammaglobulinemia following severe acute infectious mononucleosis. All three patients revealed T-cell abnormalities including inverted CD4/CD8 and increased CD8(+) T-cell numbers. The number of IFN-gamma-producing T cells were markedly increased in the two patients studied so far. In addition, patient 2 showed mainly T cells, instead of B cells, to be infected with the EBV. Apart from an uncle of patient 3, who died of malignant lymphoma, family history was unremarkable in all cases. All three patients exhibited mutations in the SH2D1A gene, establishing the diagnosis of XLP. Protein expression was found on immunoblot analysis in one patient with a missense mutation. Development of persistent hypogammaglobulinemia after severe primary EBV infection seems to be a specific diagnostic sign for XLP even in males with unremarkable family history.

Genetic analysis of the biosynthesis of non-ribosomal peptide- and polyketide-like antibiotics, iron uptake and biofilm formation by Bacillus subtilis A1/3

The Bacillus subtilis strain A1/3 shows exceptionally diverse antibiotic capacities compared to other B. subtilis strains. To analyze this phenomenon, mutants for the putative pantotheinyltransferase gene (pptS), and for several genes involved in non-ribosomal peptide synthesis and polyketide synthesis were constructed and characterized, using bioassays with blood cells, bacterial and fungal cells, and mass spectrometry. Among at least nine distinct bioactive compounds, five antibiotics and one siderophore activity were identified. The anti-fungal and hemolytic activities of strain A1/3 could be eliminated by mutation of the fen and srf genes essential for the synthesis of fengycins and surfactins. Both pptS- and dhb -type mutants were defective in iron uptake, indicating an inability to produce a 2,3-dihydroxybenzoate-type iron siderophore. Transposon mutants in the malonyl CoA transacylase gene resulted in the loss of hemolytic and anti-fungal activities due to the inhibition of bacillomycin L synthesis, and this led to the discovery of bmyLD-LA-LB* genes. In mutants bearing disruption mutations in polyketide (pksM- and/or pksR -like) genes, the biosynthesis of bacillaene and difficidins, respectively, was inactivated and was accompanied by the loss of discrete antibacterial activities. The formation of biofilms (pellicles) was shown to require the production of surfactins, but no other lipopeptides, indicating that surfactins serve specific developmental functions.

Oxygen radical inhibition of nitric oxide-dependent vascular function in sickle cell disease

Plasma xanthine oxidase (XO) activity was defined as a source of enhanced vascular superoxide (O(2)( *-)) and hydrogen peroxide (H(2)O(2)) production in both sickle cell disease (SCD) patients and knockout-transgenic SCD mice. There was a significant increase in the plasma XO activity of SCD patients that was similarly reflected in the SCD mouse model. Western blot and enzymatic analysis of liver tissue from SCD mice revealed decreased XO content. Hematoxylin and eosin staining of liver tissue of knockout-transgenic SCD mice indicated extensive hepatocellular injury that was accompanied by increased plasma content of the liver enzyme alanine aminotransferase. Immunocytochemical and enzymatic analysis of XO in thoracic aorta and liver tissue of SCD mice showed increased vessel wall and decreased liver XO, with XO concentrated on and in vascular luminal cells. Steady-state rates of vascular O(2)( *-) production, as indicated by coelenterazine chemiluminescence, were significantly increased, and nitric oxide (( *)NO)-dependent vasorelaxation of aortic ring segments was severely impaired in SCD mice, implying oxidative inactivation of ( *)NO. Pretreatment of aortic vessels with the superoxide dismutase mimetic manganese 5,10,15,20-tetrakis(N-ethylpyridinium-2-yl)porphyrin markedly decreased O(2)( small middle dot-) levels and significantly restored acetylcholine-dependent relaxation, whereas catalase had no effect. These data reveal that episodes of intrahepatic hypoxia-reoxygenation associated with SCD can induce the release of XO into the circulation from the liver. This circulating XO can then bind avidly to vessel luminal cells and impair vascular function by creating an oxidative milieu and catalytically consuming (*)NO via O(2)( small middle dot-)-dependent mechanisms.

Purified poloxamer 188 for treatment of acute vaso-occlusive crisis of sickle cell disease: A randomized controlled trial

CONTEXT

Sickle cell disease (SCD) can cause severe painful episodes that are often thought to be caused by vaso-occlusion. The current therapy for these uncomplicated painful episodes includes hydration, oxygen, and analgesics. Purified poloxamer 188 may increase tissue oxygenation and thereby reduce inflammation, pain, and the overall duration of such painful episodes in patients with SCD.

OBJECTIVE

To compare the duration of painful episodes in patients with SCD treated with purified poloxamer 188 to that of similar episodes experienced by patients who receive a placebo.

DESIGN AND SETTING

Randomized, double-blind, placebo-controlled, intention-to-treat trial conducted between March 1998 and October 1999 in 40 medical centers in the United States.

PARTICIPANTS

Two hundred fifty-five patients with SCD (aged 9-53 years) who had a painful episode sufficiently severe to require hospitalization and narcotic analgesics.

INTERVENTION

Patients were randomly assigned to receive an intravenous infusion of purified poloxamer 188, 100 mg/kg for 1 hour followed by 30 mg/kg per hour for 47 hours (n = 127), or a matching volume of saline placebo (n = 128).

MAIN OUTCOME MEASURE

Duration of the painful episode, from randomization to crisis resolution.

RESULTS

Mean (SD) duration of the painful episodes was 141 (42) hours in the placebo group compared with 133 (41) hours in those treated with purified poloxamer 188, a 9-hour reduction (P =.04). Subset analyses indicated an even more pronounced purified poloxamer 188 effect in children aged 15 years or younger (21 hours; P =.01) and in patients who were receiving hydroxyurea (16 hours; P =.02). Finally, the proportion of patients achieving crisis resolution was increased by purified poloxamer 188 (65/126 [52%] vs 45/123 [37%]; P =.02). Similar results were observed in children aged 15 years or younger (22/37 [60%] vs 10/36 [28%]; P =.009) and in patients who were also receiving hydroxyurea (12/26 [46%] vs 4/28 [14%]; P =.02).

CONCLUSIONS

A decrease in the duration of painful episodes and an increase in the proportion of patients who achieved resolution of the symptoms were observed when the purified poloxamer 188-treated patients were compared with the patients receiving placebo. However, the difference between these groups was significant but relatively small. In subgroup analysis, a more significant effect on both parameters was observed in children and in patients who were receiving concomitant hydroxyurea. It is important to confirm both of these observations in further prospective trials.

Nested deletions of the SRL pathogenicity island of Shigella flexneri 2a

In this study, we determined the boundaries of a 99-kb deletable element of Shigella flexneri 2a strain YSH6000. The element, designated the multiple-antibiotic resistance deletable element (MRDE), had recently been found to contain a 66-kb pathogenicity island (PAI)-like element (designated the SRL PAI) which carries the Shigella resistance locus (SRL), encoding resistance determinants to streptomycin, ampicillin, chloramphenicol, and tetracycline. The YSH6000 MRDE was found to be flanked by two identical IS91 elements present at the S. flexneri homologs of the Escherichia coli genes putA and mdoA on NotI fragment D. Sequence data from two YSH6000-derived MRDE deletants, YSH6000T and S2430, revealed that deletion of the MRDE occurred between the two flanking IS91 elements, resulting in a single IS91 element spanning the two original IS91 loci. Selection for the loss of tetracycline resistance confirmed that the MRDE deletion occurred reproducibly from the same chromosomal site and also showed that the SRL PAI and the SRL itself were capable of independent deletion from the chromosome, thus revealing a unique set of nested deletions. The excision frequency of the SRL PAI was estimated to be 10(-5) per cell in the wild type, and mutation of a P4-like integrase gene (int) at the left end of the SRL PAI revealed that int mediates precise deletion of the PAI.

Ferric dicitrate transport system (Fec) of Shigella flexneri 2a YSH6000 is encoded on a novel pathogenicity island carrying multiple antibiotic resistance genes

Iron uptake systems which are critical for bacterial survival and which may play important roles in bacterial virulence are often carried on mobile elements, such as plasmids and pathogenicity islands (PAIs). In the present study, we identified and characterized a ferric dicitrate uptake system (Fec) in Shigella flexneri serotype 2a that is encoded by a novel PAI termed the Shigella resistance locus (SRL) PAI. The fec genes are transcribed in S. flexneri, and complementation of a fec deletion in Escherichia coli demonstrated that they are functional. However, insertional inactivation of fecI, leading to a loss in fec gene expression, did not impair the growth of the parent strain of S. flexneri in iron-limited culture media, suggesting that S. flexneri carries additional iron uptake systems capable of compensating for the loss of Fec-mediated iron uptake. DNA sequence analysis showed that the fec genes are linked to a cluster of multiple antibiotic resistance determinants, designated the SRL, on the chromosome of S. flexneri 2a. Both the SRL and fec loci are carried on the 66,257-bp SRL PAI, which has integrated into the serX tRNA gene and which carries at least 22 prophage-related open reading frames, including one for a P4-like integrase. This is the first example of a PAI that carries genes encoding antibiotic resistance and the first report of a ferric dicitrate uptake system in Shigella.

Lateral thoracic expansion for Jeune's syndrome: midterm results

BACKGROUND

In 1995, we reported the use of lateral thoracic expansion in a patient with symptomatic Jeune's asphyxiating thoracic dystrophy. We have subsequently used lateral thoracic expansion 16 times on 10 patients during 7 years. This article reports our outcomes and provides surgical details.

METHODS

Charts of all patients undergoing lateral thoracic expansion were reviewed. Eight of the 10 patients had symptomatic Jeune's syndrome. The other 2 had similar thoracic deformities limiting thoracic capacity. In half of the patients the procedures were performed bilaterally.

RESULTS

All patients older than 1 year of age were symptomatically benefited by lateral thoracic expansion. Functional and anatomic measurements documented thoracic enlargement in several patients who had comparable preoperative and postoperative studies. However, 2 infants with significant underlying airway disease did not improve and went on to succumb to that aspect of their disease despite enlargement of the thorax. Fracture of the titanium ministruts has been a recurrent problem, and we now use larger struts.

CONCLUSIONS

Lateral thoracic expansion is a safe and effective procedure in selected patients with Jeune's syndrome older than 1 year of age as judged by short-term and midterm follow-up. More experience and longer follow-up are required to discern the place of the lateral thoracic expansion in the overall management of these patients.

Routine ventilation scans in children with cystic fibrosis: diagnostic usefulness and prognostic value

Krypton ventilation scans (VS) provide an index of peripheral lung function, and may be particularly useful in children unable to perform pulmonary function testing. This communication reports on three linked studies which investigated whether a routine VS in young children with cystic fibrosis (CF) is diagnostically or prognostically useful. Study 1: In a preliminary study in 1991, VS were compared with clinical examination and chest radiography (CXR) in 50 CF children (29 females, 21 males) aged 0.4-5.2 years (median 2.2 years). The chest was divided into six zones, and abnormalities scored from 0 (normal) to 2 (very abnormal). Clinical examination was unhelpful in predicting abnormalities on imaging. In five children (10%) with a normal CXR, VS was abnormal, and in a further eight children (16%), CXR markedly underestimated VS changes. Study 2: In order to determine the long-term prognostic significance of VS abnormalities, we followed up 27 (19 females, 8 males) of the children from study 1, who had had their first VS at presentation at median age 1.6 years (range 0.4-5.2), scoring the same six zones from 0 to 2. Follow-up was for a mean of 11.6 years (range 7.8-14.8). Spirometry at age 7 years showed a mean forced expiratory volume in 1 s (FEV1) of 96% (range 46%-145%) and a mean forced vital capacity (FVC) of 96% (range 46%-145%). A poor VS score at presentation was correlated with percent predicted FEV1 at age 7 (r=0.4, P=0.042, 16% of variance explained). Those with a normal VS at presentation had a mean FEV1 at presentation of 99% (range 80%-129%). Whereas four patients had an abnormal VS, a normal CXR and a low FEV1 at age 7 years, no patient had a normal VS, an abnormal CXR and a low FEV1 at age 7 years. Study 3: Fifty children (29 females, 21 males) aged 0.5-6.0 years (median 3.8) were prospectively studied in 1998, to determine whether the findings in study 1 were stable over time, and to assess whether VS altered clinical management. Symptoms and clinical examination did not predict abnormalities on imaging. Thirty (60%) children had a normal VS while only five (10%) had a normal CXR. There was a significant correlation between the total scores of CXR and VS (P=0.007, 14% of variance explained). Further, VS detected additional abnormalities in seven patients (14%). Sixty-five percent of patients with an abnormal VS had modifications of treatment, including bronchoscopy, compared with 23% of those with a normal VS. We conclude that VS is a simple, safe and non-invasive technique giving additional information to that provided by clinical examination and chest radiography in a number of children with CF and can be used to modify clinical management. VS at presentation gives prognostic information, which may be of use in early intervention studies. Whether using VS to guide treatment improves long-term prognosis requires a larger prospective trial.

Stable or increasing bone mineral density in HIV-infected patients treated with nelfinavir or indinavir

BACKGROUND AND OBJECTIVES

To determine the factors contributing to changes in bone mineral density (BMD) over time in HIV-infected patients receiving highly active antiretroviral therapy (HAART).

METHODS

Analyses of lumbar spine BMD in 183 male Caucasian participants in the Western Australian HIV Cohort study, comprising a longitudinal analysis of data from 54 patients on stable HAART regimens, and a cross-sectional analysis comparing data from 131 protease inhibitor (PI)-treated patients and 52 PI-naive (including 28 antiretroviral treatment-naive) patients.

RESULTS

Average lumbar spine BMD remained stable or increased over the time frame considered. Although there was no evidence of a change of average BMD over time in patients receiving nelfinavir (P = 0.92), there was evidence of increasing bone density in the indinavir group (average increase, 0.31 z-score per year; P < 0.001). Lower initial z-scores in the longitudinal analysis were significantly associated with lower pre-HAART BMI (P = 0.003), consistent with results of the cross-sectional analysis in which lowest BMI prior to initial dual X-ray absorptiometry scan was associated with decreased BMD (P = 0.02, overall group). Although PI therapy was also associated with decreased BMD in a univariate analysis of the cross-sectional data (P = 0.04), this effect was abrogated in a multiple linear regression analysis (P = 0.11) with lowest BMI remaining significant (P = 0.04).

CONCLUSIONS

We found no evidence, overall, of accelerated bone loss in patients treated with nelfinavir- or indinavir-containing HAART regimens, and propose that indinavir therapy may be associated with an increase in bone mineral density over time. Pre-HAART BMI was an independent and powerful determinant of an individual's initial z-score in the longitudinal analysis, and adjustment for this effect in a cross-sectional analysis abrogated the association between PI therapy and decreased lumbar spine z-score.

Genetic differences among the LPS biosynthetic loci of serovars of Leptospira interrogans and Leptospira borgpetersenii

The gene organization in the lipopolysaccharide biosynthetic (rfb) locus was analyzed in seven Leptospira interrogans serovars within serogroup Icterohemorrhagiae, seven non-Icterohemorrhagiae serovars and one Leptospira borgpetersenii serovar. Two groups of loci were delineated based on DNA hybridization and sequence analysis. Group 1 contained the two Hardjo subtypes, Hardjoprajitno and Hardjobovis. Group 2 (containing Copenhageni, Pomona, Naam, Mwogolo, Smithi, Lai, Canicola, Autumnalis, Pyrogenes, Australis and Icterohemorrhagiae) differed from Group 1 in its organization upstream of orf11, where five ORFs (32, 33, 34, 35, 37) were identified that were not contained in the Group 1 loci. These ORFs encoded a putative epimerase (orf32), a glycosyltransferase (orf33), two integral membrane proteins (orfs 34 and 35), and a galactosyltransferase (orf37). Serovars Australis, Pomona and Autumnalis did not contain orf37. Serovar Bataviae was excluded from the grouping because of its unique genetic organization upstream of orf13. In the Group 2 loci, comparison of the genetic layout at the 5' end revealed differences which included mutations disrupting reading frames in either or both orf34 and orf35 and apparent allelic differences between orf33 homologs that may be sufficient to account for the genetic basis of serovar identity.

Costimulation by extracellular matrix proteins determines the response to TCR ligation

Although ligation of the T-cell antigen receptor (TCR) is central to the responsiveness and antigen specificity of T-cells, it is insufficient to elicit a response. To determine whether the need for costimulation reflects inadequate strength of signal transduction through the TCR or an absolute block of signaling in the absence of a coligand, we studied T-cell activation under serum-free conditions eliminating costimulation by various extracellular matrix proteins which otherwise have an omnipresent and frequently overlooked effect. Engagement of the TCR leads to induction of Fas, but not to measurable IL-2 secretion or apoptosis. Those activation parameters are induced by costimulation through integrin alphaVbeta3. Furthermore, T-cell survival or elimination is determined by the type of ligand binding to this coreceptor with vitronectin, fibronectin, and fibrinogen efficiently inducing apoptosis and IL-2 production while osteopontin and entactin mediate IL-2 secretion comparably without causing programmed cell death. Consistent with the cytokine properties of these ligands, differential costimulation depends on their presentation in soluble rather than immobilized form. The determination of elimination versus survival of activated T-cells by coligation of beta3-integrins may have bearing on the fundamental postthymic mechanisms that shape the T-cell repertoire.

In vivo-expressed genes of Pasteurella multocida

Pasteurella multocida is the causative agent of infectious diseases of economic importance such as fowl cholera, bovine hemorrhagic septicemia, and porcine atrophic rhinitis. However, knowledge of the molecular mechanisms and determinants that P. multocida requires for virulence and pathogenicity is still limited. To address this issue, we developed a genetic expression system, based on the in vivo expression technology approach first described by Mahan et al. (Science 259:686--688, 1993), to identify in vivo-expressed genes of P. multocida. Numerous genes, such as those encoding outer membrane lipoproteins, metabolic and biosynthetic enzymes, and a number of hypothetical proteins, were identified. These may prove to be useful targets for attenuating mutation and/or warrant further investigation for their roles in immunity and/or pathogenesis.

Role of capsule in the pathogenesis of fowl cholera caused by Pasteurella multocida serogroup A

We have constructed a defined acapsular mutant in Pasteurella multocida X-73 (serogroup A:1) by disrupting the hexA gene through the insertion of a tetracycline resistance cassette. The genotype of the hexA::tet(M) strain was confirmed by PCR and Southern hybridization, and the acapsular phenotype of this strain was confirmed by electron microscopy. The hexA::tet(M) strain was attenuated in both mice and chickens. Complementation of the mutant with an intact hexAB fragment restored lethality in mice but not in chickens. In contrast to the results described previously for P. multocida serogroup B (J. D. Boyce and B. Adler, Infect. Immun. 68:3463-3468, 2000), the hexA::tet(M) strain was sensitive to the bactericidal action of chicken serum, whereas the wild-type and complemented strains were both resistant. Following inoculation into chicken muscle, the bacterial count of the hexA::tet(M) strain decreased significantly, while the wild-type and complemented strains both grew rapidly over 4 h. The capsule is thus an essential virulence determinant in the pathogenesis of fowl cholera.

Genetic organization of Pasteurella multocida cap Loci and development of a multiplex capsular PCR typing system

Current serotyping methods classify Pasteurella multocida into five capsular serogroups (serogroups A, B, D, E, and F) and 16 somatic serotypes (serotypes 1 to 16). In the present study, we have developed a multiplex PCR assay as a rapid alternative to the conventional capsular serotyping system. The serogroup-specific primers used in this assay were designed following identification, sequence determination, and analysis of the capsular biosynthetic loci of each capsular serogroup. The entire capsular biosynthetic loci of P. multocida A:1 (X-73) and B:2 (M1404) have been cloned and sequenced previously (J. Y. Chung, Y. M. Zhang, and B. Adler, FEMS Microbiol. Lett. 166:289-296, 1998; J. D. Boyce, J. Y. Chung, and B. Adler, Vet. Microbiol. 72:121-134, 2000). Nucleotide sequence analysis of the biosynthetic region (region 2) from each of the remaining three serogroups, serogroups D, E, and F, identified serogroup-specific regions and gave an indication of the capsular polysaccharide composition. The multiplex capsular PCR assay was highly specific, and its results, with the exception of those for some serogroup F strains, correlated well with conventional serotyping results. Sequence analysis of the strains that gave conflicting results confirmed the validity of the multiplex PCR and indicated that these strains were in fact capsular serogroup A. The multiplex PCR will clarify the distinction between closely related serogroups A and F and constitutes a rapid assay for the definitive classification of P. multocida capsular types.

Acapsular Pasteurella multocida B:2 can stimulate protective immunity against pasteurellosis

We have previously shown that a Pasteurella multocida cexA mutant (PBA875) was impaired in capsule export and highly attenuated in virulence for mice (J. D. Boyce and B. Adler, Infect. Immun. 68:3463-3468, 2000). In this study we show that immunization with high, but not low, doses of PBA875 can confer significant protection against wild-type challenge. We have also constructed a genetically defined acapsular P. multocida strain (AL18) by inactivation of bcbH, a gene predicted to be involved in polysaccharide biosynthesis. AL18 failed to produce immunoreactive polysaccharide as determined by immunofluorescence and Western immunoblot. Immunization of mice with live AL18 conferred significant protection against wild-type challenge, while immunization with similar doses of either killed wild-type or killed AL18 failed to confer protection.

Genetic organization of the she pathogenicity island in Shigella flexneri 2a

In this study we report the complete nucleotide sequence and genetic organization of the she pathogenicity island (PAI) of Shigella flexneri 2a strain YSH6000T. The 46 603 bp she PAI is situated adjacent to the 3' terminus of the pheV tRNA gene and includes an imperfect direct repeat of the 3'-terminal 22 bp of the pheV gene at the right boundary of the PAI. The she PAI carries a bacteriophage P4-like integrase gene within the pheV -proximal boundary of the PAI, intact and truncated mobile genetic elements, plasmid-related sequences, open reading frames exhibiting high sequence similarity to those found on the locus of enterocyte effacement (LEE) PAI of enterohemorrhagic Escherichia coli (EHEC), and the SHI-2 PAI of S. flexneri and several other open reading frames of unknown function. The she PAI also encodes two autotransporter proteins, including SigA, a cytopathic protease that contributes to intestinal fluid accumulation and Pic, a protease with mucinase, and hemagglutinin activities. In addition, an open reading frame (orf) termed sap, has high sequence similarity to the gene encoding Antigen 43, a surface-located autotransporter protein of E. coli. The ShET1 enterotoxin genes, associated predominantly with S. flexneri 2a strains, are also located on the she PAI.

Characterisation of a Pasteurella multocida esterase gene which confers a hemolytic phenotype in Escherichia coli under anaerobic conditions

Investigation of the hemolytic phenotype under anaerobic growth conditions of an avian Pasteurella multocida strain, PBA100, resulted in the identification and characterisation of a gene encoding an esterase enzyme, mesA, that conferred a hemolytic phenotype in Escherichia coli under anaerobic conditions. MesA appeared to be expressed and functional under anaerobic and aerobic conditions in both E. coli and P. multocida. A P. multocida mesA mutant was generated which resulted in the loss of acetyl esterase activity under anaerobic conditions. However, this mutation did not cause any attenuation of virulence for mice nor a detectable change to the anaerobic hemolytic phenotype of P. multocida. In E. coli MesA appeared to cause hemolysis indirectly by the induction of the latent E. coli K-12 cytolysin, sheA.