Automated Scoring of Chromogenic Media for Detection of Methicillin-Resistant Staphylococcus aureus by Use of WASPLab Image Analysis Software.

Recently, systems have been developed to create total laboratory automation for clinical microbiology. These systems allow for the automation of specimen processing, specimen incubation, and imaging of bacterial growth. In this study, we used the WASPLab to validate software that discriminates and segregates positive and negative chromogenic methicillin-resistant Staphylococcus aureus (MRSA) plates by recognition of pigmented colonies. A total of 57,690 swabs submitted for MRSA screening were enrolled in the study. Four sites enrolled specimens following their standard of care. Chromogenic agar used at these sites included MRSASelect (Bio-Rad Laboratories, Redmond, WA), chromID MRSA (bioMérieux, Marcy l'Etoile, France), and CHROMagar MRSA (BD Diagnostics, Sparks, MD). Specimens were plated and incubated using the WASPLab. The digital camera took images at 0 and 16 to 24 h and the WASPLab software determined the presence of positive colonies based on a hue, saturation, and value (HSV) score. If the HSV score fell within a defined threshold, the plate was called positive. The performance of the digital analysis was compared to manual reading. Overall, the digital software had a sensitivity of 100% and a specificity of 90.7% with the specificity ranging between 90.0 and 96.0 across all sites. The results were similar using the three different agars with a sensitivity of 100% and specificity ranging between 90.7 and 92.4%. These data demonstrate that automated digital analysis can be used to accurately sort positive from negative chromogenic agar cultures regardless of the pigmentation produced.

Differential diagnosis of cervical mycobacterial lymphadenitis in children.

BACKGROUND AND AIMS: The differential diagnosis between tuberculosis (TB) and lymphadenitis caused by nontuberculous mycobacteria (NTM) in children is often based on epidemiologic and clinical data. The aim of this study was to identify epidemiologic and clinical variables associated with TB lymphadenitis in children attending 2 TB out-patient clinics in northern Italy during a 10-year period. PATIENTS AND METHODS: All children less than 16 years of age attending the study sites suspected of mycobacterial disease from 1999 through 2008 were included in the analysis. Logistic regression was used to evaluate the variables independently associated with TB lymphadenitis. RESULTS: From 299 children diagnosed with mycobacterial disease 121 children (40%) had a clinical diagnosis of cervical mycobacterial lymphadenitis: 38 TB (31%) and 83 NTM lymphadenitis (69%) cases. Increasing age (OR, 1.29; 95% CI, 1.02-1.69; P = 0.04), being foreign born (OR, 11.60; 95% CI, 1.37-114.20; P = 0.02), and having an abnormal chest radiograph (OR, 18.32; 95% CI, 2.37-201.68; P = 0.008) were independently associated with TB lymphadenitis. In the selected model, a 5-year-old foreign born child with cervical lymphadenitis and abnormal findings on chest radiograph has an estimated 0.90 probability of having TB disease. On the other hand, an Italy born child of the same age with cervical lymphadenitis and normal chest radiograph has a 0.04 probability of having TB. CONCLUSION: Epidemiologic and clinical data are useful tools in the differential diagnosis between TB and NTM lymphadenitis when etiologic diagnosis is not available.

Validation of the agar proportion and 2 liquid systems for testing the susceptibility of Mycobacterium tuberculosis to moxifloxacin.

Moxifloxacin (MOX), an 8-methoxyquinolone compound, is now widely used for the treatment of bacterial infections and also accepted as 2nd-line drug for the treatment of multidrug-resistant (MDR) tuberculosis. To tentatively correlate the clinical outcome with in vitro results, we sought to set up susceptibility test conditions for Mycobacterium tuberculosis against MOX by using the reference agar proportion method, the BACTEC 460 radiometric system, and the recently validated nonradiometric BACTEC MGIT 960 system. Our aim was to determine the critical MOX test concentration to be used with the abovementioned methods for routine susceptibility testing. MICs were determined for 20 pan-susceptible strains, 10 MDR strains, and 10 fluoroquinolone-resistant strains with defined gyrA mutations. MOX MICs resulted in a bimodal pattern with values for gyrA mutants considerably higher than those for pan-susceptible and MDR strains. Our data showed that a concentration of 0.5 microg/mL allowed a clear-cut separation between susceptible and resistant strains when tested by all the studied methods. Confirmatory test with a subset of pan-susceptible and MDR isolates appeared to validate the selected critical concentration. The MOX-resistant strains were almost isolated from patients with prior fluoroquinolone exposure.

Long-term moxifloxacin in complicated tuberculosis patients with adverse reactions or resistance to first line drugs.

STUDY OBJECTIVES: To test safety and tolerability of long-term moxifloxacin in resistant tuberculosis (TB) patients and patients with intolerance to first line anti-TB drugs. DESIGN: Clinical evaluation of adverse events (AEs) during prolonged moxifloxacin treatment. SETTING: TB Unit of the Regional TB Reference Center, Villa Marelli Institute, Niguarda Ca'Granda Hospital, Milan, Italy PATIENTS AND INTERVENTIONS: Patients treated with moxifloxacin, 400 mg orally once daily for TB in the Villa Marelli Institute from January 2001 to December 2003 were enrolled. RESULTS: Thirty-eight patients were treated with moxifloxacin at the Villa Marelli Institute in the study period, for multidrug resistant (MDR) TB (14, 36.8%), for intolerance to first line anti-TB drugs (9, 23.7%), for combined resistance and intolerance to first line anti-TB drugs (12, 31.6%), other reasons (3, 7.9%). The mean duration of moxifloxacin treatment was 6.3 +/- 5.2 months. Twelve (31.6%) patients reported at least an AE due to moxifloxacin, mostly gastrointestinal (8, 21.0%), general (5, 13.2%) and central nervous system (3, 7.9%) AEs. In 4 (10.5%) patients the drug was withdrawn for major AEs; no irreversible or fatal events were recorded. Most of the patients (31, 81.6%) reported a treatment success, even if the success rate was lower in MDR TB patients (8/14, 51.7%). CONCLUSIONS: Despite the fact that a large proportion of patients experienced at least an AE due to moxifloxacin, the drug resulted safe in the long-term administration for complicated TB cases.