Drug susceptibility patterns of Mycobacterium tuberculosis from adults with multidrug-resistant tuberculosis and implications for a household contact preventive therapy trial.

BACKGROUND: Drug susceptibility testing (DST) patterns of Mycobacterium tuberculosis (MTB) from patients with rifampicin-resistant tuberculosis (RR-TB) or multidrug-resistant TB (MDR-TB; or resistant to rifampicin and isoniazid (INH)), are important to guide preventive therapy for their household contacts (HHCs). METHODS: As part of a feasibility study done in preparation for an MDR-TB preventive therapy trial in HHCs, smear, Xpert MTB/RIF, Hain MTBDRplus, culture and DST results of index MDR-TB patients were obtained from routine TB programs. A sputum sample was collected at study entry and evaluated by the same tests. Not all tests were performed on all specimens due to variations in test availability. RESULTS: Three hundred eight adults with reported RR/MDR-TB were enrolled from 16 participating sites in 8 countries. Their median age was 36 years, and 36% were HIV-infected. Routine testing on all 308 were confirmed as having RR-TB, but only 75% were documented as having MDR-TB. The majority of those not classified as having MDR-TB were because only rifampicin resistance was tested. At study entry (median 59 days after MDR-TB treatment initiation), 280 participants (91%) were able to produce sputum for the study, of whom 147 (53%) still had detectable MTB. All but 2 of these 147 had rifampicin DST done, with resistance detected in 89%. Almost half (47%) of the 147 specimens had INH DST done, with 83% resistance. Therefore, 20% of the 280 study specimens had MDR-TB confirmed. Overall, DST for second-line drugs were available in only 35% of the 308 routine specimens and 15% of 280 study specimens. CONCLUSIONS: RR-TB was detected in all routine specimens but only 75% had documented MDR-TB, illustrating the need for expanded DST beyond Xpert MTB/RIF to target preventive therapy for HHC.

Vitamin D status and risk of incident tuberculosis disease: A nested case-control study, systematic review, and individual-participant data meta-analysis.

BACKGROUND: Few studies have evaluated the association between preexisting vitamin D deficiency and incident tuberculosis (TB). We assessed the impact of baseline vitamins D levels on TB disease risk. METHODS AND FINDINGS: We assessed the association between baseline vitamin D and incident TB in a prospective cohort of 6,751 HIV-negative household contacts of TB patients enrolled between September 1, 2009, and August 29, 2012, in Lima, Peru. We screened for TB disease at 2, 6, and 12 months after enrollment. We defined cases as household contacts who developed TB disease at least 15 days after enrollment of the index patient. For each case, we randomly selected four controls from among contacts who did not develop TB disease, matching on gender and year of age. We also conducted a one-stage individual-participant data (IPD) meta-analysis searching PubMed and Embase to identify prospective studies of vitamin D and TB disease until June 8, 2019. We included studies that assessed vitamin D before TB diagnosis. In the primary analysis, we defined vitamin D deficiency as 25-(OH)D < 50 nmol/L, insufficiency as 50-75 nmol/L, and sufficiency as >75nmol/L. We estimated the association between baseline vitamin D status and incident TB using conditional logistic regression in the Lima cohort and generalized linear mixed models in the meta-analysis. We further defined severe vitamin D deficiency as 25-(OH)D < 25 nmol/L and performed stratified analyses by HIV status in the IPD meta-analysis. In the Lima cohort, we analyzed 180 cases and 709 matched controls. The adjusted odds ratio (aOR) for TB risk among participants with baseline vitamin D deficiency compared to sufficient vitamin D was 1.63 (95% CI 0.75-3.52; p = 0.22). We included seven published studies in the meta-analysis and analyzed 3,544 participants. In the pooled analysis, the aOR was 1.48 (95% CI 1.04-2.10; p = 0.03). The aOR for severe vitamin D deficiency was 2.05 (95% CI 0.87-4.87; p trend for decreasing 25-(OH)D levels from sufficient vitamin D to severe deficiency = 0.02). Among 1,576 HIV-positive patients, vitamin D deficiency conferred a 2-fold (aOR 2.18, 95% CI 1.22-3.90; p = 0.01) increased risk of TB, and the aOR for severe vitamin D deficiency compared to sufficient vitamin D was 4.28 (95% CI 0.85-21.45; p = 0.08). Our Lima cohort study is limited by the short duration of follow-up, and the IPD meta-analysis is limited by the number of possible confounding covariates available across all studies. CONCLUSION: Our findings suggest vitamin D predicts TB disease risk in a dose-dependent manner and that the risk of TB disease is highest among HIV-positive individuals with severe vitamin D deficiency. Randomized control trials are needed to evaluate the possible role of vitamin D supplementation on reducing TB disease risk.

Effect of baseline micronutrient and inflammation status on CD4 recovery post-cART initiation in the multinational PEARLS trial.

BACKGROUND & AIMS: Nutritional deficiency and inflammation may impact CD4+ T cell recovery during combination antiretroviral therapy (cART), particularly in resource-limited settings where malnutrition is prevalent. The aim of this study was to investigate the relationship of micronutrient and inflammation biomarkers to CD4 recovery after cART initiation. METHODS: We conducted a secondary analysis of a random sub-cohort sample (n = 270) from a multinational randomized trial of cART regimen efficacy among 1571 cART-naïve adults. We measured pre-cART serum levels of micronutrients (Vitamin A, B6, B12, D, total carotenoids, selenium, and iron) and inflammation (C-reactive protein, soluble CD14 (sCD14), IFNγ, TNFα, Interleukin-6, and C-X-C motif chemokine 10 (CXCL10/IP10), EndoCab (IgM)) biomarkers. Biomarker status (i.e. micronutrient deficiency vs. sufficiency and elevated vs. low inflammation) was defined using established cutoffs or quartiles. Mixed-effects linear regression models were used to determine the association of baseline (pre-cART) concentrations of individual biomarkers with CD4 recovery through 96 weeks post-cART initiation. RESULTS: In models adjusting for time-dependent viral load and baseline CD4 count, age, sex, body mass index, country, treatment regimen, anemia and hypoalbuminemia status, pre-cART vitamin D deficiency was associated with lower CD4 recovery (-14.9 cells/mm3, 95% CI: -27.9, -1.8) compared to sufficiency. In contrast, baseline selenium deficiency (20.8 cells/mm3, 95% CI: 3.3, 38.3), vitamin A deficiency (35.9 cells/mm3, 95% CI: 17.6, 54.3) and high sCD14 (23.4 cells/mm3, 95% CI: 8.9, 37.8) were associated with higher CD4 recovery compared to sufficient/low inflammation status. CONCLUSIONS: In summary, baseline vitamin D deficiency was associated with diminished CD4 recovery after cART initiation; impaired CD4 recovery may contribute to the poor clinical outcomes recently observed in individuals with vitamin D deficiency. Vitamin A, selenium and sCD14 were associated with CD4 recovery but future studies are needed to further explore these relationships.

Porting the synthetic D-glucaric acid pathway from Escherichia coli to Saccharomyces cerevisiae.

D-Glucaric acid can be produced as a value-added chemical from biomass through a de novo pathway in Escherichia coli. However, previous studies have identified pH-mediated toxicity at product concentrations of 5 g/L and have also found the eukaryotic myo-inositol oxygenase (MIOX) enzyme to be rate-limiting. We ported this pathway to Saccaromyces cerevisiae, which is naturally acid-tolerant and evaluate a codon-optimized MIOX homologue. We constructed two engineered yeast strains that were distinguished solely by their MIOX gene - either the previous version from Mus musculus or a homologue from Arabidopsis thaliana codon-optimized for expression in S. cerevisiae - in order to identify the rate-limiting steps for D-glucaric acid production both from a fermentative and non-fermentative carbon source. myo-Inositol availability was found to be rate-limiting from glucose in both strains and demonstrated to be dependent on growth rate, whereas the previously used M. musculus MIOX activity was found to be rate-limiting from glycerol. Maximum titers were 0.56 g/L from glucose in batch mode, 0.98 g/L from glucose in fed-batch mode, and 1.6 g/L from glucose supplemented with myo-inositol. Future work focusing on the MIOX enzyme, the interplay between growth and production modes, and promoting aerobic respiration should further improve this pathway.

Low Vitamin-D Levels Combined with PKP3-SIGIRR-TMEM16J Host Variants Is Associated with Tuberculosis and Death in HIV-Infected and -Exposed Infants.

BACKGROUND: This study examined the associations of 25-hydroxyvitamin D and specific host genetic variants that affect vitamin D levels or its effects on immune function, with the risk of TB or mortality in children. METHODS: A case-cohort sample of 466 South African infants enrolled in P1041 trial (NCT00080119) underwent 25-hydroxyvitamin D testing by chemiluminescent immunoassay. Single nucleotide polymorphisms (SNPs) that alter the effect of vitamin D [e.g. vitamin D receptor (VDR)], vitamin D levels [e.g. vitamin D binding protein (VDBP)], or toll like receptor (TLR) expression (SIGIRR including adjacent genes PKP3 and TMEM16J) were identified by real-time PCR. Outcomes were time to TB, and to the composite of TB or death by 192 weeks of follow-up. Effect modification between vitamin D status and SNPs for outcomes was assessed. FINDINGS: Median age at 25-hydroxyvitamin D determination was 8 months; 11% were breastfed, 51% were HIV-infected and 26% had low 25-hydroxyvitamin D (<32ng/mL). By 192 weeks, 138 incident TB cases (43 definite/probable, and 95 possible) and 26 deaths occurred. Adjusting for HIV status and potential confounders, low 25-hydroxyvitamin D was associated with any TB (adjusted hazard ratio [aHR] 1.76, 95% CI 1.01-3.05; p = 0.046) and any TB or death (aHR 1.76, 95% CI 1.03-3.00; p = 0.038). Children with low 25-hydroxyvitamin D and TMEM 16J rs7111432-AA or PKP3 rs10902158-GG were at increased risk for probable/definite TB or death (aHR 8.12 and 4.83, p<0.05) and any TB or death (aHR 4.78 and 3.26, p<0.005) respectively; SNPs in VDBP, VDR, and vitamin D precursor or hydroxylation genes were not. There was significant interaction between low 25-hydroxyvitamin D and, TMEM 16J rs7111432-AA (p = 0.04) and PKP3 rs10902158-GG (p = 0.02) SNPs. CONCLUSIONS: Two novel SNPs, thought to be associated with innate immunity, in combination with low vitamin D levels were identified as increasing a young child's risk of developing TB disease or death. Identifying high-risk children and providing targeted interventions such as vitamin D supplementation may be beneficial. TRIAL REGISTRATION: ClinicalTrials.gov NCT00080119.

Prevalence and risk factors of micronutrient deficiencies pre- and post-antiretroviral therapy (ART) among a diverse multicountry cohort of HIV-infected adults.

BACKGROUND & AIMS: HIV-infected adults have increased risk of several individual micronutrient deficiencies. However, the prevalence and risk factors of concurrent and multiple micronutrient deficiencies and whether micronutrient concentrations change after antiretroviral therapy (ART) initiation have not been well described. The objective of this study was to determine the prevalence and risk factors of individual, concurrent and multiple micronutrient deficiencies among ART-naïve HIV-infected adults from nine countries and assess change in micronutrient status 48 weeks post-ART initiation. METHODS: A random sub-cohort (n = 270) stratified by country was selected from the multinational PEARLS clinical trial (n = 1571 ART-naïve, HIV-infected adults). We measured serum concentrations of vitamins A, D (25-hydroxyvitamin), E, carotenoids and selenium pre-ART and 48 weeks post-ART initiation, and measured vitamins B6, B12, ferritin and soluble transferrin receptor at baseline only. Prevalence of single micronutrient deficiencies, concurrent (2 coexisting) or conditional (a deficiency in one micronutrient given a deficiency in another) and multiple (≥3) were determined using defined serum concentration cutoffs. We assessed mean changes in micronutrient concentrations from pre-ART to week 48 post-ART initiation using multivariable random effects models. RESULTS: Of 270 participants, 13.9%, 29.2%, 24.5% and 32.4% had 0, 1, 2 and multiple deficiencies, respectively. Pre-ART prevalence was the highest for single deficiencies of selenium (53.2%), vitamin D (42.4%), and B6 (37.3%) with 12.1% having concurrent deficiencies of all three micronutrients. Deficiency prevalence varied widely by country. 48 weeks post-ART initiation, mean vitamin A concentration increased (p < 0.001) corresponding to a 9% decrease in deficiency. Mean concentrations also increased for other micronutrients assessed 48 weeks post-ART (p < 0.001) but with minimal change in deficiency status. CONCLUSIONS: Single and multiple micronutrient deficiencies are common among HIV-infected adults pre-ART initiation but vary between countries. Importantly, despite increases in micronutrient concentrations, prevalence of individual deficiencies remains largely unchanged after 48 weeks on ART. Our results suggest that ART alone is not sufficient to improve micronutrient deficiency.

Pre-antiretroviral therapy serum selenium concentrations predict WHO stages 3, 4 or death but not virologic failure post-antiretroviral therapy.

A case-cohort study, within a multi-country trial of antiretroviral therapy (ART) efficacy (Prospective Evaluation of Antiretrovirals in Resource Limited Settings (PEARLS)), was conducted to determine if pre-ART serum selenium deficiency is independently associated with human immunodeficiency virus (HIV) disease progression after ART initiation. Cases were HIV-1 infected adults with either clinical failure (incident World Health Organization (WHO) stage 3, 4 or death by 96 weeks) or virologic failure by 24 months. Risk factors for serum selenium deficiency (<85 µg/L) pre-ART and its association with outcomes were examined. Median serum selenium concentration was 82.04 µg/L (Interquartile range (IQR): 57.28-99.89) and serum selenium deficiency was 53%, varying widely by country from 0% to 100%. In multivariable models, risk factors for serum selenium deficiency were country, previous tuberculosis, anemia, and elevated C-reactive protein. Serum selenium deficiency was not associated with either clinical failure or virologic failure in multivariable models. However, relative to people in the third quartile (74.86-95.10 µg/L) of serum selenium, we observed increased hazards (adjusted hazards ratio (HR): 3.50; 95% confidence intervals (CI): 1.30-9.42) of clinical failure but not virologic failure for people in the highest quartile. If future studies confirm this relationship of high serum selenium with increased clinical failure, a cautious approach to selenium supplementation might be needed, especially in HIV-infected populations with sufficient or unknown levels of selenium.

25-Hydroxyvitamin D insufficiency and deficiency is associated with HIV disease progression and virological failure post-antiretroviral therapy initiation in diverse multinational settings.

BACKGROUND: Low 25-hydroxyvitamin D (25(OH)D) has been associated with increased HIV mortality, but prospective studies assessing treatment outcomes after combination antiretroviral therapy (cART) initiation in resource-limited settings are lacking. METHODS: A case-cohort study (N = 411) was nested within a randomized cART trial of 1571 cART-naive adults in 8 resource-limited settings and the United States. The primary outcome (WHO stage 3/4 disease or death within 96 weeks of cART initiation) was met by 192 cases, and 152 and 29 cases met secondary outcomes of virologic and immunologic failure. We studied prevalence and risk factors for baseline low 25(OH)D (<32 ng/mL) and examined associated outcomes using proportional hazard models. RESULTS: Low 25(OH)D prevalence was 49% and ranged from 27% in Brazil to 78% in Thailand. Low 25(OH)D was associated with high body mass index (BMI), winter/spring season, country-race group, and lower viral load. Baseline low 25(OH)D was associated with increased risk of human immunodeficiency virus (HIV) progression and death (adjusted hazard ratio (aHR) 2.13; 95% confidence interval [CI], 1.09-4.18) and virologic failure (aHR 2.42; 95% CI, 1.33-4.41). CONCLUSIONS: Low 25(OH)D is common in diverse HIV-infected populations and is an independent risk factor for clinical and virologic failure. Studies examining the potential benefit of vitamin D supplementation among HIV patients initiating cART are warranted.

Change in vitamin d levels occurs early after antiretroviral therapy initiation and depends on treatment regimen in resource-limited settings.

STUDY BACKGROUND: Vitamin D has wide-ranging effects on the immune system, and studies suggest that low serum vitamin D levels are associated with worse clinical outcomes in HIV. Recent studies have identified an interaction between antiretrovirals used to treat HIV and reduced serum vitamin D levels, but these studies have been done in North American and European populations. METHODS: Using a prospective cohort study design nested in a multinational clinical trial, we examined the effect of three combination antiretroviral (cART) regimens on serum vitamin D levels in 270 cART-naïve, HIV-infected adults in nine diverse countries, (Brazil, Haiti, Peru, Thailand, India, Malawi, South Africa, Zimbabwe and the United States). We evaluated the change between baseline serum vitamin D levels and vitamin D levels 24 and 48 weeks after cART initiation. RESULTS: Serum vitamin D levels decreased significantly from baseline to 24 weeks among those randomized to efavirenz/lamivudine/zidovudine (mean change: -7.94 [95% Confidence Interval (CI) -10.42, -5.54] ng/ml) and efavirenz/emtricitabine/tenofovir-DF (mean change: -6.66 [95% CI -9.40, -3.92] ng/ml) when compared to those randomized to atazanavir/emtricitabine/didanosine-EC (mean change: -2.29 [95% CI -4.83, 0.25] ng/ml). Vitamin D levels did not change significantly between week 24 and 48. Other factors that significantly affected serum vitamin D change included country (p<0.001), season (p<0.001) and baseline vitamin D level (p<0.001). CONCLUSION: Efavirenz-containing cART regimens adversely affected vitamin D levels in patients from economically, geographically and racially diverse resource-limited settings. This effect was most pronounced early after cART initiation. Research is needed to define the role of Vitamin D supplementation in HIV care.

Nutrition and disease progression pre-highly active antiretroviral therapy (HAART) and post-HAART: can good nutrition delay time to HAART and affect response to HAART?

Several studies have investigated a variety of nutritional supplementation interventions in adults with HIV. In this narrative review, we summarize the evidence from 31 clinical trials that explore clinical benefits of macronutrient and micronutrient supplementation in this population while attempting to answer the question of whether good nutrition can delay the time to highly active antiretroviral therapy (HAART) initiation and response. We focused on trials published in English between 1990 and 2010 that reported on CD4 count, viral load, and disease progression or survival. Among 9 macronutrient and 22 micronutrient trials, we found that evidence for improved CD4 count and HIV viral load with nutritional supplementation was limited; only 11.1% and 36.8% of macronutrient and micronutrient supplementation trials, respectively, reported improved CD4 count; and 33.3% and 12.5% of macronutrient and micronutrient trials, respectively, reported decreased viral load. Given their utility as surrogate markers of HIV disease progression, this suggests limited evidence for nutritional interventions having an impact on delaying HAART initiation or on improving HAART response. However, there are challenges in evaluating the effects of nutritional supplementation on clinical disease in that comparisons are difficult due to heterogeneity in study design, patient population, nutrient doses and combinations, baseline levels of deficiency, and study endpoints, including lack of clarity in defining and reporting HAART status. Future studies need to adopt a more rigorous standard design with adequate power and follow-up and require a consensus on composition and dose of nutrient interventions to be tested to more specifically answer the question on the impact of nutritional interventions on HIV disease progression and HAART response.

Stigmatizing attitudes and low levels of knowledge but high willingness to participate in HIV management: a community-based survey of pharmacies in Pune, India.

BACKGROUND: The World Health Organization (WHO) recommends that the role of pharmacists in low-income settings be expanded to address the increasing complexity of HIV antiretroviral (ARV) and co-infection drug regimens. However, in many such settings including in India, many pharmacists and pharmacy workers are often neither well trained nor aware of the intricacies of HIV treatment. The aims of our study were; to determine the availability of ARVs, provision of ARVs, knowledge about ARVs, attitudes towards HIV-infected persons and self-perceived need for training among community-based pharmacies in an urban area of India. METHODS: We performed a survey of randomly selected, community-based pharmacies located in Pune, India, in 2004-2005 to determine the availability of ARVs at these pharmacies, how they were providing ARVs and their self-perceived need for training. We also assessed knowledge, attitudes and perceptions on HIV and ARVs and factors associated with stocking ARVs. RESULTS: Of 207 pharmacies included in the survey, 200 (96.6%) were single, private establishments. Seventy-three (35.3%) pharmacies stocked ARVs and 38 (18.4%) ordered ARVs upon request. The reported median number of ARV pills that patients bought at one time was 30, a two week supply of ARVs (range: 3-240 pills). Six (2.9%) pharmacy respondents reported selling non-allopathic medicines (i.e. Ayurvedic, homeopathy) for HIV. Ninety (44.2%) pharmacy respondents knew that ARVs cannot cure HIV, with those stocking ARVs being more likely to respond correctly (60.3% vs. 34.8%, p = 0.001). Respondents of pharmacies which stocked ARVs were also more likely to believe it was a professional obligation to provide medications to HIV-infected persons (91.8% vs. 78.8%, p = 0.007) but they were also more likely to believe that HIV-infected persons are unable to adhere to their medicines (79.5% vs. 40.9%, p < 0.01). Knowledge of the most common side effects of nevirapine, abnormal liver enzyme profile and skin rash, was reported correctly by 8 (3.9%) and 23 (11.1%) respondents, respectively. Seven (3.4%) respondents reported that they had received special training on HIV, 3 (1.5%) reported receipt of special training on ART and 167 (80.7%) reported that they believed that pharmacy staff should get special training on ART. CONCLUSION: There is a high willingness to participate in HIV management among community-based pharmacies but there is a tremendous need for training on HIV therapies. Furthermore, stigmatizing attitudes towards HIV-infected persons persist and interventions to reduce stigma are needed, particularly among those that stock ARVs.

Clinically significant anemia in HIV-infected pregnant women in India is not a major barrier to zidovudine use for prevention of maternal-to-child transmission.

OBJECTIVES: To determine the prevalence of anemia (serum hemoglobin <10 g/dL) and assess zidovudine use and toxicity in HIV-positive pregnant women in India. METHODS: From 2002 through 2006, 24,105 pregnant women in Pune were screened for HIV and anemia. As part of an infant prevention of mother-to-child transmission (PMTCT) trial, enrolled HIV-positive women (n = 467) were assessed for anemia and associated outcomes, comparing women receiving zidovudine for >or=2 weeks versus no zidovudine. RESULTS: The prevalence of anemia was 38.7% in HIV-positive women. Anemic women were as likely as nonanemic women to receive zidovudine. At delivery, regardless of anemia status at enrollment, women receiving >or=2 weeks of zidovudine were 70% less likely to be anemic compared with women receiving no zidovudine (odds ratio = 0.28, 95% confidence interval: 0.14 to 0.57; P < 0.01), received iron and folic acid supplements for longer periods, and had no increased adverse delivery or newborn birth outcomes. CONCLUSIONS: A significant proportion of HIV-positive pregnant women in India present for antenatal care with anemia. With concurrent iron and folic acid supplementation, however, zidovudine use is not associated with persistent or worsening anemia or associated adverse outcomes. In Indian community settings, all pregnant HIV-positive women should receive early anemia treatment. Mild anemia should not limit zidovudine use for PMTCT in India.

Antimicrobial activity of some Indian medicinal plants.

The antimicrobial potential of seventy-seven extracts from twenty-four plants was screened against eight bacteria and four pathogenic fungi, using microbroth dilution assay. Lowest concentration of the extract, which inhibits any visual microbial growth after treatment with p-iodonitrotetrazolium violet, was considered to be minimum inhibitory concentration (MIC). Water extracts of Acacia nilotica, Justicia zelanica, Lantana camara and Saraca asoca exhibited good activity against all the bacteria tested and the MIC was recorded in range of 9.375-37.5 microg/ml and 75.0-300.0 microg/ml against the bacterial and fungal pathogens, respectively. The other extracts of Phyllanthus urinaria, Thevetia nerifolia, Jatropha gossypifolia Saraca asoca, Tamarindus indica, Aegle marmelos, Acacia nilotica, Chlorophytum borivilianum, Mangifera indica, Woodfordia fruticosa and Phyllanthus emblica showed antimicrobial activity in a range of 75-1200 microg/ml.

Antimicrobial-resistant Shigella sonnei: limited antimicrobial treatment options for children and challenges of interpreting in vitro azithromycin susceptibility.

BACKGROUND: Antimicrobial-resistant Shigella sonnei is a growing problem in the United States and poses treatment challenges particularly among children. Azithromycin is recommended as an alternative oral agent for shigellosis. METHODS: All isolates of Shigella submitted to Johns Hopkins clinical laboratory during the outbreak year (2002) were compared with a historical comparison group (1996-2000). Isolates were considered multiresistant if they were resistant to ampicillin and trimethoprim-sulfamethoxazole (TS). Selected outbreak and reference isolates were tested for azithromycin susceptibility by E-test, disk diffusion and broth dilution methods. RESULTS: Between 1996-2000, among the 111 isolates submitted, 63% were from pediatric patients; 63% of isolates were resistant to ampicillin and 12% to TS. In 2002, among the 205 isolates submitted, 82% were from pediatric patients; 91% isolates were resistant to ampicillin and 67% to TS. The proportion of multiresistant isolates increased from 6% in 1996 to 65% in 2002 (P < 0.05). Azithromycin susceptibility by E-test and disk diffusion demonstrated 2 zones of inhibition for S. sonnei. Interpretation using the inner zone resulted in higher MICs (minimal inhibitory concentration) compared with the outer zones by E-test (P < 0.0001) and disk diffusion (P < 0.0001). CONCLUSIONS: With increasing interest in using azithromycin for shigellosis, clinical laboratories should be aware of the interpretation difficulty caused by the dual-zone phenomenon seen with E-test and disk diffusion methods for S. sonnei.