Molecular epidemiology and drug resistance of Mycobacterium tuberculosis in a tertiary care hospital in northeastern Mexico

INTRODUCTION

Tuberculosis (TB) is a re-emerging disease considered a public health concern. In the present study, we analyzed the epidemiology and drug resistance of Mycobacterium tuberculosis strains isolated from patients with pulmonary TB.

METHODOLOGY

Mycobacterium tuberculosis isolates (n = 190) were obtained from patients with pulmonary TB admitted to Dr. José Eleuterio González University Hospital (UH). Each M. tuberculosis isolate was analyzed by spoligotyping (spacer oligonucleotide typing) and MIRU-VNTR (Mycobacterial Interspersed Repetitive Units-Variable Number Tandem Repeat). Drug resistance was evaluated using the Anyplex™ II MTB/MDR/XDR assay.

RESULTS

The predominant spoligotypes observed were X1 (SIT 119, n = 46), T1 (SIT 53, n = 40), H3 (SIT 50, n = 13), Beijing (SIT 1, n = 11), and EAI2-Manila (SIT 19, n = 8). MIRU-VNTR analysis showed that the locus QUB-26 had the highest allelic variability. The observed drug resistance included monoresistance to rifampicin (2.6%; n = 5), isoniazid (3.2%; n = 6), and fluoroquinolones (1.6%; n = 3) as well as multidrug resistance (5.3%; n = 10). All of the Beijing strains were susceptible. Regarding comorbidities, 13.7% (26/190) of the patients were co-infected with TB and HIV (TB+HIV+), and 31.6% (55/190) had TB along with diabetes (TB + diabetes).

CONCLUSIONS

The most prevalent lineages were X1 (SIT 119; 24.3%) and T1 (SIT 53; 21%). An alarming proportion (12.6%) of M. tuberculosis isolates presented drug resistance. To effectively manage TB, continuous surveillance of regional strain dissemination, drug resistance profiles, and TB-associated comorbidities is crucial.

Genetic Diversity of Mycobacterium tuberculosis Isolates From an Amerindian Population in Chiapas, México

This is the first report of the genetic diversity of the Mycobacterium tuberculosis complex isolates found in a Mexican-Amerindian setting. In this study, we analyzed isolates collected from the Highlands region of Chiapas, Mexico, by using spoligotyping and whole-genome sequencing analyses. Seventy-three M. tuberculosis isolates were analyzed initially by spoligotyping; no new spoligotypes were identified. Nineteen percent of the isolates were identified as SIT53 (T1) (n = 14), followed by SIT42 (14%, n = 10, LAM9) and SIT119 (11%; n = 8, X1). SIT53, SIT42, and orphan isolates (16.4%, n = 12) constituted about 50% of the isolates studied and were subjected to whole-genome sequencing (WGS) analysis. Most SIT53 (10/12) isolates belonged to the Euro-American sub-lineage 4.8. Most SIT42 isolates (4/7) as .well as most orphan isolates (5/8) belonged to the lineage 4.3.3 LAM group. By comparing the single-nucleotide polymorphism (SNP) patterns of the SIT53 isolates, we found one clone (<7 SNPs) and four clustered isolates (<15 SNPs). In isolates from the SIT42 and orphan groups, we did not find any clones or clusters. This work demonstrates the success of sub-lineage 4.8 to predominate in Mexico and confirms the dominion of sub-lineage 4.3.3 in Central and South America.

Genomic analysis of virulence factors and antimicrobial resistance of group B Streptococcus isolated from pregnant women in northeastern Mexico

Introduction

Group B Streptococcus (GBS) causes infections in women during pregnancy and puerperium and invasive infections in newborns. The genes lmb, cylE, scpB, and hvgA are involved with increased virulence of GBS, and hypervirulent clones have been identified in different regions. In addition, increasing resistance of GBS to macrolides and lincosamides has been reported, so knowing the patterns of antibiotic resistance may be necessary to prevent and treat GBS infections. This study aimed to identify virulence genes and antibiotic resistance associated with GBS colonization in pregnant women from northeastern Mexico.

Methods

Pregnant women with 35–37 weeks of gestation underwent recto-vaginal swabbing. One swab was inoculated into Todd-Hewitt broth supplemented with gentamicin and nalidixic acid, a second swab was inoculated into LIM enrichment broth, and a third swab was submerged into a transport medium. All samples were subcultured onto blood agar. After overnight incubation, suggestive colonies with or without hemolysis were analyzed to confirm GBS identification by Gram staining, catalase test, hippurate hydrolysis, CAMP test, and incubation in a chromogenic medium. We used latex agglutination to confirm and serotype GBS isolates. Antibiotic resistance patterns were assessed by Vitek 2 and disk diffusion. Periumbilical, rectal and nasopharyngeal swabs were collected from some newborns of colonized mothers. All colonized women and their newborns were followed up for three months to assess the development of disease attributable to GBS. Draft genomes of all GBS isolates were obtained by whole-genome sequencing. In addition, bioinformatic analysis to identify genes encoding capsular polysaccharides and virulence factors was performed using BRIG, while antibiotic resistance genes were identified using the CARD database.

Results

We found 17 GBS colonized women out of 1154 pregnant women (1.47%). None of the six newborns sampled were colonized, and no complications due to GBS were detected in pregnant women or newborns. Three isolates were serotype I, 5 serotype II, 3 serotype III, 4 serotype IV, and 2 serotype V. Ten distinct virulence gene profiles were identified, being scpB, lmb, fbsA, acp, PI-1, PI-2a, cylE the most common (3/14, 21%). The virulence genes identified were scpB, lmb, cylE, PI-1, fbsA, PI-2a, acp, fbsB, PI-2b, and hvgA. We identified resistance to tetracycline in 65% (11/17) of the isolates, intermediate susceptibility to clindamycin in 41% (7/17), and reduced susceptibility to ampicillin in 23.5% (4/17). The tetM gene associated to tetracyclines resistance was found in 79% (11/14) and the mel and mefA genes associated to macrolides resistance in 7% (1/14).

Conclusions

The low prevalence of colonization and the non-occurrence of mother-to-child transmission suggest that the intentional search for GBS colonization in this population is not justified. Our results also suggest that risk factors should guide the use of intrapartum antibiotic prophylaxis. The detection of strains with genes coding virulence factors means that clones with pathogenic potential circulates in this region. On the other hand, the identification of decreased susceptibility to antibiotics from different antimicrobial categories shows the importance of adequately knowing the resistance patterns to prevent and to treat GBS perinatal infection.

Two New Dihydrosphingosine Analogs Against Mycobacterium tuberculosis Affect gltA1, lprQ, and rpsO Expression

The emergence of multidrug-resistant (MDR) Mycobacterium tuberculosis strains threaten the control of tuberculosis. New antitubercular dihydrosphingosine analogs, named UCIs, have been evaluated in preclinical studies but their cellular and molecular mechanisms of action against M. tuberculosis are still unknown. The aim of this study was to evaluate the effect of UCI exposure on gene expression of drug-sensitive H37Rv and MDR CIBIN:UMF:15:99 clones of M. tuberculosis which were isolated, phenotypically, and genetically characterized, cultured to log phase and treated with UCI compounds; followed by total RNA isolation, reverse transcription and hybridization assays on Affymetrix genomic microarrays. Data were validated with RT-qPCR assays. As results, UCI-05 and UCI-14 exposure increased gltA1 expression in drug-sensitive H37Rv clones. Furthermore, UCI-05 increased lprQ expression in MDR CIBIN:UMF:15:99 M. tuberculosis clones while UCI-14 reduced the expression of this gene in drug-sensitive H37Rv clones. In addition, UCI-05 reduced rpsO expression in drug-sensitive H37Rv clones. We found gene expression alterations that suggest these molecules may alter carbon and lipid metabolism as well as interfere in the protein-producing machinery in M. tuberculosis.

D-Lactate and intestinal fatty acid-binding protein are elevated in serum in patients with acute ischemic stroke

Experimental studies suggest that the intestinal barrier is affected in ischemic stroke. D-Lactate and intestinal fatty acid-binding protein (IFABP) are markers of intestinal mucosa integrity and barrier function. Our purpose was to evaluate the serum concentrations of these markers in patients with acute ischemic stroke (AIS). We included patients with AIS and used healthy subjects as controls. Clinical, demographic and outcome measures were recorded. Blood was drawn within 24 h of symptom onset. Serum concentrations of D-Lactate and IFABP were determined using commercially available colorimetric and ELISA kits, respectively. We included a total of 61 patients (median age of 64 years). The majority of patients were male (57.4%). The most common cause of stroke was atherosclerosis (34.4%), followed by small-vessel disease and cardioembolic (32.7% each). Mean admission NIHSS score was 8. Median IFABP and D-Lactate concentrations were significantly higher in patients than in controls. Concentrations were not associated with stroke severity or 3-month outcome. Patients with large-artery atherosclerosis and cardioembolic etiology had higher D-Lactate values than patients with small-vessel disease. D-Lactate and IFABP were significantly elevated in patients with AIS. This suggests that there is disruption of the intestinal barrier in patients with AIS.

Ex vivo infection of murine precision-cut lung tissue slices with Mycobacterium abscessus: a model to study antimycobacterial agents

Background

Multidrug-resistant infections due to Mycobacterium abscessus often require complex and prolonged regimens for treatment. Here, we report the evaluation of a new ex vivo antimicrobial susceptibility testing model using organotypic cultures of murine precision-cut lung slices, an experimental model in which metabolic activity, and all the usual cell types of the organ are found while the tissue architecture and the interactions between the different cells are maintained.

Methods

Precision cut lung slices (PCLS) were prepared from the lungs of wild type BALB/c mice using the Krumdieck^® tissue slicer. Lung tissue slices were ex vivo infected with the virulent M. abscessus strain L948. Then, we tested the antimicrobial activity of two drugs: imipenem (4, 16 and 64 μg/mL) and tigecycline (0.25, 1 and 4 μg/mL), at 12, 24 and 48 h. Afterwards, CFUs were determined plating on blood agar to measure the surviving intracellular bacteria. The viability of PCLS was assessed by Alamar Blue assay and corroborated using histopathological analysis.

Results

PCLS were successfully infected with a virulent strain of M. abscessus as demonstrated by CFUs and detailed histopathological analysis. The time-course infection, including tissue damage, parallels in vivo findings reported in genetically modified murine models for M. abscessus infection. Tigecycline showed a bactericidal effect at 48 h that achieved a reduction of > 4log₁₀ CFU/mL against the intracellular mycobacteria, while imipenem showed a bacteriostatic effect.

Conclusions

The use of this new organotypic ex vivo model provides the opportunity to test new drugs against M. abscessus, decreasing the use of costly and tedious animal models.

Evaluation of the intracellular activity of drugs against Mycobacterium abscessus using a THP-1 macrophage model

We evaluated the antimicrobial effectiveness against M. abscessus in a THP-1 cell line model. No intracellular activity was observed when using amikacin or imipenem. A bacteriostatic effect was observed for cefoxitin, clarithromycin and azithromycin. Tigecycline showed the best antibacterial effect by decreasing the intracellular growth up to bactericidal level.

Mycobacterium tuberculosis promotes genomic instability in macrophages

BACKGROUND

Mycobacterium tuberculosis is an intracellular pathogen, which may either block cellular defensive mechanisms and survive inside the host cell or induce cell death. Several studies are still exploring the mechanisms involved in these processes.

OBJECTIVES

To evaluate the genomic instability of M. tuberculosis-infected macrophages and compare it with that of uninfected macrophages.

METHODS

We analysed the possible variations in the genomic instability of Mycobacterium-infected macrophages using the DNA breakage detection fluorescence in situ hybridisation (DBD-FISH) technique with a whole human genome DNA probe.

FINDINGS

Quantitative image analyses showed a significant increase in DNA damage in infected macrophages as compared with uninfected cells. DNA breaks were localised in nuclear membrane blebs, as confirmed with DNA fragmentation assay. Furthermore, a significant increase in micronuclei and nuclear abnormalities were observed in infected macrophages versus uninfected cells.

MAIN CONCLUSIONS

Genomic instability occurs during mycobacterial infection and these data may be seminal for future research on host cell DNA damage in M. tuberculosis infection.

Modeling tuberculosis pathogenesis through ex vivo lung tissue infection

Tuberculosis (TB) is one of the top 10 causes of death worldwide. Several in vitro and in vivo experimental models have been used to study TB pathogenesis and induction of immune response during Mycobacterium tuberculosis infection. Precision cut lung tissue slices (PCLTS) is an experimental model, in which all the usual cell types of the organ are found, the tissue architecture and the interactions amongst the different cells are maintained. PCLTS in good physiological conditions, monitored by MTT assay and histology, were infected with either virulent Mycobacterium tuberculosis strain H37Rv or the TB vaccine strain Mycobacterium bovis BCG. Histological analysis showed that bacilli infecting lung tissue slices were observed in the alveolar septa, alveolar light spaces, near to type II pneumocytes, and inside macrophages. Mycobacterial infection of PCLTS induced TNF-α production, which is consistent with previous M. tuberculosis in vitro and in vivo studies. This is the first report of using PCLTS as a system to study M. tuberculosis infection. The PCLTS model provides a useful tool to evaluate the innate immune responses and other aspects during the early stages of mycobacterial infection.

Detection of anti-HspX antibodies and HspX protein in patient sera for the identification of recent latent infection by Mycobacterium tuberculosis

Mycobacterium tuberculosis is a pathogen causing tuberculosis (TB) a spectrum of disease including acute and asymptomatic latent stages. Identifying and treating latently-infected patients constitutes one of the most important impediments to TB control efforts. Those individuals can remain undiagnosed for decades serving as potential reservoirs for disease reactivation. Tests for the accurate diagnosis of latent infection currently are unavailable. HspX protein (α-crystallin), encoded by Rv2031c gene, is produced in vitro by M. tuberculosis during stationary growth phase and hypoxic or acidic culture conditions. In this study, using standard, and Luminex xMAP® bead capture ELISA, respectively, we report on detection of anti-HspX IgG and IgM antibodies and HspX protein in sera from acute and latent TB patients. For the antibody screen, levels of IgG and IgM antibodies were similar between non-infected and active TB patients; however, individuals classified into the group with latent TB showed higher values of anti-HspX IgM (p = 0.003) compared to active TB patients. Using the bead capture antigen detection assay, HspX protein was detected in sera from 56.5% of putative latent cases (p< 0.050) compared to the background median with an average of 9,900 pg/ml and a range of 1,000 to 36,000 pg/ml. Thus, presence of anti-HspX IgM antibodies and HspX protein in sera may be markers of latent TB.

Abstract TP219: D-lactate and Intestinal Fatty-acid Binding Protein Are Elevated in Serum in Patients with Acute Ischemic Stroke

Introduction: Ischemic stroke is associated with gastrointestinal complications such as constipation, dysphagia and fecal incontinence. However, the precise mechanisms involved have not been fully elucidated. D-Lactate and Intestinal Fatty-Acid Binding Protein (IFABP) are markers of intestinal mucosa integrity and barrier function. We evaluated serum concentrations of these markers in patients with acute ischemic stroke.

Materials and methods: We included consecutive patients with ischemic stroke, and used healthy, age and sex-matched subjects as controls. We excluded cases determined to be of other or undetermined etiology according to the TOAST classification. Blood was drawn within 24 hours of symptom onset. Serum concentrations of D-Lactate and IFABP were determined using commercially available colorimetric and ELISA kits, respectively.

Results: We included a total of 61 patients and 20 controls. The majority of patients were male (57.4%), and had a median age of 64 years. The most common cause of stroke was large-vessel atherosclerosis (34.4%), followed by small-vessel occlusion and cardioembolism (32.7% each). Mean admission NIHSS score was 8. IFABP and D-Lactate concentrations were significantly higher in patients than in controls (0.57±1 ng/ml vs. 1.84±2.7 ng/ml, p=0.04 and 0 nmol/μl vs. 0.38±0.66 nmol/μl, p=0.01, respectively). Concentrations were not associated with stroke severity or outcome. Patients with large-artery atherosclerosis and cardiombolic etiology had significantly higher D-Lactate values than patients with small-vessel disease.

Conclusions: D-Lactate and IFABP were significantly elevated in patients with ischemic stroke. This provides, to our knowledge, for the first time in humans, evidence of intestinal barrier disruption. A stroke-associated systemic stress response could be responsible, but the lack of an association with stroke severity does not support this hypothesis. Embolic or atherosclerotic involvement of the mesenteric vasculature is another possibility. Further studies should aim at looking for a plausible mechanism as well as a possible association between intestinal barrier dysfunction and post-stroke gastrointestinal and infectious complications.

Rv3351c, a Mycobacterium tuberculosis gene that affects bacterial growth and alveolar epithelial cell viability

Despite the interactions known to occur between various lower respiratory tract pathogens and alveolar epithelial cells (AECs), few reports examine factors influencing the interplay between Mycobacterium tuberculosis bacilli and AECs during infection. Importantly, in vitro studies have demonstrated that the M. tuberculosis hbha and esxA gene products HBHA and ESAT6 directly or indirectly influence AEC survival. In this report, we identify Rv3351c as another M. tuberculosis gene that impacts the fate of both the pathogen and AEC host. Intracellular replication of an Rv3351c mutant in the human AEC type II pneumocyte cell line A549 was markedly reduced relative to the complemented mutant and parent strain. Deletion of Rv3351c diminished the release of lactate dehydrogenase and decreased uptake of trypan blue vital stain by host cells infected with M. tuberculosis bacilli, suggesting attenuated cytotoxic effects. Interestingly, an isogenic hbha mutant displayed reductions in AEC killing similar to those observed for the Rv3351c mutant. This opens the possibility that multiple M. tuberculosis gene products interact with AECs. We also observed that Rv3351c aids intracellular replication and survival of M. tuberculosis in macrophages. This places Rv3351c in the same standing as HBHA and ESAT6, which are important factors in AECs and macrophages. Defining the mechanism(s) by which Rv3351c functions to aid pathogen survival within the host may lead to new drug or vaccine targets.

Intracellular activity of tedizolid phosphate and ACH-702 versus Mycobacterium tuberculosis infected macrophages

Background

Due to the emergency of multidrug-resistant strains of Mycobacterium tuberculosis, is necessary the evaluation of new compounds.

Findings

Tedizolid, a novel oxazolidinone, and ACH-702, a new isothiazoloquinolone, were tested against M. tuberculosis infected THP-1 macrophages. These two compounds significantly decreased the number of intracellular mycobacteria at 0.25X, 1X, 4X and 16X the MIC value. The drugs were tested either in nanoparticules or in free solution.

Conclusion

Tedizolid and ACH-702 have a good intracellular killing activity comparable to that of rifampin or moxifloxacin.

Dual mechanism for Mycobacterium tuberculosis cytotoxicity on lung epithelial cells

Mycobacterium tuberculosis strains CDC1551 and Erdman were used to assess cytotoxicity in infected A549 human alveolar epithelial cell monolayers. Strain CDC1551 was found to induce qualitatively greater disruption of A549 monolayers than was strain Erdman, although total intracellular and cell-associated bacterial growth rates over the course of the infections were not significantly different. Cell-free culture supernatants from human monocytic cells infected with either of the 2 M. tuberculosis strains produced a cytotoxic effect on A549 cells, correlating with the amount of tumor necrosis factor alpha (TNF-α) released by the infected monocytes. The addition of TNF-α-neutralizing antibodies to the supernatants from infected monocyte cultures did prevent the induction of a cytotoxic effect on A549 cells overlaid with this mixture but did not prevent the death of epithelial cells when added prior to infection with M. tuberculosis bacilli. Thus, these data agree with previous observations that lung epithelial cells infected with M. tuberculosis bacilli are rapidly killed in vitro. In addition, the data indicate that some of the observed epithelial cell killing may be collateral damage; the result of TNF-α released from M. tuberculosis-infected monocytes.

Antiproliferative effect from the Mexican poleo (Hedeoma drummondii)

Hedeoma drummondii (poleo) has been used by Mexicans to prepare a tea for its pleasant taste. The methanolic extract, polar fractions, and major antioxidant compounds of the Mexican herbal tea obtained from aerial parts of H. drummondii ("poleo") showed antiproliferative effects against the cancer cell lines MCF-7 (human breast) and HeLa (human cervix). Phenolic acids isolated from poleo have significant antiproliferative effects with caffeic acid the most potent. This evidence suggests that herbal poleo tea may have chemopreventive properties.

Effect of serial subculturing on the genetic composition and cytotoxic activity of Mycobacterium tuberculosis

Continuous subculture has been observed to produce changes in the virulence of micro-organisms, e.g. rabies virus, poliovirus and Mycobacterium bovis BCG. The latter has been used as a vaccine for tuberculosis for the last 100 years; however, in some instances its efficacy has been observed to be very low. In order to determine whether similar changes can be produced in Mycobacterium tuberculosis, we selected four isolates, M. tuberculosis H37Rv, a Beijing strain (DR-689), and two more isolates with deletion of the phospholipase C locus (plcA-plcB-plcC ), and subjected them to serial culturing on Middlebrook 7H9 medium, with or without ox bile. After 100 passages, we performed RFLP-IS6110 analysis to determine whether genomic changes were produced. We also checked their genomic composition by microarray analysis. Changes in virulence were studied by measuring the cytotoxic effect of parental and subcultured isolates on a THP-1 macrophage monolayer. The most visible change was the change of position of an IS6110 band of approximately 1400 bp to approximately 1600 bp in the Beijing isolate subcultured in the ox bile medium. Analysis by microarray and PCR confirmation did not reveal any genomic changes. Cytotoxic activity was decreased in the isolates at levels close to that of BCG, and more consistently in those subcultured in the presence of ox bile.

Activity of novel oxazolidinones against Nocardia brasiliensis growing within THP-1 macrophages

BACKGROUND

Nocardia are organisms that can escape the effects of both immune response and antimicrobial agents, due to their potential capacity to grow intracellularly. In previous studies, we found that experimental oxazolidinones, DA-7157 and DA-7218, are active both in vitro and in vivo.

OBJECTIVES

In this study, we compare the ability of linezolid, DA-7157 and DA-7218 to inhibit intracellular growth of Nocardia brasiliensis within the human monocyte cell line THP-1.

METHODS AND RESULTS

The addition of oxazolidinones to the infected macrophage monolayer at concentrations 0.25x, 1x, 4x and 16x the MIC for N. brasiliensis resulted in an inhibitory effect on bacterial growth as follows DA-7157 > or = DA-7218 > linezolid.

CONCLUSIONS

The excellent intracellular antimicrobial activity detected suggests that these compounds could be effective in the treatment of actinomycetoma. However, more studies are needed both in vitro and in vivo, including clinical trials, to confirm this issue.

Use of a colorimetric assay to measure differences in cytotoxicity of Mycobacterium tuberculosis strains

Several techniques have been used to quantify the cytotoxicity produced by Mycobacterium tuberculosis bacilli on cell monolayers; however, they are semi-quantitative or time consuming. Herein, a method based on crystal violet (CV) uptake by THP-1 cell monolayers is described. This colorimetric method quantifies the cytotoxic effect as a function of the number of remaining cells after the infection with M. tuberculosis. Since this micro-organism is not stained by the dye, it does not produce a background that affects absorbance readings. As determined by CV assay (CVA), M. tuberculosis strain H37Rv destroyed 10.5 % of THP-1 cell monolayers at 24 h and 50.52 % at 72 h, while M. tuberculosis strains lacking the complete phospholipase C locus produced a reduced cytotoxic effect. The damage estimated by microscopy corresponded to the effect quantified by CVA. The results show that the use of CVA is a rapid, sensitive and reliable quantitative assay to measure the cytotoxicity of different M. tuberculosis strains.

Genetic characterization of Mycobacterium tuberculosis clinical isolates with deletions in the plcA–plcB–plcC locus

SETTING

The basis for Mycobacterium tuberculosis virulence is not completely understood. Analysis of the genomic structure of clinical isolates will give information that can be related to biological activities involved in virulence.

OBJECTIVE

To determine the extension of the deletion in the plcA-plcB-plcC locus of selected M. tuberculosis isolates, as well as other changes in the chromosome.

DESIGN

In the present work we characterized a group of M. tuberculosis isolates devoid of the plcA-plcB-plcC locus by PCR, sequencing and microarrays.

RESULTS

PCR amplification of this region demonstrated a complete lack of plcA and plcB ORF's in all of the isolates. The plcC gene was completely deleted in one of the strains (DR-689) and the other three isolates still conserved part of this ORF. The loss of lateral DNA sequences ranged from 3723 to 7646bp. An IS6110 element was present in all tested strains cases, and some isolates presented the insertion of ORF's coding for proteins homologous to the ESAT-6 and QILSS families. Genomic DNA of all the strains was extracted and analyzed with an in-house microarray system to observe loss of other genes possibly implicated in attenuated virulence. Two of the strains presented novel deletions; the rest of the isolates showed deletions already reported for other M. tuberculosis strains. DR-689, a Beijing type M. tuberculosis strain isolated in Canada, showed an IS6110 RFLP and a genomic deletion pattern similar to a San Francisco family of strains, although completely unrelated epidemiologically.

CONCLUSION

Genomic changes in M. tuberculosis seem to occur in a controlled manner and they are possibly related to changes in its pathogenic properties.

Macrophage-activation inhibitor factor from L5178Y murine lymphoma and formation of hepatic abscesses in BALB/c mice

BACKGROUND

Normal mice are naturally resistant to hepatic abscesses produced by Listeria monocytogenes. A macrophage-activation inhibitor factor (MAIF) isolated from the cell-free ascitic fluid of L5178Y lymphoma-bearing mice inhibited the lipopolysaccharide-induced production of nitric oxide (NO) by the macrophages. Because macrophages are also involved in the immune response towards L. monocytogenes, the present study had the objective of investigating whether MAIF was also capable of allowing L. monocytogenes to form hepatic abscesses.

METHODS

BALC/c mice were inoculated intrahepatically with 5 x 10(5) bacteria. Experimental groups were treated daily with subcutaneous or intraperitoneal doses of 0, 1, 5 or 10 microg of MAIF/g of body weight. One dose was applied before inoculating bacteria and the remaining three doses 24, 48, and 72 h after inoculating bacteria. The development of hepatic abscess was analyzed 24 h after the last administration of MAIF.

RESULTS

All treated mice (but not controls) developed hepatic abscess showing no differences regarding MAIF administration route.

CONCLUSIONS

These results suggest a possible MAIF in vivo inhibition of NO macrophage production that allows L. monocytogenes hepatic abscess development in mice.

In vitro susceptibility of Mycobacterium tuberculosis clinical isolates to garenoxacin and DA-7867

The in vitro activities of DA-7867, a novel oxazolidinone, and garenoxacin (BMS-284756) were compared to those of linezolid in 67 susceptible and drug-resistant clinical isolates of Mycobacterium tuberculosis. DA-7867 was the most active drug with an MIC(90) of 0.125 microg/ml, compared to the MIC(90)s of 4 microg/ml of garenoxacin and 2 microg/ml of linezolid.

Identification of acidic, alkaline, and neutral sphingomyelinase activities in Mycobacterium tuberculosis

BACKGROUND

Sphingomyelinase enzymes are pathogenic factors of several intracellular bacteria species, which have been little studied in Mycobacterium tuberculosis.

MATERIAL/METHODS

Cell free extracts from H37Rv and CDC-1551 M. tuberculosis strains were assayed for sphingomyelinase activity by using [N-methyl-14C]-sphingomyelin as substrate. Double-directional thin-layer chromatography was used to separate the substrate and hydrolysis product. Sphingomyelinase activity was analyzed as a function of incubation time, dose, pH and the presence of MgCl2, CaCl2, ZnSO4, HgCl2, MnCl2, CoCl2 and EDTA (1 or 10 mM).

RESULTS

Mycobacterial preparations hydrolyzed [14C]-sphingomyelin, in time- and dose-dependent manners, producing [14C]-phosphorylcholine as a unique product. The activity of H37Rv neutral sphingomyelinase at pH 7.5 was 2.15 times higher than that of CDC-1551. This activity was inhibited 21-82% by Ca2+, Hg2+ or Zn2+ and EDTA, and stimulated 40-117% by Mn2+ and Mg2+. In addition, preparations from both strains showed two peaks of sphingomyelinase, one at pH 5.5 and the other at pH 3.0. However, these activities were 4-22 times lower than that observed at pH 7.5 for strain H37Rv. Preparations from H37Rv, but not those of CDC-1551, hydrolyzed sphingomyelin at pH 8-9, with a specific activity similar to that of the neutral CDC-1551 enzyme.

CONCLUSIONS

Both strains H37Rv and CDC-1551 of M. tuberculosis have cation-dependent acidic and neutral sphingomyelinase-C enzymes, showing the neutral as the major activity. In addition, H37Rv has an alkaline sphingomyelinase-C. The importance of SMases in M. tuberculosis pathogenesis remains to be elucidated.

Synthesis and in vitro antiprotozoal activity of 5-nitrothiophene-2-carboxaldehyde thiosemicarbazone derivatives

Several thiosemicarbazone derivatives of 5-nitrothiophene-2-carboxaldehyde were prepared by the simple process in which N(4)-thiosemicarbazone moiety was replaced by aliphatic, arylic and cyclic amine. Among these thiosemicarbazones compound 11 showed significant antiamoebic activity whereas compound 3 was more active antitrichomonal than the reference drug.

Demonstration of spread by Mycobacterium tuberculosis bacilli in A549 epithelial cell monolayers

We developed an in vitro tissue-culture model to analyze the process involved in mycobacterial spread through lung epithelial cell monolayers. A549 cells were infected with low numbers of viable Mycobacterium tuberculosis bacilli expressing the gfp gene. Subsequent addition of a soft agarose overlay prevented the dispersal of the bacilli from the initial points of attachment. By fluorescence microscopy the bacteria were observed to infect and grow within the primary target cells; this was followed by lysis of the infected cells and subsequent infection of adjacent cells. This process repeated itself until an area of clearing (plaque formation) was observed. The addition of amikacin after initial infection did not prevent intracellular growth; however, subsequent plaque formation was not observed. Plaque formation was also observed after infection with Mycobacterium bovis BCG bacilli, but the plaques were smaller than those formed after infection with M. tuberculosis. These observations reinforce the possibility that cell-to-cell spreading of M. tuberculosis bacilli, particularly early in the course of infection within lung macrophages, pneumocytes, and other cells, may be an important component in the infectious process.

Synthesis, characterization and antiamoebic activity of benzimidazole derivatives and their vanadium and molybdenum complexes

Reaction of [MoO(2)(acac)(2)] (where, acac=acetyl acetone) and KVO(3) with 2-(salicylidieneimine) benzimidazole lead to form new complexes [MoO(2)(sal-BMZ)(2)] and K [VO(2)(sal-BMZ)(2)] [where, sal-BMZ=2-(salicylidieneimine) benzimidazole], which showed the monobasic bidentate nature of the ligand in which the phenolic oxygen and the imine nitrogen of the ligand are coordinated to the metal ion. These complexes were characterized along with nine other complexes of oxoperoxovanadium (V), molybdenum (Vl) and tungsten (Vl) with benzimidazole derivatives and screened in vitro by micro dilution technique for their amoebicidal activity with a view to search for a more effective agent against Entamoeba histolytica suggests that compound 2 and 3 might be endowed with important antiamoebic properties since they showed IC(50 )values in a microM range.

Phospholipase region of Mycobacterium tuberculosis is a preferential locus for IS6110 transposition

Enzymes with phospholipase C activity in Mycobacterium tuberculosis have been recently described. The three genes encoding these proteins, plcA, plcB, and plcC, are located at position 2351 of the genomic map of M. tuberculosis H37Rv and are arranged in tandem. We have previously described the presence of variations in the restriction fragment length polymorphism patterns of the plcA and plcB genes in M. tuberculosis clinical isolates. In the present work we investigated the origin of this polymorphism by sequence analysis of the phospholipase-encoding regions of 11 polymorphic M. tuberculosis clinical isolates. To do so, a long-PCR assay was used to amplify a 5,131-bp fragment that contains the plcA and plcB genes and part of the plcC gene. In the M. tuberculosis strains studied the production of an amplicon approximately 1,400 bp larger than anticipated was observed. Sequence analysis of the PCR products indicated the presence of a foreign sequence that corresponded to an IS6110 element. We observed insertion elements in the plcA, plcB, and plcC genes. One site in plcB had the highest incidence of transposition (5 out of 11 strains). In two strains the insertion element was found in plcA in the same nucleotide position. In all the cases, IS6110 was transposed in the same direction. The high level of transposition in the phospholipase region can lead to the excision of fragments of genomic DNA by recombination of neighboring IS6110 elements, as demonstrated by finding the deletion, in two strains, of a 2,837-bp fragment that included plcA and most of plcB. This can explain the negative results obtained by some authors when detecting the mtp40 sequence (plcA) by PCR. Given the high polymorphism in this region, the use of the mtp40 sequence as a genetic marker for M. tuberculosis sensu stricto is very restricted.

Auxotrophy to lipoproteins of Entamoeba histolytica cultivated under axenic conditions

Entamoeba histolytica grows in media without serum but with a mixture of aminoacids, vitamins, lipoproteins, free cholesterol, phospholipids and fatty acids called PACSR. The ability of lipoproteins and free lipids to support growth of three E. histolytica strains (HK9, HMI:IMSS and HM3:IMSS) was analysed. Tubes containing 5 ml culture medium, amino acids, vitamins and either 120-1,200 microg lipoproteins/ml or 0.017-0.10 mg free lipids/ml (predissolved in absolute ethanol) were inoculated with 1x10(4) trophozoites/ml and incubated at 37 degrees C for 72 h. Amoebae died within 12 h in the presence of any free lipid combination, while those having 240-480 mg lipoproteins/ml reached densities similar to or higher than those of controls (depending on strain). The addition of ethanol (0.1%) to the media produced stable lipid solutions and did not show significant adverse effects. Accordingly, E. histolytica is auxotrophic to lipoproteins and unable to use free cholesterol, phospholipids or fatty acids.

Identification of Entamoeba histolytica intracellular phospholipase A and lysophospholipase L1 activities

Entamoeba histolytica phospholipase A and lysophospholipase activities from a vesicular subcellular fraction (P30) were analyzed. The products, obtained using specific substrates labeled with 14C or 3H, indicated the presence of phospholipase A1 and A2 as well as lysophospholipase L1 activities. The enzymes detected could participate in phospholipid metabolism and the alkaline phospholipase A2 may contribute to E. histolytica cytopathogenicity.

PEHPS medium: an alternative for axenic cultivation of Entamoeba histolytica and E. invadens

Knowledge of Entamoeba histolytica biology in the last 17 years has been acquired largely as a consequence of this parasite's axenic cultivation in TPS-1 or TYI-S-33 media. Unfortunately, there are often low yields in these media, due to variability of their main components, Panmede and yeast extract. We describe a medium, PEHPS, of which the main components are extracts of ox liver, and ox and swine pancreas (EHP). 5 strains of E. histolytica and 2 of E. invadens were quickly and easily adapted to PEHPS and serially cultivated for 3 years. Yields progressively rose initially, and then became stable. Depending on the strain, average yields in the last 6 months of this study were 1.3 to 3.1 x 10(5) amoebae/ml for E. histolytica and 5.5 to 5.7 x 10(5) for E. invadens. All the 18 EHP batches tested supported vigorous amoebal growth. PEHPS had 2 additional advantages: (a) it was stable at 4 degrees C or 25 degrees C for 9 months, and at -10 degrees C for at least 2 years, and (b) it supported amoebal growth with inocula as low as one trophozoite/ml. PEHPS avoids the variability shown by TPS-1 and TYI-S-33, and could therefore be a good alternative for axenic amoebal cultivation.