Assessment of seasonal relationship between polycyclic aromatic hydrocarbon accumulation and expression patterns of oxidative stress-related genes in muscle tissues of red mullet (M. barbatus) from the Northern Adriatic Sea.

In this study, we examined the seasonal association between Polycyclic Aromatic Hydrocarbon (PAH) concentrations and mRNA expression profiles of some antioxidant genes (i.e. CAT, GST and SOD), as well as lipid peroxidation (LPO), in muscle of sexually inactive females of red mullet (Mullus barbatus). Fish were captured in a fishery area of the Northern Adriatic Sea during both winter and summer. We found significantly (p < 0.05) higher ∑HMW-PAHs concentrations in muscle of specimens caught during winter than summer. On the basis of sampling season, red mullets exhibited different gene expression profiles of antioxidant enzymes showing lower levels of both CAT and GST in winter than in summer. Accordingly, CAT was found to be negatively associated with ∑PAH concentrations, especially ∑LMW-PAH, in individuals collected during winter. Seasonal-related downregulation of some oxidative stress biomarker expression is suggestive of greater susceptibility of red mullets to PAHs during winter.

Elucidation of drug resistance mutations in Mycobacterium tuberculosis isolates from North India by whole-genome sequencing.

OBJECTIVES: Rapid diagnosis of drug-resistant tuberculosis (TB) is required for better patient management and treatment outcomes. Whole-genome sequencing (WGS) can be used to detect single nucleotide polymorphisms (SNPs) and deletions/insertions that are responsible for mostMycobacterium tuberculosis drug resistance. WGS is being performed at scale in high-income countries, but there are limited reports of its use in India. METHODS: In this study, 33 clinicalM. tuberculosis isolates from the Mycobacterial Repository in Chandigarh underwent WGS. Phenotypic drug susceptibility testing was performed according to World Health Organization (WHO) recommendations. Four isolates were excluded from the analysis due to culture contamination or mislabelling during the study. RESULTS: Among the remaining 29 isolates, 21 (72.4%) were multidrug-resistant TB (MDR-TB) and 1 (3.4%) was extensively-drug resistant TB (XDR-TB). The most common mutations observed for isoniazid, rifampicin, ofloxacin and kanamycin resistance werekatG(S315T), rpoB(S450L), gyrA(A90V) and rrs(A1401G), respectively. The isolates mainly belonged to lineages 2 and 3, with most MDR-TB among lineage 2 isolates. CONCLUSION: WGS ofM. tuberculosis isolates allows the detection of drug resistance to all drugs in a single test and also provides insight into the evolution and drug-resistant TB.

Multicenter evaluation of TB-SPRINT 59-Plex Beamedex®: accuracy and cost analysis.

BACKGROUND: Molecular tests can allow the rapid detection of tuberculosis (TB) and multidrug-resistant TB (MDR-TB). TB-SPRINT 59-Plex Beamedex® is a microbead-based assay developed for the simultaneous spoligotyping and detection of MDR-TB. The accuracy and cost evaluation of new assays and technologies are of great importance for their routine use in clinics and in research laboratories. The aim of this study was to evaluate the performance of TB-SPRINT at three laboratory research centers in Brazil and calculate its mean cost (MC) and activity-based costing (ABC). METHODS: TB-SPRINT data were compared with the phenotypic and genotypic profiles obtained using Bactec™ MGIT™ 960 system and Genotype® MTBDRplus, respectively. RESULTS: Compared with MGIT, the accuracies of TB-SPRINT for the detection of rifampicin and isoniazid resistance ranged from 81 to 92% and 91.3 to 93.9%, respectively. Compared with MTBDRplus, the accuracies of TB-SPRINT for rifampicin and isoniazid were 99 and 94.2%, respectively. Moreover, the MC and ABC of TB-SPRINT were USD 127.78 and USD 109.94, respectively. CONCLUSION: TB-SPRINT showed good results for isoniazid and rifampicin resistance detection, but still needs improvement to achieve In Vitro Diagnostics standards.

Assessment of hematological, hepato-renal, antioxidant, and hormonal responses of Clarias gariepinus exposed to sub-lethal concentrations of oxyfluorfen.

Little is known about the effects of oxyfluorfen, a diphenyl ether herbicide, exposure on the African catfish (Clarias gariepinus) health. Consequently, the existing investigation was designed to highlight the impacts of oxyfluorfen exposure on C. gariepinus hematological indices, liver and kidney functions, reproductive hormones, and oxidative status. Furthermore, a consequent 10-day depuration period was adopted to evaluate the recovery of the disturbed indicators to normal values. In the first experiment, the 96-h lethal concentration 50 (LC50) of oxyfluorfen for C. gariepinus was determined using probit analysis. Next, in a second experiment, 180 healthy fish (average initial body weight: 164.23 ±â€¯0.24) were randomly assigned to 4 experimental groups exposed to 0, 1/10, 1/8, or 1/5 96-h LC50 of oxyfluorfen. The hematological profile, hepatic enzymes, kidney damage byproducts, reproductive hormones, oxidative stress, and lipid peroxidation indicators together with acetylcholinesterase (AChE) content were assessed. A histopathological examination of the hepatic, renal, brain, and testicular tissues was accomplished. Moreover, the expression of the oxidative stress-related gene was carried out. The results showed that 96-h LC50 of oxyfluorfen for C. gariepinus was 11.698 mg/L. Exposure to sublethal levels of oxyfluorfen induced macrocytic hypochromic anemia, leukopenia, lymphopenia, monocytopenia, and eosinopenia. Also, a concentration-dependent increase in alanine transaminase, alkaline phosphatase, aspartate transaminase, urea, creatinine, catalase, and malondialdehyde was detected following oxyfluorfen exposure together with upregulation of catalase gene. But, significant concentration-dependent reductions in AChE, glutathione transferase, reduced to oxidized glutathione ratio, estradiol, and testosterone activities were recorded. These biochemical alterations were accompanied by pathological perturbations in hepatic, renal, brain, and testicular tissues. Following 10 days of recovery, only the hematological impairments were abolished. Conclusively, the herbicides oxyfluorfen could induce multiple negative impacts on C. gariepinus with oxidative stress as a probable underlying mechanism. Additionally, a recovery period of 10 days was not enough to restore these impairments.

A sub-individual multilevel approach for an integrative assessment of CuO nanoparticle effects on Corbicula fluminea.

Because they are widely used, copper oxide nanoparticles (CuO NPs) are likely to enter the aquatic environment and then reach the sediment. We have examined the effect of CuO NPs in the freshwater endobenthic bivalve Corbicula fluminea. Some previous studies have investigated effects at biochemical and physiological levels, but molecular endpoints are still poorly studied despite they are sensitive in early detection of NPs effect. In the present study, we have investigated short-term effects (96 h) of CuO NP (12, 30 nm; 0, 20 and 100 µg/L) using molecular endpoints as well as more conventional biochemical and physiological markers. The expression of antioxidant (CuZnSOD, MnSOD, Cat, Se-GPx, Trxr) and antitoxic (GST-Pi, HSP70, MT, Pgp, MRP1) related genes was measured at the mRNA level while antioxidant (SOD, TAC) and antitoxic (GST, ACP) defenses, energetic reserves and metabolism (ETS, Tri, LDH), and cellular damages (LPO) were assessed using a biochemical approach. The filtration rate measured at 96 h provided information at the physiological scale. Gene expression and filtration rate were responsive to CuO NPs but the effects differed according to the NP size. The results suggest that defense mechanisms may have been set up following 30 nm-NP exposure. The response to 12 nm-NP was lower but still showed that exposure to 12 nm-NP led to activation of cellular elimination mechanisms. The lowering of the filtration rate may have protected the organisms from the contamination. However, this raised the question of further repercussions on organism biology. Together, the results (i) indicate that CuO NP may exert effects at different levels even after a short-term exposure and (ii) point out the precocity of molecular response.

Asperyellone pretreatment protects HaCaT cells from UVB irradiation induced oxidative damages: Assessment under in vitro and in vivo conditions and at molecular level.

The present study explores the UVB protective role of Asperyellone (AY), a secondary metabolite of Aspergillus niger strain AN01. The in vitro UVB protective efficacy of AY was studied using the Human Epidermal keratinocytes cells (HaCaT) cell line. The results suggest the appreciable scavenging of UVB-induced reactive oxygen species in the AY-pretreated cells compared with UVB control. Experimental results on the antioxidant enzymes (Catalase, SOD, LPO, and GPx) profile, histochemical, and molecular analyses support the UVB protective effect of AY in HaCaT cells. Further, the in vivo UVB protective efficacy of AY was studied using animal models and compared with that of commercially available UVB protective agents. Physical, biochemical, and molecular analyses of skin samples emphasized the UVB protective role of AY. Thus, the important beneficial effects of AY have been explored in the present study.

Assessment of tick antioxidant responses to exogenous oxidative stressors and insight into the role of catalase in the reproductive fitness of the Gulf Coast tick, Amblyomma maculatum.

As obligate blood-sucking ectoparasites, to avoid tissue damage, ticks must neutralize the reactive oxygen species (ROS) generated from uptake and digestion of a bloodmeal. Consequently, ticks utilize a battery of antioxidant molecules, including catalase (CAT), an enzyme that converts hydrogen peroxide (H2 O2 ) into water and oxygen. Here, we investigated the tick antioxidant machinery by exogenous injection of sublethal doses of H2 O2 or paraquat. The relative transcript levels of selected Amblyomma maculatum antioxidant targets in tissues were determined by quantitative reverse transcriptase PCR following treatment. The results showed 2-16-fold increases in target antioxidant gene transcripts, signifying the ability of Am. maculatum to regulate its antioxidant machinery when exposed to increased ROS levels. Next, RNA interference was used to determine the functional role of CAT in haematophagy, redox homeostasis and reproductive fitness. CAT gene silencing was confirmed by transcript depletion within tick tissues; however, CAT knockdown alone did not interfere with tick haematophagy or phenotype, as confirmed by the resulting differential expression of antioxidant genes, thereby indicating an alternative mechanism for ROS control. Interestingly, double stranded RNA of CAT gene (dsCAT) and the CAT inhibitor, 3-aminotriazole, together reduced tick reproductive fitness via a marked reduction in egg mass and larval eclosion rates, highlighting a role for CAT in tick redox-homeostasis, making it a potential target for tick control.

Genotypic assessment of drug-resistant tuberculosis in Baghdad and other Iraqi provinces using low-cost and low-density DNA microarrays.

We report on a molecular investigation carried out to ascertain the prevalence of drug-resistant tuberculosis (TB) and the specific gene mutations responsible for resistance to rifampicin (RIF) and/or isoniazid (INH) in Iraq. In total, 110 clinical isolates from category II TB cases from Baghdad (58%) and several Iraqi provinces (42%) were analysed using colorimetric, low-cost and low-density (LCD) microarrays (MYCO-Direct and MYCO-Resist LCD array kits) to identify the point mutations responsible for resistance in Mycobacterium tuberculosis isolates. We found 76 patients (69.1%) had resistant strains, of which 40 (36%) were multidrug-resistant (MDR)-TB. Where mono-resistance was identified, it was found to be predominantly to RIF (83%). The most common mutations were rpoB S531L (50%), inhA C15T (25%) and katG S315T (15%). The most common MDR-TB genotypes were rpoB S531L with inhA C15T (60%) and rpoB S531L with katG S315T (20%). Where phenotypic analysis of clinical isolates was also performed, genotypic data were found to show excellent correlation with phenotypic results. Correlation was found between the MYCO-Resist LCD array and GenoType MTBDRplus for detection of resistance to RIF. Our study shows MDR-TB in 36% of category II TB cases in Baghdad and surrounding Iraqi provinces, which reflects the World Health Organization findings based on phenotypic studies. Diagnosis of TB and MDR-TB using culture-based tests is a significant impediment to global TB control. The LCD arrays investigated herein are easy to use, sensitive and specific molecular tools for TB resistance profiling in resource-limited laboratory settings.

Rapid screening of rpoB and katG mutations in Mycobacterium tuberculosis isolates by high-resolution melting curve analysis.

BACKGROUND: Early detection of multidrug-resistant tuberculosis (MDR-TB) is essential to prevent its transmission in the community and initiate effective anti-TB treatment regimen. MATERIALS AND METHODS: High-resolution melting curve (HRM) analysis was evaluated for rapid detection of resistance conferring mutations in rpoB and katG genes. We screened 95 Mycobacterium tuberculosis clinical isolates including 20 rifampin resistant (RIF-R), 21 isoniazid resistant (INH-R) and 54 fully susceptible (S) isolates determined by proportion method of drug susceptibility testing. Nineteen M. tuberculosis isolates with known drug susceptibility genotypes were used as references for the assay validation. The nucleotide sequences of the target regions rpoB and katG genes were determined to investigate the frequency and type of mutations and to confirm HRM results. RESULTS: HRM analysis of a 129-bp fragment of rpoB allowed correct identification of 19 of the 20 phenotypically RIF-R and all RIF-S isolates. All INH-S isolates generated wild-type HRM curves and 18 out of 21 INH-R isolates harboured any mutation in 109-bp fragment of katG exhibited mutant type HRM curves. However, 1 RIF-R and 3 INH-R isolates were falsely identified as susceptible which were confirmed for having no mutation in their target regions by sequencing. The main mutations involved in RIF and INH resistance were found at codons rpoB531 (60% of RIF-R isolates) and katG315 (85.7% of INH-R isolates), respectively. CONCLUSION: HRM was found to be a reliable, rapid and low cost method to characterise drug susceptibility of clinical TB isolates in resource-limited settings.

Characterizing dose-responses of catalase to nitrofurazone exposure in model ciliated protozoan Euplotes vannus for ecotoxicity assessment: enzyme activity and mRNA expression.

In environmental studies, some biological responses, known as biomarkers, have been used as a powerful bioassay tool for more than four decades. Disparity between enzyme activity and mRNA abundance leads to correlation equivocality, which makes the application of biomarkers for environmental risk assessment more complicated. This study investigates this disparity in the case of catalase when used as a biomarker for detecting ecotoxicity induced by antibiotics in aquatic ecosystems. In particular, dose-responses for catalase activity and mRNA expression abundance were investigated in Euplotes vannus which were exposed to graded doses of nitrofurazone for several discrete durations, and dose-response models were developed to characterize the dose-response dynamics. Significant differences were found in both catalase activity and mRNA expression abundance among the E. vannus treated with nitrofurazone. Catalase activity showed a hormetic-like effect in terms of dose-response, characterized by a biphasic relationship which was more clearly evident after a longer exposure period, while mRNA expression abundance increased linearly with the exposure duration. Additionally, the correlation between catalase activity and mRNA expression abundance reversed along with the duration of exposure to nitrofurazone. Taken together, our results demonstrate that catalase mRNA expression offers a more straightforward dose-response model than enzyme activity. Our findings suggest that both catalase enzyme activity and mRNA expression abundance can be used jointly as bioassay tools for detecting ecotoxicity induced by nitrofurazone in aquatic ecosystems.

Biological cost in Mycobacterium tuberculosis with mutations in the rpsL, rrs, rpoB, and katG genes.

When bacteria develop drug-resistant mutations, there is often an associated biological cost; however, some strains can exhibit low- or no-cost mutations. In the present study, a quantitative resazurin reduction assay was used to measure the biological cost of Mycobacterium tuberculosis isolates that contained different mutations in the rpsL, rrs, rpoB, and katG genes, and showed different resistance profiles. Biological costs were determined by comparing the growth curves of drug-resistant isolates with drug-susceptible strains. Some strains, such as those with rpoB mutations other than S531L and strains with mutations in all of the studied genes, grew more slowly than did drug-susceptible strains. However, some strains grew more quickly than drug-susceptible strains, such as those that had only the rpsL K43R mutation. Strains with the mutation katG S315T presented heterogeneous biological costs. When analyzed individually, strains with the mutations rpsL43/katG315, rpoB531, and rpoB531/katG315 grew faster than drug-susceptible strains. The results suggest that some strains with the most common mutations correlated to a high resistance toward streptomycin, isoniazid and rifampicin can grow as well as or better than susceptible strains.

Genotoxicity assessment and detoxification induction in Dreissena polymorpha exposed to benzo[a]pyrene.

The use of DNA adduct analysis has previously focused on the use of marine organisms for biomonitoring, whereas similar investigations in freshwater organisms are sparse. In that context, we have investigated the relevance of DNA adducts as biomarkers of genotoxicity in the freshwater mussels Dreissena polymorpha. The objective of the present study is to determine the stability of DNA adducts induced by benzo[a]pyrene (B[a]P) in zebra mussels. Mussels were exposed to dissolved B[a]P (10-100 µg/l) for 4 days. Afterwards, mussels were kept in clean water for 28 days and DNA adduct levels were subsequently measured in two different organs, the digestive glands and the gills, using the (32)P-postlabelling technique. In parallel, the expression of genes involved in the detoxification system was assessed by qPCR (catalase, superoxide dismutase, glutathione S transferase, HSP70, aryl hydrocarbon receptor, P glycoprotein). We observed a higher level of DNA adducts in the digestive glands compared to the gills. Moreover, in gills, the level of DNA adduct was dependent on the B[a]P concentration. The levels of adducts tended to decrease in both organs after 28 days in clean water. In addition, an early induction of HSP70, PgP, AHR and SOD mRNA levels was noticed in the gills compared to the digestive glands. CAT and GST gene expression increased from 12h exposure in both organs. A higher gene expression level of those genes was observed in the gills, except for AHR and CAT genes. Data converge towards the fact that DNA adducts hence represent a very promising biomarker of B[a]P contamination and potentially of exposure to polycyclic aromatic hydrocarbons. In addition, for the first time in this study, B[a]P detoxification system was characterised in D. polymorpha.

[Phenotypic polymorphism of biomedical parameters of the health status in hygienic studies].

The paper presents the results of investigating the phenotypic polymorphism of a number of biochemical and immunological parameters (the values of oxidative stress, the activity of catalase and glutathione-S-transferase in red blood cells, the serum levels of catecholamines, tumor-necrosis factor-?, and IgG antibody subclasses) in the authors' hygienic studies of genotypic and nongenotypic population samples.

Multilevel ecotoxicity assessment of polycyclic musk in the earthworm Eisenia fetida using traditional and molecular endpoints.

The ecotoxicity assessment of galaxolide (HHCB) and tonalide (AHTN) was investigated in the earthworm Eisenia fetida using traditional and novel molecular endpoints. The median lethal concentration (LC(50)) for 7-day and 14-day exposures was 573.2 and 436.3 µg g(-1) for AHTN, and 489.0 and 392.4 µg g(-1) for HHCB, respectively. There was no observed significant effect on the growth rate of E. fetida after a 28-day exposure except that at the highest concentration (100 µg g(-1)) of AHTN and HHCB, whereas a significant decrease of cocoon production was found in earthworms exposed to 50 and 100 µg g(-1). To assess molecular-level effect, the expression of encoding antioxidant enzymes and stress protein genes were investigated upon sublethal exposures using the quantitative real time PCR assay. The expression level of SOD, CAT and calreticulin genes was up-regulated significantly, while the level of annetocin (ANN) and Hsp70 gene expression was down-regulated in E. fetida. Importantly, the level of ANN expression had a significant positive correlation with the reproduction rate of earthworms. Furthermore, the lowest observed effect concentration (LOECs) of ANN expression level was 3 µg g(-1) for AHTN and 10 µg g(-1) for HHCB, suggesting that ANN gene expression can serve as a more sensitive indicator of exposure to AHTN and HHCB than traditional endpoints such as cocoon production. The transcriptional responses of these genes may provide early warning molecular biomarkers for identifying contaminant exposure, and the data obtained from this study will contribute to better understand the toxicological effect of AHTN and HHCB.

Multiplex allele-specific polymerase chain reaction for detection of isoniazid resistance in Mycobacterium tuberculosis.

SETTING: Pham Ngoc Thach Tuberculosis Reference Hospital, Ho Chi Minh City, Viet Nam. DESIGN: A multiplex allele-specific polymerase chain reaction (MAS-PCR) was developed to detect mutations at the two most common sites responsible for isoniazid (INH) resistance in Mycobacterium tuberculosis: katG315 and inhA-15. The MAS-PCR is able to detect rare mutations at katG315, in addition to katG S315T. Conventional phenotypic proportion drug susceptibility testing on Löwenstein-Jensen media was used as a gold standard to compare the sensitivity and specificity of the commercial MTBDRplus line-probe assay and the MAS-PCR in 100 INH-resistant and 50 INH-susceptible isolates collected consecutively at Pham Ngoc Thach Hospital reference laboratory. RESULTS: The sensitivity and specificity on culture isolates were 90% (n = 90/100, 95%CI 0.83-0.94) and 100% (n = 50/50, 95%CI 0.93-1.0), respectively, for the MAS-PCR and the MTBDRplus assay. CONCLUSION: The MAS-PCR described here represents an alternative method for rapid screening for INH resistance in M. tuberculosis isolates.

High-resolution melting curve analysis for rapid detection of rifampin and isoniazid resistance in Mycobacterium tuberculosis clinical isolates.

We evaluated high-resolution melting (HRM) curve analysis as a tool for detecting rifampin (RIF) and isoniazid (INH) resistance in Mycobacterium tuberculosis in an accurate, affordable, and rapid manner. Two hundred seventeen M. tuberculosis clinical isolates of known resistance phenotype were used. Twenty-nine known rpoB mutant DNAs, including rare mutations, were also included. Four pairs of primers were designed: rpoB-F/R (for codons 516 to 539 of rpoB), rpoB-516F/R (for codons 508 to 536 of rpoB), katG-F/R (for the codon 315 region of katG), and inhA-F/R (for the nucleotide substitution of C to T at position -15 of inhA). An HRM curve was generated for each isolate after real-time PCR differentiated the mutant from the wild-type strains. DNA sequencing of the target regions was performed to confirm the results of the HRM curve analysis. All but one of the 73 RIF-resistant (RIF-R) strains and all 124 RIF-susceptible (RIF-S) isolates were correctly identified by HRM curve analysis of rpoB. Twenty-seven of 29 known rpoB mutants were detected. In HRM curve analysis of katG and inhA, 90 INH-R strains that harbored katG or inhA mutations, or both, and all INH-S strains were correctly identified. Ten phenotypically INH-R strains not harboring katG or inhA mutations were not detected. The HRM curve analysis will be a useful method for detection of RIF and INH resistance in M. tuberculosis in a rapid, accurate, simple, and cost-effective manner.

Rolling circle amplification and multiplex allele-specific PCR for rapid detection of katG and inhA gene mutations in Mycobacterium tuberculosis.

The aim of the study was to compare a novel, rolling circle amplification (RCA) assay for detection of common isoniazid (INH) resistance mutations in Mycobacterium tuberculosis with a multiplex allele-specific PCR (MAS-PCR) and sequencing of katG and the fabG1-inhA promoter region. One or more mutations were identified by RCA, MAS-PCR, and sequencing in 21 (68%), 22 (71%), and 23 (74%), respectively, of 31 epidemiologically unrelated INH-resistant isolates, and in none of 8 INH-susceptible isolates. The RCA assay is a rapid, inexpensive, and practical screening method for INH resistance in M. tuberculosis in countries with high prevalence of INH resistance.

PCR-restriction fragment length polymorphism for rapid, low-cost identification of isoniazid-resistant Mycobacterium tuberculosis.

PCR-restriction fragment length poymorphism (PCR-RFLP) is a simple, robust technique for the rapid identification of isoniazid-resistant Mycobacterium tuberculosis. One hundred consecutive isolates from a Vietnamese tuberculosis hospital were tested by MspA1I PCR-RFLP for the detection of isoniazid-resistant katG_315 mutants. The test had a sensitivity of 80% and a specificity of 100% against conventional phenotypic drug susceptibility testing. The positive and negative predictive values were 1 and 0.86, respectively. None of the discrepant isolates had mutant katG_315 codons by sequencing. The test is cheap (less than $1.50 per test), specific, and suitable for the rapid identification of isoniazid resistance in regions with a high prevalence of katG_315 mutants among isoniazid-resistant M. tuberculosis isolates.

Assessment of Helicobacter pylori gene expression within mouse and human gastric mucosae by real-time reverse transcriptase PCR.

Despite increasing knowledge on the biology of Helicobacter pylori, little is known about the expression pattern of its genome during infection. While mouse models of infection have been widely used for the screening of protective antigens, the reliability of the mouse model for gene expression analysis has not been assessed. In an attempt to address this question, we have developed a quantitative reverse transcriptase PCR (RT-PCR) that allowed the detection of minute amounts of mRNA within the gastric mucosa. The expression of four genes, 16S rRNA, ureA (encoding urease A subunit), katA (catalase), and alpA (an adhesin), was monitored during the course of a 6-month infection of mice and in biopsy samples from of 15 infected humans. We found that the selected genes were all expressed within both mouse and human infected mucosae. Moreover, the relative abundance of transcripts was the same (16S rRNA > ureA > katA > alpA), in the two models. Finally, results obtained with the mouse model suggest a negative effect of bacterial burden on the number of transcripts of each gene expressed per CFU (P < 0.05 for 16S rRNA, alpA, and katA). Overall, this study demonstrates that real-time RT-PCR is a powerful tool for the detection and quantification of H. pylori gene expression within the gastric mucosa and strongly indicates that mice experimentally infected with H. pylori provide a valuable model for the analysis of bacterial gene expression during infection.