"One-Two Punch": Synergistic ß-Lactam Combinations for Mycobacterium abscessus and Target Redundancy in the Inhibition of Peptidoglycan Synthesis Enzymes.

Mycobacterium abscessus subsp. abscessus is one of the most difficult pathogens to treat and its incidence in disease is increasing. Dual ß-lactam combinations act synergistically in vitro but are not widely employed in practice. A recent study shows that a combination of imipenem and ceftaroline significantly lowers the minimum inhibitory concentration of clinical isolates, despite both drugs targeting the same peptidoglycan synthesis enzymes. The underlying mechanism of this effect provides a basis for further investigations of dual ß-lactam combinations in the treatment of M. abscessus subsp. abscessus, eventually leading to a clinical trial. Furthermore, dual ß-lactam strategies may be explored for other difficult mycobacterial infections.

Toxic Metabolic Encephalopathy in Hospitalized Patients with COVID-19.

BACKGROUND: Toxic metabolic encephalopathy (TME) has been reported in 7-31% of hospitalized patients with coronavirus disease 2019 (COVID-19); however, some reports include sedation-related delirium and few data exist on the etiology of TME. We aimed to identify the prevalence, etiologies, and mortality rates associated with TME in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-positive patients. METHODS: We conducted a retrospective, multicenter, observational cohort study among patients with reverse transcriptase-polymerase chain reaction-confirmed SARS-CoV-2 infection hospitalized at four New York City hospitals in the same health network between March 1, 2020, and May 20, 2020. TME was diagnosed in patients with altered mental status off sedation or after an adequate sedation washout. Patients with structural brain disease, seizures, or primary neurological diagnoses were excluded. The coprimary outcomes were the prevalence of TME stratified by etiology and in-hospital mortality (excluding comfort care only patients) assessed by using a multivariable time-dependent Cox proportional hazards models with adjustment for age, race, sex, intubation, intensive care unit requirement, Sequential Organ Failure Assessment scores, hospital location, and date of admission. RESULTS: Among 4491 patients with COVID-19, 559 (12%) were diagnosed with TME, of whom 435 of 559 (78%) developed encephalopathy immediately prior to hospital admission. The most common etiologies were septic encephalopathy (n = 247 of 559 [62%]), hypoxic-ischemic encephalopathy (HIE) (n = 331 of 559 [59%]), and uremia (n = 156 of 559 [28%]). Multiple etiologies were present in 435 (78%) patients. Compared with those without TME (n = 3932), patients with TME were older (76 vs. 62 years), had dementia (27% vs. 3%) or psychiatric history (20% vs. 10%), were more often intubated (37% vs. 20%), had a longer hospital length of stay (7.9 vs. 6.0 days), and were less often discharged home (25% vs. 66% [all P < 0.001]). Excluding comfort care patients (n = 267 of 4491 [6%]) and after adjustment for confounders, TME remained associated with increased risk of in-hospital death (n = 128 of 425 [30%] patients with TME died, compared with n = 600 of 3799 [16%] patients without TME; adjusted hazard ratio [aHR] 1.24, 95% confidence interval [CI] 1.02-1.52, P = 0.031), and TME due to hypoxemia conferred the highest risk (n = 97 of 233 [42%] patients with HIE died, compared with n = 631 of 3991 [16%] patients without HIE; aHR 1.56, 95% CI 1.21-2.00, P = 0.001). CONCLUSIONS: TME occurred in one in eight hospitalized patients with COVID-19, was typically multifactorial, and was most often due to hypoxemia, sepsis, and uremia. After we adjustment for confounding factors, TME was associated with a 24% increased risk of in-hospital mortality.

Insights into the l,d-Transpeptidases and d,d-Carboxypeptidase of Mycobacterium abscessus: Ceftaroline, Imipenem, and Novel Diazabicyclooctane Inhibitors.

Mycobacterium abscessus is a highly drug-resistant nontuberculous mycobacterium (NTM). Efforts to discover new treatments for M. abscessus infections are accelerating, with a focus on cell wall synthesis proteins (M. abscessus l,d-transpeptidases 1 to 5 [LdtMab1 to LdtMab5] and d,d-carboxypeptidase) that are targeted by ß-lactam antibiotics. A challenge to this approach is the presence of chromosomally encoded ß-lactamase (BlaMab). Using a mechanism-based approach, we found that a novel ceftaroline-imipenem combination effectively lowered the MICs of M. abscessus isolates (MIC50 ≤ 0.25 µg/ml; MIC90 ≤ 0.5 µg/ml). Combining ceftaroline and imipenem with a ß-lactamase inhibitor, i.e., relebactam or avibactam, demonstrated only a modest effect on susceptibility compared to each of the ß-lactams alone. In steady-state kinetic assays, BlaMab exhibited a lower Ki app (0.30 ± 0.03 µM for avibactam and 136 ± 14 µM for relebactam) and a higher acylation rate for avibactam (k2/K = 3.4 × 105 ± 0.4 × 105 M-1 s-1 for avibactam and 6 × 102 ± 0.6 × 102 M-1 s-1 for relebactam). The kcat/Km was nearly 10-fold lower for ceftaroline fosamil (0.007 ± 0.001 µM-1 s-1) than for imipenem (0.056 ± 0.006 µM-1 s-1). Timed mass spectrometry captured complexes of avibactam and BlaMab, LdtMab1, LdtMab2, LdtMab4, and d,d-carboxypeptidase, whereas relebactam bound only BlaMab, LdtMab1, and LdtMab2 Interestingly, LdtMab1, LdtMab2, LdtMab4, LdtMab5, and d,d-carboxypeptidase bound only to imipenem when incubated with imipenem and ceftaroline fosamil. We next determined the binding constants of imipenem and ceftaroline fosamil for LdtMab1, LdtMab2, LdtMab4, and LdtMab5 and showed that imipenem bound >100-fold more avidly than ceftaroline fosamil to LdtMab1 and LdtMab2 (e.g., Ki app or Km of LdtMab1 = 0.01 ± 0.01 µM for imipenem versus 0.73 ± 0.08 µM for ceftaroline fosamil). Molecular modeling indicates that LdtMab2 readily accommodates imipenem, but the active site must widen to ≥8 Å for ceftaroline to enter. Our analysis demonstrates that ceftaroline and imipenem binding to multiple targets (l,d-transpeptidases and d,d-carboxypeptidase) and provides a mechanistic rationale for the effectiveness of this dual ß-lactam combination in M. abscessus infections.

The effect of respiratory viral assay panel on antibiotic prescription patterns at discharge in adults admitted with mild to moderate acute exacerbation of COPD: a retrospective before- after study.

BACKGROUND: Despite well-defined criteria for use of antibiotics in patients presenting with mild to moderate Acute Exacerbation of Chronic Obstructive Pulmonary Disease (AECOPD), their overuse is widespread. We hypothesized that following implementation of a molecular multiplex respiratory viral panel (RVP), AECOPD patients with viral infections would be more easily identified, limiting antibiotic use in this population. The primary objective of our study was to investigate if availability of the RVP decreased antibiotic prescription at discharge among patients with AECOPD. METHODS: This is a single center, retrospective, before (pre-RVP) - after (post-RVP) study of patients admitted to a tertiary medical center from January 2013 to March 2016. The primary outcome was antibiotic prescription at discharge. Groups were compared using univariable and multivariable logistic-regression. RESULTS: A total of 232 patient-episodes were identified, 133 following RVP introduction. Mean age was 68.1 (pre-RVP) and 68.3 (post-RVP) years respectively (p = 0.88). Patients in pre-RVP group were similar to the post-RVP group with respect to gender (p = 0.54), proportion of patients with BMI < 21(p = 0.23), positive smoking status (p = 0.19) and diagnoses of obstructive sleep apnea (OSA, p = 0.16). We found a significant reduction in antibiotic prescription rate at discharge in patients admitted with AECOPD after introduction of the respiratory viral assay (pre-RVP 77.8% vs. post-RVP 63.2%, p = 0.01). In adjusted analyses, patients in the pre-RVP group [OR 2.11 (CI: 1.13-3.96), p = 0.019] with positive gram stain in sputum [OR 4.02 (CI: 1.61-10.06), p = 0.003] had the highest odds of antibiotic prescription at discharge. CONCLUSIONS: In patients presenting with mild to moderate Acute Exacerbation of Chronic Obstructive Pulmonary Disease (AECOPD), utilization of a comprehensive respiratory viral panel can significantly decrease the rate of antibiotic prescription at discharge.

Kinetic and Structural Characterization of the Interaction of 6-Methylidene Penem 2 with the ß-Lactamase from Mycobacterium tuberculosis.

Mycobacterium tuberculosis is intrinsically resistant to most ß-lactam antibiotics because of the constitutive expression of the blaC-encoded ß-lactamase. This enzyme has extremely high activity against penicillins and cephalosporins, but weaker activity against carbapenems. The enzyme can be inhibited by clavulanate, avibactam, and boronic acids. In this study, we investigated the ability of 6-methylidene ß-lactams to inhibit BlaC. One such compound, penem 2, inhibited BlaC more than 70 times more efficiently than clavulanate. The compound forms a covalent complex with BlaC as shown by mass spectrometry. Crystallization of the complex revealed that the bound inhibitor was covalently attached via the Ser70 active site residue and that the covalently, acylated form of the inhibitor had undergone additional chemistry yielding a 4,7-thiazepine ring in place of the ß-lactam and a thiazapyroline ring generated as a result of ß-lactam ring opening. The stereochemistry of the product of the 7-endo-trig cyclization was the opposite of that observed previously for class A and D ß-lactamases. Addition of penem 2 greatly synergized the antibacterial properties of both ampicillin and meropenem against a growing culture of M. tuberculosis. Strikingly, penem 2 alone showed significant growth inhibition, suggesting that in addition to its capability of efficiently inhibiting BlaC, it also inhibited the peptidoglycan cross-linking transpeptidases.

Synergistic effects of sulopenem in combination with cefuroxime or durlobactam against Mycobacterium abscessus.

Mycobacterium abscessus (Mab) affects patients with immunosuppression or underlying structural lung diseases such as cystic fibrosis (CF). Additionally, Mab poses clinical challenges due to its resistance to multiple antibiotics. Herein, we investigated the synergistic effect of dual ß-lactams [sulopenem and cefuroxime (CXM)] or the combination of sulopenem and CXM with ß-lactamase inhibitors [BLIs-avibactam (AVI) or durlobactam (DUR)]. The sulopenem-CXM combination yielded low minimum inhibitory concentration (MIC) values for 54 clinical Mab isolates and ATCC19977 (MIC50 and MIC90 ≤0.25 µg/mL). Similar synergistic effects were observed in time-kill studies conducted at concentrations achievable in clinical settings. Sulopenem-CXM outperformed monotherapy, yielding ~1.5 Log10 CFU/mL reduction during 10 days. Addition of BLIs enhanced this antibacterial effect, resulting in an additional reduction of CFUs (~3 Log10 for sulopenem-CXM and AVI and ~4 Log10 for sulopenem-DUR). Exploration of the potential mechanisms of the synergy focused on their interactions with L,D-transpeptidases (Ldts; LdtMab1-LdtMab4), penicillin-binding-protein B (PBP B), and D,D-carboxypeptidase (DDC). Acyl complexes, identified via mass spectrometry analysis, demonstrated the binding of sulopenem with LdtMab2-LdtMab4, DDC, and PBP B and CXM with LdtMab2 and PBP B. Molecular docking and mass spectrometry data suggest the formation of a covalent adduct between sulopenem and LdtMab2 after the nucleophilic attack of the cysteine residue at the ß-lactam carbonyl carbon, leading to the cleavage of the ß-lactam ring and the establishment of a thioester bond linking the LdtMab2 with sulopenem. In conclusion, we demonstrated the biochemical basis of the synergy of sulopenem-CXM with or without BLIs. These findings potentially broaden the selection of oral therapeutic agents to combat Mab. IMPORTANCE: Treating infections from Mycobacterium abscessus (Mab), particularly those resistant to common antibiotics like macrolides, is notoriously difficult, akin to a never-ending struggle for healthcare providers. The rate of treatment failure is even higher than that seen with multidrug-resistant tuberculosis. The role of combination ß-lactams in inhibiting L,D-transpeptidation, the major peptidoglycan crosslink reaction in Mab, is an area of intense investigation, and clinicians have utilized this approach in the treatment of macrolide-resistant Mab, with reports showing clinical success. In our study, we found that cefuroxime and sulopenem, when used together, display a significant synergistic effect. If this promising result seen in lab settings, translates well into real-world clinical effectiveness, it could revolutionize current treatment methods. This combination could either replace the need for more complex intravenous medications or serve as a "step down" to an oral medication regimen. Such a shift would be much easier for patients to manage, enhancing their comfort and likelihood of sticking to the treatment plan, which could lead to better outcomes in tackling these tough infections. Our research delved into how these drugs inhibit cell wall synthesis, examined time-kill data and binding studies, and provided a scientific basis for the observed synergy in cell-based assays.

Durlobactam, a Diazabicyclooctane ß-Lactamase Inhibitor, Inhibits BlaC and Peptidoglycan Transpeptidases of Mycobacterium tuberculosis.

Peptidoglycan synthesis is an underutilized drug target in Mycobacterium tuberculosis (Mtb). Diazabicyclooctanes (DBOs) are a class of broad-spectrum ß-lactamase inhibitors that also inhibit certain peptidoglycan transpeptidases that are important in mycobacterial cell wall synthesis. We evaluated the DBO durlobactam as an inhibitor of BlaC, the Mtb ß-lactamase, and multiple Mtb peptidoglycan transpeptidases (PonA1, LdtMt1, LdtMt2, LdtMt3, and LdtMt5). Timed electrospray ionization mass spectrometry (ESI-MS) captured acyl-enzyme complexes with BlaC and all transpeptidases except LdtMt5. Inhibition kinetics demonstrated durlobactam was a potent and efficient DBO inhibitor of BlaC (KI app 9.2 ± 0.9 µM, k2/K 5600 ± 560 M-1 s-1) and similar to clavulanate (KI app 3.3 ± 0.6 µM, k2/K 8400 ± 840 M-1 s-1); however, durlobactam had a lower turnover number (tn = kcat/kinact) than clavulanate (1 and 8, respectively). KI app values with durlobactam and clavulanate were similar for peptidoglycan transpeptidases, but ESI-MS captured durlobactam complexes at more time points. Molecular docking and simulation demonstrated several productive interactions of durlobactam in the active sites of BlaC, PonA1, and LdtMt2. Antibiotic susceptibility testing was conducted on 11 Mtb isolates with amoxicillin, ceftriaxone, meropenem, imipenem, clavulanate, and durlobactam. Durlobactam had a minimum inhibitory concentration (MIC) range of 0.5-16 µg/mL, similar to the ranges for meropenem (1-32 µg/mL) and imipenem (0.5-64 µg/mL). In ß-lactam + durlobactam combinations (1:1 mass/volume), MICs were lowered 4- to 64-fold for all isolates except one with meropenem-durlobactam. This work supports further exploration of novel ß-lactamase inhibitors that target BlaC and Mtb peptidoglycan transpeptidases.

Can inhibitor-resistant substitutions in the Mycobacterium tuberculosis ß-Lactamase BlaC lead to clavulanate resistance?: a biochemical rationale for the use of ß-lactam-ß-lactamase inhibitor combinations.

The current emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis calls for novel treatment strategies. Recently, BlaC, the principal ß-lactamase of Mycobacterium tuberculosis, was recognized as a potential therapeutic target. The combination of meropenem and clavulanic acid, which inhibits BlaC, was found to be effective against even extensively drug-resistant M. tuberculosis strains when tested in vitro. Yet there is significant concern that drug resistance against this combination will also emerge. To investigate the potential of BlaC to evolve variants resistant to clavulanic acid, we introduced substitutions at important amino acid residues of M. tuberculosis BlaC (R220, A244, S130, and T237). Whereas the substitutions clearly led to in vitro clavulanic acid resistance in enzymatic assays but at the expense of catalytic activity, transformation of variant BlaCs into an M. tuberculosis H37Rv background revealed that impaired inhibition of BlaC did not affect inhibition of growth in the presence of ampicillin and clavulanate. From these data we propose that resistance to ß-lactam-ß-lactamase inhibitor combinations will likely not arise from structural alteration of BlaC, therefore establishing confidence that this therapeutic modality can be part of a successful treatment regimen against M. tuberculosis.

Eradicating Pulmonary Mycobacterium abscessus: The Promise of Dual ß-Lactam Therapy.

Macrolide resistance has rendered the treatment of Mycobacterium abscessus extremely difficult and is fueling a crisis. Recently, there has been dramatically increased incidence of infections by M abscessus. Select dual ß-lactam combinations have shown promising in vitro results. Herein, we present a patient whose M abscessus infection cured using dual ß-lactams as part of multidrug regimen.

Inhibiting Mycobacterium abscessus Cell Wall Synthesis: Using a Novel Diazabicyclooctane ß-Lactamase Inhibitor To Augment ß-Lactam Action.

Mycobacterium abscessus (Mab) infections are a growing menace to the health of many patients, especially those suffering from structural lung disease and cystic fibrosis. With multidrug resistance a common feature and a growing understanding of peptidoglycan synthesis in Mab, it is advantageous to identify potent ß-lactam and ß-lactamase inhibitor combinations that can effectively disrupt cell wall synthesis. To improve existing therapeutic regimens to address serious Mab infections, we evaluated the ability of durlobactam (DUR), a novel diazobicyclooctane ß-lactamase inhibitor to restore in vitro susceptibilities in combination with ß-lactams and provide a biochemical rationale for the activity of this compound. In cell-based assays, susceptibility of Mab subsp. abscessus isolates to amoxicillin (AMOX), imipenem (IMI), and cefuroxime (CXM) was significantly enhanced with the addition of DUR. The triple drug combinations of CXM-DUR-AMOX and IMI-DUR-AMOX were most potent, with MIC ranges of ≤0.06 to 1 µg/mL and an MIC50/MIC90 of ≤0.06/0.25 µg/mL, respectively. We propose a model by which this enhancement may occur, DUR potently inhibited the ß-lactamase BlaMab with a relative Michaelis constant (Ki app) of 4 × 10-3 ± 0.8 × 10-3 µM and acylation rate (k2/K) of 1 × 107 M-1 s-1. Timed mass spectrometry captured stable formation of carbamoyl-enzyme complexes between DUR and LdtMab2-4 and Mab d,d-carboxypeptidase, potentially contributing to the intrinsic activity of DUR. Molecular modeling showed unique and favorable interactions of DUR as a BlaMab inhibitor. Similarly, modeling showed how DUR might form stable Michaelis-Menten complexes with LdtMab2-4 and Mab d,d-carboxypeptidase. The ability of DUR combined with amoxicillin or cefuroxime and imipenem to inactivate multiple targets such as d,d-carboxypeptidase and LdtMab2,4 supports new therapeutic approaches using ß-lactams in eradicating Mab. IMPORTANCE Durlobactam (DUR) is a potent inhibitor of BlaMab and provides protection of amoxicillin and imipenem against hydrolysis. DUR has intrinsic activity and forms stable acyl-enzyme complexes with LdtMab2 and LdtMab4. The ability of DUR to protect amoxicillin and imipenem against BlaMab and its intrinsic activity along with the dual ß-lactam target redundancy can explain the rationale behind the potent activity of this combination.

Are we ready for novel detection methods to treat respiratory pathogens in hospital-acquired pneumonia?

Hospital-acquired pneumonia represents one of the most difficult treatment challenges in infectious diseases. Many studies suggest that the timely administration of appropriate, pathogen-directed therapy can be lifesaving. Because results of culture and antimicrobial susceptibility testing can take 48 h or longer, physicians currently rely on clinical, epidemiological, and demographic factors to assist with the choice of empiric therapy for antibiotic-resistant pathogens. At present, a number of rapid molecular tests are being developed that identify pathogens and the presence of genetic determinants of antimicrobial resistance (eg, GeneXpert [Cepheid], ResPlex [Qiagen], FilmArray [Idaho Technologies], and Microarray [Check-Points]). In this review, the potential impact that molecular diagnostics has to identify and characterize pathogens that cause hospital-acquired bacterial pneumonia at an early stage is examined. In addition, a perspective on a novel technology, polymerase chain reaction followed by electrospray ionization mass spectrometry, is presented, and its prospective use in the diagnosis of pneumonia is also discussed. The complexities of the pulmonary microbiome represent a novel challenge to clinicians, but many questions still remain even as these technologies improve.

Drug-Resistant Tuberculosis: A Glance at Progress and Global Challenges.

Multidrug-resistant Mycobacterium tuberculosis remains a major public health threat; its management poses a significant economic burden. Treatment requires a programmatic approach with access to laboratory services, second-line medications, and adequate clinical resources. In recent years, we have seen rapid developments in diagnostic techniques with whole genome sequencing-based drug susceptibility prediction now in reach, an array of new drugs that transform treatment regimens to purely oral formulations, and a steady stream of multinational trials that inform us about most efficient combinations. Our hope is that the current momentum keeps the ambitious goal to end tuberculosis in 2030 in reach.

Drug-Resistant Tuberculosis: Challenges and Progress.

Antimicrobial resistance is a natural evolutionary process, which in the case of Mycobacterium tuberculosis is based on spontaneous chromosomal mutations, meaning that well-designed combination drug regimens provided under supervised therapy will prevent the emergence of drug-resistant strains. Unfortunately, limited resources, poverty, and neglect have led to the emergence of drug-resistant tuberculosis throughout the world. The international community has responded with financial and scientific support, leading to new rapid diagnostics, new drugs and regimens in advanced clinical development, and an increasingly sophisticated understanding of resistance mechanisms and their application to all aspects of TB control and treatment.

Inhibiting the ß-Lactamase of Mycobacterium tuberculosis (Mtb) with Novel Boronic Acid Transition-State Inhibitors (BATSIs).

BlaC, the single chromosomally encoded ß-lactamase of Mycobacterium tuberculosis, has been identified as a promising target for novel therapies that rely upon ß-lactamase inhibition. Boronic acid transition-state inhibitors (BATSIs) are a class of ß-lactamase inhibitors which permit rational inhibitor design by combinations of various R1 and R2 side chains. To explore the structural determinants of effective inhibition, we screened a panel of 25 BATSIs to explore key structure-function relationships. We identified a cefoperazone analogue, EC19, which displayed slow, time-dependent inhibition against BlaC with a potency similar to that of clavulanate (Ki* of 0.65 ± 0.05 µM). To further characterize the molecular basis of inhibition, we solved the crystallographic structure of the EC19-BlaC(N172A) complex and expanded our analysis to variant enzymes. The results of this structure-function analysis encourage the design of a novel class of ß-lactamase inhibitors, BATSIs, to be used against Mycobacterium tuberculosis.

Reappraising the use of ß-lactams to treat tuberculosis.

The emergence of multidrug-resistant and extensively drug-resistant tuberculosis calls for novel approaches to treatment. Recent studies have shown that BlaC, the ß-lactamase of Mycobacterium tuberculosis, is the major determinant of ß-lactam resistance. This review invites the reader to explore evidence in order to answer the questions: can ß-lactam and ß-lactamase inhibitors adequately treat M. tuberculosis infection and are they a viable option in the management of resistant tuberculosis today?

Transcriptome-based antigen identification for Neisseria meningitidis.

The identification of suitable antigens is crucial to successful vaccine development based on subunit approaches. While many methods exist for the identification of vaccine candidates which are surface-exposed or secreted, immunogenic and conserved, contain B and T cell epitopes, most of these have a major drawback: they do not yield any information on whether the antigen is indeed expressed by the pathogen during infection. However, DNA microarrays offer a novel tool for the investigation of the transcriptional activity of all genes of a pathogenic microorganism under in vivo conditions. Employing whole genome DNA microarrays, we have analyzed the transcriptome of Neisseria meningitidis serogroup B bacteria during different stages of infection, i.e. exposure to human serum and the interaction with human epithelial and endothelial cells. Combined with data derived from genome-based approaches (such as reverse vaccinology) and immunogenicity studies, this novel transcriptome-based antigen identification should reveal ideal vaccine candidates against serogroup B meningococcal infection.

Transcriptome analysis of Neisseria meningitidis during infection.

Neisseria meningitidis is the cause of septicemia and meningococcal meningitis. During the course of infection, N. meningitidis encounters multiple environments within its host, which makes rapid adaptation to environmental changes a crucial factor for neisserial pathogenicity. Employing oligonucleotide-based DNA microarrays, we analyzed the transcriptome of N. meningitidis during two key steps of meningococcal infection, i.e., the interaction with epithelial cells (HeLa cells) and endothelial cells (human brain microvascular endothelial cells). Seventy-two genes were differentially regulated after contact with epithelial cells, and 48 genes were differentially regulated after contact with endothelial cells, including a considerable proportion of well-known virulence genes. While a considerable number of genes were in concordance between bacteria adherent to both cell types, we identified several open reading frames that were differentially regulated in only one system. The data obtained with this novel approach may provide insight into the pathogenicity mechanisms of N. meningitidis and could demonstrate the importance of gene regulation on the transcriptional level during different stages of meningococcal infection.

Analysis of the heat shock response of Neisseria meningitidis with cDNA- and oligonucleotide-based DNA microarrays.

Oligonucleotide- and cDNA-based microarrays comprising a subset of Neisseria meningitidis genes were assessed for study of the meningococcal heat shock response and found to be highly suitable for transcriptional profiling of N. meningitidis. Employing oligonucleotide arrays encompassing the entire genome of N. meningitidis, we analyzed the meningococcal heat shock response on a global scale and identified 55 heat shock-deregulated open reading frames (34 induced and 21 repressed).