Activity of the old antimicrobial nitroxoline against Mycobacterium abscessus complex isolates.

OBJECTIVES: The old antimicrobial nitroxoline is approved to treat urinary tract infection (UTI) and is currently rediscovered for treatment of drug resistant pathogens. Mycobacteria of the Mycobacterium abscessus complex (MYABS) are rapid-growing nontuberculous mycobacteria that are associated with difficult to treat infections of the lungs in patients with pulmonary disorders such as cystic fibrosis. In this study we assessed the in vitro activity of nitroxoline against molecularly characterized drug-resistant MYABS isolates from clinical samples to address potential repurposing of nitroxoline in difficult-to-treat MYABS infection. METHODS: The isolates originated from clinical samples collected between 2010 and 2019 at the University Hospital of Cologne, Germany (N=16; 10/16 M. abscessus Spp. abscessus, 4/16 M. abscessus Spp. massiliense, 2/16 M. abscessus Spp. bolletii). Nitroxoline activity was compared to standard antimicrobials recommended for treatment of MYABS infection. For drug susceptibility testing of nitroxoline and comparators broth microdilution was performed based on current Clinical and Laboratory Standards Institute (CLSI) guidelines. RESULTS: Nitroxoline yielded a MIC90 of 4 mg/L (range 2-4 mg/L), which is two twofold dilutions below the current EUCAST susceptibility breakpoint of ≤ 16 mg/L (limited to uncomplicated UTI and Escherichia coli). Resistance to other antimicrobials was common in our cohort (16/16 isolates resistant to ciprofloxacin, imipenem and doxycycline; 12/16 isolates resistant to tobramycin; 9/16 isolates resistant to cefoxitin; 7/16 isolates resistant to clarithromycin; 2/16 isolates resistant to amikacin). CONCLUSION: Nitroxoline has a promising in vitro activity against drug-resistant MYABS isolates. Future studies should investigate this finding with macrophage and in vivo models.

In vitro Activity of Repurposed Nitroxoline Against Clinically Isolated Mycobacteria Including Multidrug-Resistant Mycobacterium tuberculosis.

Antimicrobial treatment options for mycobacterial infections are limited due to intrinsic resistance and the emergence of acquired resistance in Mycobacterium tuberculosis. Isolates resisting first- and second line drugs are raising concerns about untreatable infections and make the development of new therapeutic strategies more pressing. Nitroxoline is an old oral antimicrobial that is currently repurposed for the treatment of urinary tract infection (UTI). In this study, we report the in vitro activity of nitroxoline against 18 clinical isolates of M. tuberculosis complex (MTBC) (M. tuberculosis N = 16, M. bovis BCG N = 1, M. bovis sp. bovis N = 1). Since nitroxoline achieves high concentrations in the urinary tract, we included all MTBC-isolates from urinary samples sent to our laboratory between 2008 and 2021 (University Hospital of Cologne, Germany). Isolates from other sources (N = 7/18) were added for higher sample size and for inclusion of drug-resistant M. tuberculosis isolates (N = 4/18). Based on our clinical routine the fluorescence-based liquid media system BACTEC MGIT 960 was used for susceptibility testing of nitroxoline and mainstay antitubercular drugs. Nitroxoline yielded a MIC90 of 4 mg/L for MTBC. In all M. tuberculosis isolates nitroxoline MICs were at least two twofold dilutions below the current EUCAST susceptibility breakpoint of ≤16 mg/L (limited to E. coli and uncomplicated UTI). In vitro activity of nitroxoline can be considered excellent, even in multidrug-resistant isolates. Future studies with in vivo models should evaluate a potential role of nitroxoline in the treatment of tuberculosis in the era of drug resistance.

The impact of a needs-oriented dental prophylaxis program on bacteremia after toothbrushing and systemic inflammation in children, adolescents, and young adults with chronic kidney disease.

BACKGROUND: Chronic kidney disease (CKD) still leads to high mortality rates, mainly due to cardiovascular disease. One important influencing factor is persisting low-grade chronic inflammation partly maintained by gingivitis that favors transient bacteremia during daily activities such as toothbrushing. METHODS: To examine whether intensive dental prophylaxis can restore oral health, reduce the prevalence of bacteremia and degree of systemic inflammation indicated by CRP levels, we conducted this pilot study examining 30 CKD patients aged 6-26 years, 15 receiving intensive prophylaxis (IP), 15 receiving treatment as usual (TAU) serving as control group. There were three appointments for examination, each 10 ± 1 weeks apart (at baseline, after intervention periods one and two, when TAU also received IP, and the IP group stopped prophylaxis). RESULTS: The gingival index (GI) in the IP group decreased by 90% (GI 0.09; p=0.001), resulting in almost healthy gingiva. There was no significant change in CRP or prevalence of bacteremia. General prevalence of bacteremia after toothbrushing was 9.5% affecting 7 (26%) of the participants. In three participants, bacteremia dissolved after IP, in one after TAU. Two patients developed bacteremia ≥ 10 weeks after ending IP. We identified eight different bacterial species. CONCLUSIONS: We were able to show that IP can effectively treat gingivitis. It might be a promising approach to reduce systemic inflammation and subsequently lower premature cardiovascular disease, despite the lack of statistical significance. Future research requires a larger patient cohort to enable matched treatment groups with long-term follow-up and molecular detection methods for bacteremia. A higher resolution version of the Graphical abstract is available as Supplementary information.

Bacteraemia of oral origin in children-A Systematic review and network meta-analysis.

OBJECTIVES: To systematically review the prevalence of bacteraemia, triggered by dental intervention and home oral hygiene practices, in children. The network meta-analysis (NMA) quantitatively compared the risk of bacteraemia triggered by dental extractions and home and professional cleaning procedures. MATERIALS AND METHODS: Clinical trials with the outcome "bacteraemia in children" were searched. The NMA was performed using the frequentist weighted least-squares approach comparing the odds ratios (OR) of different interventions. RESULTS: Among 11 of 13 studies, dental treatment was performed under general anaesthesia. In 2,381 patients, bacteraemia occurred in 38.7%-56% patients following single-tooth extractions, in 22%-46% after manual toothbrushing (MTB), and in 26%-78% after power toothbrushing (PTB). When MTB was set as the reference (OR 1), rubber cup polishing showed a slightly higher risk (OR 1.26) of bacteraemia. PTB presented a higher risk (OR 1.79-2.27) than with single-tooth extractions (OR 1.55) but lower than that with multiple extractions (OR 2.55). CONCLUSION: Daily use of MTB and routine professional cleaning were associated with the lowest risk of developing bacteraemia in children with gingivitis, almost as much as with a single-tooth extractions. Improved plaque control with PTB increased the risk of bacteraemia. There is limited evidence on gingivitis-free and systemically-diseased children.

Failure of Vitek2 to reliably detect vanB-mediated vancomycin resistance in Enterococcus faecium.

OBJECTIVES: The increasing prevalence of VRE necessitates their reliable detection, especially for low-level resistance mediated by vanB in Enterococcus faecium. In this prospective study we analysed if vanB-mediated vancomycin resistance can be reliably detected by Vitek2. METHODS: One thousand, three hundred and forty-four enterococcal isolates from routine clinical specimens were tested by Vitek2 (bioMérieux, Nürtingen, Germany). Additionally, a bacterial suspension (with a turbidity equivalent to that of a 0.5 McFarland standard) was inoculated on chromID VRE screening agar (bioMérieux) and incubated for 48 h. If vancomycin tested susceptible by Vitek2 but growth was detected on the screening agar, PCR for vanA/vanB was performed (GeneXpert vanA/B test, Cepheid, Frankfurt, Germany). For isolates that tested susceptible to vancomycin by Vitek2 but were vanA/B positive, MICs were determined before and after cultivation in broth with increasing concentrations of vancomycin. RESULTS: One hundred and fifty-six out of 491 E. faecium were VRE and were predominantly vanB positive (81.0%). Of these, Vitek2 did not identify 14 as VRE (sensitivity 91.0%). By broth microdilution 9/14 isolates demonstrated high MICs (≥32 mg/L) and 5/14 showed low vancomycin MICs, which did not increase despite vancomycin exposure. Three of the 14 isolates demonstrated growth on chromID VRE; after vancomycin exposure seven additional isolates were able to grow on chromID VRE. CONCLUSIONS: Vitek2 fails to detect vanB-mediated vancomycin resistance consistently, especially, but not limited to, low-level resistance. As this may lead to treatment failure and further dissemination of vanB VRE, additional methods (e.g. culture on VRE screening agar or PCR) are necessary to reliably identify vanB-positive enterococci in clinical routine.

Comparison of Two Commercially Available qPCR Kits for the Detection of Candida auris.

Candida auris is an emerging pathogen with resistance to many commonly used antifungal agents. Infections with C. auris require rapid and reliable detection methods to initiate successful medical treatment and contain hospital outbreaks. Conventional identification methods are prone to errors and can lead to misidentifications. PCR-based assays, in turn, can provide reliable results with low turnaround times. However, only limited data are available on the performance of commercially available assays for C. auris detection. In the present study, the two commercially available PCR assays AurisID (OLM, Newcastle Upon Tyne, UK) and Fungiplex Candida Auris RUO Real-Time PCR (Bruker, Bremen, Germany) were challenged with 29 C. auris isolates from all five clades and eight other Candida species as controls. AurisID reliably detected C. auris with a limit of detection (LoD) of 1 genome copies/reaction. However, false positive results were obtained with high DNA amounts of the closely related species C. haemulonii, C. duobushaemulonii and C. pseudohaemulonii. The Fungiplex Candida Auris RUO Real-Time PCR kit detected C. auris with an LoD of 9 copies/reaction. No false positive results were obtained with this assay. In addition, C. auris could also be detected in human blood samples spiked with pure fungal cultures by both kits. In summary, both kits could detect C. auris-DNA at low DNA concentrations but differed slightly in their limits of detection and specificity.

Plasma interferon-γ-inducible protein 10 (IP-10) levels correlate with disease severity and paradoxical reactions in extrapulmonary tuberculosis.

BACKGROUND: With 1.5 million deaths worldwide in 2018, tuberculosis (TB) remains a major global public health problem. While pulmonary TB (PTB) is the most common manifestation, the proportion of extrapulmonary TB (EPTB) is increasing in low-burden countries. EPTB is a heterogeneous disease entity posing diagnostic and management challenges due to the lack of reliable biomarkers. In this study, we prospectively evaluated clinical data and treatment response which were correlated with different biomarkers. METHODS: The study was conducted at the University Hospital of Cologne. 20 patients with EPTB were enrolled. We analyzed plasma interferon-γ-inducible protein 10 (IP-10) levels in plasma by ELISA for up to 12 months of treatment. In addition, the QuantiFERON®-TB Gold Plus (QFT® Plus) test was performed during the course of treatment. Clinical data were assessed prospectively and correlated with QFT® Plus and IP-10 levels. RESULTS: Plasma IP-10 levels were found to be significantly increased (p < 0.001) in patients with extensive disease compared to patients with limited disease (cervical lymph node TB) or healthy controls. In patients with clinically confirmed paradoxical reaction (PR), a further increase of IP-10 was noted. IFN-γ measured by the QFT® Plus test did not decrease significantly during the course of treatment. Of note, in four EPTB patients (20%) without radiographic pulmonary involvement, sputum culture was positive for Mycobacterium tuberculosis. CONCLUSION: Our data demonstrate that IP-10 may be a valuable biomarker for estimation of disease severity in EPTB and monitoring of the disease course in extensive forms. However, IP-10 may be less suitable for diagnosis and monitoring of EPTB patients with limited disease. The QFT® Plus test does not appear to be a suitable marker for therapy monitoring. Sputum should be examined in EPTB patients even in case of normal diagnostic imaging of the chest.

Toxigenic Corynebacterium diphtheriae-Associated Genital Ulceration.

In October 2016, an adolescent boy sought care for acute genital ulceration in Cologne, Germany. We presumed a sexually transmitted infection, but initial diagnostic procedures yielded negative results. He was hospitalized because swab samples from the lesion grew toxigenic Corynebacterium diphtheriae, leading to the diagnosis of possibly sexually transmitted cutaneous diphtheria.

Leptin signaling impairs macrophage defenses against Salmonella Typhimurium.

The dynamic interplay between metabolism and immune responses in health and disease, by which different immune cells impact on metabolic processes, are being increasingly appreciated. However, the potential of master regulators of metabolism to control innate immunity are less understood. Here, we studied the cross-talk between leptin signaling and macrophage function in the context of bacterial infections. We found that upon infection with Gram-negative pathogens, such as Salmonella Typhimurium, leptin receptor (Lepr) expression increased in both mouse and human macrophages. Unexpectedly, both genetic Lepr ablation in macrophages and global pharmacologic leptin antagonization augmented lysosomal functions, reduced S Typhimurium burden, and diminished inflammation in vitro and in vivo. Mechanistically, we show that leptin induction activates the mTORC2/Akt pathway and subsequently down-regulates Phlpp1 phosphatase, allowing for phosphorylated Akt to impair lysosomal-mediated pathogen clearance. These data highlight a link between leptin signaling, the mTORC2/Phlpp1/Akt axis, and lysosomal activity in macrophages and have important therapeutic implications for modulating innate immunity to combat Gram-negative bacterial infections.

Severe disseminated tuberculosis in HIV-negative refugees.

In high-income countries, the presentation of tuberculosis is changing, primarily because of migration, and understanding the specific health needs of susceptible populations is becoming increasingly important. Although disseminated tuberculosis is well documented in HIV-positive patients, the disease is poorly described and less expected in HIV-negative individuals. In this Grand Round, we report eight HIV-negative refugees, who presented with extensively disseminated tuberculosis. We discuss the multifactorial causes, such as deprivations during long journeys, precarious living conditions, and the experience of violence, which might add to nutritional factors and chronic disorders, eventually resulting in a state of predisposition to immune deficiency. We also show that disseminated tuberculosis is often difficult to diagnose when pulmonary symptoms are absent. Communication difficulties between refugees and health-care workers are another major hurdle, and every effort should be made to get a valid patient history. This medical history is crucial to guide imaging and other diagnostic procedures to establish a definite diagnosis, which should be confirmed by a positive tuberculosis culture. Because many of these patients are at risk for multidrug-resistant tuberculosis, drug susceptibility testing is imperative to guide therapy. In the absence of treatment guidelines for this entity, clinicians can determine treatment duration according to recommendations provided for extrapulmonary tuberculosis and affected organs. Paradoxical expansion of tuberculous lesions during therapy should be treated with corticosteroids. In many cases, treatment duration must be individualised and might even exceed 12 months.

Surgical Implications for Diagnosis and Treatment of Intestinal Aspergillosis in Pediatric Patients with ALL.

BACKGROUND: The incidence of invasive aspergillosis (IA) in children with hematooncological malignancies is increasing as a result of intensive treatment, immunosuppression, and extended use of broad-spectrum antibiotics. Infection of the GI tract by Aspergillus spp. is a rare and fatal complication, which often requires surgical diagnostic and therapeutic exploration. OBJECTIVE: The aim of this study was to determine the characteristics of symptomatic intestinal aspergillosis, diagnosis, treatment, and outcome of pediatric patients with an underlying hemato-oncologic disease. PATIENTS AND METHODS: We analyzed 2,307 German patients with acute lymphoblastic leukemia (ALL) from age 1 to 17 years registered in the AIEOP-BFM ALL 2000 study from 2000 to 2006. All reported adverse events were assessed for symptoms of IA and retrospectively reviewed for any sign or proof of intestinal involvement of IA. RESULTS: In this cohort, IA was reported in 30 of 2,307 patients while intestinal involvement was documented in five patients. Four of these patients had intestinal symptoms and three patients underwent explorative laparotomy. Among clinical cases with IA, gastrointestinal manifestation of IA mostly occurred in adolescent patients (10-16 years). Symptoms varied from abdominal tenderness and pain to constipation. Intestinal aspergillosis was proven by microbiological and histopathological examination and fungal infection was observed macroscopically in the jejunal lumen during surgery. Despite the extended surgery and antifungal therapy, outcome of disseminated IA with intestinal involvement remains poor. CONCLUSION: Surgeons should be aware of surgical complications of intestinal aspergillosis in children with hematooncological diseases requiring exploration and resection. IA is a rare event and still difficult to diagnose due to unspecific abdominal symptoms. Thus, biopsy sampling is of utmost importance to ensure diagnosis, and resection of necrotic or perforated tissue should be attempted early.

Hollow silica capsules for amphiphilic transport and sustained delivery of antibiotic and anticancer drugs.

Hollow mesoporous silica capsules (HMSC) are potential drug transport vehicles due to their biocompatibility, high loading capacity and sufficient stability in biological milieu. Herein, we report the synthesis of ellipsoid-shaped HMSC (aspect ratio ∼2) performed using hematite particles as solid templates that were coated with a conformal silica shell through cross-condensation reactions. For obtaining hollow silica capsules, the iron oxide core was removed by acidic leaching. Gas sorption studies on HMSC revealed mesoscopic pores (main pore width ∼38 Å) and a high surface area of 308.8 m2 g-1. Cell uptake of dye-labeled HMSC was confirmed by incubating them with human cervical cancer (HeLa) cells and analyzing the internalization through confocal microscopy. The amphiphilic nature of HMSC for drug delivery applications was tested by loading antibiotic (ciprofloxacin) and anticancer (curcumin) compounds as model drugs for hydrophilic and hydrophobic therapeutics, respectively. The versatility of HMSC in transporting hydrophilic as well as hydrophobic drugs and a pH dependent drug release over several days under physiological conditions was demonstrated in both cases by UV-vis spectroscopy. Ciprofloxacin-loaded HMSC were additionally evaluated towards Gram negative (E. coli) bacteria and demonstrated their efficacy even at low concentrations (10 µg ml-1) in inhibiting complete bacterial growth over 18 hours.

Isolation of Salmonella typhimurium-containing Phagosomes from Macrophages.

Salmonella typhimurium is a facultative intracellular bacterium that causes gastroenteritis in humans. After invasion of the lamina propria, S. typhimurium bacteria are quickly detected and phagocytized by macrophages, and contained in vesicles known as phagosomes in order to be degraded. Isolation of S. typhimurium-containing phagosomes have been widely used to study how S. typhimurium infection alters the process of phagosome maturation to prevent bacterial degradation. Classically, the isolation of bacteria-containing phagosomes has been performed by sucrose gradient centrifugation. However, this process is time-consuming, and requires specialized equipment and a certain degree of dexterity. Described here is a simple and quick method for the isolation of S. typhimurium-containing phagosomes from macrophages by coating the bacteria with biotin-streptavidin-conjugated magnetic beads. Phagosomes obtained by this method can be suspended in any buffer of choice, allowing the utilization of isolated phagosomes for a broad range of assays, such as protein, metabolite, and lipid analysis. In summary, this method for the isolation of S. typhimurium-containing phagosomes is specific, efficient, rapid, requires minimum equipment, and is more versatile than the classical method of isolation by sucrose gradient-ultracentrifugation.

Repurposing QuantiFERON for Detection of Neutralizing Interferon-γ Autoantibodies in Patients With Nontuberculous Mycobacterial Infections.

Nontuberculous mycobacterial infections due to autoantibodies targeting interferon-γ are an emerging medical problem. However, case finding is hampered due to highly complex diagnostic procedures not available in routine laboratories. We show that QuantiFERON assays can be exploited as a simple screening tool that may facilitate adequate and timely treatment.

Low prevalence of DHFR and DHPS mutations in Pneumocystis jirovecii strains obtained from a German cohort.

BACKGROUND: Pneumocystis pneumonia (PCP) is an opportunistic and potentially life-threatening infection of immunocompromised individuals. A combination of trimethoprim-sulfamethoxazole is widely used for prophylaxis and treatment of PCP. Polymorphisms in the drug targets, the dihydropteroate synthase (DHPS) or the dihydrofolate reductase (DHFR) are presumably a reason for treatment failure. METHODS: We retrospectively examined the prevalence of DHPS and DHFR mutations in Pneumocystis jirovecii isolates obtained from HIV-infected and non-HIV-infected PCP patients. DHFR and DHPS genes were amplified using semi-nested PCR followed by sequencing. Obtained data were correlated with clinical findings. RESULTS: Sequencing of the DHPS gene was achieved in 81 out of 128 isolates (63%), the DHFR-gene was successfully sequenced in 96 isolates (75%). The vast majority of DHFR and DHPS sequences were either wild-type or showed synonymous single nucleotide polymorphisms. Only one sample contained a double mutation at DHPS codon 55 and codon 57 which was associated with treatment failure in some studies. No linkage of treatment failure to a DHFR or DHPS genotype was observed. In our cohort, 35 of 95 Patients (37%) were HIV-positive and 60 (63%) were HIV-negative. The overall mortality rate was 24% with a much higher rate among non-HIV patients. CONCLUSION: DHPS and DHFR mutations exist but are infrequent in our cohort. The contribution of gene polymorphisms to treatment failure needs further research. In immunocompromised HIV-negative patients PCP is associated with high mortality rates. Prophylactic treatment is warranted in this patient subset.

Comparison of Phenotypic Tests and an Immunochromatographic Assay and Development of a New Algorithm for Detection of OXA-48-like Carbapenemases.

OXA-48 is the most prevalent carbapenemase in Enterobacteriaceae in Europe and the Middle East, but it is frequently missed because many isolates display low MICs for carbapenems. Furthermore, in contrast to metallo-ß-lactamases or Klebsiella pneumoniae carbapenemases (KPC), no specific inhibitor is available for the phenotypic detection of OXA-48. Molecular detection of blaOXA-48 is the "gold standard" but is not available in many laboratories. A few phenotypic assays have been described but have not been independently evaluated. The aim of this study was the systematic comparison of phenotypic tests and an immunochromatographic assay (ICT) for the detection of OXA-48/OXA-48-like carbapenemases and the development of an algorithm for reliable phenotypic detection of OXA-48. Four phenotypic tests (temocillin disk test, faropenem disk test, OXA-48 disk test, and high-inoculum [HI] OXA-48 disk test) and a new ICT (OXA-48 K-SeT) were compared by using a set of 166 Enterobacteriaceae isolates, including isolates producing OXA-48/OXA-48-like carbapenemases (n = 84) or Ambler class A and B carbapenemases (n = 41) and carbapenemase-negative isolates (n = 41). The sensitivity and specificity for the different assays were 100% and 43.9% for temocillin, 57.1% and 98.8% for faropenem, 53.6% and 100% for the OXA-48 disk test, 98.8% and 97.6% for the HI OXA-48 disk test, and 100% and 100% for the ICT, respectively. The ICT displayed the highest sensitivity and specificity and was the most rapid assay, but it is more costly than phenotypic assays. Based on these results, a new algorithm incorporating temocillin, faropenem, and ICT which allows cost-effective detection of OXA-48 with 100% sensitivity and specificity was developed.

Keim oder kein Keim: Herausforderungen bei der Diagnose mykobakterieller Infektionen der Haut.

Kutane Mykobakteriosen sind in Deutschland selten. Dennoch ist es für eine frühzeitige Diagnose und anschließende wirksame Behandlung erforderlich, dass diese Krankheitsbilder im ärztlichen Bewusstsein verankert sind. Darüber hinaus stehen Infektionen mit Mykobakterien auf der Liste der Differentialdiagnosen vieler Hautkrankheiten. Diagnosen kutaner Mykobakteriosen beruhen auf klinischen Merkmalen und auf Laboruntersuchungen, einschließlich bakterieller Kulturen, histopathologischer Untersuchungen und PCR-basierten Verfahren. Das Wissen um Möglichkeiten und Grenzen dieser Laboruntersuchungen ist von zentraler Bedeutung, um eine angemessene klinische Entscheidung zu treffen. In diesem Beitrag diskutieren wir die aktuellen diagnostischen Möglichkeiten, die in Verdachtsfällen kutaner Mykobakteriosen zur Verfügung stehen.

Bug or no bug: challenges in diagnosing cutaneous mycobacterial infections.

Cutaneous mycobacterioses are rare in Germany. Nevertheless, early diagnosis and subsequent effective treatment requires awareness of these conditions. Moreover, mycobacterial infections are on the differential diagnosis list of many skin diseases. Diagnoses of cutaneous mycobacterioses are based on clinical features, but also on laboratory investigations, including bacterial culture, histopathology and PCR-based methods. Knowledge about the opportunities and limitations of theses laboratory tests is pivotal to reasonable clinical decision-making. In this paper, we review the current diagnostic options when suspecting a case of cutaneous mycobacterial infection.

Imatinib Triggers Phagolysosome Acidification and Antimicrobial Activity against Mycobacterium bovis Bacille Calmette-Guérin in Glucocorticoid-Treated Human Macrophages.

Glucocorticoids are extensively used to treat inflammatory diseases; however, their chronic intake increases the risk for mycobacterial infections. Meanwhile, the effects of glucocorticoids on innate host responses are incompletely understood. In this study, we investigated the direct effects of glucocorticoids on antimycobacterial host defense in primary human macrophages. We found that glucocorticoids triggered the expression of cathelicidin, an antimicrobial critical for antimycobacterial responses, independent of the intracellular vitamin D metabolism. Despite upregulating cathelicidin, glucocorticoids failed to promote macrophage antimycobacterial activity. Gene expression profiles of human macrophages treated with glucocorticoids and/or IFN-γ, which promotes induction of cathelicidin, as well as antimycobacterial activity, were investigated. Using weighted gene coexpression network analysis, we identified a module of highly connected genes that was strongly inversely correlated with glucocorticoid treatment and associated with IFN-γ stimulation. This module was linked to the biological functions autophagy, phagosome maturation, and lytic vacuole/lysosome, and contained the vacuolar H(+)-ATPase subunit a3, alias TCIRG1, a known antimycobacterial host defense gene, as a top hub gene. We next found that glucocorticoids, in contrast with IFN-γ, failed to trigger expression and phagolysosome recruitment of TCIRG1, as well as to promote lysosome acidification. Finally, we demonstrated that the tyrosine kinase inhibitor imatinib induces lysosome acidification and antimicrobial activity in glucocorticoid-treated macrophages without reversing the anti-inflammatory effects of glucocorticoids. Taken together, we provide evidence that the induction of cathelicidin by glucocorticoids is not sufficient for macrophage antimicrobial activity, and identify the vacuolar H(+)-ATPase as a potential target for host-directed therapy in the context of glucocorticoid therapy.