In vitro activity of various antibiotics against clinical strains of Legionella species isolated in Japan

Synthesis and antibacterial activity evaluation of N (7) position-modified balofloxacins

A series of small-molecule fluoroquinolones were synthesized, characterized by HRMS and NMR spectroscopy, and screened for their antibacterial activity against MRSA, P. aeruginosa, and E. coli as model G+/G− pathogens. Compounds 2-e, 3-e, and 4-e were more potent than the reference drug balofloxacin against MRSA and P. aeruginosa (MIC values of 0.0195 and 0.039 μg/ml for 2-e, 0.039 and 0.078 μg/ml for each of 3-e and 4-e, respectively). Analysis of the time-dependent antibacterial effect of compound 2-e toward MRSA showed that in the early logarithmic growth phase, bactericidal effects occurred, while in the late logarithmic growth phase, bacterial inhibition occurred because of concentration effects and possibly the development of drug resistance. Compound 2-e exhibited low toxicity toward normal mammalian cell lines 3T3 and L-02 and tumor cell lines A549, H520, BEL-7402, and MCF-7. The compound was not hemolytic. Atomic force microscopy (AFM) revealed that compound 2-e could effectively destroy the membrane and wall of MRSA cells, resulting in the outflow of the cellular contents. Docking studies indicated the good binding profile of these compounds toward DNA gyrase and topoisomerase IV. ADMET’s prediction showed that most of the synthesized compounds followed Lipinski’s “rule of five” and possessed good drug-like properties. Our data suggested that compound 2-e exhibited potent anti-MRSA activity and is worthy of further investigation.

Detection of highly macrolide-resistant Legionella pneumophila strains from a hotel water network using systematic whole-genome sequencing

OBJECTIVES

Implementation of an antibiotic resistance detection tool in Legionella daily surveillance at the French National Reference Centre for Legionella.

METHODS

Systematic WGS of Legionella pneumophila isolates and bioinformatics detection of specific mutations linked to antibiotic resistance. Phenotypic validation of antibiotic resistance detected by WGS was performed by the broth microdilution method.

RESULTS

More than 3000 L. pneumophila strains were screened for antibiotic resistance. A macrolide resistance-associated A2052G mutation in the 23S rRNA gene was identified in the genome of eight isolates from a hotel water network. High-level macrolide resistance (i.e. MICs of 1024-2048 mg/L for azithromycin and erythromycin) with no cross-resistance to other antimicrobials was phenotypically confirmed by antimicrobial susceptibility testing for the eight isolates.

CONCLUSIONS

Systematic WGS of L. pneumophila is a powerful tool for first-line high-throughput screening of antibiotic resistance before phenotypic validation.

Overview of the Clinical and Molecular Features of Legionella Pneumophila: Focus on Novel Surveillance and Diagnostic Strategies

Legionella pneumophila (L. pneumophila) is one of the most threatening nosocomial pathogens. The implementation of novel and more effective surveillance and diagnostic strategies is mandatory to prevent the occurrence of legionellosis outbreaks in hospital environments. On these bases, the present review is aimed to describe the main clinical and molecular features of L. pneumophila focusing attention on the latest findings on drug resistance mechanisms. In addition, a detailed description of the current guidelines for the disinfection and surveillance of the water systems is also provided. Finally, the diagnostic strategies available for the detection of Legionella spp. were critically reviewed, paying the attention to the description of the culture, serological and molecular methods as well as on the novel high-sensitive nucleic acid amplification systems, such as droplet digital PCR.

Atypical pneumonia: Pathophysiology, diagnosis, and treatment

Atypical pneumonia is caused by atypical pathogens that are not detectable with Gram stain and cannot be cultured using standard methods. The most common causative organisms of atypical pneumonia are Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella species. The therapeutic approach for atypical pneumonias is different than that for typical pneumonia. Typical bacterial pathogens classically respond to β-lactam antimicrobial therapy because they have a cell wall amenable to β-lactam disruption. On the contrary, most atypical pathogens do not have a bacterial cell wall, some are intracellular (e.g., Legionella), and some are paracellular (e.g., M. pneumoniae). To prevent an increase in the number of antimicrobial-resistant strains, the Japanese pneumonia guidelines have proposed a differential diagnosis for typical bacterial pneumonia and atypical pneumonia to select an appropriate antibiotic for the management of mild-to-moderate pneumonia. The guidelines have set up six parameters and criteria based on the clinical symptoms, physical signs, and laboratory data. However, in the elderly individuals and patients with underlying diseases, the differential diagnosis may be difficult or a mixed infection may be latent. Therefore, in these individuals, the administration of a β-lactam drug plus a macrolide or tetracycline, or only fluoroquinolone should be considered from the beginning to cover bacterial and atypical pneumonia.

Legionella antimicrobial sensitivity testing: comparison of microbroth dilution with BCYE and LASARUS solid media

OBJECTIVES

There is a lack of international unification for AST methodology for Legionella pneumophila. Current literature contains multiple possible methods and this study compares each of them to determine methodological concordance.

METHODS

Antibiotic susceptibility of 50 L. pneumophila strains was determined using broth microdilution (BMD), serial antimicrobial dilution in traditional buffered charcoal yeast extract (BCYE) agar (as well as comparison with gradient strip overlay on BCYE) and in a novel charcoal-free agar (LASARUS) for rifampicin, azithromycin, levofloxacin and doxycycline.

RESULTS

The deviation of tested media relative to BMD highlighted the overall similarity of BMD and LASARUS across all antimicrobials tested (within one serial dilution). BCYE agar dilution showed an increased MIC of up to five serial dilutions relative to BMD, while MICs by gradient strip overlay on BCYE were elevated by two to three serial dilutions, with the exception of doxycycline, which was decreased by three serial dilutions relative to MIC values determined by BMD. The MIC range for azithromycin was wider than for other antimicrobials tested and found to be caused by the presence or absence of the lpeAB gene.

CONCLUSIONS

BMD-based antimicrobial susceptibility testing (AST) methodology should be the internationally agreed gold standard for Legionella spp. AST, as is common for other bacterial species. Traditional BCYE gave significantly elevated MIC results and its use should be discontinued for Legionella spp., while MIC determination using LASARUS solid medium gave results concordant (within one serial dilution) with BMD for all antimicrobials tested. To the best of our knowledge, this study is the first to identify the lpeAB gene in UK isolates.

Legionella longbeachae pneumonia: Case report and review of reported cases in non-endemic countries

Legionella longbeachae pneumonia is much less common than Legionella pneumophila pneumonia in most of the world and may evade timely diagnosis in settings that rely primarily on urine antigen testing, which detects Legionella pnuemophila serogroup 1 only. It is, however, widely recognized in Australia and New Zealand, where it is endemic and associated with exposure to compost and potting soils, rather than contaminated water systems as seen with L. pneumophila. L. longbeachae can cause a similar spectrum and severity of illness as L. pneumophila. Here we present a case of a 47-year-old man with L. longbeacheae necrotizing pneumonia following exposure to possibly contaminated soil from a wastewater treatment facility. Initial presentation included cough, chest pain, and dyspnea, and progressed to hypoxic respiratory failure, tension pneumothorax, and cardiac arrest. L. pneumophila urine antigen was negative, but bronchioalveolar lavage samples grew L. longbeachae on buffered charcoal yeast extract agar. A review of cases reported in the literature in non-endemic regions over a 20-year period identified 38 cases in Europe, 33 in Asia, and 8 in North America. Average age was 65, 65 % were male, and 35 % had potentially relevant environmental exposures. L. longbeachae should be considered in cases of severe community acquired pneumonia, particularly following a consistent environmental exposure or if initial testing for other pathogens is unrevealing. A thorough exposure history including questions about contact with potting soil or compost, and utilization of specialized agar for culture can both be key in identifying this pathogen.

Meta-analysis of fluoroquinolones versus macrolides for treatment of legionella pneumonia

BACKGROUND

Only a single meta-analysis has reported the clinical benefit of fluoroquinolones (FQs) for Legionella pneumonia; however, there is no robust data available to confirm this result, based on current guidelines.

METHODS

We performed a systematic review and meta-analysis comparing FQs with macrolides (MCs) on their efficacy and safety in Legionella pneumonia, using studies published until January 2020. The outcomes included mortality (overall; 30-day), clinical cure, time to apyrexia, length of hospital stay, and adverse events.

RESULTS

Five RCTs and twelve retrospective studies were identified. Clinical cure was comparable between the treatment groups (risk rate (RR) 1.07, 95% confidential interval (CI) 0.86-1.31). Mortality was significantly higher for MCs than for FQs (overall, odd rate (OR) 0.59, 95% CI 0.35-0.98; 30-day, OR 0.41, 95% CI 0.20-0.85). FQs significantly reduced the length of hospital stay, compared to MCs (mean difference -3.58, 95% CI -5.48-1.69). Other outcomes were not significantly different between the treatment groups (time to apyrexia; mean difference -1.83, 95% CI -5.15-1.5, adverse events; OR 0.61, 95% CI 0.33-1.15). In subgroup analyses, levofloxacin significantly reduced the length of hospital stay over two specific MCs (azithromycin and clarithromycin) (mean difference -3.03, 95% CI -5.33-0.72), whereas mortality was not significantly different between the treatment groups (overall, OR 0.49, 95% CI 0.19-1.24; 30-day, OR 0.38, 95% CI 0.13-1.13).

CONCLUSIONS

FQs exhibited superior effects in terms of mortality and length of hospital stay in Legionella pneumonia. These results support current guidelines recommending FQs for the treatment of Legionella pneumonia.

Antibiotic Resistance of Legionella pneumophila in Clinical and Water Isolates-A Systematic Review

The current systematic review investigates the antibiotic susceptibility pattern of Legionella pneumophila isolates from the 1980s to the present day, deriving data from clinical and/or water samples from studies carried out all over the world. Eighty-nine papers meeting the inclusion criteria, i.e., “Legionella pneumophila” and “resistance to antibiotics”, were evaluated according to pre-defined validity criteria. Sixty articles referred to clinical isolates, and 18 articles reported water-related L. pneumophila isolates, while 11 articles included both clinical and water isolates. Several methods have been proposed as suitable for the determination of MICs, such as the E-test, broth and agar dilution, and disk diffusion methods, in vivo and in vitro, using various media. The E-test method proposed by the European Society of Clinical Microbiology and Infectious Diseases (EUCAST) seems to be the second most frequently used method overall, but it is the preferred method in the most recent publications (2000–2019) for the interpretation criteria. Erythromycin has been proved to be the preference for resistance testing over the years. However, in the last 19 years, the antibiotics ciprofloxacin (CIP), erythromycin (ERM), levofloxacin (LEV) and azithromycin (AZM) were the ones that saw an increase in their use. A decrease in the sensitivity to antibiotics was identified in approximately half of the reviewed articles.

Fatal Fulminant Legionnaires' Disease in a Patient on Maintenance Hemodialysis

We herein report a case of fulminant Legionnaires' disease with autopsy findings in a patient on maintenance hemodialysis (HD). Chronic kidney disease is a strong risk factor for Legionnaires' disease, although there have been only a few reports in HD patients. Because most patients on HD are anuric, the use of rapid assay kits to detect antigens in urine samples for the diagnosis of Legionnaires' disease is not always feasible. We suggest the use of clinical predictive tools or the loop-mediated isothermal amplification (LAMP) method, which can be applied for anuric patients, such as those on HD, with pneumonia.

Distribution of Legionella species and serogroups in patients with culture-confirmed Legionella pneumonia

Legionella species are consistently identified as some of the most common causative agents of severe community-acquired pneumonia (CAP) or nosocomial pneumonia. Although the number of reported Legionella infection cases is gradually increasing in Japan, most cases are diagnosed by a urinary antigen test, which identifies only L. pneumophila serogroup 1. Therefore, assessment of pneumonia-causing Legionella species and serogroups would be important. The Japan Society for Chemotherapy Legionella committee has collected the isolates and clinical information on cases of sporadic community-acquired Legionella pneumonia throughout Japan. Between December 2006 and March 2019, totally 140 sporadic cases were identified, in which L. pneumophila was the most frequently isolated species (90.7%) followed by L. bozemanae (3.6%), L. dumofii (3.6%), L. micdadei (1.4%), and L. longbeachae (0.7%). Among 127 isolates of L. pneumophila, 111 isolates were of serogroup 1, two of serogroup 2, four of serogroup 3, one of serogroup 4, one of serogroup 5, seven of serogroup 6, and one was of serogroup 10. We also assessed in vitro activity of antibiotics against these isolates and showed that quinolones and macrolides have potent anti-Legionella activity. Our study showed that pneumonia-causing Legionella species and serogroup distribution was comparable to that reported in former surveillances. L. pneumophila was the most common etiologic agent in patients with community-acquired Legionella pneumonia, and L. pneumophila serogroup 1 was the predominant serogroup.

Antibiotic susceptibility of environmental Legionella pneumophila isolated in India

Aim: Data are limited regarding the antibiotic susceptibility of Legionella pneumophila in India. The aim of this study was to determine the drug susceptibility of environmental L. pneumophila isolates in India for antibiotics commonly used in clinical practice for Legionnaires' disease treatment. Materials & methods: The activities of seven antibiotics against 46 environmental isolates of L. pneumophila were evaluated by using E-test on buffered charcoal yeast extract-α agar. Results: Among the L. pneumophila isolates tested, no tendency toward drug resistance was observed. Rifampicin was the most potent drug followed by levofloxacin, while doxycycline and tetracycline were found to be the less active agents. Conclusion: Susceptibility testing of Legionella environmental isolates could be beneficial to notify resistance to antibiotics in the environment before it becomes evident in clinical strains.