Antimicrobial susceptibility testing reveals reduced susceptibility to azithromycin and other antibiotics in Legionella pneumophila serogroup 1 isolates from Portugal.

BACKGROUD: Although not fully investigated, studies show that Legionella pneumophila can develop antibiotic resistance. As there is limited data available for Portugal, we determined the antibiotic susceptibility profile of Portuguese L. pneumophila serogroup 1 (LpnSg1) isolates against antibiotics used in the clinical practice in Portugal. METHODS: Minimum inhibitory concentrations (MICs) were determined for LpnSg1 clinical (n = 100) and related environmental (n = 7) isolates, collected between 2006-2022 in the context of the National Legionnaire´s Disease Surveillance Programme, against azithromycin, clarithromycin, erythromycin, levofloxacin, ciprofloxacin, moxifloxacin, rifampicin, doxycycline, tigecycline, and amoxicillin/clavulanic acid, using three different assays. Isolates were also PCR-screened for the presence of the lpeAB gene. RESULTS: Twelve isolates had azithromycin MICs above the EUCAST tentative highest WT MIC, 9 of which were lpeAB negative; for erythromycin and clarithromycin, all isolates tested within the susceptible range. The number of isolates with MICs above the tentative highest WT MIC for the remaining antibiotics was: ciprofloxacin: 7; levofloxacin: 17; moxifloxacin: 8; rifampicin: 11; doxycycline: 82; tigecycline: 4. EUCAST breakpoints are not available for amoxicillin/clavulanic acid. We estimated the ECOFFs and one isolate had a MIC eightfold higher than the E-test ECOFF. Additionally, a clinical isolate generated three colonies growing on the E-test inhibition zone that resulted in MICs fourfold higher than for the parental isolate. CONCLUSIONS: We report, for the first time, elevated MICs against first-line and other antibiotics (including azithromycin, fluoroquinolones and amoxicillin/clavulanic acid commonly used to treat pneumonia patients in Portugal) in Portuguese L. pneumophila strains. Results point towards decreased susceptibility in circulating strains, justifying further investigation.

Quantitative Microbial Risk Assessment of Antibiotic-Resistant E. coli, Legionella pneumophila, and Mycobacteria in Nonpotable Wastewater Reuse Applications.

Antibiotic-resistant bacteria (ARB) have become a major threat to public health and modern medicine. A simple death kinetics-based dose-response model (SD-DRM) was incorporated into a quantitative microbial risk assessment (QMRA) to assess the risks of exposure to reclaimed wastewater harboring antibiotic-resistant E. coli, Legionella pneumophila, and Mycobacterium avium for multiple exposure scenarios. The fractions of ARB and trace antibiotics present in the body were incorporated to demonstrate their impact on infection risks. Both ARB and antibiotic susceptible bacteria, ASB, are assumed to have the same dose-response in the absence of antibiotics but behave differently in the presence of residual antibiotics in the body. Annual risk of L. pneumophila infection exceeded the EPA 10-4 pppy (per person per year) benchmark at concentrations in reclaimed water greater than 103-104 CFU/L, depending on parameter variation. Enteropathogenic E. coli infection risks meet the EPA annual benchmark at concentrations around 105-106 total E. coli. The results illustrated that an increase in residual antibiotics from 0 to 40% of the minimum inhibitory concentration (MIC) reduced the risk by about 1 order of magnitude for E. coli but was more likely to result in an untreatable infection.

Efficacy of omadacycline in the treatment of Legionella pneumonia: a case report.

Legionella, one of the main pathogens that causes community-acquired pneumonia, can lead to Legionella pneumonia, a condition characterized predominantly by severe pneumonia. This disease, caused by the bacterium Legionella pneumophila, can quickly progress to critical pneumonia and is often associated with damage to multiple organs. As a result, it requires close attention in terms of clinical diagnosis and treatment. Omadacycline, a new type of tetracycline derivative belonging to the aminomethylcycline class of antibiotics, is a semi-synthetic compound derived from minocycline. Its key structural feature, the aminomethyl modification, allows omadacycline to overcome bacterial resistance and broadens its range of effectiveness against bacteria. Clinical studies have demonstrated that omadacycline is not metabolized in the body, and patients with hepatic and renal dysfunction do not need to adjust their dosage. This paper reports a case of successful treatment of Legionella pneumonia with omadacycline in a patient who initially did not respond to empirical treatment with moxifloxacin. The patient also experienced electrolyte disturbance, as well as dysfunction in the liver and kidneys, delirium, and other related psychiatric symptoms.

Epidemiological surveillance and wild-type MIC distribution of Legionella pneumophila in north-western Spain. 2003-2016 / Vigilancia epidemiológica y distribución de CMIs de cepas salvajes de Legionella pneumophila en el noroeste de España. 2003-2016

PURPOSE: To perform epidemiological surveillance of Legionella pneumophila in recreational swimming pools in the city of Valladolid (Spain), an area with a continental climate and low incidence of legionella-associated infections. Additionally, wild-type minimum inhibitory concentration (MIC) distributions for eight antibiotics commonly used for the treatment of legionellosis were calculated from the isolates obtained. METHODS: Twelve recreational pools were enrolled between June 2003 and December 2016 and 7221 water samples were taken from three different points of the water network (tank, tap and shower). Legionella culture was performed according to ISO 11731 and 11731-2 standards. MICs of antibiotics were obtained by a gradient test. RESULTS: 1.44% of the water samples were positive for L. pneumophila. 60 strains (57.69%) were isolated from showers, 26 (25.00%) from tanks and 18 (17.31%) from taps. L. pneumophila counts were < 100 CFU/L in 75 samples (72.12%), 100-1000 CFU/L in 17 (16.35%) and > 1000 CFU/L in 12 (11.54%). The MIC90 values obtained were for Rifampicin 0.125 mg/L; Trimethoprim-Sulfamethoxazole 0.25mg/L; Azithromycin and Levofloxacin 0.5 mg/L; Clarithromycin and Ciprofloxacin 1.0mg/L; Doxycycline and Tigecycline 4.0 mg/L. CONCLUSIONS: The use of showers in recreational pools can become a potential pathway for exposure to L. pneumophila, even in cold climates. The wild-type MIC distributions presented in this article may be useful for a better detection of antibiotic resistance and can contribute to improvements in the choice of the antibiotic treatment of legionellosis

PROPÓSITO: Realizar la vigilancia epidemiológica de Legionella pneumophila en piscinas recreacionales de Valladolid (España), un área con clima continental y baja incidencia de legionelosis. La distribución de las CMIs de ocho antibióticos usados en la legionelosis fue calculada a partir de los aislados obtenidos. MÉTODOS: Se incluyeron doce piscinas recreacionales entre junio 2003-diciembre 2016. 7.221 muestras de agua fueron tomadas en tres puntos de la red (vaso, grifo y ducha). El cultivo de legionela se realizó acorde a las normas ISO 11731 y 11731-2. Las CMIs de los antibióticos se obtuvieron mediante un método en gradiente. RESULTADOS: 1,44% de las muestras proporcionaron crecimiento de L. pneumophila. 60 cepas (57,69%) se aislaron en duchas, 26 (25,00%) en vasos y 18 (17,31%) en grifos. Los recuentos de L. pneumophila fueron < 100 UFC/L en 75 muestras (72,12%), 100-1.000 UFC/L en 17 (16,35%) y > 1.000 UFC/L en 12 (11,54%). Las CMI90 obtenidas fueron para rifampicina 0,125 mg/L; trimetoprim-sulfametoxazol 0,25 mg/L; azitromicina y levofloxacino 0,5 mg/L; clarithromicina y ciprofloxacino 1,0 mg/L; doxiciclina y tigeciclina 4, 0mg/L. CONCLUSIONES: El uso de las duchas en piscinas recreacionales puede convertirse en una vía potencial para la exposición a L. pneumophila, incluso en climas fríos. Las CMIs presentadas en este artículo son útiles para la detección de la resistencia a antibióticos y pueden mejorar la elección del tratamiento antibiótico de la legionelosis

Aspectos microbiológicos de las nuevas quinolonas: levofloxacina, sparfloxacina, trovafloxacina y grepafloxacina / Microbiological aspects of the new quinolones: levofloxacin, sparfloxacin, trovafloxacin and grepafloxacin

Las nuevas quinolonas "de tercera generación": levofloxacina, sparfloxacina, trovafloxacina, y grepafloxacina se caracterizan por mayor actividad in vitro que sus predecesoras sobre Streptococcus pneumoniae, Streptococcus pyogenes y Staphylococcus aureus sensible a meticilina, conservan actividad sobre bacilos Gram negativos entéricos (pero menos que ciprofloxacina), también son activas sobre agentes causales de neumonías atípicas (Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella pneumoniae) y en algunos casos, sobre especies anaerobias estrictas (trovafloxacina, sparfloxacina). Considerando los avances en espectro antibacteriano, constituirán en los próximos años un aporte significativo en el manejo de algunas patologías ambulatorias y de manejo intrahospitalario

Macrólidos en vías respiratorias bajas / Macrolides in lower respiratory tract

Los nuevos macrólidos se han constituido en terapias alternativas seguras para el tratamiento de neumonías leves o moderadas adquiridas en la comunidad y en individuos sin patología asociada. Son los antibióticos de elección frente a neumonías atípicas excepto para la producida por C. psittaci. Las mayores ventajas que aportan los macrólidos son la excelente tolerancia oral, su elevada concentración tisular e intracelular y una vida media prolongada que permite la fácil dosificación y la introducción de terapias acortadas asegurando una mejor adherencia al tratamiento. Las desventajas destacables son sus bajos niveles séricos y el elevado costo actual. Por último, se requiere de un uso racional de estos antibióticos y estudios de sensibilidad para estar alertas a la emergencia de resistencia como ya se ha descrito en otras latitudes, v.g. S. pneumoniae y S. pyogenes resistentes a todos los macrólidos