Assessment of three antibiotic combination regimens against Gram-negative bacteria causing neonatal sepsis in low- and middle-income countries.

Gram-negative bacteria (GNB) are a major cause of neonatal sepsis in low- and middle-income countries (LMICs). Although the World Health Organization (WHO) reports that over 80% of these sepsis deaths could be prevented through improved treatment, the efficacy of the currently recommended first- and second-line treatment regimens for this condition is increasingly affected by high rates of drug resistance. Here we assess three well known antibiotics, fosfomycin, flomoxef and amikacin, in combination as potential antibiotic treatment regimens by investigating the drug resistance and genetic profiles of commonly isolated GNB causing neonatal sepsis in LMICs. The five most prevalent bacterial isolates in the NeoOBS study (NCT03721302) are Klebsiella pneumoniae, Acinetobacter baumannii, E. coli, Serratia marcescens and Enterobacter cloacae complex. Among these isolates, high levels of ESBL and carbapenemase encoding genes are detected along with resistance to ampicillin, gentamicin and cefotaxime, the current WHO recommended empiric regimens. The three new combinations show excellent in vitro activity against ESBL-producing K. pneumoniae and E. coli isolates. Our data should further inform and support the clinical evaluation of these three antibiotic combinations for the treatment of neonatal sepsis in areas with high rates of multidrug-resistant Gram-negative bacteria.

Nocardia keratitis after small incision lenticule extraction (SMILE).

We report the case of a female patient in her late 20s who visited the clinic with concerns about poor vision, redness, watering and a burning sensation in her left eye 2 weeks after undergoing a small incision lenticule extraction. She had no history of systemic illness or immunosuppressed status. On slit lamp examination, she was found to have corneal stromal infiltrates in the interface at multiple locations. Given the clinical diagnosis of microbial keratitis, corneal scraping of the interface infiltrate was performed and sent for microbiological examination revealing gram-positive, thin, beaded filaments that were acid-fast positive and later identified by growth in culture media as Nocardia species. This case was managed successfully with the use of topical amikacin and systemic trimethoprim-sulfamethoxazole with complete resolution of infection.

Mycobacterium senegalense catheter-related bloodstream infection.

Catheter-related bloodstream infection (CRBSI) is one of the common healthcare-acquired infections imposing a high burden of morbidity and mortality on the patients. Non-tuberculous mycobacterium is a rare aetiology for CRBSI and poses challenges in laboratory diagnosis and clinical management. This is a case of a woman in her early 60s with underlying end-stage renal failure, diabetes mellitus and hypertension presented with a 2-week history of high-grade fever postregular haemodialysis, vomiting, lethargy and altered mental status.Blood cultures from a permanent catheter and peripheral taken concurrently yielded Mycobacterium senegalense, identified by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, which established the diagnosis of CRBSI atypically presented with concurrent acute intracranial bleeding and cerebrovascular infarction at initial presentation. She was started on a combination of oral azithromycin, oral amikacin and intravenous imipenem, and the permanent catheter was removed. Despite the treatments instituted, she developed septicaemia, acute myocardial infarction and macrophage activation-like syndrome, causing the patient's death.

D-histidine combated biofilm formation and enhanced the effect of amikacin against Pseudomonas aeruginosa in vitro.

Pseudomonas aeruginosa is an opportunistic gram-negative pathogenic microorganism that poses a significant challenge in clinical treatment. Antibiotics exhibit limited efficacy against mature biofilm, culminating in an increase in the number of antibiotic-resistant strains. Therefore, novel strategies are essential to enhance the effectiveness of antibiotics against Pseudomonas aeruginosa biofilms. D-histidine has been previously identified as a prospective anti-biofilm agent. However, limited attention has been directed towards its impact on Pseudomonas aeruginosa. Therefore, this study was undertaken to explore the effect of D-histidine on Pseudomonas aeruginosa in vitro. Our results demonstrated that D-histidine downregulated the mRNA expression of virulence and quorum sensing (QS)-associated genes in Pseudomonas aeruginosa PAO1 without affecting bacterial growth. Swarming and swimming motility tests revealed that D-histidine significantly reduced the motility and pathogenicity of PAO1. Moreover, crystal violet staining and confocal laser scanning microscopy demonstrated that D-histidine inhibited biofilm formation and triggered the disassembly of mature biofilms. Notably, D-histidine increased the susceptibility of PAO1 to amikacin compared to that in the amikacin-alone group. These findings underscore the efficacy of D-histidine in combating Pseudomonas aeruginosa by reducing biofilm formation and increasing biofilm disassembly. Moreover, the combination of amikacin and D-histidine induced a synergistic effect against Pseudomonas aeruginosa biofilms, suggesting the potential utility of D-histidine as a preventive strategy against biofilm-associated infections caused by Pseudomonas aeruginosa.

A simulation study on model-informed precision dosing of amikacin for achieving target area under the concentration-time curve.

AIMS: Amikacin requires therapeutic drug monitoring for optimum efficacy; however, the optimal model-informed precision dosing strategy for the area under the concentration-time curve (AUC) of amikacin is uncertain. This simulation study aimed to determine the efficient blood sampling points using the Bayesian forecasting approach for early achievement of the target AUC range for amikacin in critically ill patients. METHODS: We generated a virtual population of 3000 individuals using 2 validated population pharmacokinetic models identified using a systematic literature search. AUC for each blood sampling point was evaluated using the probability of achieving a ratio of estimated/reference AUC at steady state in the 0.8-1.2 range. RESULTS: On day 1, the 1-point samplings for population pharmacokinetic models showed a priori probabilities of 26.3 and 45.6%, which increased to 47.3 and 94.4% at 23 and 15 h, respectively. Using 2-point sampling at the peak (3 and 4 h) and trough (24 h) on day 1, these probabilities further increased to 72.3 and 99.5%, respectively. These probabilities were comparable on days 2 and 3, regardless of 3 and 6 sampling points or estimated glomerular filtration rate. These results indicated the higher predictive accuracy of 2-point sampling than 1-point sampling on day 1 for amikacin AUC estimation. Moreover, 2-point sampling was a more reasonable approach than rich sampling. CONCLUSIONS: This study contributes to the development of an efficient model-informed precision dosing strategy for early targeting of amikacin AUC in critically ill patients.

Molecular pharmacodynamics of meropenem for nosocomial pneumonia caused by Pseudomonas aeruginosa.

Hospital-acquired pneumonia (HAP) is a leading cause of morbidity and mortality, commonly caused by Pseudomonas aeruginosa. Meropenem is a commonly used therapeutic agent, although emergent resistance occurs during treatment. We used a rabbit HAP infection model to assess the bacterial kill and resistance pharmacodynamics of meropenem. Meropenem 5 mg/kg administered subcutaneously (s.c.) q8h (±amikacin 3.33-5 mg/kg q8h administered intravenously[i.v.]) or meropenem 30 mg/kg s.c. q8h regimens were assessed in a rabbit lung infection model infected with P. aeruginosa, with bacterial quantification and phenotypic/genotypic characterization of emergent resistant isolates. The pharmacokinetic/pharmacodynamic output was fitted to a mathematical model, and human-like regimens were simulated to predict outcomes in a clinical context. Increasing meropenem monotherapy demonstrated a dose-response effect to bacterial kill and an inverted U relationship with emergent resistance. The addition of amikacin to meropenem suppressed the emergence of resistance. A network of porin loss, efflux upregulation, and increased expression of AmpC was identified as the mechanism of this emergent resistance. A bridging simulation using human pharmacokinetics identified meropenem 2 g i.v. q8h as the licensed clinical regimen most likely to suppress resistance. We demonstrate an innovative experimental platform to phenotypically and genotypically characterize bacterial emergent resistance pharmacodynamics in HAP. For meropenem, we have demonstrated the risk of resistance emergence during therapy and identified two mitigating strategies: (i) regimen intensification and (ii) use of combination therapy. This platform will allow pre-clinical assessment of emergent resistance risk during treatment of HAP for other antimicrobials, to allow construction of clinical regimens that mitigate this risk.IMPORTANCEThe emergence of antimicrobial resistance (AMR) during antimicrobial treatment for hospital-acquired pneumonia (HAP) is a well-documented problem (particularly in pneumonia caused by Pseudomonas aeruginosa) that contributes to the wider global antimicrobial resistance crisis. During drug development, regimens are typically determined by their sufficiency to achieve bactericidal effect. Prevention of the emergence of resistance pharmacodynamics is usually not characterized or used to determine the regimen. The innovative experimental platform described here allows characterization of the emergence of AMR during the treatment of HAP and the development of strategies to mitigate this. We have demonstrated this specifically for meropenem-a broad-spectrum antibiotic commonly used to treat HAP. We have characterized the antimicrobial resistance pharmacodynamics of meropenem when used to treat HAP, caused by initially meropenem-susceptible P. aeruginosa, phenotypically and genotypically. We have also shown that intensifying the regimen and using combination therapy are both strategies that can both treat HAP and suppress the emergence of resistance.

Methylobacterium infection-induced peritonitis in a patient with renal insufficiency: A case report and literature review.

Clinical pharmacists participated in the drug therapy of peritonitis caused by Methylobacterium infection in a patient with renal insufficiency. Based on the knowledge of clinical pharmacy, the patient's condition and laboratory parameters, the literature, and the pharmacokinetic/pharmacodynamic characteristics of antibiotics, amikacin in combination with ciprofloxacin was suggested for anti-infection therapy. During the treatment, clinical pharmacists timely evaluated the efficacy of antibiotics, monitored the adverse reactions, and provided individualized pharmaceutical care in the patient.

Comparing minimum inhibitory concentrations of amikacin for pulmonary Mycobacterium avium complex disease: An analysis of culture media differences.

Mycobacterium avium complex (MAC) is considered a paramount microbe, especially in East Asia, including Japan. The commonly used commercial Minimum Inhibitory Concentrations (MIC) assay using Middlebrook 7H9 (7H9) medium deviates from the latest Clinical and Laboratory Standards Institute (CLSI) guidelines. Alternatively, measurement with cation-adjusted Mueller-Hinton broth (CAMHB) that conforms to CLSI standards is not yet widely available. Following the approval and commercialization of amikacin liposome inhalation suspension (ALIS) in 2021, a more precise evaluation of amikacin (AMK) susceptibility in MAC is necessary for treatment decisions. In the present study, 33 sputum samples were extracted from 27 patients, and MICs of AMK were compared between the frequently used 7H9 and the recommended CAMHB of the isolated MAC strains. The history of exposure to aminoglycosides for each sample was also added as clinical information. The findings indicated that there was only an 18% concordance rate in MIC between the two media, with 19 samples (58%) indicating lower MICs in 7H9 relative to CAMHB. The 17 samples had a history of exposure to aminoglycosides for periods ranging from 1.5 to 28 months. Specifically, 10 samples were exposed to amikacin by inhalation and intravenous injection, and the remaining seven samples had a history of ALIS inhalation. Samples with a prior utilization of aminoglycosides were significantly predisposed to developing resistance to ALIS compared to those without such a history (P = 0.046). Physicians are encouraged to scrutinize the findings of susceptibility testing utilizing CLSI-endorsed MIC assay using CAMHB medium to ascertain the optimal therapeutic approach.

Outcomes of Intermittent Multidrug IV Therapy for Refractory Mycobacterium abscessus Pulmonary Disease.

BACKGROUND: No studies have reported therapies for the treatment of patients with refractory Mycobacterium abscessus pulmonary disease (MAB-PD). We implemented intermittent multidrug IV therapy (IMIT) through repeated hospitalizations for patients with MAB-PD who were refractory to antibiotics for more than 12 months. RESEARCH QUESTION: What are the effects of IMIT on patients with refractory MAB-PD? STUDY DESIGN AND METHODS: The IV antibiotics administered for IMIT included amikacin, imipenem, and tigecycline, and the outcomes for 36 patients who underwent IMIT for refractory MAB-PD were evaluated. Patients were repeatedly hospitalized and administered IMIT on recurrent symptoms or radiographic evidence of deterioration, while maintaining oral/inhaled antibiotics. RESULTS: Of the 36 patients, 26 (72%) had M abscessus subspecies abscessus (herein, M abscessus)-PD, and 10 (28%) had M abscessus subspecies massiliense (herein, M massiliense)-PD. The median number of hospitalizations for IMIT was two (interquartile range, 1-3) for patients with M abscessus-PD and one (interquartile range, 1-2) for patients with M massiliense-PD. At least one negative culture result and culture conversion were observed in 62% and 12% of patients with M abscessus-PD, and in 80% and 60% of patients with M massiliense-PD, respectively. Symptomatic improvement was observed in all patients, and radiologic improvement, including cavity amelioration or no deterioration, was observed in 42% and 70% of patients with M abscessus-PD and with M massiliense-PD, respectively. No resistance to clarithromycin or amikacin was acquired. INTERPRETATION: IMIT with intermittent hospitalization can be a beneficial palliative treatment for patients with refractory MAB-PD. This therapy alleviated symptoms, slowed radiologic progression, and reduced the bacterial burden in some patients. However, radiologic and microbiological responses to IMIT were more apparent in M massiliense-PD than in M abscessus-PD.

Increased expression of Mycobacterium tuberculosis Rv3737 gene associated with low-level amikacin resistance.

INTRODUCTION: As an infectious disease, tuberculosis (TB) poses a serious threat to public health. Although amikacin (AMK) is an important antibiotic for the treatment of drug-resistant TB, its resistance mechanisms are not fully understood. METHODS: To investigate the role of Rv3737 gene on AMK drug susceptibility, a Mycobacterium tuberculosis (M.tb) Rv3737 knockout strain (H37Rv△Rv3737) and a Mycobacterium smegmatis (M.sm) Rv3737 overexpressing strain (Msm/pMV261-Rv3737) were used to detect their minimal inhibitory concentrations (MICs) in this study. RESULTS: The AMK MICs of Rv3737 knockout and overexpressing strains were 4-fold lower and 2-fold higher than those of the wild-type and empty plasmid strains, respectively. The results of clinical isolates showed that no Rv3737 gene mutation was found to be associated with AMK susceptibility, while the rrs A1401G mutation remained the main mechanism of high level of AMK resistance (MIC>32 µg/ml). There was a positive correlation between Rv3737 mRNA expression level and AMK MIC. In the isolates with low-level AMK resistance (MIC = 4 µg/ml) without rrs A1401G mutation, the expression level of Rv3737 gene was significantly higher than those of susceptible isolates. CONCLUSIONS: In this study, the Rv3737 gene was reported for the first time for its effect on AMK susceptibility in M.tb. Although the rrs A1401G mutation remains the main reason of high-level AMK resistance, high expression of the Rv3737 gene was associated with low-level AMK resistance in clinical isolates.

Aortic endograft infection by Mycobacterium abscessus subsp. massiliense with acquired clarithromycin resistance: a case report.

BACKGROUND: Mycobacterium abscessus subsp. massiliense (MMA) comprises a group of non-tuberculous, rapidly growing mycobacteria. Although MMA can cause pulmonary diseases, surgical site infections, and disseminated diseases, aortic endograft infection has not been reported. Here, we describe the first case of aortic endograft infection caused by MMA. CASE PRESENTATION: Two months after stent-graft insertion for an abdominal aortic aneurysm, an 85-year-old man was admitted with fever and abdominal pain and was diagnosed with aortic endograft infection. Despite 14 days of meropenem and vancomycin intravenous administration, periaortic fluid pooling increased as compared to that before antibiotic administration. The abscess was drained, and fluorescent acid-fast staining of the abscess fluid revealed bacilli. We conducted genetic tests on the genes hsp65, rpoB, and sodA, performed Whole Genome Sequencing (WGS), and identified the organism as MMA. Intravenous imipenem-cilastatin (IPM/CS), amikacin (AMK), and oral clarithromycin (CAM) were administered. After 2 months, oral CAM and sitafloxacin were administered because the abscess had decreased in size. However, after 6 weeks, the abscess increased in size again. Antimicrobial susceptibility testing of the drainage fluid from the abscess resulted in the isolation of an MMA strain that had acquired resistance to CAM. Intravenous IPM/CS, AMK, and oral linezolid were added to the treatment regimen along with oral CAM and STFX. However, he was not fully cured and died 6 months later. Neither the full-length erythromycin ribosome methyltransferase (erm)(41) gene nor the rrl or rpIV gene mutations were found by Sanger sequencing in the pre- and post-treatment strains. Whole-genome sequence analysis of the post-treatment strain revealed mutations in genes with no previous reports of association with macrolide resistance. CONCLUSIONS: Aortic endograft infection caused by MMA strain is extremely rare; nonetheless, MMA should be suspected as the causative microorganism when broad-spectrum antimicrobials are ineffective.

Treatment of Mycobacterium avium Complex Pulmonary Disease: When Should I Treat and What Therapy Should I Start?

Treatment of M avium pulmonary disease requires a three-drug, macrolide-based regimen that is administered for 12 months beyond culture conversion. The regimen can be administered 3 days a week in non-cavitary, nodular bronchiectatic disease but should be given daily when cavitary disease is present. For treatment refractory disease, amikacin liposome inhalation suspension is added to the regimen. Parenteral amikacin or streptomycin should be administered in the setting of extensive radiographic involvement or macrolide resistance. Recurrence of disease is common and often due to reinfection. Novel and repurposed agents are being evaluated in clinical trials.

Inhaled Amikacin to Prevent Ventilator-Associated Pneumonia.

BACKGROUND: Whether preventive inhaled antibiotics may reduce the incidence of ventilator-associated pneumonia is unclear. METHODS: In this investigator-initiated, multicenter, double-blind, randomized, controlled, superiority trial, we assigned critically ill adults who had been undergoing invasive mechanical ventilation for at least 72 hours to receive inhaled amikacin at a dose of 20 mg per kilogram of ideal body weight once daily or to receive placebo for 3 days. The primary outcome was a first episode of ventilator-associated pneumonia during 28 days of follow-up. Safety was assessed. RESULTS: A total of 850 patients underwent randomization, and 847 were included in the analyses (417 assigned to the amikacin group and 430 to the placebo group). All three daily nebulizations were received by 337 patients (81%) in the amikacin group and 355 patients (83%) in the placebo group. At 28 days, ventilator-associated pneumonia had developed in 62 patients (15%) in the amikacin group and in 95 patients (22%) in the placebo group (difference in restricted mean survival time to ventilator-associated pneumonia, 1.5 days; 95% confidence interval [CI], 0.6 to 2.5; P = 0.004). An infection-related ventilator-associated complication occurred in 74 patients (18%) in the amikacin group and in 111 patients (26%) in the placebo group (hazard ratio, 0.66; 95% CI, 0.50 to 0.89). Trial-related serious adverse effects were seen in 7 patients (1.7%) in the amikacin group and in 4 patients (0.9%) in the placebo group. CONCLUSIONS: Among patients who had undergone mechanical ventilation for at least 3 days, a subsequent 3-day course of inhaled amikacin reduced the burden of ventilator-associated pneumonia during 28 days of follow-up. (Funded by the French Ministry of Health; AMIKINHAL ClinicalTrials.gov number, NCT03149640; EUDRA Clinical Trials number, 2016-001054-17.).

In vitro evaluation of human intravenous immunoglobulin in combination with antimicrobials and human serum against multidrug-resistant isolates of Acinetobacter baumannii.

The high incidence of multidrug-resistant (MDR) Acinetobacter baumannii has been a challenge for health worldwide, due to the reduction of therapeutic options, making the use of antimicrobial combinations necessary for the treatment, such as meropenem, amikacin, and colistin. Antibodies against bacterial species, mainly immunoglobulins G (IgG), are produced for acting as effector mechanisms (neutralization, opsonization, phagocytosis, and complement system activation). Some studies have demonstrated promising results of IgG in combination with antimicrobial preparations against bacterial infections, in which the direct action of IgG has restored the immune system balance. Serious problem caused by the increase of MDR A. baumannii isolates results in a constant search for therapeutic alternatives to defeat these infections. However, this study aims to verify in vitro the phagocytosis rate of the A. baumannii-infected human monocytes, as well as to analyze possible morphological changes induced by intravenous immunoglobulin G (IVIG) with human serum in association with antimicrobials. The phagocytosis rate and bacterial cell binding capacity of IVIG were determined for two A. baumannii isolates submitted to 4 mg/mL of human IVIG alone and in combination with different sub-minimum inhibitory concentrations (sub-MICs) of meropenem, amikacin, and colistin and processed for indirect immunofluorescence. Subsequently, these isolates were resubmitted and coupled with human serum and processed for scanning electron microscopy. There was no statistical difference for phagocytosis rates in the isolates tested. Bacterial isolates showed alterations in cell morphology when exposed to IVIG/human serum alone and in combination with antimicrobials such as alteration in shape, wrinkling, membrane depression, and especially cell rupture with extravasation of cytoplasmic material. The isolates visually differed in the IVIG binding to the bacterial cell, with higher fluorescence intensity, which corresponds to the highest IVIG binding, in the isolate more sensitive to meropenem, amikacin, and colistin. No differences between treatments were observed in the IVIG binding to the bacterial cell. The combined action of IVIG with meropenem, amikacin, and colistin against A. baumannii MDR isolates induced several bacterial cell damages. And when associated with human serum, a massive destruction of cells can be observed. These results may suggest the analysis of the use of IgG preparations for the treatment of A. baumannii MDR infections.

Antimicrobial drug resistant features of Mycobacterium tuberculosis associated with treatment failure.

Tuberculosis stands as a prominent cause of mortality in developing countries. The treatment of tuberculosis involves a complex procedure requiring the administration of a panel of at least four antimicrobial drugs for the duration of six months. The occurrence of treatment failure after the completion of a standard treatment course presents a serious medical problem. The purpose of this study was to evaluate antimicrobial drug resistant features of Mycobacterium tuberculosis associated with treatment failure. Additionally, it aimed to evaluate the effectiveness of second line drugs such as amikacin, linezolid, moxifloxacin, and the efflux pump inhibitor verapamil against M. tuberculosis isolates associated with treatment failure. We monitored 1200 tuberculosis patients who visited TB centres in Lahore and found that 64 of them were not cured after six months of treatment. Among the M. tuberculosis isolates recovered from the sputum of these 64 patients, 46 (71.9%) isolates were simultaneously resistant to rifampicin and isoniazid (MDR), and 30 (46.9%) isolates were resistant to pyrazinamide, Resistance to amikacin was detected in 17 (26,5%) isolates whereas resistance to moxifloxacin and linezolid was detected in 1 (1.5%) and 2 (3.1%) isolates respectively. Among MDR isolates, the additional resistance to pyrazinamide, amikacin, and linezolid was detected in 15(23.4%), 4(2.6%) and 1(1.56%) isolates respectively. One isolate simultaneously resistant to rifampicin, isoniazid, amikacin, pyrazinamide, and linezolid was also identified. In our investigations, the most frequently mutated amino acid in the treatment failure group was Serine 315 in katG. Three novel mutations were detected at codons 99, 149 and 154 in pncA which were associated with pyrazinamide resistance. The effect of verapamil on the minimum inhibitory concentration of isoniazid and rifampicin was observed in drug susceptible isolates but not in drug resistant isolates. Rifampicin and isoniazid enhanced the transcription of the efflux pump gene rv1258 in drug susceptible isolates collected from the treatment failure patients. Our findings emphasize a high prevalence of MDR isolates linked primarily to drug exposure. Moreover, the use of amikacin as a second line drug may not be the most suitable choice in such cases.