Skin hyperpigmentation following intravenous polymyxin B treatment associated with melanocyte activation and inflammatory process

Molecular mechanisms underlying Tao-Hong-Si-Wu decoction treating hyperpigmentation based on network pharmacology, Mendelian randomization analysis, and experimental verification

CONTEXT

Hyperpigmentation, a common skin condition marked by excessive melanin production, currently has limited effective treatment options.

OBJECTIVE

This study explores the effects of Tao-Hong-Si-Wu decoction (THSWD) on hyperpigmentation and to elucidate the underlying mechanisms.

MATERIALS AND METHODS

We employed network pharmacology, Mendelian randomization, and molecular docking to identify THSWD's hub targets and mechanisms against hyperpigmentation. The Cell Counting Kit-8 (CCK-8) assay determined suitable THSWD treatment concentrations for PIG1 cells. These cells were exposed to graded concentrations of THSWD-containing serum (2.5%, 5%, 10%, 15%, 20%, 30%, 40%, and 50%) and treated with α-MSH (100 nM) to induce an in vitro hyperpigmentation model. Assessments included melanin content, tyrosinase activity, and Western blotting.

RESULTS

ALB, IL6, and MAPK3 emerged as primary targets, while quercetin, apigenin, and luteolin were the core active ingredients. The CCK-8 assay indicated that concentrations between 2.5% and 20% were suitable for PIG1 cells, with a 50% cytotoxicity concentration (CC50) of 32.14%. THSWD treatment significantly reduced melanin content and tyrosinase activity in α-MSH-induced PIG1 cells, along with downregulating MC1R and MITF expression. THSWD increased ALB and p-MAPK3/MAPK3 levels and decreased IL6 expression in the model cells.

DISCUSSION AND CONCLUSION

THSWD mitigates hyperpigmentation by targeting ALB, IL6, and MAPK3. This study paves the way for clinical applications of THSWD as a novel treatment for hyperpigmentation and offers new targeted therapeutic strategies.

A pharmacovigilance study of adverse events associated with polymyxins based on the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) database

BACKGROUND

Polymyxins have been regarded as last-line treatment for multidrug-resistant gram-negative bacterial infections. Nonetheless, concerns regarding toxicity persist. This study aimed to explore and compare potential adverse events (AEs) between colistin and polymyxin B (PMB).

METHODS

Outpatient antibiotic use associated with acute upper respiratory infections in China: a nationwide cross-sectional study Polymyxins-related AEs were retrieved from the U.S. Food and Drug Administration Adverse Event Reporting System between 2004 and 2022. Potential signals were estimated by the reporting odds ratio (ROR), and subgroup analyses were preformed to adjust for potential factors in AEs with significant disproportionality.

RESULTS

Analysis of 3,915 records involving 718 patients revealed a higher disproportionality of renal and urinary disorders (ROR 1.62, 95% CI 1.01-2.59) and acute kidney injury (ROR 1.75, 95% CI 1.07-2.87) with colistin treatment. Conversely, colistin exhibited a lower risk for neurotoxicity (ROR 0.47, 95% CI 0.30-0.73). Seven cases of skin hyperpigmentation were reported with PMB, whereas none were reported with colistin. Over 80% of cases involving polymyxin-related AEs occurred during the first two weeks of therapies, with a median onset time of 4.5 days.

CONCLUSIONS

Outpatient antibiotic use associated with acute upper respiratory infections in China: a nationwide cross-sectional study Patients received colistin displayed a higher potential risk of nephrotoxicity but a lower risk of neurotoxicity. Clinicians should be vigilant in monitoring the AEs of hyperpigmentation disorders induced by PMB.

The Influence of Blue Light Exposure on Reconstructed 3-Dimensional Skin Model: Molecular Changes and Gene Expression Profile

Recent studies have provided information about digital eye strain and the potential damage that blue light from digital devices can cause to the eyes. In this study, we analyzed the influence of blue light exposure on reconstructed 3-dimensional skin model using RNA sequencing to identify the expression of transcripts and abnormal events. Three-dimensional skin was exposed to visible light spectrum and isolated blue wavelength for 1, 2, and 4 hours to represent acute exposure and 1 hour over 4 sequential days to represent repeated exposure, respectively, in this in vitro model. We compared gene expression levels with those of unexposed control. Samples submitted to repeated exposure showed reduced AK2 and DDX47, whereas they showed increased PABPC3 gene expression, revealing a significantly negative impact. RT-PCR validation assay with exposed 3-dimensional skin compared with unexposed control regarding 1 and 4 days of incubation showed increased IL-6 signaling mechanism activation and signal transducer and activator of transcription 3 gene STAT3 gene expression, whereas it showed decreased peroxisome proliferator-activated receptor signaling mechanism activation, suggesting an influence on inflammatory pathways. We also demonstrate upregulated gene expression of KIT, MAPK2, and PI3KC in samples from exposed condition, corroborating previous findings related to pigmentation signaling stimuli. These results reveal, to our knowledge, previously unreported data that enable studies on molecular response correlation of in vitro digital blue light exposure and human skin studies.

Clinical Efficacy and Safety of Colistin Sulfate in the Treatment of Carbapenem-Resistant Organism Infections in Patients with Hematological Diseases

INTRODUCTION

Carbapenem-resistant organisms (CRO) have emerged as a significant worldwide issue. However, the availability of efficacious antibiotics for treating CRO infections remains limited. Polymyxins, including colistin sulfate, represent the last-line therapeutic option against CRO infections. This study aims to retrospectively evaluate the clinical effectiveness and safety of colistin sulfate in managing CRO infections among patients with hematological diseases.

METHODS

Between April 2022 and January 2023, a total of 118 hematological patients diagnosed with CRO infection were treated with colistin sulfate at Suzhou Hongci Hospital of Hematology. The assessment encompassed the clinical efficacy, bacterial clearance rate, adverse reactions, and 30-day all-cause mortality.

RESULTS

The study found that the total effective rate of colistin sulfate in the treatment of CRO infection was 74.6%, with a bacterial clearance rate of 72.6%. Throughout the treatment, nephrotoxicity occurred in 7.6% of cases, neurotoxicity in 2.5% of cases, and the 30-day all-cause mortality rate was 22.9%. Multivariate logistic analysis revealed that the treatment course and combination medication with other antimicrobials were independent factors affecting the clinical efficacy of colistin sulfate.

CONCLUSION

Our study demonstrates that the treatment of colistin sulfate can achieve high clinical efficacy and microbial responses, with a low risk of nephrotoxicity. This study provides evidence of the positive clinical efficacy and safety of colistin sulfate treatment in these patients. High-quality randomized controlled trials are still needed to further confirm the beneficial role of colistin sulfate.

Hyperpigmentation on head and neck caused by polymyxin B: A rare case

Polymyxin B was widely used to treat drug-resistant gram-negative bacteria and showed a better antibacterial effect. However, it is associated with some side effects. It should be remembered that polymyxin B may cause hyperpigmentation, albeit rare. This is a case report of a 68-year-old male patient who developed hyperpigmentation following treatment of a chest infection with polymyxin B. He was a known patient with chronic kidney diasease and chronic obstructive pulmonary disease followed up in the intensive care unit due to acute exacerbation of COPD. Later, polymyxin B treatment was started due to the development of pneumonia caused by the multidrug-resistant Acinetobacter baumannii. On the second day of polymyxin B treatment, hyperpigmentation developed in the face and neck region. The fact that the patient had chronic kidney disease possibly facilitated the development of skin hyperpigmentation due to the cumulative effect of polymyxin B. Hyperpigmentation which a rare side effect of polymyxin B may occur in those with underlying kidney disease.

Rare occurrence of polymyxin B-induced hyperpigmentation in a child with ventriculitis

Polymyxin B (PB) is a polypeptide bactericidal antibiotic that is commonly used for extensively drug-resistant (XDR) microorganisms such as Acinetobacter baumanii and Klebsiella pneumoniae It can be administered intravenously or intrathecally. Common side effects are nephrotoxicity, neurotoxicity, pruritus and skin hyperpigmentation (SH). The latter is an uncommon adverse reaction of intravenously administered PB. We report a rare occurrence of PB-induced SH secondary to intrathecal administration of PB in a child with A. baumanii XDR ventriculitis. We describe the management of him and a brief review of PB.

Treatment of Carbapenem-Resistant Multidrug-Resistant Gram-Negative Bacilli with Intracerebroventricular Injection of Polymyxin B: A Retrospective Study

Purpose

We evaluated the efficacy and administration time of intraventricular (IVT) polymyxin B in the treatment of carbapenem-resistant and multidrug-resistant/extensively drug-resistant (MDR/XDR) Gram-negative bacilli in central nervous system (CNS) infections and investigated prognostic factors.

Patients and Methods

This retrospective analysis comprised 41 post-surgical carbapenem-resistant CNS infections from October 2016 to October 2021. All patients were treated with effective intravenous antibiotics and IVT polymyxin B. Patient characteristics, therapeutic procedure, symptoms, cerebrospinal fluid (CSF) examination, laboratory tests, and complications were recorded. The effectiveness of IVT polymyxin B was evaluated using temperature, Glasgow Coma Scale, CSF contents, bacterial clearance rate, cure rate, and mortality. Mortality between early (7 days) and late administration of IVT polymyxin B was compared. Prognostic factors were evaluated using the pupillary light reflex and multiloculated hydrocephalus.

Results

The 41 patients acquired carbapenem-resistant MDR/XDR bacteria, including 24 Klebsiella pneumoniae, 15 Acinetobacter baumannii, 3 Pseudomonas aeruginosa, and 1 Enterobacter cloacae. The bacterial clearance rate was 32/41 (78.0%), and 9 patients (22.0%) with uncured bacterial infections died. Adverse events included 1 case of skin pigmentation. Among the 32 cured patients, 31 received a ventriculoperitoneal shunt, and 1 patient had an extraventricular drainage tube removed. Mortality in the late (>7 days) group was higher (39.1% vs 0%, P < 0.05). The group without pupillary light reflex showed a higher death rate (41.2% vs 8.3%; P < 0.05). The multiloculated hydrocephalus group had a higher mortality rate than that of the normal group (34.8% vs 5.6%, P < 0.05). All 32 cured patients were followed up for 9 to 66 months, and all survived without recurrent infections.

Conclusion

Intraventricular polymyxin B is an effective treatment for carbapenem-resistant MDR/XDR Gram-negative bacilli, with a 78% cure rate and significant mortality reduction if administered within 7 days of bacterial identification. Multiloculated hydrocephalus and the pupillary light reflex may be used as prognostic indicators of mortality.

Low-dose intravenous plus inhaled versus intravenous polymyxin B for the treatment of extensive drug-resistant Gram-negative ventilator-associated pneumonia in the critical illnesses: a multi-center matched case-control study

Background

The mortality of extensively drug-resistant Gram-negative (XDR GN) bacilli-induced ventilator-associated pneumonia (VAP) is extremely high. The purpose of this study was to compare the efficacy and safety of inhaled (IH) plus intravenous (IV) polymyxin B versus IV polymyxin B in XDR GN bacilli VAP patients.

Methods

A retrospective multi-center observational cohort study was performed at eight ICUs between January 1^st 2018, and January 1^st 2020 in China. Data from all patients treated with polymyxin B for a microbiologically confirmed VAP were analyzed. The primary endpoint was the clinical cure of VAP. The favorable clinical outcome, microbiological outcome, VAP-related mortality and all-cause mortality during hospitalization, and side effects related with polymyxin B were secondary endpoints. Favorable clinical outcome included clinical cure or clinical improvement.

Results

151 patients and 46 patients were treated with IV polymyxin B and IH plus IV polymyxin B, respectively. XDR Klebsiella pneumoniae was the main isolated pathogen (n = 83, 42.1%). After matching on age (± 5 years), gender, septic shock, and Apache II score (± 4 points) when polymyxin B was started, 132 patients were included. 44 patients received simultaneous IH plus IV polymyxin B and 88 patients received IV polymyxin B. The rates of clinical cure (43.2% vs 27.3%, p = 0.066), bacterial eradication (36.4% vs 23.9%, p = 0.132) as well as VAP-related mortality (27.3% vs 34.1%, p = 0.428), all-cause mortality (34.1% vs 42.0%, p = 0.378) did not show any significant difference between the two groups. However, IH plus IV polymyxin B therapy was associated with improved favorable clinical outcome (77.3% vs 58.0%, p = 0.029). Patients in the different subgroups (admitted with medical etiology, infected with XDR K. pneumoniae, without bacteremia, with immunosuppressive status) were with odd ratios (ORs) in favor of the combined therapy. No patient required polymyxin B discontinuation due to adverse events. Additional use of IH polymyxin B (aOR 2.63, 95% CI 1.06, 6.66, p = 0.037) was an independent factor associated with favorable clinical outcome.

Conclusions

The addition of low-dose IH polymyxin B to low-dose IV polymyxin B did not provide efficient clinical cure and bacterial eradication in VAP caused by XDR GN bacilli.

Keypoints

Additional use of IH polymyxin B was the sole independent risk factor of favorable clinical outcome. Patients in the different subgroups were with HRs substantially favoring additional use of IH polymyxin B. No patients required polymyxin B discontinuation due to adverse events.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01033-5.

Outcome of Using Intraventricular Plus Intravenous Polymyxin B in Post-neurosurgical Patients With Multi/Extensively Drug-Resistant Gram-Negative Bacteria-Induced Intracranial Infection

Introduction

Post-neurosurgical central nervous system (CNS) infection caused by multidrug-resistant (MDR)/extensively drug-resistant (XDR) Gram-negative bacteria remains a major clinical challenge. This study describes our experience of treating such patients with combined intraventricular (IVT) and intravenous (IV) polymyxin B administration.

Methods

This retrospective study included six patients with post-neurosurgical CNS infections of carbapenem-resistant Acinetobacter baumannii (CRAB) or carbapenem-resistant Klebsiella pneumoniae (CRKP). All patients were treated in the intensive care unit (ICU) of First Affiliated Hospital, Zhejiang University School of Medicine (Hangzhou, China) between November 2020 and November 2021, and all received IVT plus IV polymyxin B. Data including patients' characteristics, therapeutic process, symptoms, cerebrospinal fluid (CSF) examination, laboratory tests, and complications were collected.

Results

Six patients with post-neurosurgical CNS infection were enrolled in the study. The patients comprised five males and one female, and the average age was 58 years (range, 38–73 years). Four out of the six cases were CRAB-positive in CSF culture, while two cases were CRKP-positive. The mean duration of polymyxin B administration was 14 ± 5.69 days (range, 6–20 days). The average period of patients reaching CSF sterilization was 10.33 ± 3.67 days (range, 5–14 days). All six cases were cured without acute kidney injury or epilepsy.

Conclusion

IVT plus IV polymyxin B is a safe and effective treatment for post-neurosurgical patients with intracranial infection caused by MDR/XDR Gram-negative bacteria.

Higher Incidence of Neurotoxicity and Skin Hyperpigmentation in Renal Transplant Patients Treated With Polymyxin B

BACKGROUND

Toxicity is a major concern related to the clinical use of polymyxin B, and available safety data for renal transplant patients are limited.

AIMS

We investigated the safety of polymyxin B and toxicity risk factors in renal transplant patients.

METHODS

A prospective study was performed on a group of renal transplant patients who received intravenous polymyxin B between January 2018 and August 2021. Polymyxin B treatment was monitored to evaluate toxicity and risk factors.

RESULTS

A total of 235 courses of polymyxin B were administered to 213 patients. Of these, 121 (51.5%) developed SH, 149 (63.4%) developed neurotoxicity, and 10 (5.5%) developed acute kidney injury of which 80% was reversible. Risk factors for developing SH included a high total dose by weight (OR=1.31, 95%CI: 1.08-1.60, p=0.008) and the presence of neurotoxicity (OR=2.86, 95%CI: 1.56-5.26, p=0.001). Neurotoxicity manifested during the first two days of treatment. Neurotoxicity occurred most commonly in women (OR=3.84, 95%CI: 1.82-8.10, p<0.0001), and the presence of SH (OR=1.98, 95%CI: 1.13-3.46, p=0.016) was also an independent risk factor.

CONCLUSIONS

Neurotoxicity and SH are the two major adverse effects of polymyxin B in renal transplant patients, which may limit its clinical use.

Proteomic Response Revealed Signaling Pathways Involving in the Mechanism of Polymyxin B-Induced Melanogenesis

Polymyxin B is a last-line antibiotic for extensively resistant Gram-negative bacterial infection. Skin hyperpigmentation is a serious side effect induced by polymyxin B that severely compromises the psychological health and compliance of patients. The literature lacks mechanistic studies that explain how hyperpigmentation occurs, and this substantially hinders the development of intervention strategies and improved compliance. SK-MEL-2 cells were used for the polymyxin B-induced hyperpigmentation mechanism study. Melanin content and tyrosinase activity were measured after polymyxin B treatment. Tandem mass tag (TMT)-labeling quantitative proteomics was employed to investigate the response of SK-MEL-2 cells to polymyxin B treatment. Real-time quantitative PCR and Western blot were applied to validate the mRNA and protein levels of related genes and proteins. The melanin content and tyrosinase activity were significantly upregulated after polymyxin B treatment in SK-MEL-2 cells at 48 h and 72 h. Quantitative proteomics showed that 237 proteins were upregulated and 153 proteins were downregulated in the 48 h group, and 49 proteins were upregulated and 49 proteins were downregulated in the 72 h group. The differentially expressed proteins were involved in pathways such as lysosome, PI3K/Akt signaling pathway, and calcium signaling pathway. The upregulation of melanogenic enzymes and microphthalmia-associated transcription factor (MITF) was validated by qPCR and Western blot. Meanwhile, phosphorylation of PI3K, β-catenin, and cyclic-AMP response binding protein (CREB) in response to polymyxin B treatment was observed. The present study reveals the proteomic response of polymyxin B-induced melanogenesis in SK-MEL-2 cells for the first time. Signaling pathways, including melanin biosynthesis, PI3K/Akt, and calcium signaling pathways may be involved in the mechanism of melanogenesis. IMPORTANCE Polymyxin B-induced skin hyperpigmentation seriously affects the psychological health and compliance of patients. This study provides a proteomic clue to the mechanism at the cellular level for understanding polymyxin B-induced hyperpigmentation, contributing to a follow-up investigation of the corresponding PI3K/Akt signaling transduction pathway and calcium signaling pathway. The elucidation of its underlying mechanism is of great significance for patients' compliance improvement, intervention strategy, and new drug development.

Role of Amine Neurotransmitters and Their Receptors in Skin Pigmentation: Therapeutic Implication

Skin pigmentation can occur due to increased melanin, including melanocyte proliferation, melanin biosynthesis, or melanocyte migration. There are many factors that influence the melanin production process, but the role of neurotransmitters in this process is still unclear. We found that histamine and serotonin influence the different stages of melanogenesis and melanogenesis, which increase melanogenesis. Since then, several related papers have been published, and from these papers, it has been recognised that the role of neurotransmitters in skin-pigment-related diseases needs to be summarised. By introducing the role of neurotransmitters in the regulation of various pigment disorders, including vitiligo and melasma, through this review, many researchers can be expected to try to apply neurotransmitter-related agonists and antagonists as treatments for skin pigment disorders.

Rescuing the Last-Line Polymyxins: Achievements and Challenges

Antibiotic resistance is a major global health challenge and, worryingly, several key Gram negative pathogens can become resistant to most currently available antibiotics. Polymyxins have been revived as a last-line therapeutic option for the treatment of infections caused by multidrug-resistant Gram negative bacteria, in particular Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacterales. Polymyxins were first discovered in the late 1940s but were abandoned soon after their approval in the late 1950s as a result of toxicities (e.g., nephrotoxicity) and the availability of "safer" antibiotics approved at that time. Therefore, knowledge on polymyxins had been scarce until recently, when enormous efforts have been made by several research teams around the world to elucidate the chemical, microbiological, pharmacokinetic/pharmacodynamic, and toxicological properties of polymyxins. One of the major achievements is the development of the first scientifically based dosage regimens for colistin that are crucial to ensure its safe and effective use in patients. Although the guideline has not been developed for polymyxin B, a large clinical trial is currently being conducted to optimize its clinical use. Importantly, several novel, safer polymyxin-like lipopeptides are developed to overcome the nephrotoxicity, poor efficacy against pulmonary infections, and narrow therapeutic windows of the currently used polymyxin B and colistin. This review discusses the latest achievements on polymyxins and highlights the major challenges ahead in optimizing their clinical use and discovering new-generation polymyxins. To save lives from the deadly infections caused by Gram negative "superbugs," every effort must be made to improve the clinical utility of the last-line polymyxins. SIGNIFICANCE STATEMENT: Antimicrobial resistance poses a significant threat to global health. The increasing prevalence of multidrug-resistant (MDR) bacterial infections has been highlighted by leading global health organizations and authorities. Polymyxins are a last-line defense against difficult-to-treat MDR Gram negative pathogens. Unfortunately, the pharmacological information on polymyxins was very limited until recently. This review provides a comprehensive overview on the major achievements and challenges in polymyxin pharmacology and clinical use and how the recent findings have been employed to improve clinical practice worldwide.

Acute toxicity is a dose-limiting factor for intravenous polymyxin B: A safety and pharmacokinetic study in healthy Chinese subjects

OBJECTIVES

Polymyxin B is a last-line antibiotic for multidrug-resistant gram-negative bacterial infections. However, limited safety and pharmacokinetic information is available. We investigated the safety and pharmacokinetics of intravenous polymyxin B in healthy subjects.

METHODS

An open-label, single-dose clinical trial was conducted in healthy Chinese subjects. Polymyxin B (sulphate) was administered intravenously at 0.75 or 1.5 mg/kg (n = 10 per dose, 5 males and 5 females) to examine the safety and pharmacokinetics.

RESULTS

One female subject in the 1.5-mg/kg group discontinued due to abdominal pain during administration. The most frequently reported adverse events were perioral paraesthesia, dizziness, and numbness of extremities (7/10 subjects in the 0.75-mg/kg group, all subjects in the 1.5-mg/kg group). All neurotoxicity-related events dissipated without treatment within a maximum of 23 h. Notably, abdominal pain (3/5) and vulvar pruritus (2/5), colpitis (2/5) or abnormal uterine bleeding (1/5) were reported in female subjects receiving the 1.5-mg/kg dose. In the 0.75-mg/kg group, the total clearance, volume of distribution and half-life of polymyxin B were 0.028±0.002 L/h/kg, 0.219±0.023 L/kg and 5.44±0.741 h, respectively; similar values were observed in the 1.5-mg/kg group. Urinary recovery was 3.7 ± 1.1% and 8.1 ± 1.3% in the 0.75- and 1.5-mg/kg groups, respectively. Population pharmacokinetics of polymyxin B was consistent with a three-compartment model. The clearance and distribution of the central compartment were 0.027 L/h/kg and 0.071 L/kg, respectively.

CONCLUSIONS

This study is the first to examine the safety and pharmacokinetics of polymyxin B in healthy subjects. Our results highlight that acute toxicity is a dose-limiting factor for intravenous polymyxin B.

Polymyxin B-Induced Skin Hyperpigmentation

Polymyxin B-induced skin hyperpigmentation is a rare adverse drug reaction (ADR). In this report, we present the case of a patient who underwent an abscess resection with right epididymitis, in which a multidrug-resistant Klebsiella pneumoniae infection (KPI) is formed. The patient was treated with polymyxin B and subsequently developed skin hyperpigmentation and desquamation. The desquamation improved and the pigmentation gradually returned to normal after sixty days after the withdrawal of polymyxin B.

Polymyxins and Bacterial Membranes: A Review of Antibacterial Activity and Mechanisms of Resistance

Following their initial discovery in the 1940s, polymyxin antibiotics fell into disfavor due to their potential clinical toxicity, especially nephrotoxicity. However, the dry antibiotic development pipeline, together with the rising global prevalence of infections caused by multidrug-resistant (MDR) Gram-negative bacteria have both rejuvenated clinical interest in these polypeptide antibiotics. Parallel to the revival of their use, investigations into the mechanisms of action and resistance to polymyxins have intensified. With an initial known effect on biological membranes, research has uncovered the detailed molecular and chemical interactions that polymyxins have with Gram-negative outer membranes and lipopolysaccharide structure. In addition, genetic and epidemiological studies have revealed the basis of resistance to these agents. Nowadays, resistance to polymyxins in MDR Gram-negative pathogens is well elucidated, with chromosomal as well as plasmid-encoded, transferrable pathways. The aims of the current review are to highlight the important chemical, microbiological, and pharmacological properties of polymyxins, to discuss their mechanistic effects on bacterial membranes, and to revise the current knowledge about Gram-negative acquired resistance to these agents. Finally, recent research, directed towards new perspectives for improving these old agents utilized in the 21st century, to combat drug-resistant pathogens, is summarized.

Polymyxin B-induced skin hyperpigmentation

Polymyxin B (PMB) is a potent antibiotic targeting gram-negative bacteria and is associated with serious side effects including nephrotoxicity, neurotoxicity, and hypersensitivity reactions. PMB is a therapeutic option for the management of infections caused by multi-drug-resistant (MDR) bacteria and used in combination with other antibiotics when options are limited. We describe the case of a 30-year-old female patient with a complex medical history who underwent a multi-visceral transplantation complicated by intra-abdominal infections. Subsequently, patient developed diffuse skin darkening after initiation of intravenous PMB for treatment of MDR Pseudomonas aeruginosa. Her skin hyperpigmentation was most prominent on her face and forearms. Hyperpigmentation peaked at around 2 weeks following PMB initiation and was discontinued after 3 weeks when the possibility of PMB hyperpigmentation was raised and other causes were ruled out. Skin biopsy showed hypermelanosis of the basal layer and melanin deposition in the dermis. Overall clinical picture was consistent with PMB-induced hyperpigmentation. The patient demonstrated some improvement in discoloration within 4 weeks of PMB discontinuation.

Polymyxin B-induced skin hyperpigmentation: a rare case report and literature review

Background

Polymyxin B (PMB), which is regarded as the ultimate antibacterial treatment against some intractable gram-negative bacteria with its outstanding anti-bacterial activities, inflicts several adverse effects on patients. However, skin hyperpigmentaion (SH) induced by PMB is very rare. Here, we report a case of polymyxin B-induced skin hyperpigmentation (PMB-iSH) in a 21-year-old female. To the best of our knowledge, this is the first case of PMB-iSH in China.

Case presentation

A 21-year-old female patient with sepsis received the administration of PMB by intravenous injection for the treatment of multi-drug resistant Klebsiella pneumoniae (MDR-KP) infection. She later suffered from a rare adverse drug reaction (ADR), namely PMB-iSH, after 5-day PMB administration during her treatment. There were multiple red rashes spread on the whole body skin at first. With the rashes fading away, SH with dark round spots appeared, associated with no pain or pruritus. The skin of the head and neck was darkened evidently, and dark brown spots were spread on the skin of trunk and limbs. About a month after her admission, urged by the relatives, the patient was transferred back to the local hospital for further treatment in the end, and her skin color didn’t recover to the previous state at that time.

Conclusion

Both our case and the literature review highlight that PMB can give rise to SH indeed. Clinicians and pharmacists should attach great importance to this rare pigmentary disorder and further investigation is warranted.