Complicated skin and soft-tissue infections--consider gram-negative pathogens

In vitro activity of ceftaroline and comparators against bacterial isolates collected globally from patients with skin infections

OBJECTIVES

This study reports the antimicrobial activities of ceftaroline and comparators against bacterial isolates from patients with skin and skin-structure infections (2015-2018).

METHODS

A central laboratory performed antimicrobial susceptibility testing according to CLSI broth microdilution methodology. EUCAST breakpoints were used.

RESULTS

Isolates were collected in Europe (14 408 isolates; 53.9%), Asia/South Pacific (SP) (5317; 19.9%), Latin America (4268; 16.0%) and Africa/Middle East (ME) (2753; 10.3%). In all regions, all 7950 methicillin-susceptible Staphylococcus aureus (MSSA) isolates were susceptible to ceftaroline and vancomycin; susceptibility to daptomycin, linezolid, teicoplanin and tigecycline was ≥99.6%. Susceptibility of all 9174 methicillin-resistant S. aureus (MRSA) isolates to daptomycin, linezolid, teicoplanin, tigecycline and vancomycin was ≥97.7%, with 90.8-96.5% susceptible to ceftaroline. The ceftaroline MIC90 was 0.008 mg/L against Streptococcus pyogenes, 0.015-0.03 mg/L against Streptococcus agalactiae and 0.008-0.015 mg/L against Streptococcus dysgalactiae. All β-haemolytic streptococci were susceptible to vancomycin. Susceptibility of extended-spectrum β-lactamase (ESBL)-negative Escherichia coli to ceftaroline ranged from 67.0% in Asia/SP to 91.0% in Africa/ME; susceptibility to amikacin, meropenem and tigecycline was ≥96.7% in all regions. Susceptibility of ESBL-negative Klebsiella pneumoniae to ceftaroline ranged from 78.4% in Europe to 83.2% in Africa/ME, and among ESBL-negative Klebsiella oxytoca was 76.3% in Asia/SP and 89.0-93.5% in other regions. Among ESBL-negative K. pneumoniae and ESBL-negative K. oxytoca, susceptibility was highest to amikacin (93.7-96.4% and 95.7-100%, respectively) and meropenem (89.7-97.4% and 98.3-100%, respectively).

CONCLUSION

Ceftaroline was active against the Gram-positive isolates collected. Susceptibility of ESBL-negative Gram-negative isolates showed regional variations.

High-Throughput Identification of Antibacterials Against Pseudomonas aeruginosa

Antibiotic resistance is a growing public health concern, though the constant development of new antibiotics. The combination of high-throughput screening and drug repurposing is an effective way to develop new therapeutic uses of drugs. In this study, we screened a drug library consisting of 1,573 drugs already approved by the Food and Drug Administration and 903 drugs from the natural product library, to identify antimicrobials against Pseudomonas aeruginosa. A high-throughput screening assay based on microtiter plate was used to screen 39 drugs that inhibit the planktonic or biofilm formation of P. aeruginosa while most of them are antibiotics. The antimicrobial activities of these drugs were evaluated by phenotypic analysis. Further studies showed the combined therapy of tetracycline antibiotics demeclocycline hydrochloride (DMCT) and the novel antimicrobial peptide SAAP-148 has an effective synergistic antibacterial effect on P. aeruginosa PAO1 and P. aeruginosa ATCC27853. Moreover, the time-kill curve assay and murine model of cutaneous abscesses further confirmed the synergistic effect. In addition, the combination of DMCT and SAAP-148 has the potential to combat clinically isolated multidrug-resistant (MDR) P. aeruginosa strains. Our results clearly indicate that DMCT and SAAP-148 combined therapy could be an effective method to combat MDR P. aeruginosa-related infections.

Skin microbiome differences relate to the grade of acne vulgaris

The skin microbiome plays important roles in the pathogenesis and development of acne. We aimed to investigate the facial skin microbiome of acne and microbiome differences related to different grades of acne. Skin swabs from nine healthy controls and 67 acne patients were collected, and the skin microbiomes were analyzed using 16S rRNA gene sequencing. Compared with healthy controls, acne patients harbored significantly altered skin microbiomes. The skin microbiomes of patients with grade 1-3 acne were similar, but patients with grade 4 acne showed a significantly different skin microbiome compared with grade 1-3 acne, including increased alpha diversity and increased proportions of four Gram-negative bacteria (Faecalibacterium, Klebsiella, Odoribacter and Bacteroides). In conclusion, acne patients harbored an altered skin microbiome, and more significant dysbiosis was found in patients with grade 4 acne (severe acne). Our findings may provide evidence for the pathogenic mechanisms of acne and microbial-based strategies to avoid and treat acne, especially grade 4 acne.

Impact of health care-associated community-onset cellulitis in Korea: a multicenter study

We conducted a multicenter study to determine the clinical and microbiological characteristics of health care-associated (HCA) cellulitis in Korea. We retrospectively reviewed the medical records of patients who had been diagnosed with community-onset cellulitis. Of the 2208 cellulitis patients, 232 (10.5%) had HCA cellulitis, 1243 (56.3%) patients were hospitalized, and 15 (0.7%) died in hospital. Compared with community-acquired (CA) cellulitis, patients with HCA cellulitis were older and more frequently presented with comorbidity and septic shock. A total of 355 microorganisms were isolated from 314 patients (14.2%). Staphylococcus aureus (134 isolates) was the most common organism, followed by Streptococcus spp. (86 isolates) and Gram-negative fermenters (58 isolates). Methicillin-resistant S. aureus (MRSA) accounted for 29.1% (39/134) of S. aureus infections. None of the Gram-negative fermenters were resistant to carbapenem. The antibiotic susceptibility pattern of isolated microorganisms was not different between HCA and CA cellulitis. In patients with HCA cellulitis, S. aureus (11.2% [26/232] vs. 5.5% [108/1976], p = 0.001), including MRSA (4.3% [10/232] vs. 1.5% [29/1976], p = 0.003) and Gram-negative fermenters (6.0% [14/232] vs. 2.3% [44/1976], p = 0.002), were more common causative organisms than in CA-cellulitis patients. Age ≥ 65 years, septic shock, and HCA infection were statistically significant factors associated with in-hospital mortality.

Infectious Adverse Events Following Acupuncture: Clinical Progress and Microbiological Etiology

BACKGROUND

We investigated the clinical progress and bacteriological characteristics of infectious adverse events (AEs) following acupuncture and compared patient characteristics between serious and non-serious outcome groups.

METHODS

A retrospective observational study was conducted in 1,174 patients with infectious complications associated with acupuncture at the emergency department (ED) in a tertiary hospital in Korea between 2010 and 2014. Serious outcome was defined as development of septic shock, admission to intensive care unit (ICU) or attaining permanent morbidity.

RESULTS

Forty-eight patients had certain causality and cellulitis, necrotizing fasciitis and osteomyelitis were common in order. Among them, 9 patients (18.8%) were categorized into serious outcome group, and they showed devastating outcomes such as septic shock (n = 2), ICU admission (n = 4), and permanent sequelae (n = 5). The serious group had delayed admission to the ED after acupuncture (30.0 [4.0-55.0] vs. 3.0 [1.0-10.0] days, P = 0.023). Methicillin-sensitive Staphylococcus aureus was the most frequently identified microorganism. The patients in the serious group required longer treatment duration (139.0 [49.0-183.5] vs. 14.0 [7.0-34.0] days, P < 0.001) as well as more operation with local (44.4% vs. 10.3%, P = 0.031) or general anaesthesia (33.3% vs. 2.6%, P = 0.017).

CONCLUSION

The infectious AEs after acupuncture may cause serious outcomes. Patients and primary physicians should be aware of the risk of infectious complications and make efforts to prevent them.

New Mouse Model for Chronic Infections by Gram-Negative Bacteria Enabling the Study of Anti-Infective Efficacy and Host-Microbe Interactions

Only a few, relatively cumbersome animal models enable long-term Gram-negative bacterial infections that mimic human situations, where untreated infections can last for weeks. Here, we describe a simple murine cutaneous abscess model that enables chronic or progressive infections, depending on the subcutaneously injected bacterial strain. In this model, Pseudomonas aeruginosa cystic fibrosis epidemic isolate LESB58 caused localized high-density skin and soft tissue infections and necrotic skin lesions for up to 10 days but did not disseminate in either CD-1 or C57BL/6 mice. The model was adapted for use with four major Gram-negative nosocomial pathogens, Acinetobacter baumannii, Klebsiella pneumoniae, Enterobacter cloacae, and Escherichia coli. This model enabled noninvasive imaging and tracking of lux-tagged bacteria, the influx of activated neutrophils, and production of reactive oxygen-nitrogen species at the infection site. Screening antimicrobials against high-density infections showed that local but not intravenous administration of gentamicin, ciprofloxacin, and meropenem significantly but incompletely reduced bacterial counts and superficial tissue dermonecrosis. Bacterial RNA isolated from the abscess tissue revealed that Pseudomonas genes involved in iron uptake, toxin production, surface lipopolysaccharide regulation, adherence, and lipase production were highly upregulated whereas phenazine production and expression of global activator gacA were downregulated. The model was validated for studying virulence using mutants of more-virulent P. aeruginosa strain PA14. Thus, mutants defective in flagella or motility, type III secretion, or siderophore biosynthesis were noninvasive and suppressed dermal necrosis in mice, while a strain with a mutation in the bfiS gene encoding a sensor kinase showed enhanced invasiveness and mortality in mice compared to controls infected with wild-type P. aeruginosa PA14.

More than two-thirds of hospital infections are chronic or high-density biofilm infections and difficult to treat due to adaptive, multidrug resistance. Unfortunately, current models of chronic infection are technically challenging and difficult to track without sacrificing animals. Here we describe a model of chronic subcutaneous infection and abscess formation by medically important nosocomial Gram-negative pathogens that is simple and can be used for tracking infections by imaging, examining pathology and immune responses, testing antimicrobial treatments suitable for high-density bacterial infections, and studying virulence. We propose that this mouse model can be a game changer for modeling hard-to-treat Gram-negative bacterial chronic and skin infections.

The Antimicrobial Activity of (-)-Epigallocatehin-3-Gallate and Green Tea Extracts against Pseudomonas aeruginosa and Escherichia coli Isolated from Skin Wounds

Background

Skin infections with Gram-negative bacteria are sometimes challenging to treat, because these bacteria show multidrug resistance against commonly used antibiotics and patients with Gram-negative bacterial infection overall have deteriorated in conditions in many cases. Studies have shown that epigallocatechin gallate (EGCG) and green tea extracts (GTE) inhibit the growth of several Gram-positive bacteria species.

Objective

The purpose of this study was to investigate the minimum inhibitory concentrations (MICs) of EGCG and GTE in Pseudomonas aeruginosa and Escherichia coli, and assess the use of these chemicals as an alternative or adjunct topical antimicrobial agent against P. aeruginosa and E. coli with multidrug resistance.

Methods

The MICs of EGCG, GTE, and other tested antibiotics were measured and compared to determine the antibacterial efficacy and the differences in pattern of resistance.

Results

The P. aeruginosa and E. coli strains used in this study showed multidrug resistance. EGCG inhibited the growth of P. aeruginosa at a MIC level of 200~400 µg/ml. The MIC of GTE was a 1 : 16 dilution for P. aeruginosa. EGCG showed antimicrobial activity against E. coli at a MIC of 400 µg/ml. In the case of GTE, the MIC was a dilution between 1:8 and 1:4 for E. coli.

Conclusion

EGCG and GTE showed potential as alternative or adjunct topical antimicrobial agents for infections that are resistant to traditional antibiotic therapy.

Fatal Escherichia coli skin and soft tissue infections in liver transplant recipients: report of three cases

Gram-negative bacilli are unusual agents of skin and soft tissue infections. Most previous cases have been reported in cirrhotic or immunocompromised patients, including a single case in a liver transplant recipient. The present report describes 3 cases of fatal skin or soft tissue infections caused by Escherichia coli that occurred in the postoperative course of liver transplantation. The 3 patients were profoundly immunosuppressed as a result of pre-transplant cirrhosis and the postoperative administration of a potent immunosuppressive therapy. Skin and soft tissue infections developed within the first week after liver transplantation, while graft liver function was satisfactory. The 3 patients presented with fever and skin lesions with or without bullae. Despite prompt appropriate antibiotic therapy and surgical debridement, the outcome was rapidly fatal (24 h on average). E. coli was isolated from subcutaneous tissues in 2 cases and from several blood cultures in the third one. The 3 isolates belonged to distinct phylogenetic groups, and did not harbor most of the virulence factors usually reported in extraintestinal pathogenic E. coli isolates. Our report suggests that E. coli can cause severe skin or soft tissue infection in the postoperative course of liver transplantation. The onset of infection is very early and the outcome is extremely poor, despite prompt adapted medical and surgical treatment. Host factors, rather than E. coli bacterial virulence potential, appear to be the major determinants of severity in these patients.

Acinetobacter baumannii-associated skin and soft tissue infections: recognizing a broadening spectrum of disease

BACKGROUND

Acinetobacter baumannii is gaining importance as a cause of nosocomial infections, but its role in skin and soft tissue infection (SSTI) is not well defined. As a result of the outbreak of A. baumannii occurring in military personnel in Iraq and Afghanistan, reports of severe wound infections and SSTI caused by this pathogen are increasing in frequency.

METHODS

We describe four cases of monomicrobial and polymicrobial A. baumannii-associated necrotizing SSTI accompanied by A. baumannii bacteremia and offer a review of similar experiences published in the literature.

RESULTS

Our comparative analysis reveals four unique features associated with necrotizing SSTI associated with A. baumannii: i) Occurs in hosts with underlying comorbidities (e.g., trauma, cirrhosis); ii) is often accompanied by bacteremia; iii) multiple drug resistance and the presence of co-pathogens frequently complicated treatment (64% of cases); iv) the cases reported here and in our review required surgical debridement (84% of cases) and led to substantial mortality (approximately 30%).

CONCLUSIONS

As the prevalence of A. baumannii continues to increase in our health care system, SSTIs caused by this organism may become more common. Clinicians must be aware that the spectrum of disease caused by A. baumannii could include severe necrotizing SSTI and that vigilance for potential complications is necessary.