Methicillin-resistant Staphylococcus aureus infection epidemiology and clinical response from tigecycline soft tissue infection trials

Community-associated methicillin-resistant Staphylococcus aureus infection of diabetic foot ulcers in an eastern diabetic foot center in a tertiary hospital in China: a retrospective study

BACKGROUND

Diabetic foot concerns are a major public health problem. Methicillin-resistant Staphylococcus aureus (MRSA) plays a significant role in diabetic foot ulcers. Community-associated MRSA has become notorious for skin and skin soft tissue infections over the last two decades. This study investigated MRSA infection in diabetic foot patients at a tertiary hospital, focusing on the epidemiology and characteristics of community-associated MRSA.

METHODS

A total of 149 patients with diabetic foot infection whose culture results indicated Staphylococcus aureus as the source were selected. Epidemiological investigations, clinical characteristics, laboratory index records, antibiotic susceptibility analysis, and clinical outcome tracking were performed in all cases. Based on oxacillin resistance using the Vitek Compact 2 system, cases were divided into methicillin-sensitive Staphylococcus aureus and MRSA groups. Subgroup analysis of the MRSA group was performed in accordance with the Centers for Disease Control definition: community-associated MRSA and hospital-associated MRSA.

RESULTS

The MRSA group (n = 41, 27.5%) had a longer duration of ulcers and hospital stay and higher hospitalization costs than the methicillin-sensitive Staphylococcus aureus group (n = 108, 72.5%). According to the classification criteria of Infectious Diseases Society of America, the severity of infection in the community-associated MRSA group was higher than that in the hospital-associated MRSA group. The analysis of antimicrobial susceptibility of 41 MRSA isolates showed that the resistance rates to erythromycin, clindamycin, quinolone, gentamicin, tetracycline, and rifampicin were 78.0%, 68.3%, 31.7%, 17.1%, 9.8%, and 2.4%, respectively. All the MRSA strains were sensitive to linezolid, tigecycline, and vancomycin. The resistance rates to quinolones and gentamycin in the community-associated MRSA group (both 0%) were lower than those in the hospital-associated MRSA group.

CONCLUSION

Emergence of MRSA in diabetic foot ulcer was associated with a prolonged wound duration and increased consumption of medical resources. Community-associated MRSA strains predominated among MRSA isolates from diabetic foot wounds and caused more severe infections.

[Off label uses of tigecycline]

INTRODUCTION

Tigecycline is a relatively new antibiotic that have very limited valid indications. When no other alternative is available, this drug is widely used off label with promising results. The objective of this study is to summarize the different off label uses of tigecycline so that we can decide when and how to prescribe it in the absence of guidelines.

MATERIAL AND METHODS

This study a revue of the literature collecting all the articles concerning the off label uses of tigecycline.

RESULTS

Tigecycline was widely prescribed, off label, to treat infections with controversial results. Randomised clinical trials were conducted to evaluate its use to treat pneumonia. The results for this indication have a respectable level of evidence. For the other indications, the data collected was insufficient to support tigecycline prescription. In fact, different protocols were used which makes it hard to evaluate the efficacy and to conclude to the best treatment regimen. A tendency to prescribe high doses of the molecule was noted in different studies. When prescribed off label, tigecycline prescriptions were associated with a higher mortality and incidence of side effects.

CONCLUSION

The tigecycline remains a valid option for the treatment of infections dues to multi-resistant bacteria especially when other alternatives are scarce or in cases of renal failure.

Methicillin-Resistant Staphylococcus aureus in Diabetic Foot Infection in India: A Growing Menace

Diabetic foot infection (DFI) is a serious and common complication of diabetes mellitus. These infections are potentially disastrous and rapidly progress to deeper spaces and tissues. If not treated promptly and appropriately, DFI can be incurable or even lead to septic gangrene, which may require foot amputation. Mostly, these infections are polymicrobial, where Gram-positive pathogens mainly Staphylococcus aureus play a dominant causative role. Methicillin-resistant Staphylococcus aureus (MRSA) is present in 10% to 32% of diabetic infections and is associated with a higher rate of treatment failure, morbidity, and hospitalization cost in patients with DFIs. The increasing resistance of bacteria and the adverse effects pertaining to the safety and tolerability towards currently available anti-MRSA agents have limited the available treatment options for patients with DFI. Infection control, antimicrobial stewardship, and rapid diagnostics based on the microbiological culture and the antimicrobial susceptibility testing results are important components in helping curb this disturbing trend. Emphasis to revisit a vigorous research effort in order to improve the therapeutic options for the increasingly resistant and highly adaptable MRSA is the need of hour. Through this review article, we have made an attempt to explore the ongoing therapeutic trends in the management of DFI and highlighted the challenges in treatment of DFI. We have also given a brief overview of a few novel drugs that are under development to treat MRSA infections.

Virulence genes fliC, toxA and phzS are common among Pseudomonas aeruginosa isolates from diabetic foot infections

BACKGROUND

Outcomes of antibiotic treatment of diabetic foot infections (DFIs) may depend not only on the antimicrobial susceptibility of the aetiologic agents, but also their ability to produce virulence factors. This study aimed to use polymerase chain reaction (PCR) with specific primers to investigate the presence of virulence genes among isolates of Pseudomonas aeruginosa isolates cultured from specimens from diabetic foot and other infections.

METHODS

We examined 63 P. aeruginosa isolates from inpatients at two University Hospitals for the presence of 23 known bacterial virulence genes, including lasI, lasR, lasA, lasB, rhll, rhlR, rhlAB, aprA, fliC, toxA, plcH, plcN, ExoS, ExoT, ExoU, ExoY, phzI, phzII, phzM, phzS, pvdA, pilA and pilB.

RESULTS

Seven virulence genes (lasl, lasR, lasB, rhll, rhlR, rhlABand Exo T) were present in each isolate. No isolate expressed or presented aprA gene. We found that fliC (p = .01), toxA (p = .041) and phzS (p < .001) were statistically and significantly more common in diabetic foot isolates, while plcH (p < .001) was significantly more common in other infections.

CONCLUSIONS

Among clinical isolates of P. aeruginosa from patients with DFIs, three virulence genes that can play important roles in tissue penetration (fliC), tissue damage and survival under anaerobic condition (phzS) and cell death (toxA) were significantly more common than isolates from other infections. The Multilocus sequence typing (MLST) analysis of diabetic foot isolates failed to point/indicate the existence of a specific clone or was not able to characterize/identify a specific clone/clonal complex group. Development of new agents to inhibit the synthesis of these genes may improve outcomes in DFIs treatment.

Adjunctive Hyperbaric Oxygen Therapy or Alone Antibiotherapy? Methicillin Resistant Staphylococcus aureus Mediastinitis in a Rat Model

OBJECTIVE

In the post-sternotomy mediastinitis patients, Staphylococcus aureus is the pathogenic microorganism encountered most often. In our study, we aimed to determine the efficacy of antibiotic treatment with vancomycin and tigecycline, alone or in combination with hyperbaric oxygen treatment, on bacterial elimination in experimental S. aureus mediastinitis.

METHODS

Forty-nine adult female Wistar rats were used. They were randomly divided into seven groups, as follows: non-contaminated, contaminated control, vancomycin, tigecycline, hyperbaric oxygen, hyperbaric oxygen + vancomycin and hyperbaric oxygen + tigecycline. The vancomycin rat group received 10 mg/kg/day of vancomycin twice a day through intramuscular injection. The tigecycline group rats received 7 mg/kg/day of tigecycline twice a day through intraperitoneal injection. The hyperbaric oxygen group underwent 90 min sessions of 100% oxygen at 2.5 atm pressure. Treatment continued for 7 days. Twelve hours after the end of treatment, tissue samples were obtained from the upper part of the sternum for bacterial count assessment.

RESULTS

When the quantitative bacterial counts of the untreated contaminated group were compared with those of the treated groups, a significant decrease was observed. However, comparing the antibiotic groups with the same antibiotic combined with hyperbaric oxygen, there was a significant reduction in microorganisms identified (P<0.05). Comparing hyperbaric oxygen used alone with the vancomycin and tigecycline groups, it was seen that the effect was not significant (P<0.05).

CONCLUSION

We believe that the combination of hyperbaric oxygen with antibiotics had a significant effect on mediastinitis resulting from methicillin-resistant Staphylococcus aureus. Methicillin-resistant Staphylococcus aureus mediastinitis can be treated without requiring a multidrug combination, thereby reducing the medication dose and concomitantly decreasing the side effects.

Staphylococcus aureus Toxins and Diabetic Foot Ulcers: Role in Pathogenesis and Interest in Diagnosis

Infection of foot ulcers is a common, often severe and costly complication in diabetes. Diabetic foot infections (DFI) are mainly polymicrobial, and Staphylococcus aureus is the most frequent pathogen isolated. The numerous virulence factors and toxins produced by S. aureus during an infection are well characterized. However, some particular features could be observed in DFI. The aim of this review is to describe the role of S. aureus in DFI and the implication of its toxins in the establishment of the infection. Studies on this issue have helped to distinguish two S. aureus populations in DFI: toxinogenic S. aureus strains (harboring exfoliatin-, EDIN-, PVL- or TSST-encoding genes) and non-toxinogenic strains. Toxinogenic strains are often present in infections with a more severe grade and systemic impact, whereas non-toxinogenic strains seem to remain localized in deep structures and bone involving diabetic foot osteomyelitis. Testing the virulence profile of bacteria seems to be a promising way to predict the behavior of S. aureus in the chronic wounds.