Sternal wound infection caused by Mycobacterium chelonae

Non-tuberculous mycobacterial disease: progress and advances in the development of novel candidate and repurposed drugs

Non-tuberculous mycobacteria (NTM) are opportunistic pathogens that can infect all body tissues and organs. In particular, the lungs are the most commonly involved organ, with NTM pulmonary diseases causing serious health issues in patients with underlying lung disease. Moreover, NTM infections have been steadily increasing worldwide in recent years. NTM are also naturally resistant to many antibiotics, specifically anti-tuberculosis (anti-TB) drugs. The lack of drugs targeting NTM infections and the increasing drug resistance of NTM have further made treating these mycobacterial diseases extremely difficult. The currently recommended NTM treatments rely on the extended indications of existing drugs, which underlines the difficulties of new antibiotic discovery against NTM. Another challenge is determining which drug combinations are most effective against NTM infection. To a certain extent, anti-NTM drug development depends on using already available antibiotics and compounds. Here, we aimed to review new antibiotics or compounds with good antibacterial activity against NTM, focusing on their mechanisms of action, in vitro and in vivo antibacterial activities.

Successful long-term management for postoperative sternal infection with multiple disseminated lymphadenitis caused by Mycobacterium abscessus

BACKGROUND

Postoperative sternal infection caused by Mycobacterium abscessus (M. abscessus) is rare, but associated with a high 2-year mortality rate of 40%. Decision-making around treatment strategy is challenging. Here, we present a successfully treated case of postoperative M. abscessus sternal infection with multiple disseminated lymphadenitis.

CASE PRESENTATION

The patient, an 80-year-old woman with anterior mediastinal tumor and myasthenia gravis, underwent extended thymectomy under median sternotomy. Redness appeared around the scar two months after the operation. Sternal wires were removed, debridement was performed, and the wound was kept open. Mycobacterium abscessus was isolated from the wound culture. The disseminated lesions in the right axillary, parasternal, and bilateral supraclavicular lymph nodes, rendered surgical options for infection control difficult; therefore, she was treated conservatively with antibiotics and negative pressure wound therapy (NPWT). The wound diminished but infectious granulation tissue remained after NPWT. Two disseminated lesions were percutaneously punctured and drained of pus, which resulted in negative cultures. Additional debridement and wound closure were performed. She was discharged after switching to oral antibiotics. No recurrence was observed five months after the antibiotics were completed (total sensitive antibiotics use: 366 days).

CONCLUSIONS

Repeated culture assessment of disseminated lesions is recommended to facilitate the development of appropriate therapeutic strategies. Localized procedures may be an option for patients with controlled disseminated lesions evidenced by negative cultures.

"Hot Tub Lung" With M. avium complex in an Immunocompetent Adolescent

We describe a case of pulmonary Mycobacterium avium complex (MAC) infection in an immunocompetent pediatric patient after a hot tub near drowning event with a literature review of pediatric MAC-associated disease after hot tub exposure.

A case of Mycobacterium chelonae mediastinitis and acute humoral rejection after heart transplantation

Mediastinitis is one of the life-threating complications that can occur after cardiac surgery. However, to the best of our knowledge, there has been no report of mediastinitis caused by Mycobacterium chelonae, which is one of the rapidly growing nontuberculous mycobacteria species. As far as we know, our case is the first case describing the curative management for mediastinitis caused by M. chelonae after heart transplantation.

Epidemiologic Review of Veterans Health Administration Patients with Isolation of Nontuberculous Mycobacteria after Cardiopulmonary Bypass Procedures

We evaluated the isolation of postoperative nontuberculous mycobacteria (NTM) associated with heater-cooler devices (HCDs) used during cardiopulmonary bypass (CPB) surgery in the Veterans Health Administration from January 1, 2010, to December 31, 2016. In more than 38,000 CPB procedures, NTM was isolated in 111 patients; 1 Mycobacterium chimaera mediastinitis case and 1 respiratory isolate were found.

Infect Control Hosp Epidemiol 2017;38:1103–1106

Insidious Risk of Severe Mycobacterium chimaera Infection in Cardiac Surgery Patients

BACKGROUND

An urgent UK investigation was launched to assess risk of invasive Mycobacterium chimaera infection in cardiothoracic surgery and a possible association with cardiopulmonary bypass heater-cooler units following alerts in Switzerland and The Netherlands.

METHODS

Parallel investigations were pursued: (1) identification of cardiopulmonary bypass-associated M. chimaera infection through national laboratory and hospital admissions data linkage; (2) cohort study to assess patient risk; (3) microbiological and aerobiological investigations of heater-coolers in situ and under controlled laboratory conditions; and (4) whole-genome sequencing of clinical and environmental isolates.

RESULTS

Eighteen probable cases of cardiopulmonary bypass-associated M. chimaera infection were identified; all except one occurred in adults. Patients had undergone valve replacement in 11 hospitals between 2007 and 2015, a median of 19 months prior to onset (range, 3 months to 5 years). Risk to patients increased after 2010 from <0.2 to 1.65 per 10000 person-years in 2013, a 9-fold rise for infections within 2 years of surgery (rate ratio, 9.08 [95% CI, 1.81-87.76]). Endocarditis was the most common presentation (n = 11). To date, 9 patients have died. Investigations identified aerosol release through breaches in heater-cooler tanks. Mycobacterium chimaera and other pathogens were recovered from water and air samples. Phylogenetic analysis found close clustering of strains from probable cases.

CONCLUSIONS

We identified low but escalating risk of severe M. chimaera infection associated with heater-coolers with cases in a quarter of cardiothoracic centers. Our investigations strengthen etiological evidence for the role of heater-coolers in transmission and raise the possibility of an ongoing, international point-source outbreak. Active management of heater-coolers and heightened clinical awareness are imperative given the consequences of infection.

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.

Sternal mycobacterial infections

Sternal mycobacterial infections are rare. Due to the rarity, its clinical characteristics, diagnoses, and regular management strategies are still scanty. A total of 76 articles on this topic were obtained by a comprehensive literature collection. The clinical features, diagnosis, management strategies and prognosis were carefully analyzed. There were totally 159 patients including 152 (95%) cases of tuberculosis (TB) and seven (5%) cases of non-TB sternal infections. Sternal mycobacterial infections can be categorized into three types: Primary, secondary, and postoperative, according to the pathogenesis; and categorized into isolated, peristernal, and multifocal, according to the extent of the lesions. Microbiological investigation is more sensitive than medical imaging and Mantoux tuberculin skin test in the diagnosis of sternal infections. Most patients show good responses to the standard four-drug regimen and a surgical intervention was necessary in 28.3% patients. The prognoses of the patients are good with a very low mortality. A delayed diagnosis of sternal mycobacterial infections may bring about recurrent sternal infections and sustained incurability. An early diagnosis and prompt antibiotic regimens may significantly improve the patients' outcomes.

Sternal wound tuberculosis following cardiac operations: a review

Objective

The diagnosis and treatment of sternal wound infections with mycobacteria are challenging. Such an infection is often associated with a delayed diagnosis and improper treatment that may lead to a worsened clinical outcome. The present study is designed to highlight its clinical features so as to facilitate a prompt diagnosis and timely treatment.

Methods

MEDLINE, Highwire Press, and Google search engine were searched for publications in the English language, with no time limit, reporting on sternal wound infection caused by tuberculosis after cardiac surgery.

Results

A total of 12 articles reporting on 14 patients were included in this study. Coronary artery bypass grafting was the underlying surgical procedure in more than half of the cases. Purulent discharge and cold abscess were the two main presenting symptoms. Diagnosis of sternal wound infection was evidenced in all 14 patients by different investigations, with culture of samples being the most sensitive method of identifying the pathogen. Good response to first-line anti-tuberculous agents was noted. Almost all patients required surgical debridement/resection and, sometimes, sternal reconstruction. A delayed diagnosis of sternal wound infection may lead to repeated recurrences. A comparison between patients with sternal wound infection due to tuberculosis and non-tuberculous mycobacterial infections showed that the former infections took an even longer period of time. Comparisons also revealed patients with sternal tuberculosis infection had a significantly higher mortality than patients with sternal non-tuberculous infection (29.2% vs. 0%, P=0.051).

Conclusion

Sternal infection caused by tuberculosis after cardiac surgery has a longer latency, better response to first-line drugs, and better outcomes in comparison with non-tuberculous sternal infection. Early diagnosis and early anti-tuberculous treatment can surely improve the patients' prognosis.