Incidence, risk factors and clinical outcome of multidrug-resistant organisms after heart transplantation.

BACKGROUND: Transplant recipients commonly harbor multidrug-resistant organisms (MDROs), as a result of frequent hospital admissions and increased exposure to antimicrobials and invasive procedures. AIM: To investigate the impact of patient demographic and clinical characteristics on MDRO acquisition, as well as the impact of MDRO acquisition on intensive care unit (ICU) and hospital length of stay, and on ICU mortality and 1-year mortality post heart transplantation. METHODS: This retrospective cohort study analyzed 98 consecutive heart transplant patients over a ten-year period (2013-2022) in a single transplantation center. Data was collected regarding MDROs commonly encountered in critical care. RESULTS: Among the 98 transplanted patients (70% male), about a third (32%) acquired or already harbored MDROs upon transplantation (MDRO group), while two thirds did not (MDRO-free group). The prevalent MDROs were Acinetobacter baumannii (14%), Pseudomonas aeruginosa (12%) and Klebsiella pneumoniae (11%). Compared to MDRO-free patients, the MDRO group was characterized by higher body mass index (P = 0.002), higher rates of renal failure (P = 0.017), primary graft dysfunction (10% vs 4.5%, P = 0.001), surgical re-exploration (34% vs 14%, P = 0.017), mechanical circulatory support (47% vs 26% P = 0.037) and renal replacement therapy (28% vs 9%, P = 0.014), as well as longer extracorporeal circulation time (median 210 vs 161 min, P = 0.003). The median length of stay was longer in the MDRO group, namely ICU stay was 16 vs 9 d in the MDRO-free group (P = 0.001), and hospital stay was 38 vs 28 d (P = 0.006), while 1-year mortality was higher (28% vs 7.6%, log-rank-χ 2: 7.34). CONCLUSION: Following heart transplantation, a predominance of Gram-negative MDROs was noted. MDRO acquisition was associated with higher complication rates, prolonged ICU and total hospital stay, and higher post-transplantation mortality.

Pseudomonas aeruginosa susceptible only to colistin in intensive care unit patients.

BACKGROUND: Gram-negative bacilli, including multi-drug-resistant (MDR) Pseudomonas aeruginosa, are responsible for severe intensive care unit (ICU)-acquired infections, mainly pneumonia and bacteremia. The aim of this study was to determine the incidence of MDR strains of Pseudomonas in patients undergoing cardiac surgery, to elucidate the effectiveness of treating these patients with colistin, and to assess the safety of the drug. METHODS: A prospective study was conducted among 1,452 patients who underwent surgery for a variety of cardiac lesions over a one-year period, and who spent a portion of the recovery period in the surgical ICU. Their case histories were analyzed to identify infectious complications. Diagnosis of infection was based on clinical data, and the pathogen was tested with respect to its susceptibility to colistin (polymyxin E). The clinical response to the antibiotic was evaluated. RESULTS: Over the 12-month period, among 115 infected patients, 15 were affected by strains of P. aeruginosa. In 10 patients, this pathogen proved resistant to all potentially active antibiotics except colistin. All of the affected patients were being ventilated mechanically, and eight of them presented with ventilator-associated pneumonia (VAP), whereas one patient suffered a deep incisional surgical site infection and bacteremia and the remaining patient had a superficial infection of a lower-extremity vein graft donor site. The MDR pathogen was introduced to the hospital by three patients transferred from three institutions. All patients were treated with intravenous colistin. In cases of VAP, aerosolized colistin was added. Deterioration of renal function occurred in three patients (30%), all of whom had a history of renal insufficiency. Cure or clinical improvement was observed in seven patients (70%), whereas four patients, including one who improved initially, developed sepsis and died with multiple organ dysfunction syndrome (mortality rate 40%). CONCLUSIONS: The increasing prevalence of MDR P. aeruginosa in ICU patients has rekindled interest in polymyxins, which had been abandoned because of toxic side effects. Colistin retained significant in vitro activity against this virulent organism, had an acceptable safety profile, and should be considered as a treatment option in critically ill patients with infection caused by MDR gram-negative bacilli. Aerosolized colistin may merit further consideration as a therapeutic intervention for patients with refractory pulmonary infections.

Methicillin-resistant Staphylococcus aureus preventing strategy in cardiac surgery.

OBJECTIVES: The aim of this survey was to elucidate the efficacy of methicillin-resistant Staphylococcus aureus (MRSA) preventing strategy in our institution by investigating the incidence and evaluating the morbidity and mortality associated with this multi-resistant virulent organism. METHODS: A prospective observational cohort among patients submitted to cardiovascular surgical procedures was conducted from 1 January 1997 to 31 December 2005. Preventing strategy included active screening programs by nasal swabs for all patients admitted from other hospitals or being at risk for developing infectious complications. Carriers or infected patients remained isolated and were treated promptly. Furthermore, all newly employed health care workers were screened for MRSA and carriers were treated with mupirocin until the eradication of the pathogen. RESULTS: Throughout the 9-year study period 826 infectious complications were registered among 15,270 cardiac surgical patients. Total infection rate was 5.4%. MRSA was identified in 86 patients; 56 patients proved carriers and 30 infected. The MRSA associated infection rate was 0.2%. During this period of time mean ICU stay was 1.7 days and ICU mortality rate was 2.9%. MRSA infected patients presented a mean ICU stay of 46.5 days and a mortality rate of 30%. In ten patients, MRSA was detected in tracheal secretions, in four patients in swabs taken from donor site infection and in four patients from superficial sternal surgical wound. In ten patients the pathogen was isolated from cultures of the surgical site drainage and the diagnosis of post-sternotomy mediastinitis was confirmed. The remaining two patients were defined as having severe sepsis; MRSA was documented in central venous catheter tips and blood cultures. CONCLUSIONS: The prompt determination, isolation and appropriate treatment of MRSA patients admitted from other institutions combined with the detection and elimination of carriers among new health care workers and patients at high risk of developing infectious complications prevented further spread of the pathogen.

Preventing strategy of multidrug-resistant Acinetobacter baumanii susceptible only to colistin in cardiac surgical intensive care units.

OBJECTIVE: The study aimed to determine the incidence and mortality of multidrug-resistant Acinetobacter baumannii in cardiac surgery, to elucidate the effectiveness of colistin treatment and to identify if the additional measures to the recommended procedures were able to control the dissemination of the pathogen. METHODS: A prospective observational cohort was conducted among cardiac surgical patients from 1 September 2005 to 31 December 2006. We reviewed the prophylactic measures of the surgical intensive care unit and implemented a two scale multiple program. Scale I included classical infection control measures, while Scale II referred to the geographic isolation of multidrug-resistant Acinetobacter baumannii patients and environmental intense surveillance. RESULTS: Among 151 out of 1935 infected patients 20 were colonized and infected by strains of multidrug-resistant A. baumannii susceptible only to colistin. Seventeen patients presented respiratory tract infection, one patient suffered deep surgical site infection and two patients catheter related infection. Transmission of the pathogen occurred via two patients transferred from two other institutions. They were all treated with colistin. Cure or clinical improvement was observed only in four patients (20%). Scale I measures were implemented for the whole 16-month period while scale II for two separate periods of 3 weeks. Environmental specimens (n>350) proved negative. CONCLUSIONS: The increasing prevalence of multidrug-resistant A. baumannii in surgical intensive care unit patients creates demand on strict screening and contact precautions. Following this infection control strategy we were able to achieve intermittent eradication of the pathogen during a 16-month period with continuous function of the intensive care unit. Despite the significant in vitro activity of colistin against multidrug-resistant Acinetobacter baumannii the results were discouraging.