Bacteriology, antibiotic resistance and risk stratification of patients with culture-positive, community-acquired pleural infection.

BACKGROUND: Community-acquired pleural infection (CAPI) is a growing health problem worldwide. Although most CAPI patients recover with antibiotics and pleural drainage, 20% require surgical intervention. The use of inappropriate antibiotics is a common cause of treatment failure. Awareness of the common causative bacteria along with their patterns of antibiotic resistance is critical in the selection of antibiotics in CAPI-patients. This study aimed to define CAPI bacteriology from the positive pleural fluid cultures, determine effective antibiotic regimens and investigate for associations between clinical features and risk for death or antibiotic-resistance, in order to advocate with more invasive techniques in the optimal timing. METHODS: We examined 158 patients with culture positive, CAPI collected both retrospectively (2012-2013) and prospectively (2014-2018). Culture-positive, CAPI patients hospitalized in six tertiary hospitals in Greece were prospectively recruited (N=113). Bacteriological data from retrospectively detected patients were also used (N=45). Logistic regression analysis was performed to identify clinical features related to mortality, presence of certain bacteria and antibiotic resistance. RESULTS: Streptococci, especially the non-pneumococcal ones, were the most common bacteria among the isolates, which were mostly sensitive to commonly used antibiotic combinations. RAPID score (i.e., clinical score for the stratification of mortality risk in patients with pleural infection; parameters: renal, age, purulence, infection source, and dietary factors), diabetes and CRP were independent predictors of mortality while several patient co-morbidities (e.g., diabetes, malignancy, chronic renal failure, etc.) were related to the presence of certain bacteria or antibiotic resistance. CONCLUSIONS: The dominance of streptococci among pleural fluid isolates from culture-positive, CAPI patients was demonstrated. Common antibiotic regimens were found highly effective in CAPI treatment. The predictive strength of RAPID score for CAPI mortality was confirmed while additional risk factors for mortality and antibiotic resistance were detected.

Unravelling the Features of Success of VIM-Producing ST111 and ST235 Pseudomonas aeruginosa in a Greek Hospital.

The objective of this study was to analyze the characteristics that contribute to the successful dissemination of VIM-producing Pseudomonas aeruginosa (P. aeruginosa), belonging to ST111 and ST235, in a Greek hospital. A total of 120 non-repetitive P. aeruginosa, which had meropenem minimal inhibitory concentrations (MICs) greater than 2 mg/L, were studied. VIM-encoding genes were amplified and sequenced within their integrons. Isolates were typed by multilocus sequence typing (MLST). Six VIM-producers, representative of different integron structures and sequence types (STs), were completely sequenced using Illumina platform. Sixty-one P. aeruginosa were confirmed to produce VIM-type carbapenemases. ST111 dominated (n = 34) among VIM-producers, while 15 VIM-producers belonged to ST235. The blaVIM-like genes were located in three integron types, including In59, In595 and In1760, which were integrated into P. aeruginosa chromosomes. Whole genome sequencing (WGS) data demonstrated that ST111 and ST235 MBL producers carried several resistance and virulence genes. Additionally, the presence of type I-C and type I-E clustered regularly interspaced short palindromic repeats (CRISPR)/Cas locus was observed in ST235 and ST395 isolates, respectively. In conclusion, our findings confirmed the clonal spread of ST111 P. aeruginosa, carrying the VIM-2-encoding integron In59, in the University Hospital of Larissa (UHL). In addition, they highlighted the important role of high-risk clones, ST111 and ST235, in the successful dissemination and establishment into hospital settings of clinically important pathogens carrying resistance determinants.

Implementation of the Rapid Polymyxin™ NP test directly to positive blood cultures bottles.

The present study assessed the performance of Rapid Polymyxin™ NP test to detect colistin resistance directly from 132 blood cultures found positive for Enterobacterales by FilmArray. Additionally, colistin MICs of isolated microorganisms were determined by the commercial broth microdilution method ComASP™ Colistin, used as the gold standard comparator. The Rapid Polymyxin™ NP test correctly detected all colistin-resistant isolates. However, the test has misidentified as resistant 4 colistin-susceptible isolates (1 Escherichia coli and 3 Klebsiella pneumoniae). Molecular characterization of colistin-resistant isolates showed that K. pneumoniae, which belonged to ST15 and ST147, carried alterations in the mgrB. Moreover, the first Greek mcr-1-positive colistin-resistant E. coli was detected. The rapidity (2-3 h) of the results, combined with its excellent negative predictive value (100%), allows implementation of the test for routine testing of blood cultures mainly in the clinical settings that are endemic for carbapenem-resistant bacteria, avoiding misuse of colistin and preventing the spread of colistin-resistant bacteria.

Evaluation of rapid polymyxin NP test to detect colistin-resistant Klebsiella pneumoniae isolated in a tertiary Greek hospital.

The efficiency of Rapid Polymyxin NP test for detection of colistin-resistant isolates was tested against a collection of 131 non-repetitive Klebsiella pneumoniae, including 98 colistin-resistant and 33 colistin-susceptible isolates. In addition, the performance of this test was compared with those of the automated systems, BD Phoenix™ and VITEK®2, and the Etest. Determination of imipenem and meropenem MICs showed that 95 of colistin-resistant (Col-R) isolates were also resistant to at least one carbapenem. Characterization of colistin resistance mechanisms showed that 75 out of 98 Col-R isolates were associated with the presence of alterations in the mgrB gene, while no mcr genes were detected among our isolates. Rapid Polymyxin NP correctly detected 97 out of 98 colistin-resistant isolates (Geometric mean MIC value 9.89 mg/L), except one ST147 K. pneumoniae harboring a wild-type mgrB gene (MIC: 8 mg/L), yielding a sensitivity 99%. The other methods gave more false-negative results with colistin-resistant strains; BD Phoenix™,VITEK®2, and the gradient Etest missed five, two and three colistin-resistant, respectively (95%, 98% and 97%). The Rapid Polymyxin NP test gave false positive results with six isolates, for which colistin MICs were 1-2 mg/L (specificity 82%). Despite the fact that Rapid Polymyxin exhibited lower specificity than other methods (82% versus 94%, 88% and 85%), it is easy-to-perform and rapid. Thus, these findings indicate that the Rapid Polymyxin NP test can be an initial tool for the detection of colistin-resistant isolates.

Nebulised colistin for ventilator-associated pneumonia prevention.

We evaluated whether prophylactic nebulised colistin could reduce ventilator-associated pneumonia (VAP) rates in an intensive care unit (ICU) setting with prevalent multidrug-resistant (MDR) bacteria.We used a single-centre, two-arm, randomised, open-label, controlled trial in a 12-bed ICU in the University Hospital of Larissa, Greece. Patient inclusion criteria included mechanical ventilation of >48 h. The two arms consisted of prophylaxis with 500 000 U colistin (Col group) or normal saline (NS group), thrice daily, for the first 10 ICU days or until extubation. The primary outcome of the study was the 30-day VAP incidence.In total, 168 patients entered the study. VAP incidence was not different between Col and NS group patients (14 (16.7%) versus 25 (29.8%), respectively, p=0.07). Regarding the secondary outcomes, the intervention resulted in a lower VAP incidence density rate (11.4 versus 25.6, respectively, p<0.01), and less Gram-negative bacteria-VAP (p=0.03) and MDR-VAP (p=0.04). Among VAP patients (n=39), prophylaxis with inhaled colistin improved ICU survival (p=0.016). There was no evidence of increased resistance to colistin or multidrug resistance.Our findings suggest that nebulised colistin had no significant effect on VAP incidence.