Azithromycin regulates bacterial virulence and immune response in a murine model of ceftazidime-treated Pseudomonas aeruginosa acute pneumonia.

Pseudomonas aeruginosa (PA) remains one of the leading causes of nosocomial acute pneumonia. The array of virulence factors expressed by PA and the intense immune response associated with PA pneumonia play a major role in the severity of these infections. New therapeutic approaches are needed to overcome the high resistance of PA to antibiotics and to reduce the direct damage to host tissues. Through its immunomodulatory and anti-virulence effects, azithromycin (AZM) has demonstrated clinical benefits in patients with chronic PA respiratory infections. However, there is relatively little evidence in PA acute pneumonia. We investigated the effects of AZM, as an adjunctive therapy combined with ceftazidime (CAZ), in a murine model of PA acute pneumonia. We observed that the combined therapy (i) reduces the weight loss of mice 24 h post-infection (hpi), (ii) decreases neutrophil influx into the lungs at 6 and 24 hpi, while this effect is absent in a LPS-induced pneumonia or when PA is pretreated with antibiotics and mice do not receive any antibiotics, and that (iii) AZM, alone or with CAZ, modulates the expression of PA quorum sensing regulators and virulence factors (LasI, LasA, PqsE, PhzM, ExoS). Our findings support beneficial effects of AZM with CAZ on PA acute pneumonia by both bacterial virulence and immune response modulations. Further investigations are needed to clarify the exact underlying mechanisms responsible for the reduction of the neutrophils influx and to better discriminate between direct immunomodulatory properties of AZM, and indirect effects on neutrophilia resulting from bacterial virulence modulation.

Clostridial prosthetic joint infections: A series of 16 cases and literature review.

OBJECTIVES: Prosthetic joint infections (PJIs) due to the Clostridium species have not been widely investigated. We aimed to characterize these uncommon infections. METHODS: We conducted a retrospective study between 2003 and 2020 in six French hospitals combined with a review of the literature. RESULTS: The main conclusions obtained from the 16 patients included were reinforced by the literature analysis: (i) Clostridium perfringens was the most frequently involved species, (ii) patients presented an advanced age at the time of prosthesis placement and infection, (iii) most of the infections were early- or delayed-onset, (iv) the prognosis for these PJIs remains poor, (v) when performed (n = 5), DAIR with 12-week antimicrobial therapy led to a favorable outcome in 80% of cases. CONCLUSIONS: Given the low incidence of this infection, our work represents the largest series of clostridial PJIs reported to date and highlights some specificities of these infections. Further prospective studies are needed to confirm these results.

Bartonella quintana infective endocarditis in a homeless man with unexpected positive blood culture.

Bartonella species represent important causative agents of blood culture-negative infective endocarditis (IE). Their diagnosis represents a challenge for microbiologists and often relies on serological and molecular tools. However, even if the sensitivity of blood culture remains low, it should not be definitely ruled out. Indeed, we report the unusual case of a 22 year-old Guinean homeless man diagnosed with an IE due to Bartonella quintana. Unexpectedly, conventional blood cultures were positive after 13 days of incubation. Subculture was obtained on blood and chocolate agar, after 15 days of incubation in a 5 % CO2 atmosphere. Bacterial identification was obtained up to the species level using molecular tools (16S rRNA gene amplification and sequencing). A literature review of B. quintana blood culture-positive IE was conducted and revealed eighteen similar reported cases on a 25-year period. This case illustrates that, despite low sensitivity, Bartonella IE may be diagnosed thanks to prolonged blood culture.

Accuracy of gradient diffusion method for susceptibility testing of dalbavancin and comparators.

OBJECTIVES: This multicenter study aimed to assess the performances of gradient diffusion (GD) method in comparison to broth microdilution (BMD) method for susceptibility testing of dalbavancin, daptomycin, vancomycin, and teicoplanin. METHODS: Minimum Inhibitory Concentrations (MICs) were retrospectively determined concomitantly by BMD and GD methods, for 93 staphylococci and enterococci isolated from clinical samples. BMD was considered as the gold standard. Essential (EA) and categorical agreements (CA) were calculated. Discordant categorical results were categorized as major (ME) and very major errors (VME). RESULTS: EA and CA were 95.7% and 96.8%, 82.8% and 100%, 97.8% and 96.8%, and 94.6% and 95.7% for dalbavancin, daptomycin, vancomycin, and teicoplanin respectively. Concerning dalbavancin, 3 ME without any VME were observed and discrepancies were low (≤ to 2 two-fold dilutions) between both methods. VME were noted in 1 and 3 cases for vancomycin and teicoplanin, respectively, and resulted from 1 two-fold dilution discrepancy in each case. EA was lower for daptomycin. When they were discrepant, BMD MICs were systematically higher than GD ones. Nevertheless, no categorical discrepancy was noted. CONCLUSIONS: GD appears as an acceptable and convenient alternative for dalbavancin, vancomycin, and teicoplanin MICs determination. Our study also emphasizes how achieving accurate daptomycin MICs remains challenging.

Low prevalence of Cutibacterium acnes in prostatic tissue biopsies in a French hospital.

We evaluated the Cutibacterium acnes prevalence in prostatic biopsies and characterized the strains at a molecular level. 18 out of 36 biopsies (50%) were sterile after seven days in culture. C. acnes was observed in only two biopsies. Its prevalence was low (5.6%). Finally, the molecular characterization revealed diverse clusters including phylotypes IA1, IB and II.

Should we reconsider cefazolin for treating staphylococcal meningitis? A retrospective analysis of cefazolin and cloxacillin cerebrospinal fluid levels in patients treated for staphylococcal meningitis.

OBJECTIVES: To assess the meningeal penetration of cefazolin and cloxacillin in individuals treated for methicillin-susceptible staphylococcal meningitis. METHODS: We retrospectively identified individuals treated for Staphylococcus meningitis with measurements of cefazolin or cloxacillin concentrations in cerebrospinal fluid (CSF) using a validated assay of liquid chromatography coupled with mass spectrometry at the Nantes University Hospital between January 2009 and October 2019. Staphylococcus meningitis was defined by a compatible clinical presentation and a microbiological confirmation (positive CSF culture or positive specific PCR). Medical charts were retrospectively reviewed to collect microbiological and clinical data, and to assess therapeutic success. RESULTS: Among the 17 included individuals, eight (47%) were treated with cefazolin and nine (53%) with cloxacillin. Median daily dosages of cefazolin and cloxacillin were 8 g (range 6-12 g) and 12 g (range 10-13 g), respectively. Cefazolin and cloxacillin were mainly administered by continuous infusion. Eleven individuals (65%) were men, median (interquartile range (IQR)) age was 54 years (50; 70), 14 (82%) had postoperative meningitis and 3 (18%) had haematogenous meningitis. Median (IQR) antibiotic CSF concentrations were 2.8 mg/L (2.1; 5.2) and 0.66 mg/L (0.5; 0.9) for cefazolin and cloxacillin groups, respectively. Cloxacillin was discontinued in two individuals for therapeutic failure. CONCLUSIONS: Patients with staphylococcal meningitis treated with high-dose continuous intravenous infusion of cefazolin achieved therapeutic concentrations in CSF. Cefazolin appears to be a therapeutic candidate that should be properly evaluated in this indication.

Catheter-related bloodstream infection due to Tsukamurella pulmonis identified by MALDI-TOF spectrometry, 16S rRNA gene sequencing, and secA1 gene sequencing in an immunocompromised child: a case report and literature review.

Tsukamurella species are Gram-positive bacilli related to aerobic Actinomyces. Originally reported from the environment, Tsukamurella species have also been described in human infections, especially in bacteremia. A literature review analysis revealed that Tsukamurella spp. are often initially considered as contaminant microorganisms, especially due to bacterial identification issues. Here, we report a catheter-related bloodstream infection in an immunocompromised child caused by Tsukamurella pulmonis. Matrix-Assisted Laser Desorption/Ionization-Time Of Flight (MALDI-TOF) mass spectrometry allowed rapid genus-level identification and contributed to better patient care. However, accurate species-level identification required 16S rRNA gene sequencing and secA1 gene sequencing. Considering the increased number of Tsukamurella infections, the implementation of new Tsukamurella species in MALDI-TOF databases is required to be more discriminant.

Propionibacterium/Cutibacterium species-related positive samples, identification, clinical and resistance features: a 10-year survey in a French hospital.

A 10-year retrospective study of Propionibacterium/Cutibacterium-positive samples gathered from hospitalized patients was conducted at Nantes University hospital. A total of 2728 Propionibacterium/Cutibacterium-positive samples analyzed between 2007 and 2016 were included. Due to the implementation of MALDI-TOF identification in 2013, most non-Cutibacterium acnes isolates were identified a second time using this technology. Over that period, Cutibacterium acnes remained the most predominant species accounting for 91.5% (2497/2728) of the isolates, followed by Cutibacterium avidum (4.2%, 115/2728) and Cutibacterium granulosum (2.4%, 64/2728). Regarding the origin of samples, the orthopaedic department was the main Cutibacterium sample provider representing 51.9% (1415/2728) of all samples followed by the dermatology department (11.5%, 315/2728). Samples were recovered from various tissue locations: 31.5% (858/2728) from surgery-related samples such as shoulder, spine or hip replacement devices and 19.1% (520/2728) from skin samples. MALDI-TOF method revealed misidentification before 2013. Cutibacterium avidum was falsely identified as C. granulosum (n = 33). Consequently, MALDI-TOF technology using up-to-date databases should be preferred to biochemical identification in order to avoid biased species identification. Regarding antibiotic resistance, 14.7% (20/136) of C. acnes was resistant to erythromycin. 4.1% (41/1005) of C. acnes strains, 17.9% (12/67) of C. avidum strains and 3.6% (1/28) of C. granulosum strains were found resistant to clindamycin.

Assessment of the automated multiplex-PCR Unyvero i60 ITI® cartridge system to diagnose prosthetic joint infection: a multicentre study.

OBJECTIVES: Prosthetic joint infections (PJI) are responsible for significant morbidity and mortality and their number continues to rise. Their management remains complex, especially the microbiological diagnosis. Besides 'homemade' tests developed by several teams, new molecular biology methods are now available with different analytical performance and usability. METHODS: We studied the performances of one of these tests: ITI® multiplex PCR (mPCR) by the Curetis® company and compared it to either 'optimized' culture or 16S rRNA PCR. We performed a retrospective multicentre study to assess the contributions of mPCR in the diagnosis of PJI. We randomly selected 484 intraoperative specimens among 1252 of various types (biopsy, bone, tissue around the prosthesis, synovial fluid) from 251 patients in seven different hospitals. Each sample was treated according to the recommendations of the manufacturer. RESULTS: In all, 154 out of 164 (93.9%) samples negative in culture were negative with the mPCR. Among the 276 positive samples in culture, 251 (90.9%) were monomicrobial, of which 119 (47.4%) were positive with the mPCR, and 25 (9.1%) were polymicrobial, of which 12 (48%) were positive with the mPCR. The concordance rate of mPCR with culture was 58.1% (53.6%-62.7%) and the concordance rate with 16S rRNA PCR was 70.1% (65.5%-74.6%). CONCLUSION: This new standardized molecular test showed a lack of detection when the bacterial inoculum was low (number of positive media per sample and number of colonies per media) but can be useful when patients have received antibiotic therapy previously.

Simultaneous determination of ceftaroline, daptomycin, linezolid and rifampicin concentrations in human plasma by on-line solid phase extraction coupled to high-performance liquid chromatography-tandem mass spectrometry.

Methicillin-resistant Staphylococcus aureus infection is a serious clinical problem worldwide. Ceftaroline, daptomycin, linezolid in combination with rifampicin are particularly used in this indication. To allow monitoring of these antibiotics, an on-line solid phase extraction coupled to high-performance liquid chromatography-tandem mass spectrometry assay requiring a 100 µL aliquot of human plasma has been developed. Besides, significance of 25-O-desacetylrifampicin concentrations was evaluated. Sample pre-treatment is limited to protein precipitation with methanol. After centrifugation 10 µL of supernatant are injected into the chromatographic system, which consists of an on-line solid phase extraction followed by a separation on a phenyl-hexyl column and detected by a tandem mass spectrometer. Plasma drug concentrations were determined by multiple reaction monitoring in positive ion mode, and assay performance was evaluated. 25-O-Desacetylrifampicin activity, was compared to rifampicin using a microbiological method. Sample preparation using methanol precipitation followed by solid-phase extraction yielded good recovery and ionization efficiency, with chromatographic separation achieved within 3 min per sample. Within-run and between-run precisions ranged respectively from 1.22% to 9.35% and from 1.61% to 9.36%. Lower limits of quantification were 0.04 mg/L for linezolid, 0.1mg/L for rifampicin, 0.2mg/L for ceftaroline and 0.5mg/L for daptomycin. It appears that 25-O-desacetylrifampicin displays a substantial intrinsic bactericidal activity against S. aureus. This assay provides simple, rapid, sensitive and accurate quantification of the four antibiotic drugs and one metabolite and can be routinely used to monitor drug concentration in methicillin-resistant S. aureus infected patients.