Pierre-Yves Donnio

Partial Excision of the Chromosomal Cassette Containing the Methicillin Resistance Determinant Results in Methicillin-Susceptible Staphylococcus aureus

ABSTRACT We report a detailed characterization of methicillin-susceptible Staphylococcus aureus isolates from five French hospitals negative for both the mecA and the ccrAB loci but positive for the IS431::pUB110::IS431::dcs structure, present in some Staphylococcus cassette chromosome mec (SCCmec) types. The presence of SCCmec-associated elements suggests that this unusual resistant phenotype is due to a partial excision of SCCmec from epidemic methicillin-resistant S. aureus. The hypothesis of a genetic relatedness is strengthened by common sequence and spa types and similar susceptibility patterns.

Effect of oropharyngeal povidone-iodine preventive oral care on ventilator-associated pneumonia in severely brain-injured or cerebral hemorrhage patients: a multicenter, randomized controlled trial.

Objective:To evaluate the efficacy and safety of oral care with povidone-iodine on the occurrence of ventilator-associated pneumonia in a high-risk population. Design:A multicenter, placebo-controlled, randomized, double-blind, two-parallel-group trial performed between May 2008 and May 2011. Setting:Six ICUs in France. Patients:One hundred seventy-nine severely brain-injured patients (Glasgow Coma Scale ⩽ 8) or cerebral hemorrhage expected to be mechanically ventilated for more than 24 hours. Interventions:Participants were randomly assigned to receive oropharyngeal care with povidone-iodine (n = 91) or placebo (n = 88) six times daily until mechanical ventilation withdrawal. Measurements and Main Results:Primary endpoint was the rate of ventilator-associated pneumonia. Secondary endpoint included the rates of ventilator-associated tracheobronchitis and acute respiratory distress syndrome and patient’s outcome. The number of patients evaluable for the primary endpoint (preplanned modified intention-to-treat population) was 150 (78 in the povidone-iodine group, 72 in the placebo group). Ventilator-associated pneumonia occurred in 24 patients (31%) in the povidone-iodine group and 20 (28%) in the placebo group (relative risk, 1.11 [95% CI, 0.67–1.82]; p = 0.69). There was no significant difference between the two groups for ventilator-associated tracheobronchitis: eight patients (10%) in the povidone-iodine group and five patients (7%) in the placebo group (relative risk, 1.48 [95% CI, 0.51–4.31]; p = 0.47). Acute respiratory distress syndrome occurred in five patients in the povidone-iodine group but not in the placebo group (p = 0.06). There was no difference between groups for ICU and hospital lengths of stay, as well as ICU and 90-day mortality. Conclusions:There is no evidence to recommend oral care with povidone-iodine to prevent ventilator-associated pneumonia in high-risk patients. Furthermore, this strategy seems to increase the rate of acute respiratory distress syndrome.

Methicillin-Susceptible ST398 Staphylococcus aureus Responsible for Bloodstream Infections: An Emerging Human-Adapted Subclone?

In the course of an annual 3-month bloodstream infections (BSI) survey conducted during a four-year period in 31 healthcare institutions located in three noncontiguous French regions, we report 18 ST398 Staphylococcus aureus BSI. ST398 BSI incidence showed a seven-fold increase during the study period (0.002 per 1,000 patient days in 2007 vs. 0.014 in 2010). ST398 BSI isolates differed from the pig-borne multiresistant clone: 17/18 BSI isolates were methicillin susceptible and none was of t011, t034 or t108 pig-borne spa-types. ST398 BSI isolates had homogenous resistance patterns (15/18 with only Eryr) and prophagic content (all harboured the hlb-converting Sau3int phage). The clustering of BSI and pig-borne isolates by spa-typing and MLVA, the occurrence of Sau3int phage in BSI isolates and the lack of this phage in pig-borne isolates suggest that the emergence of BSI isolates could have arisen from horizontal transfer, at least of the Sau3int phage, in genetically diverse MSSA ST398 isolates. The acquisition of the phage likely plays a role in the increasing ability of the lysogenic ST398 isolates to colonize human. The mode of acquisition of the non pig-borne ST398 isolates by our 18 patients remains unclear. ST398 BSI were diagnosed in patients lacking livestock exposure and were significantly associated with digestive portals of entry (3/18 [16.7%] for ST398 vs. 19/767 [2.5%] for non ST398 BSI; p = .012). This raises the question of possible foodborne human infections. We suggest the need for active surveillance to study and control the spread of this human-adapted subclone increasingly isolated in the hospital setting.

Molecular and Epidemiological Evidence for Spread of Multiresistant Methicillin-Susceptible Staphylococcus aureus Strains in Hospitals

ABSTRACT The excision of the staphylococcal chromosomal cassette mec (SCCmec) from methicillin-resistant Staphylococcus aureus (MRSA) strains results in methicillin-susceptible S. aureus (MSSA) strains. In order to determine the proportion and diversity of multidrug-resistant MSSA (MR-MSSA) strains derived from MRSA strains, 247 mecA-negative isolates recovered in 60 French hospitals between 2002 and 2004 were characterized. The spa types of all strains were determined, and a subset of the strains (n = 30) was further genotyped by multilocus sequence typing. The IDI-MRSA assay was used to test the isolates for the presence of the SCCmec element, which was detected in 68% of all isolates analyzed. Molecular analysis of the samples suggested that 92% of the MR-MSSA isolates were derived from MRSA clones of diverse genetic backgrounds, of which the clone of sequence type 8 and SCCmec type IVA accounted for most of the samples. High variations in incidence data and differences in the molecular characteristics of the isolates from one hospital to another indicate that the emergence of MR-MSSA resulted from independent SCCmec excisions from epidemic MRSA isolates, as well as the diffusion of methicillin-susceptible strains after the loss of SCCmec. MR-MSSA could constitute a useful model for the study of the respective genetic and environmental factors involved in the dissemination of S. aureus in hospitals.

Risk factors for multidrug-resistant bacteria in patients with post-operative peritonitis requiring intensive care

OBJECTIVES This prospective non-interventional study investigated the risk factors for multidrug-resistant bacteria (MDRB) in patients with post-operative peritonitis (POP), to provide guidance for empirical antimicrobial therapy. METHODS All consecutive patients, >15 years old, admitted to a surgical intensive care unit (ICU) between September 2006 and January 2009 for a first episode of POP were included. Antibiotic susceptibilities of microorganisms recovered from blood cultures and peritoneal fluid were determined by disc diffusion. Amoxicillin/clavulanic acid, ticarcillin/clavulanic acid, piperacillin/tazobactam, cefotaxime, ceftazidime, cefepime, imipenem, gentamicin, amikacin and ciprofloxacin were tested against Gram-negative bacteria, and oxacillin, amoxicillin, vancomycin, gentamicin and erythromycin were tested against aerobic Gram-positive bacteria. Results were reported as susceptible or resistant. RESULTS MDRB were isolated from 20/115 (17%) patients. In univariate analysis, use of antimicrobial therapy during the 3 months prior to hospitalization and a long duration between hospital admission or first operation and relaparotomy were significantly associated with MDRB recovery. In multivariate analysis, only antimicrobial treatment in the 3 months preceding hospitalization and duration between first operation and relaparotomy were independent risk factors for MDRB [odds ratio (OR) = 5.80, 95% confidence interval (95% CI) = 1.99-16.91 and OR = 1.10, 95% CI = 1.02-1.19, respectively]. No MDRB were found when the delay between the first operation and relaparotomy was <5 days. POP severity, non-surgical and surgical complications, hospital and ICU length of stay, and mortality were similar in patients with and without MDRB. CONCLUSIONS Our results suggest that broad-spectrum antibiotics should be used in ICU patients with POP who have received antimicrobial therapy in the 3 months prior to hospitalization, or with >5 days between the first operation and relaparotomy.

At-risk drinkers are at higher risk to acquire a bacterial infection during an intensive care unit stay than abstinent or moderate drinkers.

Objectives:To determine whether excessive alcohol consumption increases the risk for intensive care unit (ICU)-acquired bacterial infection, especially ventilator-associated pneumonia (VAP), in nontrauma patients. Design:Prospective observational cohort study. Setting:A 21-bed polyvalent ICU in a university hospital. Patients:A total of 358 adult patients admitted over a 1-yr period who had an ICU stay ≥3 days and in whom alcohol consumption could be assessed. Interventions:None. Measurements and Mean Results:Thirty-one percent of the patients (111 of 358) were identified as at-risk drinkers according to the National Institute on Alcohol Abuse and Alcoholism criteria. Among these, 61 had a daily intake of five or more drinks per day and 73 had Simplified Michigan Alcohol Short Test scores ≥3. ICU-acquired bacterial infections were diagnosed in 88 patients, and 69 patients had one or more VAPs. Forty (36%) at-risk drinkers acquired bacterial infections vs. 48 (19%) not-at-risk drinkers (p < .001). Among at-risk drinkers, the proportion of patients who developed bacterial infection was higher in at-risk drinkers consuming five or more drinks per day compared with at-risk drinkers consuming fewer than five drinks per day (p = .048). After adjustment for age, gender, Simplified Acute Physiology Score II, length of hospital stay before ICU admission, prior antibiotic administration within 24 hrs before ICU admission, type of admission, immunosuppression, duration of mechanical ventilation, and central venous and urinary catheter exposure, at-risk drinking remained significantly associated with the acquisition of bacterial infection at any site (hazard ratio 1.92; 95% confidence interval, 1.17–3.14; p = .009) and of VAP (hazard ratio 1.76; 95% confidence interval, 1.05–3.06; p = .04). Conclusions:At-risk drinking was a significant risk factor for acquisition of ICU-acquired bacterial infection.

Constipation in long-term ventilated patients: associated factors and impact on intensive care unit outcomes.

Objectives:To characterize the factors associated with delayed defecation in long-term ventilated patients and to examine the relationship between delayed defecation and logistic organ dysfunction scores, acquired bacterial infections, and mortality in the intensive care unit. Design:Prospective observational cohort study. Setting:A 21-bed polyvalent intensive care unit in a university hospital. Patients:A total of 609 adult patients admitted over a 41-month period who underwent mechanical ventilation for ≥6 days. Interventions:None. Measurements and Main Results:Three hundred fifty-three patients (58%) passed stools ≥6 days after they were admitted to the intensive care unit (“late” defecation). Patients with early and late defecation had similar general characteristics when admitted to the intensive care unit and had similar logistic organ dysfunction scores on the first day of mechanical ventilation. Several variables were independently associated with a delay in defecation: a Pao2/Fio2 ratio of less than 150 mm Hg (adjusted hazard ratio 1.40; 95% confidence interval: 1.06–1.60; p = .0073), a systolic blood pressure between 70 and 89 mm Hg (adjusted hazard ratio 1.48; 95% confidence interval: 1.17–1.79; p = .002), and systolic blood pressure <68 mm Hg (adjusted hazard ratio 1.29; 95% confidence interval: 1.01–1.60; p = .03). Logistic organ dysfunction scores were significantly higher on the fourth and ninth days of mechanical ventilation in patients with late defecation than in those with early defecation. The crude intensive care unit mortality rate was 18% in patients with early defecation and 30% in patients with late defecation (p < .001). Acquired bacterial infections at any site occurred in 34% of patients with early defecation and 66% of patients with late defecation (p < .001). Conclusion:A Pao2/Fio2 ratio of <150 mm Hg and systolic blood pressure of <90 mm Hg during the first 5 days of mechanical ventilation were independently associated with a delay in defecation. Our results suggest that constipation is associated with adverse outcomes in long-term ventilated patients.

A portrait of Staphylococcus aureus from the other side of the Mediterranean Sea: molecular characteristics of isolates from Western Algeria

Algerian hospitals have experienced a dramatic increase in methicillin-resistant Staphylococcus aureus (MRSA) prevalence in recent years. To investigate this phenomenon, we have determined molecular characteristics of 61 methicillin-resistant or -susceptible strains isolated between 2003 and 2007 in Oran Hospital. Susceptible isolates were related to diverse genetic backgrounds, of which clone with sequence type (ST) 8 accounted for most of the samples. Resistance to methicillin was almost limited to two international spreading clones; the most frequent, ST80, contained isolates producing Panton-Valentine leukocidine, with SCCmec type IV. The increase of MRSA prevalence observed in Western Algeria, in outpatients as well as in hospitalized patients, is linked to dissemination of ST80 strains usually considered as community-acquired MRSA.

Genotypic characterization of Porphyromonas gingivalis isolated from subgingival plaque and blood sample in positive bacteremia subjects with periodontitis

AIM The objective of this study was to investigate clonal relationship among Porphyromonas gingivalis isolated from subgingival plaque and blood samples in positive transient bacteremia subjects with periodontitis. MATERIAL AND METHODS Unrelated patients with general chronic periodontitis or general aggressive periodontitis requiring scaling and root planing (SRP) were included in the study. Genotyping of each isolate was performed using pulsed field gel electrophoresis technique. Genetic relatedness of strains isolated within an individual or between different patients was determined by dendogram analysis. RESULTS Following SRP, from 16 patients, seven patients showed positive P. gingivalis bacteremia and nine were negative. Thirty-two strains were isolated from subgingival plaque and blood samples before and during induced transient bacteremia. The majority of the patients harboured one clonal type. Two patients showed different clones in plaque and blood samples suggesting that more than one clone can be found in subgingival plaque. P. gingivalis isolates from periodontitis patients after transient bacteremia following SRP, revealed a high heterogeneity among isolates. CONCLUSION In 6/16 subjects the same P. gingivalis isolate was found in the blood and in oral cavity. P. gingivalis heterogeneity suggests no association of a unique clonal type with transient bacteremia.

Analysis of prophages harbored by the human-adapted subpopulation of Staphylococcus aureus CC398

Staphylococcus aureus clonal complex 398 is a livestock-associated pathogen that poses a worldwide threat because of its ability to colonize and infect both humans and animals. We used high-resolution whole-genome microarrays, prophage profiling, immune evasion cluster characterization and whole-genome sequencing to investigate the roles of prophages in the emerging human-adapted subpopulation of CC398 that has been associated with invasive infections in humans living in animal-free environments. We characterized one phage and two prophages specifically harbored by CC398 isolates belonging to the emerging subpopulation. We introduced the phage into permissive prophage-free isolates. We investigated the effects of lysogeny on the host ability to resist further phage infection and transformation, to acquire the capacity to invade human cells, and to express virulence factors encoded by prophages. We report evidence of a defective ϕMR11-like helper prophage, named StauST398-5pro, specifically associated with the emerging non-LA CC398 subpopulation. StauST398-5pro confers substantial protection against horizontal genetic transfer to its host. It interacts with a human-associated β-converting prophage encoding immune-modulating proteins such that virulence genes are expressed during stress situations. Our findings provide insight into the role of phages in the expression of virulence and in the spread of genetic information among new host-adapted S. aureus isolates. We demonstrate that functional prophage elements can condition host specificity and confer new virulence traits on emerging intra-species clones of bacteria.