Pan-genome multilocus sequence typing and outbreak-specific reference-based single nucleotide polymorphism analysis to resolve two concurrent Staphylococcus aureus outbreaks in neonatal services.

We used a two-step whole genome sequencing analysis for resolving two concurrent outbreaks in two neonatal services in Belgium, caused by exfoliative toxin A-encoding-gene-positive (eta+) methicillin-susceptible Staphylococcus aureus with an otherwise sporadic spa-type t209 (ST-109). Outbreak A involved 19 neonates and one healthcare worker in a Brussels hospital from May 2011 to October 2013. After a first episode interrupted by decolonization procedures applied over 7 months, the outbreak resumed concomitantly with the onset of outbreak B in a hospital in Asse, comprising 11 neonates and one healthcare worker from mid-2012 to January 2013. Pan-genome multilocus sequence typing, defined on the basis of 42 core and accessory reference genomes, and single-nucleotide polymorphisms mapped on an outbreak-specific de novo assembly were used to compare 28 available outbreak isolates and 19 eta+/spa-type t209 isolates identified by routine or nationwide surveillance. Pan-genome multilocus sequence typing showed that the outbreaks were caused by independent clones not closely related to any of the surveillance isolates. Isolates from only ten cases with overlapping stays in outbreak A, including four pairs of twins, showed no or only a single nucleotide polymorphism variation, indicating limited sequential transmission. Detection of larger genomic variation, even from the start of the outbreak, pointed to sporadic seeding from a pre-existing exogenous source, which persisted throughout the whole course of outbreak A. Whole genome sequencing analysis can provide unique fine-tuned insights into transmission pathways of complex outbreaks even at their inception, which, with timely use, could valuably guide efforts for early source identification.

Efficacy of the decolonization of methicillin-resistant Staphylococcus aureus carriers in clinical practice.

BACKGROUND: Nasal and extra nasal carriage of methicillin-resistant S. aureus (MRSA) is a pre-existing condition that often leads to invasive MRSA infection, as MRSA colonization is associated with a high risk of acquiring MRSA infection during hospital stays. Decolonization may reduce the risk of meticillin-resistant Staphylococcus aureus (MRSA) infection in individual carriers and prevent transmission to other patients. METHODS: A retrospective cohort study was conducted to evaluate the effectiveness of two decolonization protocols for newly diagnosed MRSA carriage in hospitalized patients and to assess the impact of decolonization on the rate of MRSA infection. The study population consisted of all patients diagnosed as MRSA-positive between January 2006 and June 2010. Patients diagnosed as carriers were designated as requiring contact precautions by the hospital infection control team. The standing order protocol of the hospital pertaining to decolonization procedures was then applied, and all newly diagnosed patients were administered one of the two decolonization treatments outlined in the hospital protocol, with the exception of MRSA respiratory carriers (MRSA obtained from sputum or other lower respiratory tract samples). The two decolonization treatments consisted of the application of intranasal mupirocin 2 % and washing with chlorhexidine soap (40 mg/mL) (mupi/CHX) or application of intranasal povidone-iodine and washing with povidone-iodine soap (PVPI), with each treatment lasting for 5 days. Success was determined by at least three successive nose swabs and throat and other screened site swabs that tested negative for MRSA before patient discharge. RESULTS: A total of 1150 patients admitted to the hospital were found to be infected or colonized with MRSA. Of the 1150 patients, 268 were prescribed decolonization treatment. 104 out of 268 patients (39 %) were successfully decolonized. There was no significant success after two decolonization failures. MRSA infection rate among the successes and failures were 0.0 and 4.3 %, respectively [P = 0.04]. CONCLUSIONS: Our results fit well with the prescription of decolonization based on local strategy protocols but reflect a low rate of successful treatment. Although the success rate of decolonization was not high in our study, the effectiveness of decolonization on the infection rate, justifies the continuation of this strategy, even if a marginal cost is incurred.

Comparative epidemiology of Staphylococcus epidermidis isolates from patients with catheter-related bacteremia and from healthy volunteers.

Staphylococcus epidermidis is a major cause of catheter-related bloodstream infections (CRBSIs). Recent studies suggested the existence of well-adapted, highly resistant, hospital-associated S. epidermidis clones. The molecular epidemiology of S. epidermidis in Belgian hospitals and the Belgian community has not been explored yet. We compared a set of 33 S. epidermidis isolates causing CRBSI in hospitalized patients with a set of 33 commensal S. epidermidis isolates. The factors analyzed included resistance to antibiotics and genetic diversity as determined by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and SCCmec typing. Additionally, the presence of virulence-associated mobile genetic elements, the ica operon and the arginine catabolic mobile element (ACME), was assessed and compared against clinical data. CRBSI S. epidermidis isolates were significantly resistant to more antibiotics than commensal S. epidermidis isolates. The two populations studied were very diverse and genetically distinct as only 23% of the 37 PFGE types observed were harbored by both CRBSI and commensal isolates. ACME was found in 76% of S. epidermidis strains, regardless of their origin, while the ica operon was significantly more prevalent in CRBSI isolates than in commensal isolates (P < 0.05). Nine patients presented a clinically severe CRBSI, eight cases of which were due to an ica-positive multiresistant isolate belonging to sequence type 2 (ST2) or ST54. S. epidermidis isolates causing CRBSI were more resistant and more often ica positive than commensal S. epidermidis isolates, which were genetically heterogeneous and susceptible to the majority of antibiotics tested. Clinically severe CRBSIs were due to isolates belonging to two closely related MLST types, ST2 and ST54.

Pseudo-outbreak of extremely drug-resistant pseudomonas aeruginosa urinary tract infections due to contamination of an automated urine analyzer.

By the end of May 2010, an increase in the number of urine specimens that were culture positive for extremely drug-resistant (XDR) Pseudomonas aeruginosa was observed in our 800-bed university hospital. This led to an infection control alert. No epidemiological link between the patients and no increase in the frequency of XDR P. aeruginosa in non-urine samples were observed. Therefore, a pseudo-outbreak due to analytical contamination in the laboratory was rapidly suspected. A prospective and retrospective search of cases was initiated, and the sampling of the automated urine analyzers used in the laboratory was performed. Antibiotypes were determined by disc diffusion, and genotypes were determined by pulsed-field gel electrophoresis (PFGE). From February to July 2010, 17 patients admitted to 12 different departments and 6 outpatients were included. The mixing device of the cytometric analyzer used for the numeration of urinary particles (Sysmex UF1000i) proved to be heavily contaminated. Isolates recovered from 12 patients belonged to the same antibiotype and PFGE type as the isolate recovered from the analyzer. Extensive disinfection with a broad-spectrum disinfectant and the replacement of the entire tubing was necessary to achieve the complete negativity of culture samples taken from the analyzer. A pseudo-outbreak caused by an XDR P. aeruginosa clone was proven to be due to the contamination of the cytometric analyzer for urinary sediment. Users of such analyzers should be aware that contamination can occur and should always perform culture either before the processing of the urine sample on the analyzer or on a distinct sample tube.

Positive predictive value of the Xpert MRSA assay diagnostic for universal patient screening at hospital admission: influence of the local ecology.

The purpose of this study was to assess the accuracy of the Xpert MRSA assay (XP) for the detection of methicillin-resistant Staphylococcus aureus (MRSA) carriage upon hospital admission. Nasal swabs were prospectively collected for MRSA screening from 1,891 patients admitted to a teaching hospital. XP results were compared to chromogenic agar culture results. MRSA was cultured in 61 specimens (3%). Compared with culture, XP had a sensitivity, specificity, positive, and negative predictive value of 60.7, 97.3, 37.8, and 98.9%, respectively. The median turnaround time (TAT) for the results was 3 h. Of 24 MRSA isolated from XP-negative samples, three harbored composite SCCmec. Among 61 samples with culture-negative but XP-positive results, 15 methicillin-susceptible S. aureus (MSSA) isolates tested positive by XP on pure colony lysates. These MSSA included: (i) strains with SCCmec deletion encompassing mecA and (ii) multilocus sequence typing (MLST) clonal complex (CC) 1 strains harboring a chromosomal sequence homologous to one of the orfX-SCCmec junction sequences targeted by XP. On account of the low sensitivity and positive predictive value in a hospital patient population with moderate prevalence of MRSA, culture still appears to be necessary in order to confirm polymerase chain reaction (PCR) results. The emergence of new SCCmec variants and the presence of MSSA harboring cross-reactive SCCmec-like elements may challenge the successful implementation of such detection systems.

[From MRSA to MRSA's in general practice]. / Du MRSA aux MRSA en médecine générale.

Methicilline resistant Staphylococcus aureus (MRSA) remains a major cause of healthcare associated infections. Limited therapeutic options, the fact that MRSA disease burden do not replace but adds to the sensitive strains burden and its association with increased morbidity and mortality justify reinforced efforts in both prevention of transmission and treatment. Although transmission in acute hospital is decreasing in Belgium, general practitioners face actually to an important prevalence of carriage in nursing homes. Hand hygiene, promotion of prudent use of antimicrobial agents, MRSA surveillance and control are all preventive strategies whom improvement should result in control of MRSA transmission and progressive prevalence decrease in this particular setting. More recently, community acquired strains (CA-MRSA) harboring Panton Valentin Leucocidin were associated with skin and soft tissue among younger people, and livestock associated strains were identified as causing agents of infection in farmer population. CA-MRSA are now transmitted in general population and are causative agents of recurrent or chronic skin infections resistant to beta-lactamine. The diagnosis needs to be evoked in particular settings such as frequent close skin contact (sport, ...). CA-MRSA may also cause necrotising pneumonia. The general practitioner is a central actor in the battle against MRSA both in the field of prevention and treatment by the prudent use of antibiotics, the promotion of hand hygiene and associated specific measures and the accuracy to detect clinical situation evoking infection due to CA-MRSA in the general population.

Intensive care unit outbreak of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae controlled by cohorting patients and reinforcing infection control measures.

OBJECTIVE: To describe an outbreak of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae in the intensive care units (ICUs) of a hospital and the impact of routine and reinforced infection control measures on interrupting nosocomial transmission. DESIGN: Outbreak report. SETTING: A 31-bed intensive care department (composed of 4 ICUs) in a university hospital in Belgium. INTERVENTION: After routine infection control measures (based on biweekly surveillance cultures and contact precautions) failed to interrupt a 2-month outbreak of ESBL-producing K. pneumoniae, reinforced infection control measures were implemented. The frequency of surveillance cultures was increased to daily sampling. Colonized patients were moved to a dedicated 6-bed ICU, where they received cohorted care with the support of additional nurses. Two beds were closed to new admissions in the intensive care department. Meetings between the ICU and infection control teams were held every day. Postdischarge disinfection of rooms was enforced. Broad-spectrum antibiotic use was discouraged. RESULTS: Compared with a baseline rate of 0.44 cases per 1,000 patient-days for nosocomial transmission, the incidence peaked at 11.57 cases per 1,000 patient-days (October and November 2005; rate ratio for peak vs baseline, 25.46). The outbreak involved 30 patients, of whom 9 developed an infection. Bacterial genotyping disclosed that the outbreak was polyclonal, with 1 predominant genotype. Reinforced infection control measures lasted for 50 days. After the implementation of these measures, the incidence fell to 0.08 cases per 1,000 patient-days (rate ratio for after the outbreak vs during the outbreak, 0.11). CONCLUSION: These data indicate that, in an intensive care department in which routine screening and contact precautions failed to prevent and interrupt an outbreak of ESBL-producing K. pneumoniae, reinforced infection control measures controlled the outbreak without major disruption of medical care.

Clostridium difficile colitis in cystic fibrosis patients with and without lung transplantation.

BACKGROUND: Despite a large carriage rate of Clostridium difficile among cystic fibrosis (CF) patients, C. difficile-associated disease (CDAD) is rather rare. In case of lung transplantation, the incidence and clinical aspects of CDAD in this patient population are not well known. METHODS: We reviewed the medical files of all CF patients who presented with symptomatic C. difficile infection from January 1998 to December 2004 and compared the incidence, clinical aspects, severity of disease, and clinical outcome between non-transplanted and transplanted CF patients. RESULTS: Between 1998 and 2004, 106 adult CF patients were followed at our clinic. Forty-nine patients underwent lung transplantation; 15 before 1998 and 34 after 1998. The incidence density of CDAD was higher in transplanted CF patients as compared with non-transplanted CF patients (24.2 vs. 9.5 episodes/100,000 patient-days; risk ratio: 2.93 [1.41-6.08]; P=0.0044). Diarrhea was a very frequent feature, but was notably absent in 20% of the cases. Rates of moderate and severe colitis were similar in both groups. However, only transplanted patients developed complicated colitis. CT scan and endoscopy were performed more frequently in the transplant group. Two transplant recipients died because of CDAD. CONCLUSION: CF patients who undergo lung transplantation are at a higher risk of developing CDAD and seem to present more often atypical and/or complicated disease. CDAD should be part of the differential diagnosis in case of digestive symptoms, even in the absence of diarrhea, and requires early treatment.

Outbreak of hospital-adapted clonal complex-17 vancomycin-resistant Enterococcus faecium strain in a haematology unit: role of rapid typing for early control.

OBJECTIVES: To describe the investigation and molecular characterization of a vancomycin-resistant Enterococcus faecium (VREF) strain responsible for a nosocomial outbreak in the haematology unit of a tertiary-care university hospital. PATIENTS AND METHODS: Two patients admitted to the haematology unit developed infection/colonization with VREF over a 3 month period when compared with none in the 2 previous years. On the basis of the identification of a clonal link between these two strains, weekly rectal screening was implemented for all patients in the haematology unit and contact precautions were extended to VREF carriers. In the following 6 month period, 11 patients colonized with VREF were detected. No further case was detected in the following 1 year period. RESULTS: VREF isolates from the haematology unit carried the vanA gene and were multiresistant to antimicrobial agents, including high-level resistance to vancomycin, teicoplanin and ampicillin. This resistance profile restricted the choice of antimicrobial therapy to linezolid or investigational drugs such as tigecycline. Molecular analysis showed that 11 of 13 (85%) VREF isolates belonged to pandemic clonal complex-17 carrying the esp and hyl virulence genes. CONCLUSIONS: Rapid typing and infection control measures, including early reinforcement of barrier precautions combined with weekly rectal surveillance cultures, were followed by control of nosocomial spread of this VREF clone.

Outcome of totally implantable venous access device-related bacteraemia without device removal.

The optimal management of bacteraemia related to the presence of totally implantable venous access devices (TIVADs) remains controversial, particularly in terms of whether to remove the infected catheter. The objective of this study was to determine the factors associated with success or failure of treatment of TIVAD-related bacteraemia in patients from whom the infected device was not removed. The outcome of 92 episodes of TIVAD-related bacteraemia and the factors predictive of an unfavourable outcome were evaluated retrospectively. In 32 (35%) episodes, the devices were removed immediately. In 60 episodes, patients were treated with antibiotics infused through the device; treatment was successful in 56% of these cases (66% for infections caused by coagulase-negative staphylococci). Only the presence of sepsis (OR 9.42, 95% CI 1.29-68.92, p 0.0271) and of local signs of infection (OR 9.61, 95% CI 1.98-46.49, p 0.0049) independently predicted the failure of catheter-retaining treatment. Finally, only one-third of the devices were retained. In conclusion, the large number of TIVADs that are removed because of infection justifies reconsidering the criteria for device removal. During catheter-retaining treatment, the presence of local signs of infection or reported sepsis were independent factors for reduced probability of retaining the device.

Management of an outbreak of Clostridium difficile-associated disease among geriatric patients.

OBJECTIVE: To describe a nosocomial outbreak of Clostridium difficile-associated disease (CDAD). DESIGN: A traditional outbreak investigation. SETTING: Geriatric department of a tertiary care teaching hospital from March through April 2003. METHODS: The outbreak was detected by the C. difficile surveillance program of the infection control unit. CDAD was diagnosed by stool culture and fecal toxin A detection with a qualitative rapid immunoassay. Isolates of C. difficile were serotyped and genotyped using pulsed-field gel electrophoresis. RESULTS: The incidence of CDAD increased from 27 cases per 100,000 patient-days in the 6-month period before the outbreak to 99 cases per 100,000 patient-days during the outbreak. This outbreak involved 21 of 92 patients in 4 geriatric wards, which were located at 2 geographically distinct sites and staffed by the same medical team. The mean age of patients was 83 years (range, 71-100 years). Five (24%) of the 21 patients had community-acquired diarrhea, and secondary hospital transmission resulted in 3 clusters involving 16 patients. Serotyping and genotyping were performed on isolates in stool specimens from 19 different patients; 16 of these isolates were serotype A1, whereas 3 displayed profiles different from the outbreak strain. Management of this outbreak consisted in reinforcement of contact isolation precautions for patients with diarrhea, cohorting of infected patients in the same ward, and promotion of hand hygiene. Relapses occurred in 6 (29%) of 21 patients. CONCLUSION: Control of this rapidly developing outbreak of CDAD was obtained with early implementation of cohorting and ward closure and reinforcement of environmental disinfection, hand hygiene, and enteric isolation precautions.

Molecular characterization of an epidemic clone of panantibiotic-resistant Pseudomonas aeruginosa.

We describe the molecular characterization of a multiresistant Pseudomonas aeruginosa clone causing an outbreak in the intensive care unit (ICU) of a tertiary-care university hospital. Analysis included antimicrobial susceptibility profile, O-serotyping, pulsed-field gel electrophoresis, and amplified fragment length polymorphism. Resistance mechanisms were characterized, including production of naturally occurring and acquired beta-lactamases, porin expression, and efflux pump systems. Eighteen patients were colonized or infected with multiresistant P. aeruginosa. Multiresistant P. aeruginosa was panresistant to penicillins, cephalosporins, carbapenems, aminoglycosides, and fluoroquinolones and remained susceptible only to colistin. Sixteen isolates (89%) belonged to serotype O:11, pulsed-field gel electrophoresis type A1, and amplified fragment length polymorphism type A. Resistance characterization of this epidemic clone showed an overexpression of the chromosomal cephalosporinase AmpC combined with decreased expression of porin OprD and the absence of metallo-beta-lactamase or extended-spectrum beta-lactamase. An upregulation of the MexXY efflux system due to an agrZ mutation in the mexZ repressor was detected. This epidemic clone was restricted to the ICU and was not found elsewhere in hospital. Contamination of the ICU environment and the hands of an ICU nurse with this clone suggests possible hand-borne transmission. Implementation of contact precautions effectively controlled transmission of the epidemic clone. This study illustrates the ability of multiresistant P. aeruginosa to cause an outbreak with significant morbidity and mortality and underscores the need to identify clonal outbreaks, which require targeted infection control measures.

Clinical impact of a PCR assay for identification of Staphylococcus aureus and determination of methicillin resistance directly from blood cultures.

We evaluated the clinical usefulness of a PCR assay that discriminates Staphylococcus aureus from coagulase-negative staphylococci and detects methicillin resistance on blood cultures by measuring the adaptation of antimicrobial therapy based on the PCR results. Only 7 of 28 patients (25%) benefited from a modification of antibiotic therapy based on the PCR results, since empirical therapy was appropriate in a majority of cases.

OM197-MP-AC induces the maturation of human dendritic cells and promotes a primary T cell response.

Dendritic cell (DC) maturation is critical for the induction of antigen-specific T lymphocyte responses and may be essential for the development of human vaccines relying on T cell immunity. We investigated the effects on human DC of OM-197, a synthetic pseudodipeptide derived from amino acids, linked to three fatty acid chains and devoid of endotoxin properties. OM-197 upregulated the expression of HLA-DR, CD80, CD86, CD83, CD40 and CD54 at the surface of myeloid DC naturally present in blood as well as of DC generated in vitro from monocytes using IL-4 and GM-CSF. OM-197 also induced the release of IL-12 and TNF-alpha from DC. Finally, DC incubated with OM-197 after pulsing with hepatitis B surface antigen (HBs Ag) induced in vitro expansion of IFN-gamma-secreting HBs Ag-specific CD4(+) T lymphocytes from naive individuals. Taken together, these data identify OM-197 as a potential vaccine adjuvant for the induction of Th1-type responses.

[The hospital epidemiology and hygiene unit]. / L'Unite d'Epidémiologie et d'Hygiène Hospitalière.

The hospital Epidemiology and Infection Control Unit aims at preventing nosocomial infections and controlling epidemics. In this field, several researches have contributed to improve the knowledge of infections secondary to biliary endoscopy, of epidemics of nosocomial Legionella and multiresistant gram negative and Staphylococcus aureus infections. Studies about the rational use of antibiotics have contributed to a better control of the transmission of multiresistant pathogens.

[The infective diseases clinic]. / La Clinique des Maladies Infectieuses.

The Clinic of Infectious Diseases was created at Erasme Hospital in 1980. Its main activity consists in taking care of patients with infectious complications in various hospital departments. Its main scientific contributions concern the evaluation of new treatments, pharmacokinetics of antimicrobial agents and physiopathology of sepsis. The evaluation of the impact of infectious diseases on the appropriateness of antimicrobial therapy and the control of infection is a major contribution of the clinic. Several works concern the study of the immune response in case of infection due to an intracellular pathogen and in response to vaccination.

Fatal primary infection due to human herpesvirus 6 variant A in a renal transplant recipient.

We describe a fatal primary human herpesvirus 6 (HHV-6) variant A infection in a kidney transplanted adult woman. On day 20 post transplantation (TX), after rejection therapy, the patient presented an acute hemophagocytic syndrome with hepatitis and central nervous system involvement. HHV-6 IgG and IgM antibodies seroconversion was demonstrated. HHV-6 variant A was the sole pathogen detected by nested PCR and/or culture in blood, bone marrow aspiration, liver biopsy, cerebrospinal fluid and bronchoalveolar lavage. The graft was HHV-6 seropositive and the patient was not transfused before day 28 post TX, suggesting that the virus was transmitted by the graft. Despite immunoglobulins, ganciclovir and foscarnet therapy, the HHV-6 infection progressed and led to severe aplasia. The patient developed Aspergillus fumigatus pneumonia and died from fulminant candidemia. This case demonstrated for the first time that HHV-6 variant A primary infection can cause life-threatening disseminated infection in immunosuppressed patients.

Ceftazidime- and imipenem-induced endotoxin release during treatment of gram-negative infections.

To determine whether ceftazidime and imipenem, which target two different penicillin-binding proteins, result in different amounts of endotoxin and cytokine release in patients with gram-negative infection, plasma endotoxin, interleukin-6, and tumor necrosis factor alpha were measured during the first 24 h of antibiotic therapy in 27 patients with gram-negative infection who had been randomized to receive either ceftazidime 2 g t.i.d. (n=12) or imipenem/cilastatin 1 g t.i.d. (n=15). The source of infection was the digestive tract (n=13), the urinary tract (n=5), the respiratory tract (n=2), soft tissue (n=2), i.v. line (n=2), or other (n=3). After the first antibiotic injection, a significant increase in the median concentration of plasma interleukin-6 and plasma tumor necrosis factor alpha was noted, without significant differences related to the antibiotic administered. Antibiotic-induced endotoxemia was detectable in nine patients (including 7 with bacteremia). In conclusion, ceftazidime and imipenem had similar effects on endotoxin and cytokine release during the treatment of gram-negative infections.