Anne Lotthé

From Environment to Man: Genome Evolution and Adaptation of Human Opportunistic Bacterial Pathogens

Environment is recognized as a huge reservoir for bacterial species and a source of human pathogens. Some environmental bacteria have an extraordinary range of activities that include promotion of plant growth or disease, breakdown of pollutants, production of original biomolecules, but also multidrug resistance and human pathogenicity. The versatility of bacterial life-style involves adaptation to various niches. Adaptation to both open environment and human specific niches is a major challenge that involves intermediate organisms allowing pre-adaptation to humans. The aim of this review is to analyze genomic features of environmental bacteria in order to explain their adaptation to human beings. The genera Pseudomonas, Aeromonas and Ochrobactrum provide valuable examples of opportunistic behavior associated to particular genomic structure and evolution. Particularly, we performed original genomic comparisons among aeromonads and between the strictly intracellular pathogens Brucella spp. and the mild opportunistic pathogens Ochrobactrum spp. We conclude that the adaptation to human could coincide with a speciation in action revealed by modifications in both genomic and population structures. This adaptation-driven speciation could be a major mechanism for the emergence of true pathogens besides the acquisition of specialized virulence factors.

Staphylococcus aureus in a neonatal care center: methicillin-susceptible strains should be a main concern

BackgroundIn the context of a methicillin-susceptible Staphylococcus aureus (MSSA) outbreak, we aimed to improve our knowledge of S. aureus (SA) epidemiology in the neonatal care center (NCC) of a tertiary care teaching hospital.MethodsWe performed a complete one-year review of SA carrier, colonized or infected patients. Monthly prevalence and incidence of SA intestinal carriage, colonization and infection were calculated and the types of infection analysed. During the MSSA outbreak, strains were studied for antimicrobial resistance, content of virulence genes and comparative fingerprint in Pulsed-Field Gel Electrophoresis. Hand hygiene and catheter-related practices were assessed by direct observational audits. Environmental investigation was performed in search of a SA reservoir.ResultsEpidemiological analyses showed 2 or 3 prevalence peaks on a background of SA endemicity. In the NCC, during 2009, overall MSSA prevalence did not decrease below 5.5%, while mean MRSA prevalence was about 1.53%. Analysis of infection cases revealed that the outbreak corresponded to the emergence of catheter-related infections and was probably related to the relaxation in infection control practices in a context of high colonization pressure. Health care workers’ white coats appeared as a potential environmental reservoir that could perpetuate SA circulation in the ward.ConclusionThis report emphasizes the importance of integrating MSSA along with methicillin-resistant SA in a program of epidemiological surveillance in the NCC.

An Outbreak of Heterogeneous Glycopeptide-Intermediate Staphylococcus aureus Related to a Device Source in an Intensive Care Unit

OBJECTIVE The emergence of Staphylococcus aureus with reduced susceptibility to glycopeptides (glycopeptide-intermediate S. aureus [GISA] and heterogeneous GISA [h-GISA]) leads to intensive care unit (ICU) outbreaks that frequently result in ward closure. We investigated the role of hospital hygiene in the transmission and eradication of an h-GISA outbreak. DESIGN The study is a description of an original environmental investigation around a series of 12 cases. SETTING AND PATIENTS The outbreak occurred in a 20-bed polyvalent/trauma ICU in a 2,800-bed tertiary care university hospital in France. INTERVENTIONS Specimens were obtained for surveillance and diagnostic cultures from all patients in the unit. Surface sampling was also performed. Geographic cohorting, contact isolation, emphasis on adherence to infection control practices, and environmental cleaning were implemented. RESULTS Twelve patients with h-GISA infection (n = 5) or colonization (n = 7) were identified. The mean interval between admission and h-GISA detection was 23.6 days (range, 10-89 days), with a median of 16.5 days. Environmental investigation identified an unexpected reservoir, namely, SpO(2) sensors. The outbreak was controlled by a combination of measures, including eradication of this reservoir, avoiding total ward closure. CONCLUSIONS Targeted surface sampling helps to secure the environment through active investigation of various reservoirs while maintaining normal activity on the ward. In our study, this method led to the detection of an unsuspected reservoir, the eradication of which helped control the h-GISA epidemic. Further applications of this original investigative procedure should allow confirmation of its relevance and efficiency.

Peripheral Venous Catheter and Bloodstream Infection Caused by Pseudomonas aeruginosa after a Contaminated Preoperative Shower

was reduced in the presence of organic load (Figure 1). On patient wards, application of Sterilox HG resulted in significant reductions in total aerobic and facultative bacterial counts (mean CFU, 39 vs 0.73; P = .0003) and in positive C. difficile cultures (8/66 [12%] vs 0/66; P = .006). Spraying of Sterilox HG on sets of equipment was simple and required only approximately 15 seconds per application. Application of Sterilox HG did not result in production of noticeable noxious fumes but was described as producing an odor similar to that of swimming pool water. There were no reported complaints from nursing staff or patients.

Validation of nosocomial infection in neonatology: A new method for standardized surveillance

BACKGROUND Nosocomial infections (NIs) are a leading cause of mortality and morbidity in premature infants. We present a new method for detecting and confirming NIs in a neonatal intensive care unit. METHODS Newborns with birth weight < 1,500 g or gestational age (GA) < 33 weeks were included prospectively over 2 years in a single-center tertiary neonatal intensive care unit. The computerized physician order entry system (CPOE) generated alerts when antibiotics were prescribed for at least 5 consecutive days and these cases were reviewed by an expert group following international recommendations. RESULTS Four hundred sixty-one neonates were included, with a mean GA of 30 weeks (range, 26-32 weeks) and mean birth weight 1,270 g (range, 950-1600 g). The CPOE flagged 158 cases of potential NI, 85.1% of which were classified as true NI and 14.9% of which were false positive. Incidence and device-associated nosocomial bloodstream infection rates were 21.9% and 10.8 per 1,000 central venous catheter days, respectively. GA ≤ 28 weeks (odds ratio, 2.18; 95% confidence interval, 1.2-4) and > 7 central venous catheter days (odds ratio, 1.47; 95% confidence interval, 1.3-1.7) were independently associated with the risk of nosocomial bloodstream infection. CONCLUSION Combining CPOE and interdisciplinary review may improve the accuracy of NI recording in a neonatal intensive care unit.

Atypical Pneumonia Linked to Community-Acquired Staphylococcus aureus Cross-Transmission in the Nursery

We report the observation of a necrotizing pneumonia due to methicillin-resistant Staphylococcus aureus harboring the Panton-Valentine leukocidin-encoding gene in a previously healthy neonate, with favorable clinical outcome in spite of extensive radiologic lesions. The case was linked to a cluster of 3 neonates colonized by Panton-Valentine leukocidin-producing, methicillin-resistant S. aureus through cross-transmission in the nursery, underlining the need to comply with standard infection control precautions in the maternity ward.

Carbapenemase-producing Enterobacteriaceae: use of a dynamic registry of cases and contacts for outbreak management.

BACKGROUND The emergence and spread of carbapenemase-producing Enterobacteriaceae (CPE) have become a major public health problem. Control and prevention of CPE infections hinge on isolation precautions for carriers and active screening and follow-up of contacts. AIM To implement an open registry of cases and contacts for acute outbreak management, long-term data collection and epidemiological investigation. METHODS All cases, defined as patients (infected or colonized) with a CPE-positive culture during their hospitalization, and contacts (e.g. patients cared for by the same healthcare team as a case) were registered in an ongoing database. Hospital stays were cross-referenced for every new entry and epidemiological links (e.g. shared contacts) investigated. All cases and contacts not cleared by complete screening were registered on an active list. FINDINGS Between October 2012 and November 2014, we registered 30 cases and 1268 contacts, among which 24 were linked to two or three separate cases. Only 6.5% of contacts fulfilled complete screening with three rectal swabs, and 1145 contacts are still registered on the active surveillance list. Two outbreaks (12 and nine cases) occurred nine months apart. Cross-referencing of hospital stays using the registry revealed epidemiological links between seemingly unrelated cases of CPE-positive patients and suggested an environmental source of transmission, which was demonstrated thereafter. CONCLUSION We implemented a simple and multi-purpose tool to manage CPE episodes and investigate epidemiological links. Efforts are necessary to improve screening of contact patients who may be occult sources of transmission. A regional registry could be helpful.

Intraclonal variations of resistance and phenotype in Pseudomonas aeruginosa epidemic high-risk clone ST308: a key to success within a hospital?

Most multidrug-resistant (MDR) and extensively drug-resistant (XDR) P. aeruginosa strains belonged to epidemic high-risk (EHR) clones that succeeded worldwide in the context of hospital outbreaks. In order to study the intraclonal diversity in EHR P. aeruginosa, we selected clinical and environmental strains of the EHR clone ST308 that caused outbreak clusters over five years in a hospital and then persisted in the hospital environment during four additional years, causing sporadic infections. Unexpectedly, resistance phenotype was very diverse within the population, independently of the origin (environmental or human) and the period of isolation (during or after outbreaks). Most MDR/XDR strains belonged to clusters in pulsed-field gel electrophoresis (PFGE) while singleton strains instead displayed susceptible or moderately resistant phenotypes. High diversity was observed for motility and biofilm formation without correlation with the origin and the period. Resistance to biocides was not linked to epidemic success or to environmental persistence. Finally, the EHR clone ST308 did not display common adaptive traits, nor traits related to an origin or a period of isolation in the hospital. The major character of this EHR clone ST308 is its intraclonal diversity that probably warrants its adaptation and persistence in hospital whatever the conditions and therefore its epidemic behaviour. This diversity could result from adaptive radiation with the evolution of multiple lineages that fill available niches within a complex ecosystem such as a hospital.