Méningite néonatale à Bacillus cereus, à propos d'un cas

Bacillus cereus Invasive Infections in Preterm Neonates: an Up-to-Date Review of the Literature

Bacillus cereus group species are widespread, Gram-positive, spore-forming environmental bacteria. B. cereus sensu stricto is one of the major causes of food poisoning worldwide. In high-risk individuals, such as preterm neonates, B. cereus infections can cause fatal infections. It is important to note that the phenotypic identification methods commonly used in clinical microbiology laboratories make no distinction between B. cereus sensu stricto and the other members of the group (Bacillus anthracis excluded). As a result, all the invasive infections attributed to B. cereus are not necessarily due to B. cereus sensu stricto but likely to other closely related species of the B. cereus group. Next-generation sequencing (NGS) should be used to characterize the whole genome of the strains belonging to the B. cereus group. This could confirm whether the strains involved in previously reported B. cereus invasive infections preferentially belong to formerly known or emerging individual species. Moreover, infections related to B. cereus group species have probably been overlooked, since their isolation in human bacteriological samples has for a long time been regarded as an environmental contaminant of the cultures. Recent studies have questioned the emergence or reemergence of B. cereus invasive infections in preterm infants. This review reports our current understanding of B. cereus infections in neonates, including taxonomical updates, microbiological characteristics, bacterial identification, clinical features, host-pathogen interactions, environmental sources of contamination, and antimicrobial resistance.

Bacillus cereus Induces Severe Infections in Preterm Neonates: Implication at the Hospital and Human Milk Bank Level

Human breast milk (HBM) is a source of essential nutrients for infants and is particularly recommended for preterm neonates when their own mother's milk is not available. It provides protection against infections and decreases necrotizing enterocolitis and cardiovascular diseases. Nevertheless, HBM spoilage can occur due to contamination by pathogens, and the risk of a shortage of HBM is very often present. B. cereus is the most frequent ubiquitous bacteria responsible for HBM being discarded. It can contaminate HBM at all stages, from its collect point to the storage and delivery. B. cereus can induce severe infection in newborns with very low birth weight, with sometimes fatal outcomes. Although the source of contamination is rarely identified, in some cases, HBM was suspected as a potential source. Even if the risk is low, as infection due to B. cereus in preterm infants should not be overlooked, human milk banks follow strict procedures to avoid contamination, to accurately identify remaining bacteria following pasteurization and to discard non-compliant milk samples. In this review, we present a literature overview of B. cereus infections reported in neonates and the suspected sources of contamination. We highlight the procedures followed by the human milk banks from the collection of the milk to its microbiological characterization in Europe. We also present improved detection and decontamination methods that might help to decrease the risk and to preserve the public's confidence in this vital biological product for infants whose mothers cannot breastfeed.

Bacillus cereus Isolated From Vegetables in China: Incidence, Genetic Diversity, Virulence Genes, and Antimicrobial Resistance

Bacillus cereus is a food-borne opportunistic pathogen that can induce diarrheal and emetic symptoms. It is widely distributed in different environments and can be found in various foods, including fresh vegetables. As their popularity grows worldwide, the risk of bacterial contamination in fresh vegetables should be fully evaluated, particularly in vegetables that are consumed raw or processed minimally, which are not commonly sterilized by enough heat treatment. Thereby, it is necessary to perform potential risk evaluation of B. cereus in vegetables. In this study, 294 B. cereus strains were isolated from vegetables in different cities in China to analyze incidence, genetic polymorphism, presence of virulence genes, and antimicrobial resistance. B. cereus was detected in 50% of all the samples, and 21/211 (9.95%) of all the samples had contamination levels of more than 1,100 MPN/g. Virulence gene detection revealed that 95 and 82% of the isolates harbored nheABC and hblACD gene clusters, respectively. Additionally, 87% of the isolates harbored cytK gene, and 3% of the isolates possessed cesB. Most strains were resistant to rifampicin and β-lactam antimicrobials but were sensitive to imipenem, gentamicin, ciprofloxacin, kanamycin, telithromycin, ciprofloxacin, and chloramphenicol. In addition, more than 95.6% of the isolates displayed resistance to three kinds of antibiotics. Based on multilocus sequence typing, all strains were classified into 210 different sequence types (STs), of which 145 isolates were assigned to 137 new STs. The most prevalent ST was ST770, but it included only eight isolates. Taken together, our research provides the first reference for the incidence and characteristics of B. cereus in vegetables collected throughout China, indicating a potential hazard of B. cereus when consuming vegetables without proper handling.

Bacillus cereus, a serious cause of nosocomial infections: Epidemiologic and genetic survey

Bacillus cereus is the 2^nd most frequent bacterial agent responsible for food-borne outbreaks in France and the 3^rd in Europe. In addition, local and systemic infections have been reported, mainly describing individual cases or single hospital setting. The real incidence of such infection is unknown and information on genetic and phenotypic characteristics of the incriminated strains is generally scarce. We performed an extensive study of B. cereus strains isolated from patients and hospital environments from nine hospitals during a 5-year study, giving an overview of the consequences, sources and pathogenic patterns of B. cereus clinical infections. We demonstrated the occurrence of several hospital-cross-contaminations. Identical B. cereus strains were recovered from different patients and hospital environments for up to 2 years. We also clearly revealed the occurrence of inter hospital contaminations by the same strain. These cases represent the first documented events of nosocomial epidemy by B. cereus responsible for intra and inter hospitals contaminations. Indeed, contamination of different patients with the same strain of B. cereus was so far never shown. In addition, we propose a scheme for the characterization of B. cereus based on biochemical properties and genetic identification and highlight that main genetic signatures may carry a high pathogenic potential. Moreover, the characterization of antibiotic resistance shows an acquired resistance phenotype for rifampicin. This may provide indication to adjust the antibiotic treatment and care of patients.

Recent actuality about Bacillus cereus and human milk bank: a new sensitive method for microbiological analysis of pasteurized milk

Three cases of Bacillus cereus infection or colonization occurred in the same region in France, and milk from the milk bank was suspected as a possible common source of contamination. All Batches delivered to the three cases complied with the requirements of the bacteriological reference method recommended by good practices guidelines. Still, a retrospective analysis with a more sensitive method showed one batch to contain B. cereus, however straincomparison revealed no epidemiological link betweenisolates from patients and those from the milk. Consequently, in accordance with the precautionary principle, we developed a new sensitive method for the screening of pasteurized milk for pathogenic bacteria. From January 1 to August 31, 2017, 2526 samples of pasteurized milk were prospectively included in the study. We showed that a 20 mL sample of pasteurized milk incubated for 18 h at 37 °C under aerobic conditions was favoring the detection of B. Cereus. The nonconformity rate was 6.3% for the reference method and 12.6% for the improved method (p < 0.0001). Nonconformity was due to the presence of B. cereus in 88.5% of cases for the improved method and 53% of cases for the reference method (p < 0.0001). Thus our new method is improves the microbiological safety of the product distributed and only moderately increases the rate of bacteriological nonconformity .

Bacillus cereus immune escape: a journey within macrophages

During bacterial infection, professional phagocytes are attracted to the site of infection, where they constitute a first line of host cell defense. Their function is to engulf and destroy the pathogens. Thus, bacteria must withstand the bactericidal activity of professional phagocytes, including macrophages to counteract the host immune system. Bacillus cereus infections are characterized by bacteremia despite the accumulation of inflammatory cells at the site of infection. This implies that the bacteria have developed means of resisting the host immune system. Bacillus cereus spores survive, germinate, and multiply in contact with macrophages, eventually producing toxins that kill these cells. However, the exact mechanism by which B. cereus evades immune attack remains unclear. This review addresses the interaction between B. cereus and macrophages, highlighting, in particular, the ways in which the bacteria escape the microbicidal activities of professional phagocytes.

Bacillus cereus in infant foods: prevalence study and distribution of enterotoxigenic virulence factors in Isfahan Province, Iran

This study was carried out in order to investigate the presences of Bacillus cereus and its enterotoxigenic genes in infant foods in Isfahan, Iran. Overall 200 infant foods with various based were collected and immediately transferred to the laboratory. All samples were culture and the genomic DNA was extracted from colonies with typical characters of Bacillus cereus. The presences of enterotoxigenic genes were investigated using the PCR technique. Eighty-four of two hundred samples (42%) were found to be contaminated with B. cereus with a ranges of 3 × 10¹–9.3 × 10¹ spore per gram sample. Totally, entFM had the highest (61.90%) incidences of enterotoxigenic genes while hblA had the lowest (13.09%) incidences of enterotoxigenic genes. Overall, 6.7% of B. cereus isolates had all studied enetrotoxigenic genes while 25.5% of B. cereus strains had all studied enetrotoxigenic genes expectance bceT gene. Thisstudyisthe first prevalence report of B. cereus and its enterotoxigenic genes in infant foods in Iran. Results showed that the infant food is one of the main sources of enterotoxigenic genes of B. cereus in Iran. Therefore, the accurate food inspection causes to reducing outbreak of diseases.

N-acyl-homoserine lactones from Enterobacter sakazakii (Cronobacter spp.) and their degradation by Bacillus cereus enzymes

A chemical study of acyl-homoserine lactones (acyl-HSLs) produced by Enterobacter sakazakii resulted in the identification of three molecules: (S)-N-heptanoyl-HSL, (S)-N-dodecanoyl-HSL and (S)-N-tetradecanoyl-HSL. Mixed cultures of E. sakazakii and Bacillus cereus depleted E. sakazakii acyl-HSLs, suggesting acyl-HSL degradation by B. cereus hydrolases (hydrolysis of the lactone or amide moiety). The expression of B. cereus acyl-HSL lactonase and acyl-homoserine acylase was confirmed by monitoring the biotransformation of (S)-N-dodecanoyl-HSL into (S)-N-dodecanoyl-homoserine, dodecanoic acid and homoserine in the presence of B. cereus whole cells, using electrospray-mass spectrometry (ESI-MS).