Nosocomial listeria gastroenteritis in a newborn, confirmed by random amplification of polymorphic DNA

Surveillance of listeriosis in the Tel Aviv District, Israel, 2010-2015

This study analyses the epidemiologic, clinical and molecular findings of all culture-confirmed cases of listeriosis notified from 2010 to 2015 in the Tel Aviv District, which is known to have high rates of listeriosis. All clinical isolates of Listeria monocytogenes were subtyped using two-enzyme pulsed-field gel electrophoresis. During the studied period, 102 cases of listeriosis were notified, including 23 pregnancy-associated cases (23%). Among 79 non-pregnancy-associated cases, 18 had neuro-invasive disease (21%). There were 26 deaths associated with the disease. Using molecular identification, we found a number of clusters of identical bacterial clones, which pointed to possible sources of infection. The high rates of morbidity and mortality resulting from listeriosis, as well as the diverse ways of infection demonstrated in this study, accentuate the need to boost public health actions, in order to raise awareness and better control high-risk contamination routes.

Release of silver and copper nanoparticles from polyethylene nanocomposites and their penetration into Listeria monocytogenes

Since infection is a major cause of death in a patient whose immune responses have been compromised (immunocompromised patient), considerable attention has been focused on developing materials for the prevention of infections. This has been directed primarily at suppressing or eliminating the host's endogenous microbial burden and decreasing the acquisition of new organisms. In this study, the antibacterial properties of two nanocomposites, polyethylene modified with silver nanoparticles (PE-AgNps) or copper nanoparticles (PE-CuNps), against Listeria monocytogenes have been investigated. In order to elucidate the antibacterial mechanism, specifically whether this mechanism corresponds to bactericidal or bacteriolytic activities, we have determined the extent of release of metal ions (Ag(+) and Cu(2+)) and, also, the morphology of the bacteria. The metal ion release from nanocomposites was followed by inductively coupled plasma spectrometry and the morphology of the bacteria was revealed through examination of ultramicrotomed sections of bacteria in a transmission electron microscope. The study of metal ion release from the nanocomposites shows that for both nanocomposites the amount of ions released varies with time, which initially displays a linear behavior until an asymptotic behavior is reached. Further, TEM images show that silver nanoparticles (AgNps) and copper nanoparticles (CuNps), which are released from the nanocomposites, can penetrate to the cell wall and the plasma membrane of bacteria. Resulting morphological changes involve separation of the cytoplasmic membrane from the cell wall, which is known to be an effect of plasmolysis. It was revealed that the antibacterial abilities of the two nanocomposites against L. monocytogenes are associated with both bactericidal and bacteriolytic effects.

Emergence of sporadic non-clustered cases of hospital-associated listeriosis among immunocompromised adults in southern Taiwan from 1992 to 2013: effect of precipitating immunosuppressive agents

BACKGROUND

Sporadic non-clustered hospital-associated listeriosis is an emerging infectious disease in immunocompromised hosts. The current study was designed to determine the impact of long-term and precipitating immunosuppressive agents and underlying diseases on triggering the expression of the disease, and to compare the clinical features and outcome of hospital-associated and community-associated listeriosis.

METHODS

We reviewed the medical records of all patients with Listeria monocytogenes isolated from sterile body sites at a large medical center in southern Taiwan during 1992-2013. Non-clustered cases were defined as those unrelated to any other in time or place. Multivariable regression analysis was used to determine factors associated with prognosis.

RESULTS

Thirty-five non-clustered cases of listeriosis were identified. Twelve (34.2%) were hospital-associated, and 23 (65.7%) were community-associated. The 60-day mortality was significantly greater in hospital-associated than in community-associated cases (66.7% vs. 17.4%, p = 0.007). Significantly more hospital-associated than community-associated cases were treated with a precipitating immunosuppressive agent within 4 weeks prior to onset of listeriosis (91.7% vs. 4.3%, respectively p < 0.001). The median period from the start of precipitating immunosuppressive treatment to the onset of listeriosis-related symptoms was 12 days (range, 4-27 days) in 11 of the 12 hospital-associated cases. In the multivariable analysis, APACHE II score >21 (p = 0.04) and receipt of precipitating immunosuppressive therapy (p = 0.02) were independent risk factors for 60-day mortality.

CONCLUSIONS

Sporadic non-clustered hospital-associated listeriosis needs to be considered in the differential diagnosis of sepsis in immunocompromised patients, particularly in those treated with new or increased doses of immunosuppressive agents.

Probable nosocomial transmission of listeriosis in neonates

Listeria monocytogenes was isolated in two neonates born consecutively in the same hospital in France. The isolates had indistinguishable pulsed-field electrophoresis profiles. Retrospective epidemiological investigations found no evidence of a food-borne or environmental source. Infection control protocols and decontamination processes were in accordance with standard recommendations. The timing of onset of these infections within the same maternity unit, and the similarity of pulsed-field gel electrophoresis profiles suggests cross-infection of L. monocytogenes between the two neonates.

How can the microbiologist help in diagnosing neonatal sepsis?

Neonatal sepsis can be classified into two subtypes depending upon whether the onset of symptoms is before 72 hours of life (early-onset neonatal sepsis—EONS) or later (late-onset neonatal sepsis—LONS). These definitions have contributed greatly to diagnosis and treatment by identifying which microorganisms are likely to be responsible for sepsis during these periods and the expected outcomes of infection. This paper focuses on the tools that microbiologist can offer to diagnose and eventually prevent neonatal sepsis. Here, we discuss the advantages and limitation of the blood culture, the actual gold standard for sepsis diagnosis. In addition, we examine the utility of molecular techniques in the diagnosis and management of neonatal sepsis.

A cluster of Listeria monocytogenes infections in hospitalized adults

BACKGROUND

Listeriosis occurs mainly in persons at extremes of age and with immunocompromising conditions. It is believed that most cases of listeriosis are acquired in the community. A cluster of listeriosis in hospitalized patients prompted the present investigation.

METHODS

We conducted a case series study of listeriosis from August 21, 2006, to June 1, 2007, in a hospital in the city of Rio de Janeiro, Brazil.

RESULTS

Six patients with Listeria monocytogenes infection were identified: 5 during hospitalization and 1 at a day clinic. By the time the infection was diagnosed, 5 patients had been in the hospital for a mean of 9 days. All patients were elderly (median age, 80 years) and had immunocompromising conditions. Five (83%) patients died. Four patients developed bloodstream infections, 3 caused by serotype 1/2b. Two patients had peritonitis: one caused by serotype 3b and another by serotype 1/2b. Four L monocytogenes isolates belonged to a single pulse-field gel electrophoresis genotype, suggesting a common source. An epidemiologic investigation pointed to the hospital kitchen as the possible contamination.

CONCLUSION

Data suggest a health care-associated outbreak of listeriosis and highlight the importance of developing guidelines for prevention and treatment of health care-associated foodborne diseases, especially in hospitals with immunocompromised adult patients.

Clinical microbiology of bacterial and fungal sepsis in very-low-birth-weight infants

Twenty percent of very-low-birth-weight (<1500 g) preterm infants experience a serious systemic infection, and despite advances in neonatal intensive care and antimicrobials, mortality is as much as threefold higher for these infants who develop sepsis than their counterparts without sepsis during their hospitalization. Outcomes may be improved by preventative strategies, earlier and accurate diagnosis, and adjunct therapies to combat infection and protect the vulnerable preterm infant during an infection. Earlier diagnosis on the basis of factors such as abnormal heart rate characteristics may offer the ability to initiate treatment prior to the onset of clinical symptoms. Molecular and adjunctive diagnostics may also aid in diagnosing invasive infection when clinical symptoms indicate infection but no organisms are isolated in culture. Due to the high morbidity and mortality, preventative and adjunctive therapies are needed. Prophylaxis has been effective in preventing early-onset group B streptococcal sepsis and late-onset Candida sepsis. Future research in prophylaxis using active and passive immunization strategies offers prevention without the risk of resistance to antimicrobials. Identification of the differences in neonatal intensive care units with low and high infection rates and implementation of infection control measures remain paramount in each neonatal intensive care unit caring for preterm infants.