THE JOHNS HOPKINS MICROBIOLOGY NEWSLETTER Vol. 24, No. 14
Tuesday, April 12, 2005
A. Provided by Sharon Wallace, Division of Outbreak Investigation, Maryland Department of
Health and Mental Hygiene.
B. The Johns Hopkins Hospital, Department of Pathology, Information provided by,
Kathleen Burns, M.D., Ph. D
3 outbreaks were reported to DHMH during MMWR Week 14 (April 3 – April 9):
3 Gastroenteritis Outbreaks
2 outbreaks of GASTROENTERITIS associated with Assisted Living Facilities in Prince
Georges Co. and Montgomery Co.
1 outbreak of GASTROENTERITIS associated with a Nursing Home in Montgomery Co.
Two Cases.
A 60 year old man failing chemotherapeutic regimens for multiple myeloma and
plasma cell leukemia returned to this country from his home in Belgium to be admitted at
The Johns Hopkins Hospital. He had developed acute renal failure related to paraprotein and
bacteremia with a gram positive rod abroad which was treated, and here he developed sepsis
again. We were able to identify and treat the organism, so that symptoms of sepsis resolved
and he became blood culture negative. He died several days thereafter due to complications
of his underlying disease.
A 58 year old woman with a past medical history of recurring urinary tract
infections presented with symptoms of meningitis with a history suspicious for seizures. A
lumbar puncture revealed a CSF with counts of 355 polynuclear neutrophils and 175
monocytes, a glucose of 56, and protein of 165.
Intracellular bacteria could be seen by direct gram stain of he centrifuged CSF, and the gram
positive rod was identified after culture. (Picture from Up To Date website.)
Listeria.
Both of the patients briefly described above had infections with Listeria. The organisms
grew well on blood agar, and were-hemolytic, though this was not readily visible without
moving the colonies. As typical for Listeria, they were catalase positive, and had umbrella-type
motility in an agar stab. Final identification was made through the GLC reference area.
Manifestations of Listeria infection are host-dependent. It is contracted by ingestion of
contaminated foods. Immunocompetent persons may experience acute febrile gastroenteritis. In the
elderly and immunocompromised persons, sepsis and meningitis can be seen, such as described in
the two cases above. Pregnant women may experience a mild, flu-like illness and their pregnancy
is at risk for fetal loss, or bacteremia (with or without granulomatosis) and meningitis in their
newborn.
According to the CDC website, the annual incidence of listeriosis decreased by 44%
between 1989 and 1993, and an analysis of the incidence trend from 1996 to 2002 revealed a 38%
decline. However, outbreaks continue to occur by their report. In 2002, an outbreak that resulted in
54 illnesses, 8 deaths, and 3 fetal deaths in 9 states was traced to consumption of contaminated
turkey meat.
Insights into Listeria as a Pathogen.
Part of the danger of Listeria as a food-borne pathogen is because of its ability to survive
and grow at temperatures from 5 to 45 degrees Celsius. The ability of Listeria as an infectious
agent is also related to its expression of virulence factors that allow intracellular invasion and
cell-to-cell trafficking. Their virulence gene products include the two invasion proteins: InlA and
InlB, a hemolysin, listeriolysin O (LLO), and two phospholipases, PlcA and PlcB. Expression of
these genes is maximal at 37C and almost silent at 30C.
The expression of these genes is regulated by PrfA, a Crp/Fnr family transcription factor,
and it is the regulation of PrfA transcript translation that imparts this temperature-dependence. A
secondary stem-loop structure of the PrfA RNA untranslated region (UTR) prevents ribosomal
binding at low temperatures, and it destabilized at high temperatures. Loss of this secondary
structure leads to PrfA protein expression and transactivation of its target virulence genes.
Similar RNA structures have been recently implicated in temperature-dependent characteristics
of E. coli and rhizoids, and appreciation of these types of regulatory systems may hold broad
relevance to microbial pathogenesis.
References:
2005 UpToDate® • www.uptodate.com Department of Health & Human Services Centers for Disease Control and
Prevention website http://www.cdc.gov/
1. Johansson J, Mandin P, Renzoni A, Chiaruttini C, Springer M, Cossart P. An RNA thermosensor controls
expression of virulence genes in Listeria monocytogenes. Cell 2002;110 (5):551-61.
2. Morita MT, Tanaka Y, Kodama TS, Kyogoku Y, Yanagi H, Yura T. Translational induction of heat
shock transcription factor sigma32: evidence for a built-in RNA thermosensor. Genes Dev 1999;13 (6):65565.
3. Nocker A, Hausherr T, Balsiger S, Krstulovic NP, Hennecke H, Narberhaus F. A mRNA-based
thermosensor controls expression of rhizobial heat shock genes. Nucleic Acids Res 2001;29 (23):4800-7.