Transcript Hot Topics in Microbiology

Hot Topics in Microbiology
FALL 2010
Course: Biology 225
Instructor: Dr. Janie Sigmon
Question #1:
 There has been publicity about a “superbug” that has
made its way from India/Pakistan to the U.S.

What is this new superbug?
There isn’t just one species of bacteria. The enteric bacteria are developing this
resistance.

How did it develop?
The antibiotic resistance developed when a new gene, NDM-1 (New Delhi metallo-blactamase), was passed to these different species of bacteria by way of a plasmid (extra
DNA).
Answers

What have humans done to promote its evolution?
Humans promote the evolution of antibiotic-resistance in bacteria by exposing the
bacteria unnecessarily to the antibiotics. There are many ways that this occurs.
Elective surgery “vacations” are helping to promote the spread of this type of
resistance.
Answers
Detection of Enterobacteriaceae Isolates Carrying Metallo-Beta-Lactamase — United States, 2010
During January–June 2010, three Enterobacteriaceae isolates carrying a newly described resistance mechanism, the New Delhi
metallo-beta-lactamase (NDM-1) (1), were identified from three U.S. states at the CDC antimicrobial susceptibility laboratory. This
is the first report of NDM-1 in the United States, and the first report of metallo-beta-lactamase carriage among Enterobacteriaceae
in the United States. These isolates, which include an Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae, carry
blaNDM-1, which confers resistance to all beta-lactam agents except aztreonam (a monobactam antimicrobial) (1); all three
isolates were aztreonam resistant, presumably by a different mechanism. In the United Kingdom, where these organisms are
increasingly common, carriage of Enterobacteriaceae containing blaNDM-1 has been closely linked to receipt of medical care in
India and Pakistan (2). All three U.S. isolates were from patients who received recent medical care in India.
Carbapenem resistance and carbapenemase production conferred by blaNDM-1 is detected reliably with phenotypic testing methods
currently recommended by the Clinical and Laboratory Standards Institute (3), including disk diffusion testing and the modified
Hodge test (4). Carbapenem resistance in all three of these isolates was detected in the course of routine testing. Current CDC
infection control guidance for carbapenem-resistant Enterobacteriaceae also is appropriate for NDM-1–producing isolates (5).
This includes recognizing carbapenem-resistant Enterobacteriaceae when cultured from clinical specimens, placing patients
colonized or infected with these isolates in contact precautions, and in some circumstances, conducting point prevalence surveys
or active-surveillance testing among other high-risk patients. Laboratory identification of the carbapenem- resistance mechanism
is not necessary to guide treatment or infection control practices but should instead be used for surveillance and epidemiologic
purposes.
Clinicians should be aware of the possibility of NDM-1–producing Enterobacteriaceae in patients who have received medical care in
India and Pakistan, and should specifically inquire about this risk factor when carbapenem-resistant Enterobacteriaceae are
identified. CDC asks that carbapenem-resistant isolates from patients who have received medical care within 6 months in India or
Pakistan be forwarded through state public health laboratories to CDC for further characterization. Infection control interventions
aimed at preventing transmission, as outlined in current guidance (5), should be implemented when NDM-1–producing isolates
are identified, even in areas where other carbapenem-resistance mechanisms are common among Enterobacteriaceae. Additional
information is available by contacting Brandi Limbago or Alex Kallen at [email protected].
http://www.cdc.gov/mmwr/PDF/wk/mm5924.pdf
Question #2:
 There has been the perception in the public realm that
autism is caused by vaccines, in particular either the
MMR vaccine or the thimerosal (mercury compound) in
pediatric vaccines.

What is this perception based on?
The Lancet journal published an article in 1998 by Wakefield et al. that came to the
conclusion that autism was caused by exposure to thimerosal in the MMR vaccine.

Is it true?
After this work was published many studies have been done to show that this is
true. The consensus in the scientific community is that there is no evidence to
support this idea. Wakefield’s article was retracted from The Lancet and he has
been disbarred from medicine in the U.K.
Answers

How safe are vaccinations?
Vaccines are very safe. They protect us from diseases that kill or disable us. There can be side
effects from the vaccines, however, including death. The incidence of serious side effects is much
lower than the effects of the disease. It is estimated that the mortality rate for vaccines is on the
order of 1 in 1 million vaccinations (or lower) – in other words, very rare.

Why should anyone be vaccinated against diseases?
People should be vaccinated against diseases in order to prevent illness and/or death.
Question #3:
 If you’ve ever worked in healthcare, you’ve probably
heard of “C. diff” infections.

What does “C. diff” stand for?
C. diff = Clostridium difficile

Why do people develop “C. diff” infections?
People develop C. difficile infections following an antibiotic regimen.

How are “C. diff” infections treated?
C. difficile infections are treated with probiotics and antibiotics, such as metronidazole or
vancomycin
Answers:

What ground-breaking therapy has been used to treat this
infection?
The ground-breaking therapy is a fecal transplant where feces was taken from a father and
introduced into his 2 year old daughter’s large intestine.
http://www.infectiousdiseasenews.com/article/65702.aspx
Question #4:
 You should wash your hands after handling dry dog
or cat food.

Why? Isn’t this type of food safe?
Salmonella bacteria have been found in dry pet foods.

Who is most at risk for this type of infection?
Children, the elderly, and anyone who is immunocompromised is at risk for severe
salmonellosis.
Answers

What are the symptoms of this illness?
Salmonellosis is a gastrointestinal disease with diarrhea, cramps, and fever.

What happened to the manufacturer of these “tainted” pet
foods?
The pet foods were recalled and the production plant was eventually permanently closed.
http://www.infectiousdiseasenews.com/article/67398.aspx
Question #5:
 During the summer, one member of a swim team in
Tega Cay developed whooping cough.

Why is this unusual?
Most people have been vaccinated against pertussis (whooping cough) or have been exposed to it.

Can the disease be prevented?

This disease can be prevented by vaccination with DTaP (diphtheria/tetanus/acellular
pertussis) or TdaP vaccines, the former is the childhood vaccine and the later is the
adolescent/adult version.
Answers

Why is this becoming more of a problem around the nation?
It is becoming a problem around the U.S. because more people are opting not to have their
children immunized or are spacing out immunizations.

What is whooping cough like?
This is the sound of whooping cough:
http://www.whoopingcough.net/sound%20of%20whooping%20cough%20with%20much%20whoopi
ng.htm
Answers
 http://www.whoopingcough.net/sound%20of%20w
hooping%20cough%20with%20much%20whooping.
htm
 http://www.cdc.gov/ncidod/dbmd/diseaseinfo/pert
ussis_t.htm
 http://www.cdc.gov/vaccines/recs/schedules/childschedule.htm#printable
The End