Up-and-Coming Bugs: Evaluating the Latest Infectious Trends

January 1, 2006

Up-and-Coming Bugs: Evaluating the Latest Infectious Trends


By Kris Ellis

As all infection control practitioners
(ICPs) know, the world of dangerous microorganisms is in a state of constant
evolution and flux. New threats must be closely monitored along with those that
are well established, and maintaining an up-to-date base of knowledge can be the
difference between success and failure in terms of outbreak prevention and
treatment. Currently, several pathogens are gaining notoriety for the potential
havoc they can wreak in hospitals and communities alike.


Community-Acquired MRSA

Community-acquired methicillin-resistant Staphylococcus
aureus
(CA-MRSA) is a relatively recent phenomenon
that has firmly entrenched itself in many locations. The first thing to note
is variable penetration into different areas, says Trish Perl, MD, MSc,
associate professor of medicine at Johns Hopkins University and hospital
epidemiologist at Johns Hopkins Hospital. Perl is also president-elect of the
Society of Healthcare Epidemiology of America (SHEA). She points out that some
communities such as Baltimore, Dallas, and Chicago see CA-MRSA frequently, while
it is relatively rare in others. Perl notes that the pathogen initially
presented primarily in children as skin and soft tissue infections and also
toxic shock-like presentation. With adults, again weve seen similar
presentations with a lot of skin and soft tissue stuff. Also, some very
impressive necrotizing pneumonias and pneumonic processes, some of which were
clearly post-influenza. People could have septic shock, multi-organ failure, end
up on ventilators for long periods of time these are very different
presentations than we have seen with hospital-acquired MRSA. This is not at all
to say that hospital-acquired MRSA is not a bad infection it is, but we just
really didnt see these very impressive acute presentations, and the
predominance of skin and soft tissue.

Perl cites anecdotal reports of CA-MRSA transmission among
families as an interesting phenomenon as well. She also says there is much to be
learned about how the bug is spread and how it can be controlled. The nasal
carriage data suggests that the epidemiology of this may be different, and its
not clear what the ecologic niche is right now. Perl notes that even without
a significant amount of data showing that people are nasal carriers,
decolonization using Mupirocin is often performed. I think were missing two wonderful opportunities one
is to understand the epidemiology better and two, to use this as an educational
tool; you really have to culture before you treat. From an epidemiologic point
of view, I think thats very important.

The other thing thats interesting about this organism is
that we dont understand the role of the environment, but we know its
important, Perl continues. She points to a study from the New
England Journal of Medicine
describing an MRSA
outbreak among members of the St. Louis Rams football team as illustration.1
Perl says pushing for improved hygiene will be important in combating CAMRSA, as
will taking the focus off of treatment with Mupirocin.

Nancy Church, RN, BSN, MT (ASCP), CIC, director of infection
control at Portland, Ore.- based Providence St. Vincent Medical Center, says
CA-MRSA in her community seems to be related to environmental factors as well.
We started seeing it here in our ER with what were known as spider bites
probably about three years ago, she says The ER doesnt culture every
boil they would lance, but they did culture a few of them and suddenly we
started to see MRSAs in this population. So when we looked at the first 10
patients that we saw, I and another colleague found that we were seeing these
primarily in meth amphetamine users. A common characteristic of this type of
population involves a large number of people sharing a relatively small living
space. I notified the county health department that this is what we were
seeing and then they took a look at their clientele in which they were starting
to see the same thing, and they also found that it was linked to behavioral
health issues with drug use. Those were our first cases that we saw and from
there its certainly gone on to spread out into a much larger segment of the
population.

Church used the information she discovered to encourage the ER
to perform cultures in order to determine what antibiotics the strains would be
sensitive to. The historical treatment that was used was to lance the boil
and put them on Keflex, and I think lancing the soft tissue
abscess was the key and that the Keflex wasnt really doing much of anything,
she explains. So with some education and with the infectious disease
physicians working with them here, we managed to primarily switch them to
different antibiotics depending on the sensitivity, with Bactrim being one of
the main treatments.

The other thing thats really important about these
strains is that theyre different theyre susceptible to more
antibiotics, Perl explains. Theyve got this SCC type IV cassette which
is smaller; it cant hold as many resistance genes, but these strains carry a
lot more toxins than other strains. Everyone was talking about something called
the Panton-Valentine Leukocidin (PVL), but when you look at the data, they
carry a lot of different potential toxins. Thats important. Thats whats
probably leading to these dramatic presentations of clinical disease that I was
talking about. We have to look at new prevention and control strategies.

Sheldon Kaplan, MD, professor and vice chairman for clinical
affairs in the Department of Pediatrics at Baylor College of Medicine, as well
as chief of the infectious disease service at Texas Childrens Hospital, notes
that CA-MRSA has been an issue in the Houston area for years. Weve been
studying this very extensively for the past five years and we have, at Texas
Childrens Hospital (TCH), each year about 1,700 to 1,800 kids who are seen
from the community with a staph infection, and 75 percent of those are
methicillin resistant, so 75 percent of the staphs in our community in kids are
methicillin resistant, he says. Thats just at TCH, so then youve got
all the private offices, clinics, and pediatricians who are seeing kids with
skin and soft tissue infections that are mild enough that they dont need
surgery for drainage of an abscess theyre being taken care of by their
own physicians or clinics.

So we know that the infections that we see are just the tip of
the iceberg. The vast majority 95 percent of the MRSAs from the community
are associated with skin and soft tissue infections. Many of those kids, as
I mentioned, end up in the hospital and need to have an incision and drainage
and then theyre here for a few days on IV therapy. Five percent of those kids
have serious invasive infections, such as bone, muscle, and lung infections, and
I think weve had six deaths as well, so its a very serious problem.

Kaplan notes that many clinicians are struggling with how to
handle this emerging issue. Some people are promoting surveillance cultures
on all patients who come in the hospital to see if theyre colonized and then
put them into isolation; I dont think we really know what the right answer
is, he says. The community strains are now circulating in many areas of
the country in hospitals. Nosocomial staph infections, many of these are now the strains
that are from the community MRSA isolates from the community are now being
associated with hospitalacquired infections and Im sure this is going to
increase with time.


Extended-spectrum beta-lactamases (ESBL)

Extended-spectrum beta-lactamases (ESBLs) are described as a
rapidly-evolving group of beta-lactamases that are able to hydrolyze
third-generation cephalosporins and aztreonam, but are inhibited by clavulanic acid.2
ESBLs provide a sobering illustration of the ability of
gram-negative bacteria to develop new patterns of antibiotic resistance. There
are currently a very limited number of options for antibiotic treatment of
ESBL-producing organisms.

ESBLs arent getting as much attention, at least in the
lay press, but theyre potentially as scary if not scarier organisms [than
CAMRSA], Perl says. This actually can involve a group of
gram-negatives, so its not just one bug, but its multiple bugs
Coxiella, E. coli, there are many different organisms that can produce these.

Proper identification of ESBLs and understanding their
significance in certain serious infections is vital in order to avoid treatment
failures, according to Perl. The Clinical and Laboratory Standards Institute
(CLSI) has developed guidelines for the detection of ESBLs produced by E. coli, Klebsiella
pneumoniae
, Klebsiella
oxytoca
, and Proteus mirabilis. These guidelines
recommend the use of K. pneumoniae ATCC 700603 (an ESBL producer) as a quality
control organism in tests to detect the presence of ESBLs.3

What ICPs might be seeing are people who arent
responding appropriately to therapy for gram-negative infections, Perl says.
That requires education to make sure that people who are prescribers actually
understand what an ESBL is. The other thing to say, and my perspective on MRSA
and ESBLs is identical, is that again, this is an organism thats easily
transmitted; it can be transmitted on hands just like MRSA and we should be
identifying these people and isolating it. Im a firm believer that isolation
in the healthcare setting for ESBLs is important, especially in high-risk
settings like ICUs where its really easy for this to be transmitted from
patient to patient.

Church notes that ESBLs were quite rare in her facility until
about a year ago, when they began to increase in number. In our case they are
primarily seen in urine cultures, and these are often in patients who have been
exposed to multiple antibiotics because theyve got underlying conditions,
she says. Many physicians didnt really understand what this was, so we
have an electronic system here that we put in the computer where, once weve
identified something, it will pop up again if theyre readmitted. The purpose of that is not so much just to designate the
patient with an isolatable type of issue, but more to inform the physicians so
they can know when they have to pay attention to the antibiotics they may
need to talk to pharmacy or ID. Thats how we utilize it here.


Other Resistant Organisms

To me acinetobacter is one of the scariest ones thats
out there, Perl says. Its a pathogen that really came into its own
about three or four years ago in New York City where there was an outbreak that
involved 10 or 12 hospitals that shut down units to actually get control of it.
I think whats been most concerning is that this organism has become resistant
to everything except a drug called polymyxin B. That drug was developed in the
40s and I had never used it until last year. Its got a lot of associated
toxicities with it. This is a pathogen that weve had in Baltimore since about
1995, and there are a lot of places that are seeing this.


Acinetobacter baumannii is a
gram-negative bacillus that commonly colonizes aquatic environments. The organism is often cultured from hospitalized patients
sputum or respiratory secretions, wounds, and urine. Acinetobacter can also be
found in irrigating solutions and intravenous solutions. Infections often
manifest as nosocomial pneumonia, infections associated with continuous
ambulatory peritoneal dialysis, or catheter-associated bacteruria. Acinetobacter pneumonias often occur as outbreaks and are
usually associated with colonized respiratory support equipment or fluids.4

It has an unbelievable ability to contaminate the
environment much more so than MRSA, Perl continues. You have to throw
out tons of equipment because you cant figure out where it is. Weve
actually been criticized here because we have a pretty draconian approach to
that organism we require oneon- one nursing and people signing in and out of
rooms, but weve had no transmission since weve done that. The thing thats
also concerning to me is that now as were getting more and more data, at
least at our institution, that one of the sources of this is patients who come
in from nursing homes and chronic ventilation facilities.

Hospital-acquired MRSA is, of course, still a significant
concern as well. Church explains that, at her facility, studying MRSA in greater
detail has proven to be beneficial. We had some work done here that showed
our fluoroquinolone use was directly contributing to our increase in some MRSA
we were seeing, so we revised some antibiotic prescribing habits in the ER to
try and reduce that, she says. We did a study in 2002-2003 to try and
understand where ours was coming in from. We looked at all the patients who were
admitted to the clinical care unit for five months with active surveillance
cultures and learned that the primary source of that was coming from residential
facilities such as nursing homes, foster homes, and those types of institutions
where you have large numbers of people living together.

As a result of these findings, Church says efforts were made
to work with and educate staff at these types of facilities in order to promote
hand hygiene. We still have some problems, but I think there have been some
significant successes. In Oregon we have short lengths of stay, and that was
offset by using our nursing homes and our rehabilitation centers, so when we
began to see patients who were having surgery and coming back in with MRSA, and
we didnt believe it had been acquired in the facility, we brought a lot of
nursing homes together to take a look at what was going on and tell them what we
were seeing from our side and determine what we could do to help them. That
precipitated a number of changes that weve made, which I think have helped,
but the education on the alcohol hand gels in particular, and good
communication, were most important.

Ultimately, contending with antimicrobial-resistant organisms
will continue to be a significant challenge for clinicians. The bugs are
smarter than we are; theyll adapt and produce toxins and become resistant
they will keep on adapting and were dealing with a more compromised
population so well have new and evolving challenges, Perl says. I think
the thing thats universal across all of these is that theres a very
important role for very basic infection control and prevention strategies. I
personally think that does involve surveillance.

Theres a very emotional debate thats going on right now
in the infection control community about whether or not to do surveillance, and
the whole concept of this is just the tip of the iceberg. Being extremely
proactive and admitting that those bugs are there has really helped prevent
transmission in our institution. The other thing to point out about it is that
traditionally people thought it was the academic centers where all the
resistance and bad bugs were created, but thats no longer true its
very clear that theyre coming in from long-term care facilities, from the
community, day care centers, and other places.


Communicable Diseases

In addition to antibiotic resistance, communicable diseases
are an ongoing concern for ICPs. From the apparent reemergence of certain
diseases to decreases in vaccination rates in subsets of the population, the
potential for an outbreak is always a concern for clinicians.

Pertussis (whooping cough) is one such condition that has
received a seemingly increased amount of attention as of late. Were
recognizing it more, probably because of better diagnostic techniques, Kaplan
says. There may be some issues with regard to seeing it more because of
waning immunity, especially in adolescents and older individuals, because now
theres some pretty good evidence to show that its college-age people who
are a reservoir for this organism. There are three or four studies now that show
that if you have a college-age individual or an adult whos coughing for two
or three weeks and its unexplained, pertussis is probably responsible for 25
percent of these cases.

Kaplan notes that it is difficult to make that diagnosis in
older individuals. Diagnosis in children, however, has improved recently. In
the past, you mainly had culture or fluorescent antibody testing, neither of
which was very sensitive, but now you have polymerase chain reaction (PCR),
which seems to be very good and is probably the lab test of choice in proving
that youve got a pertussis infection, he says. So its probably a
combination of better diagnostics as well as some waning immunity, thus the
recommendation for immunizing adolescents and adults with this new acellular
pertussis vaccine.

Churchs community has seen pertussis outbreaks, and she
says many adults thought they were protected from childhood vaccination. Learning that the vaccine wanes in its effectiveness over
time was kind of a surprise to people. We also have areas where weve had
difficulty in getting immunizations into certain sub-pockets of the population,
and so we would see an occasional pertussis case pop up there and then spread.
Weve done a huge amount of work to educate people and I think the advent of
the newer vaccine that can be given to adolescents and young adults will be
extremely helpful.

In October 2005, three children in Minnesota were found to be
infected with the polio virus. All members of the same family, which is part of the Amish
community, the children had not been vaccinated against the disease. Minnesota
Department of Health officials said the virus strain appears to be a variant of
the one used in oral (live) polio vaccine. Before this version of the vaccine
was discontinued in 2000, it caused approximately eight cases of paralytic polio
per year in the United States. The current version is injected using a killed
polio virus.

Dealing with outbreaks in populations that dont believe in
vaccination can be extremely challenging for the healthcare community. If
something starts in those populations then you have a whole group of people who
are susceptible and that can be really problematic, Church says. Also,
with the mobility of society today, it can complicate the situation.

References:

1. Kazakova, SV, et al. A clone of methicillinresistant
Staphylococcus aureus among professional football players. N
Engl J Med
. 2005 Feb 3;352(5):468-75.

2. Paterson DL, Bonomo RA. Extended-spectrum beta-lactamases:
a clinical update.


Clin Microbiol Rev. 2005
Oct;18(4):657-86, table of contents.

3. Clinical and Laboratory Standards Institute. 2005. Performance standards for antimicrobial susceptibility
testing. Fifteenth international supplement M100-S15. Clinical and Laboratory
Standards Institute, Wayne, Pa.

4. http://www.emedicine.com/med/topic3456.htm


Staying Vigilent Against TB

Some clinicians may have dismissed
tuberculosis (TB) as qualifying as an emerging disease these days, but until it
is completely eradicated, it remains a concern for public health officials.

Consider these facts from the World Health Organization (WHO):

  • Someone in the world is newly infected with TB bacilli
    every second
  • Overall, one-third of the worlds population is currently
    infected with the TB bacillus
  • Five percent to 10 percent of people who are
    infected with TB bacilli (but who are not infected with HIV) become sick or
    infectious at some time during their life

TB is a contagious disease, and like
the common cold, its transmission is airborne. When infectious people cough,
sneeze, talk, or spit, they propel TB bacilli into the air; a person needs only
to inhale a small number of these bacteria to be infected. Left untreated, each
person with active TB disease will infect on average between 10 and 15 people
every year. But people infected with TB bacilli will not necessarily become sick
with the disease. The immune system walls off the TB bacilli which,
protected by a thick waxy coat, can lie dormant for years. When an individuals
immune system is weakened, the chances of becoming sick are greater.

Starting in the 1940s, scientists discovered the first of
several medicines now used to treat TB. As a result, TB slowly began to decrease
in the United States. But in the 1970s and early 1980s, the country let down its
guard and TB control efforts were neglected. As a result, between 1985 and 1992,
the number of TB cases increased. However, with increased funding and attention
to the TB problem, there has been a steady decline in the number of persons with
TB since 1992. But TB is still a problem; more than 14,000 cases were reported in 2003 in the United
States.

Until 50 years ago, there were no medicines to cure TB. Now,
strains that are resistant to a single drug have been documented in every
country surveyed; strains of TB resistant to all major anti- TB drugs also have
emerged. A particularly dangerous form of drug-resistant TB is
multi-drug-resistant TB (MDR-TB), which is defined as the disease caused by TB
bacilli resistant to at least isoniazid and rifampicin, the two most powerful
anti-TB drugs. Rates of MDR-TB are high in some countries, and threaten TB
control efforts.

The most important way to keep from spreading TB in a hospital
setting is taking isolation measures with patients who are suspected or known TB
carriers. Patients placed in isolation should remain in their isolation rooms
with the door closed. To prevent the escape of droplet nuclei, the TB isolation
room should be maintained under negative pressure. If possible, diagnostic and
treatment procedures should be performed in the isolation rooms to avoid
transporting patients through other areas of the facility. If patients who may
have infectious TB must be transported outside their isolation rooms for
medically essential procedures that cannot be performed in the isolation rooms,
they should wear surgical masks that cover their mouths and noses during
transport. Persons transporting the patients do not need to wear respiratory
protection outside the TB isolation rooms. The number of persons entering an
isolation room should be minimal. All persons who enter an isolation room should
wear respiratory protection; the patients visitors should be given
respirators to wear while in the isolation room, and they should be given
general instructions on how to use their respirators. Personal respiratory
protection should be used by persons entering rooms in which patients with known
or suspected infectious TB are being isolated, persons present during
cough-inducing or aerosol-generating procedures performed on such patients, and
persons in other settings where administrative and engineering controls are not
likely to protect them from inhaling infectious airborne droplet nuclei.
Respiratory protective devices used in healthcare settings for protection
against M. tuberculosis should meet the following standard performance criteria:
the ability to filter particles 1mm in size in the unloaded state with a filter
efficiency of greater or equal to 95 percent, given flow rates of up to 50L per
minute; the ability to be qualitatively or quantitatively fit tested in a
reliable way to obtain a face-seal leakage of less than or equal to 10 percent;
the ability to fit the different facial sizes and characteristics of HCWs; and the ability to be checked for face-piece fit, in accordance
with standards established by the Occupational Safety and Health Administration
(OSHA) and good industrial hygiene practice, by HCWs each time they don their respirators.