Incidence of Pathogenic Bacteria in Hospitalacquired Infections

1
Incidence of Pathogenic Bacteria in
Hospital-acquired Infections
Europe
USA
S. aureus
Coagulase-negative staphylococci
Enterococci
P. aeruginosa
Enterobacteriaceae
Acinetobacter
Others
M. E. Jones et al., Emerging resistance among
bacterial pathogens in the intensive care unit
a European and North American Surveillance study
(20002002). Annals of Clinical Microbiology and
Antimicrobials 2004, 314     
2
Increasing Incidence of Gram-negative Infections
Occurrence of Bacterial Infections in Liver
Transplant Patients
Occurrence of Monomicrobial Infections in Cancer
Patients
20
15
Incidence ( of all febrile episodes)
Incidence ( of Infections)
10
5
0
1975
1980
1985
1990
1995
2000
Gram-positive infections
Year
Study period
Gram-negative infections
3
Incidence of Gram-negative Bacteria in Nosocomial
Infections
Incidence ()
4
Incidence in Ventilator-associated Pneumonia
Relative Frequency of Isolation
Prevalence of pathogens 40-50
polymicrobial 20-40 P. aeruginosa 15-30 S.
aureus 4-15 Acinetobacter Associated
mortality 71 if P. aeruginosa or
Acinetobacter 41 for other organisms
Fagon, Am Rev. respir. Dis. 1989 139 877  
5
Resistance Rates are Already High
Resistant
P. aeruginosa
Acinetobacter sp.
USA
Cefepime
Cefotaxime
Europe
Ceftazidime
Ceftriaxone
Ciprofloxacin
Gentamicin
Imipenem
Levofloxacin
Meropenem
Piperacillin
Piperacillin/tazobactam
Trimethoprim/sulfamethoxazole
M. E. Jones et al., Emerging resistance among
bacterial pathogens in the intensive care unit
a European and North American Surveillance study
(20002002). Annals of Clinical Microbiology and
Antimicrobials 2004, 314     
6
Staphylococcus aureus

• Gram-positive bacterium
• The most frequently isolated hospital pathogen
• Commonly carried in the nostrils
• High rate of associated mortality even with
  proper antibiotic choice
• High incidence of resistance to the most used
  antibiotics
• Strains with multiple resistance mechanisms
  increasingly common
• Resistant strains expressing necrotizing toxin
  have appeared

7
b-Lactam Resistance in Staphylococcus aureus
Penicillinase-producing S. aureus
Methicillin-resistant S. aureus
MRS 1st report
VRS 1st report
(Pooled US hospital/nursing home reports)
8
Staphylococcus epidermidis

• Gram-positive bacterium
• The commonest of the coagulase-negative
  staphylococci
• Commensual flora, common on skin
• Shares resistance with S. aureus
• Causes many infections related to implanted
  devices, e.g. catheters, joint replacements,
  heart pacemakers
• Strong propensity to form biofilms in which it
  has decreased susceptibility

9
Enterococci

• Gram-positive bacteria
• Common commensual organisms in gut flora
• High levels of intrinsic resistance to
  antibiotics
• Not highly pathogenic and usually low mortality
  associated with infection
• More virulent strains have appeared in the USA
  and have been cause of considerable concern

10
Pseudomonas aeruginosa

• Gram-negative bacterium
• Common opportunistic pathogen
• Widely distributed in the environment
• Causes infections of the respiratory tract,
  urinary tract, burns, wounds, and blood stream
  infections
• High levels of intrinsic resistance to
  antibiotics
• High mortality associated with infection, can
  occur rapidly
• Readily forms biofilms in which it has decreased
  susceptibility

11
Increasing Resistance in P. aeruginosa
Resistance towards individual antibiotics is
increasing
Incidence ()
Imipenem
Ciprofloxacin
Ceftazidime
Resistance towards multiple antibiotics is
increasing
Incidence ()
Strains resistant to 3 or more antibiotics
12
Acinetobacter

• Gram-negative bacteria
• Opportunistic pathogens
• High levels of intrinsic resistance
• Can persist on human skin and in dry
  environments (e.g. medical equipment)
• Causes nosocomial pneumonia, skin and wound
  infections, bacteremia, meningitis
• Immunocompromized patients particularly at risk

13
Increased Resistance Linked to Increased
Prevalence of Acinetobacter
Incidence ()
Strains that are resistant to most of the
available antibiotics have become more
abundant.
U.K. in 1975
U.K. in 2002
Resistance pattern (Number of antibiotics)
The occurrence of Acinetobacter sp. in hospital
infections has risen sharply. Epidemic outbreaks
are frequently associated with natural disasters
(earthquakes) or man-made disturbance (Gulf war)
where the soil is disturbed
Incidence ()
14
Klebsiella pneumoniae

• Gram-negative bacterium
• Found in the normal flora of the mouth, skin, and
  intestines
• New antibiotic resistant strains are appearing,
  and it is increasingly found as a nosocomial
  infection
• Causes infections of the urinary tract,
  respiratory tract, bloodstream skin and wounds
• Has been associated with alcoholism

15
Increasing Resistance in Klebsiella pneumoniae
Resistance towards individual antibiotics is
increasing
Resistance ()
Ciprofloxacin
Ceftazidime
At the moment Klebsiellae are mostly sensitive to
imipenem
- but plasmid-mediated carbapenemases are
appearing in US, Asia and Europe. VIM-2 Greece
17 isolates 2003 20 of clinical
isolates 2007 KPC-1 USA
1 isolate
2001 KPC-2 USA 4 isolates
2003 KPC-3 USA
24 patients
2003 KPC-2 USA
96 isolates 2005 KPC-2 US,
Europe, China 30 NYC, epidemic in NE
US 2008
16
Clostridium difficile

• Gram-positive bacterium
• Common commensual organism in gut
• Causes severe infections if the normal balance of
  flora is depleted by antibiotic treatment
• the most significant cause of pseudomembranous
  colitis a potentially fatal disease of the
  colon
• More virulent toxin-producing strains strains
  have appeared in the USA and parts of Europe and
  are cause of considerable concern

17
Escherichia coli

• Gram-negative bacterium
• The most commonly isolated organism but not
  usually associated with high mortality
• Predominantly causes urinary tract infections but
  complications may result in infection of other
  sites
• New antibiotic resistant strains are appearing,
  and are of increasing concern
• Toxin-producing strains (O157H57) have been
  associated with severe food-poisoning

18
Streptococcus pneumoniae

• Gram-positive bacterium
• Carried by 10-20 of human population, especially
  children, in nose throat
• Commonest cause of bacterial pneumonia
• Also causes acute sinusitis, otitis media,
  meningitis, bacteremia, osteomyelitis, septic
  arthritis, endocarditis, peritonitis,
  pericarditis, cellulitis, and brain abscess
• Resistance rates have been rising in many
  countries