| The Gram stain report to be issued based on the microscopic characteristics seen in the accompanying picture would most correctly be, "many wbc with..." | View Page |
| Based on the gram stain morphology observed before, the possible presumptive identifications might include "gram positive cocci consistent with... | View Page |
| The patient was admitted to the hospital. The sputum specimen was inoculated to sheep blood agar. Based on the colony morphology and the alpha hemolysis seen in the accompanying photograph, the most likely identification is: | View Page |
| The name of the rapid test as illustrated in this photograph, often used to differentiate S. pneumoniae from viridans streptococci, in which a drop of 10% deoxycholate was placed on an area of growth, is: | View Page |
| The zone of inhibition around the disk shown in the photograph has been measured at 23 mm. Based on this result, you should: | View Page |
| The oxacillin screen test alone is not sufficient for determining the susceptibility to penicillin for S. pneumoniae isolates recovered from cerebrospinal fluid (CSF). | View Page |
| MIC susceptibility tests should also be performed against other select beta lactam antibiotics on important S. pneumoniae isolates from blood cultures and other sterile body fluids. | View Page |
| Pneumococcal Resistance Most S. pneumoniae strains gain penicillin resistance by altering the penicillin-binding proteins in their cell wall.Penicillin molecules that cannot find a penicillin binding site cannot interfere with cell wall synthesis.Several different types of penicillin binding proteins may be involved, explaining the various levels of intermediate resistance that may be encountered with different strains of S. pneumoniae.Because different penicillin binding proteins may be involved, the level of penicillin resistance cannot be predicted by the oxacillin screening test.Infections caused by isolates of S. pneumoniae showing penicillin resistance in the intermediate range may be successfully treated by administering high doses of antibiotic.For this reason, the level of resistance with an accurate MIC test must be determined for all clinically significant isolates of S. pneumoniae. | View Page |
| Streptococcus pnemoniae is the most common cause of fatal community-acquired pneumonia. | View Page |
| Middle ear damage in cases of S. pneumoniae infections are caused primarily by: | View Page |
| The colonies shown in the blood agar (upper) and MacConkey agar (lower) biplate are a 24 hour growth from an aerobic blood culture bottle that became positive at 12 hours after inoculation. The appearance of the colonies on MacConkey agar rules out the following two bacterial species: | View Page |
| Clinical isolates of Escherichia coli and Klebsiella pneumoniae may possess ESBL activity. Therefore, clinical laboratories should be screening all clinically significant isolates of these two species. | View Page |
| ESBL Activity Illustrated is the picture of the surface of a disk diffusion test including a ceftazidime disk (left) and a combintation ceftazidime/clavulanic acid disk (right).Observe in the photograph that the zone of inhibition around the the combination ceftazidime/clavulanic acid disk (right) is at least 5 mm larger than around the clavulanic acid disk (left).This observation that the presence of clavulanic acid, a beta-lactamase inhibitor, has resulted in such a large increase in the zone of inhibition indicates that an extended spectrum beta lactamase (ESBL)is being produced.When an organism is producing an ESBL, the susceptibility to individual cephalosporins cannot be predicted, thus requiring that each drug must be tested individually.It may be important to detect ESBL-producing stains of K. pneumoniae and E. coli as treatment failure may occur if the wrong cephalosporin is selected. | View Page |
| Extended Spectrum Beta Lactamases In follow-up to the observations of the ESBL screening test, the following antibiotic susceptibility profile was later reported:
Ampicillin = R;
Cefazolin = R;
Cefoxitin 1 = S;
Ciprofloxacin 0.25 = S;
Gentamicin 1 = S;
Ceftazidime 32 = R;
Imipenem The susceptibility of the 2nd generation drug cefoxitin, with resistance of the 1st generation cefazolin and the 3rd generation ceftazidime, is another way in addition to the screening test in which ESBL activity may be detected.
It is recommended that clinical microbiologists check the antibiotic susceptibility profiles for possible ESBL activity of clinically significant isolates of K. pneumoniae and E. coli.Most automated systems have built in methods for automatically detecting an ESBL isolate, or provide an "alert" that such a strain may be present. | View Page |
| Review 1 Podschun R. Ullmann U.:
Klebsiella spp. as nosocomial pathogens: epidemiology, taxonomy, typing methods, and pathogenicity factors
Clinical Microbiology Reviews. 11(4):589-603, 1998Bacteria belonging to the genus Klebsiella frequently cause human nosocomial infections. In particular, the medically most important Klebsiella species, Klebsiella pneumoniae, accounts for a significant proportion of hospital-acquired urinary tract infections, pneumonia, septicemias, and soft tissue infections.The principal pathogenic reservoirs for transmission of Klebsiella are the gastrointestinal tract and the hands of hospital personnel. Because of their ability to spread rapidly in the hospital environment, these bacteria tend to cause nosocomial outbreaks. Hospital
outbreaks of multidrug-resistant Klebsiella spp., especially those in neonatal wards, are often caused by new types of strains, the so-called extended-spectrum-beta-lactamase (ESBL) producersThe incidence of ESBL-producing strains among clinical Klebsiella isolates has been steadily increasing over the past years. The resulting limitations on the therapeutic options demand new measures for the management of Klebsiella hospital infections.While the different typing methods are useful epidemiological tools for infection control, recent findings about Klebsiella virulence factors have provided new insights into the pathogenic strategies of these bacteria. Klebsiella pathogenicity factors such as capsules or lipopolysaccharides are presently considered to be promising candidates for vaccination efforts that may serve as immunological infection control measures. | View Page |
| The hands of hospital personnel represents one of the major reservoirs for the persistence and potential spread of ESBL producing strains of Klebsiella pneumoniae in the hospital environment. | View Page |
| The bacterial species shown growing on 5% sheep blood agar was recovered from the spun sediment of a midstream urine specimen after 24 hours incubation at 35C. Each of the following tests would be useful in supporting the presumptive identification of Enterococcus species except: | View Page |
| The spot test that is helpful in separating Enterococcus species (positive as shown in the photograph) from the viridans streptococci and S. pneumoniae (both negative) is: | View Page |
| Enterococcus ID Illustrated in this composite photograph is the gram stain of Enterococcus species (upper), illustrating gram positive cocci arranged in pairs and short chains.The viridans streptococci generally form gram positive cocci in long chains; the gram-positive cells of S. pneumoniae, on the other hand, may appear similar in gram stain.In the lower right is shown a 6.5% NaCl tube. The turbidity indicates growth, a unique characteristic for Enterococcus species.In the lower left frame is a picture of a bile esculin hydrolysis slant, showing a positive reaction (black pigment) characteristic of Enterococcus species. The streptococci are uniformly negative.Some strains of Leuconostoc species and Pediococcus species can grow in 6.5% NaCl and are bile-esculin positive; however, they should be ruled out because of the negative PYR reaction. | View Page |