Ventilator-associated pneumonia due to meticillin-resistant Staphylococcus aureus: risk factors and outcome in a large general hospital

BACKGROUND

Data about risk factors and impact on outcome of methicillin-resistant S. aureus (MRSA) in unselected patients with ventilator-associated pneumonia (VAP) are limited.

AIM

To assess predisposing factors and outcome of VAP due to MRSA in a large teaching institution.

METHODS

Prospective study carried out over four years in the three adult ICUs of our hospital. Patients with MRSA-VAP were compared with those with bacterial VAP due to other microorganisms.

FINDINGS

Overall, 474 episodes of bacterial VAP were collected. Significant differences between MRSA-VAP (111) and VAP due to other microorganisms (363) were found for median age (68 vs. 62 years), median APACHE II score (12 vs. 11), neurosurgery (5.4% vs. 13.8%), abdominal surgery (35% vs. 19%), prior treatment with any antibiotic (82.9% vs. 64.5%) and with imipenem (24% vs. 11%) at present admission before VAP, and pleural effusion (12% vs. 5%). Multivariate analysis adjusted for confounding factors showed that higher APACHE II score, prior treatment with any antibiotic and pleural effusion were independent risk factors for MRSA. As for treatment and outcome, the differences between MRSA-VAP and other VAP were inadequate empiric treatment (70% vs. 53%), median cost of antibiotics per episode (€974 vs. €726), and in-hospital mortality (60% vs. 47%). At multivariate analysis, however, MRSA was not found to be an independent risk factor for mortality.

CONCLUSION

MRSA is a common cause of VAP. Underlying conditions predispose to its high mortality.

A comparison between disk diffusion and microdilution for susceptibility testing of Mycobacterium fortuitum complex

We evaluated a disk diffusion method using Mueller-Hinton agar for susceptibility testing of Mycobacterium fortuitum complex organisms. Ninety-five strains were tested both by broth microdilution and disk diffusion. Global results showed good correlation for all antimicrobials except for clarithromycin and erythromycin. However, when the results were analyzed according to species, correlation was poor except for a few antimicrobials. The analysis of the resistant/susceptible results was good for all the antimicrobials tested except azithromycin and erythromycin. In conclusion, the disk diffusion technique could be useful as a screening technique for some antibiotics, but the results must be confirmed by using an accepted reference technique.

Cervical lymphadenitis caused by Mycobacterium lentiflavum

We report a case of human infection caused by Mycobacterium lentiflavum and review the literature for infections caused by this bacterium. The patient was a 19-month-old boy with involvement of a cervical lymph node. Surgical removal of the lymphadenopathy was both diagnostic and curative.

Satellite oligodendrocytes and myelin are displaced in the cortex of the reeler mouse

The spatial distribution of satellite (perineuronal) oligodendrocytes and myelin was studied in the cortices of normal and reeler mice. In normal mice, satellite oligodendrocytes were concentrated in the inner third of the cortex. In reeler mice, satellite oligodendrocytes were present beneath the pial surface and distributed throughout the width of the cortex. In reeler mice, but not normal mice, myelin was present in patches beneath the pia and distributed throughout the width of the cortex. The abnormal position of satellite oligodendrocytes and myelin coincides with the displacement of neurons and axons in the cortex of reeler mice. These studies indicate that the distribution of cortical oligodendrocytes is influenced by neuronal/axonal position.

Morphological features of degenerating oligodendrocytes in twitcher mice

The morphological features of degenerating oligodendrocytes in twitcher mice were examined by a modified iron histochemical technique. Oligodendrocytes in twitcher mice were found to have several features distinct from oligodendrocytes in normal mice; swellings at different sites along their processes, swollen soma and an increase in iron-rich, oval structures in their cytoplasm. In addition to changes in oligodendrocyte morphology, endothelial cells in brains of twitcher mice were found to be highly enriched with iron.