Pseudomonas aeruginosa is the most common MDR Gram-negative bacterium causing VAP. Pseudomonas has natural resistance to many antibiotics and has been known to acquire resistance to every antibiotic except for polymyxin B. Resistance is typically acquired through upregulation or mutation of a variety of efflux pumps which pump antibiotics out of the cell. Resistance may also occur through loss of an outer membrane porin channel (OprD)
Klebsiella pneumoniae has natural resistance to some beta-lactam antibiotics such as ampicillin. Resistance to cephalosporins and aztreonam may arise through induction of a plasmid-based extended spectrum beta-lactamase (ESBL) or plasmid-based ampC-type enzyme
Serratia marcescens has an ampC gene which can be induced by exposure to antibiotics such as cephalosporins. Thus, culture sensitivities may initially indicate appropriate treatment which fails due to bacterial response. Enterobacter as a group also have an inducible ampC gene. Enterobacter may also develop resistance by acquiring plasmids. Citrobacter also has an inducible ampC gene. Stenotrophomonas maltophilia often colonizes people who have tracheal tubes but can also cause pneumonia. It is often resistant to a wide array of antibiotics but is usually sensitive to co-trimoxazole
Acinetobacter are becoming more common and may be resistant to carbapenems such as imipenem and meropenem
Burkholderia cepacia is an important organism in people with cystic fibrosis and is often resistant to multiple antibiotics
Methicillin-resistant Staphylococcus aureus is an increasing cause of VAP. As many as fifty percent of Staphylococcus aureus isolates in the intensive care setting are resistant to methicillin. Resistance is conferred by the mecA gene.
Fovilles syndrome is caused by the blockage of the perforating branches of the basilar artery in the region of the brainstem known as the pons. It is most frequently caused by vascular disease or tumors involving the dorsal pons. Structures affected by the infarct are the dorsal pons(pontine tegmentum) which comprises paramedian pontine reticular formation (PPRF), nuclei of cranial nerves VI and VII, corticospinal tract, medial lemniscus, and the medial longitudinal fasciculus. There is involvement of the fifth to eighth cranial nerves, central sympathetic fibres (Horner syndrome) and horizontal gaze palsy. Presentation
This produces ipsilateral horizontal gaze palsy and facial nerve palsy and contralateral hemiparesis, hemisensory loss, and internuclear ophthalmoplegia. Diagnosis
Treatment
History
Fovilles syndrome was initially described by Achille-Louis Foville, a French physician, in 1859. References


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