‹stanbul Üniversitesi Cerrahpafla T›p Fakültesi Radyoloji AB Dal›, ‹stanbul
fiekil 1-2
Tbc granülomunun T1 a¤›rl›kl› koronal kesitte çepersel kontrastlanmas› T2 a¤›rl›kl› koronal kesit- te ise granulom sant- ralinde hipointensite görülmektedir.Lez- yon çevresinde ödem olmamas› dik- kat çekicidir.
1
gusu yok ,ek semptom yada bulgu saptanmaz ise 3.-4. ay kontrolu ye- terlidir.E¤er kontrol döneminde yeni ortaya ç›kan bulgular fokal bir alan› iflaret ediyor ise kontrol incelemenin kontrastl› MR ile yap›lma- s› yeni parankimal bir lezyon aç›s›ndan tercih edilir.Kontrastl› MR ya- da kontrastl› BT’nin, saptanm›fl tüberkülomlar›n verilen tedaviye ce- vab›n›n moniterizasyonundada yeri vard›r.Önerilen süre en erken 3 ay- 6ayd›r.‹laca cevab›n azald›¤› durumlarda tüberkülomlar›n paradoksik
expansiyonu bu kontrollerde incelenmelidir.
Alt kafa çiftlerinin tutulumlar›nda meningeal tutulum gibi kontrast- l› MR tercih edilmelidir.Bazal meniks ve vasküler tutulumlar›nda ge- ne MR, BT’ye göre üstündür.Kavernöz sinüs infiltrasyonlar›nda ge- rek ay›r›c› tan›da gerekse takipte MR , MRAngio özelli¤ide kullan›l- d›¤›nda ilk kullan›lacak radyolojik tetkiktir.
Otit yada sinüsit komplikasyonu olarak geliflen abse formasyonu gi- derek azalan oranda görülmektedir.BT kemik destrüksiyonunu MR’a göre daha iyi göstermesine karfl›n abse oluflumu için kemik harabiye- ti flart de¤ildir.Emisser venler ajan patojeni destruksiyon olmadanda uygun flartlar var ise intraaksiel plana tafl›yabilir.Diffüzyon a¤›rl›kl› MR inceleme ve MR spektroskopinin kullan›lmas› ile nekrotik tümör- abse ay›r›c› tan›s› daha kolay yap›labilir.
Viral tutulumlar ve post enfeksiyöz ensefalomyelitlerin gerek tan›s› gerekse takibi baz› zorluklar içermektedir.Özellikle Herpes en- sefalitinde tan› olabilecek en k›sa zamanda konulmal›d›r.Parankimde gri ak made ay›r›m›n›n yapabilen, hemorajik transformasyonusap- tayabilen MR, flüpheli durumlarda ilk tercih edilmelidir.Gene ADEM(akut dissemine ensefalomyelit),ANE(Akut nekrotizan en- sefalit),SSPE(subakut sklerozon ensefalomyelit) ‘te Fokal ak madde veya gri madde tutulumlar›n›,derin gri madde de¤iflikliklerini MR ile de¤erlendirmek gereklidir.
Genel olarak morfolojideki de¤iflimler üzerine kurulmufl olan rad- yolojik de¤erlendirmeler, olgunun semptom ve klinik bul- gular›,laboratuar de¤erleri ile yo¤urulduktan sonra her bir radyolojik modalitenin teknik özellikleri göz önüne al›n›p yorumlanmal›d›r.Bu perspektif içinde olgular kendi içlerinde de¤erlendirilmeli,kesin tan›s› konulduktan sonra benzer yaklafl›mla radyolojik modalitelerin teknik kapasiteleri düflünülüp, radyolojik takip protokolleri belirlenmelidir.
KAYNAKLAR
1. Zee CH,Go JL.Intracranial Infectious Diseases.Neuroimaging Clin N Am 2000 May 10;2: 297-459
2. Goodman PC,Jinkins JR. Imaging of tuberculosis and craniospinal tuberculosis. Radiol Clin North Am 1995 Jul 33;4:619-824
KL‹M‹K 2003 XI. TÜRK KL‹N‹K M‹KROB‹YOLOJ‹ ve ‹NFEKS‹YON HASTALIKLARI KONGRES‹
fiekil 3 TBC hidrosefali
fiekil 4-5
Mukor mikosis tan›s› alan olgunun kontrastl› aksial MR incelemesi sol sfenoid sinüste mukozal kal›nlafl- ma,sol kavernöz sinüs- te ve internal karotis arter çeperinde patolo- jik kontrast tutulumu görülmektedir.Koronal T2 a¤›rl›kl› kesitte, in- ternal karotis arter ka- vernöz segmentinde anevrizma formasyonu ve vasküler komplikas- yona sekonder MCA terituar›nda iskemik degifliklikler vard›r.
3
30 Mart - 03 Nisan 2003
fiekil 6-7-8
Sa¤ temporal abse .Kontrass›z ve kontrasl› Bt incelemesinde abse s›n›rlar› ve çevresel ödemi seçilebilmektedir.Kemik pence- resinde otite ba¤l› orta kulak ve mastoit havalanmalar›n›n kay- boldu¤u.ve temporal kemikte local destruksiyon alanlar› dikka- ti çekmektedir.
fiekil 9 Bilateral mezial temporal ve insuler bölgerin herpes tutulumu. T2WI.
6
7
8
Mapping, and ultimately preventing, the dissemination of infectious agents is an important topic in public health. Newly developed mole- cular–microbiological methods have contributed significantly to ad- vances in the efficient tracking of the nosocomial and environmental spread of microbial pathogens.
Identification and typing was routinely carried out on the basis of microbiological, biochemical, serological, and physiological charac- ters, gathered by the so-called ‘phenotypic’ procedures which, even combined have limited discrimination power. The molecular typing methods (genotypic) have several advantages over conventional (phe- notypic) testing in being faster and unambiguous, more accurate, and able to detect masked resistances. They are used to address many dif- ferent problems such as the study of genomic organization and evolu- tion, the identification of patterns of infection and sources of transmis- sion, the epidemiological surveillance of infectious diseases and outb- reak investigations. Currently, genetic identification of microbes is within the reach of clinical microbiology laboratory professionals inc- luding those without specialized technology research interests.
The emergence of antibiotic resistance is one of the most worriso- me phenomena of the last 20 years. The spread of micro-organisms that have become resistant to many clinically important antibiotics and the various mechanisms of resistant-gene exchange (rapid diffusion of plasmid-mediated enzymes, transposons, mobile gene cassettes and integrons…), underscores the need of molecular techniques capable of distinguishing the clonality of antibiotic-resistant micro-organisms with respect to horizontal transfer of the determinants of resistance.
In order to discriminate bacterial strains as much as possible, the best approach would be to sequence the whole genome of each strain. That would however, be time consuming and not cost effective, and therefore only parts of the genome are examined. The most widely used molecular typing methods [for example, pulsed-field gel elect- rophoresis (PFGE) and arbitrarily primed PCR (AP-PCR)] rely on
comparisons of DNA fragment patterns on agarose gels. These met- hods are highly discriminatory and rely on uncharacterized genomic differences between isolates of bacterial species and the genetic vari- ation indexed by these methods appears to accumulate relatively ra- pidly. This is important for short-term epidemiological studies, as it le- ads to extensive variation within the pathogen of interest. Multi-locus sequence typing (MLST) provides a new approach to molecular epide- miology that can identify and track the global spread of virulent or an- tibiotic resistant isolates of bacterial pathogens using the Internet. MLST databases, together with interrogation software, are available for N. meningitidis, S. pneumoniae, S. pyogenes and S. aureus. MLST is based on the well-tested principles of MLEE but assigns the alleles at each locus directly by nucleotide sequencing, rather than indirectly from the electrophoretic mobilities of their gene products on starch gels. The nucleotide sequence of 500-bp internal fragments of seven housekeeping genes, provides sufficient variation to identify many dif- ferent alleles within a population.
Several molecular techniques are available for determining the ge- notypic drug-resistance and monitoring epidemic spread of a particu- lar antimicrobial resistance gene in a hospital or patient population. These techniques, ranging from simple plasmid analysis, through Restriction Fragment Length Polymorphism (RFLP), Polymerase Chain Reaction (PCR), PCR coupled with RFLP (PCR-RFLP), PCR- single strand conformational polymorphism (SSCP) analysis up to sequencing, have been shown useful for epidemiological studies invol- ving resistance genes. These molecular tests will be addressed in res- pect to their applications and limitations using several examples. Furt- hermore, the latest trends in the search for new approaches to improve understanding of the constantly evolving molecular epidemiology of antibiotic resistance in microorganisms will be discussed. New tech- niques for investigation will always need to be developed in order to keep pace with nature’s inexhaustible resources for survival.