SummaryThe genome of uropathogenic Escherichia coli isolate 536 contains five well-characterized pathogenicity islands (PAIs) encoding key virulence factors of this strain. Except PAI IV536, the four other PAIs of strain 536 are flanked by direct repeats (DRs), carry intact integrase genes and are able to excise sitespecifically from the chromosome. Genome screening of strain 536 identified a sixth putative asnWassociated PAI. Despite the presence of DRs and an intact integrase gene, excision of this island was not detected. To investigate the role of PAI-encoded integrases for the recombination process the int genes of each unstable island of strain 536 were inactivated. For PAI I 536 and PAI II536, their respective P4-like integrase was required for their excision. PAI III536 carries two integrase genes, intA, encoding an SfX-like integrase, and intB, coding for an integrase with weak similarity to P4-like integrases. Only intB was required for site-specific excision of this island. For PAI V536, excision could not be abolished after deleting its P4-like integrase gene but additional deletion of the PAI II536-specific integrase gene was required. Therefore, although all mediated by P4-like integrases, the activity of the PAI excision machinery is most often restricted to its cognate island. This work also demonstrates for the first time the existence of a cross-talk between integrases of different PAIs and shows that this cross-talk is unidirectional.

Varicella infections are usually considered to be benign, even though varicella disease may cause serious complications. However, in Europe, the incidence of varicella infections (and complications) has been reported to peak in the spring [1]. An increased risk of complications is well known in immunocompromised individuals and in neonates, if maternal varicella has erupted close to birth. Severe complications (0.82/100,000 children/year) can also occur in previously healthy children, including central nervous system manifestations (61%), secondary bacterial infections (38%), haematological disorders (5%) and occasional fatal outcome (6%) [1,2]. Purpura fulminans is a thrombotic disease that can occur during infections, disseminated intravascular coagulation (DIC) or in the context of an acquired or congenital protein C or S deficiency. The importance of protein S and C as two inhibitors in haemostasis is well known because severe inherited deficiency is associated with neonatal purpura fulminans and heterozygous protein S or C deficiency is associated with venous thromboembolism.We report a Caucasian 6-year-old boy with DIC in addition to presumptive vasculitis and endocarditis in the aftermath of a varicella infection.The young patient (height 121 cm, weight 21 kg) was admitted 2 weeks after otherwise uncomplicated chickenpox with painful and bluish discolouration of both lower limbs. The examination revealed normal body temperature and blood pressure. Peripheral pulses were palpable. We found an accelerated heart beat (130/min) and a normal respiratory rate. The skin lesions showed a red to livedolike discolouration, they were significantly painful on palpation and indurated. There was no skin necrosis. On the left lower leg, pretibial superficial skin erosion of 6 cm in diameter was present in addition to an otherwise intact skin. The clinical diagnosis of vasculitis or atypical Henoch-Schönlein purpura was made.Blood investigations showed normal values for the leukocyte count (total leukocytes 11,900/ll, neutrophil granulocytes 67%, lymphocytes 19%), haemoglobin concentration (11.9 g/dl), platelet count (187,000/ll), renal (besides microhaematuria with a maximum of 431 erythrocytes/ll) and liver function tests. There were signs of inflammation (C-reactive protein [CRP] 7.8 mg/dl).Of importance, the coagulation profile was grossly altered: the activated partial thromboplastin time (PTT) was prolonged (52 s, normal \36 s) and the prothrombin time (PT given as the prothrombin ratio [PR]) was reduced (36%). The international normalized ratio (INR) was 2.0. Fibrinogen was significantly reduced (0.4 g/l) and fibrin d-dimers were elevated ([35 mg/l, normal range: 0-0.5 mg/l). There were considerably reduced values of proteins S and C, coagulation factors II, V, VIII and XIII (Fig. 1), whereas coagulation factors VII, IX, X, XI and XII showed normal activities. The serum immunoglobulins G, A and M were normal. The lupus anticoagulant was 37 s (normal range: