From April to December 2014 Four hundred and ninty mid stream urin specimens were collected from patients suffering from urinary tract infections and from urinary catheterized patients in Baquba Teaching Hospital and Al -Betul Hospital, and Baghdad Teaching Hospital. Out of 14 Providencia isolates, 9 isolates were diagnosed as Providencia rettgeri. This identification was confirmed by biochemical tests, Api 20 E system and vitek 2 compact system. The results of susceptibility of isolates to antibiotics were tested, using disc diffusion method showed the bacterial isolates have complete resistance for Ampicillin, Tetracyclin,Vancomycin with a percentage of 100%, the results indicate that the antibiotics Amikacin and imipeneme were found to be the most effective drugs against the strains under the study i.e. the resistance to these antibiotics were 0%. All strains of P. rettgeri isolates were tested to ability to biofilm production, by two methods TCP and CRA , out of nine isolates only 4(44.5%) and 1(11.2%) were found tobe strong biofilm producer by CRA and TCP, respectively. The histological section of mice (kidney and bladder) injected ineraperitonial with two groups of P. rettgeri isolates, group (A) injected mice with P. rettgeri P9 isolate (strong biofilm producer and multi drug resistant especially beta – lactam) and group (B) injected mice with P.rettgeri P7 isolate(weak or non biofilm producer and sensitive to different antibiotics especially beta-lactam) , results showed Several pathological changes have been caused by P.rettgeri isolates in mice represented by sever inflammatory cell infiltration with congestion and degeneration with necrosis of epithelial mucosal layer in urinary bladder, while the Kidney suffered from sever inflammatory cells infiltration of PMN into Glomerulus and deposition of red fibrinoid material within glomerulus capillaries with necrosis of epithelial renal tubules. It was clear that the strong producer isolate P. rettgeri P9 was more virulent than the weak(non producer producing isolate P.rettgeri P7.