Enterococcus faecium has become an increasingly important nosocomial pathogen due to formation of biofilms on several surfaces. Sixty one (61) E. faecium strains isolated from blood, urine and fecal were assessed for biofilm production, the effect of different glucose concentration on biofilm production and also the presence of esp, fsr and gelE genes. Pulsed field gel electrophoresis (PFGE) method was performed to show chromosomal similarities and also to determine correlation between biofilm formation ability and genetic identity of E. faecium strains. It was observed that glucose concentration of the medium and incubation period can affect biofilm formation of the bacteria. When tested strains were incubated in a medium containing 1% glucose for 48 h, 66.66% of urine isolates, 60.71% fecal isolates and 25% of blood isolates produced strong biofilm structures. esp-positive strains (80% of the all isolates) were also identified as strong biofilm producers compared to esp-negative isolates. As a result of PFGE analyses, isolates numbered 14 (isolated from fecal sample) and 81 (isolated from blood sample) were classified in minor group B at a level of 48% similarity. Out of these two isolates, all the isolates were included in major group A with 43% similarity level and this group was subdivided into six subgroups.

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Biofilm formation of Salmonella Virchow was monitored with respect to time at three different temperature (20, 25 and 27.5 °C) and pH (5.2, 5.9 and 6.6) values. As the temperature increased at a constant pH level, biofilm formation decreased while as the pH level increased at a constant temperature, biofilm formation increased. Modified Gompertz equation with high adjusted determination coefficient (R 2 adj ) and low mean square error (MSE) values produced reasonable fits for the biofilm formation under all conditions. Parameters of the modified Gompertz equation could be described in terms of temperature and pH by use of a second order polynomial function. In general, as temperature increased maximum biofilm quantity, maximum biofilm formation rate and time of acceleration of biofilm formation decreased; whereas, as pH increased; maximum biofilm quantity, maximum biofilm formation rate and time of acceleration of biofilm formation increased. Two temperature (23 and 26 °C) and pH (5.3 and 6.3) values were used up to 24 h to predict the biofilm formation of S. Virchow. Although the predictions did not perfectly match with the data, reasonable estimates were obtained. In principle, modeling and predicting the biofilm formation of different microorganisms on different surfaces under various conditions could be possible.

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