A total of 975 residents resided in the LTCF during the study period. The average age for this population was 88.2 years (standard deviation ± 7.9) of whom 74.6% were women. Caucasians represented 98.5% of the study population, with other racial groups, including Native American, Black, and Hispanic, accounting for less than 1% each. A total of 313 (32.1%) residents died during the study period. A total of 3,578 clinical cultures were obtained during the study period, of which 3,029 (84.7%) were from urine, 307 (8.6%) from blood, and 242 (6.8%) from wound specimens. Bacterial growth was identified among 2,032 (56.8%) cultures, of which 1,789 (88%), 224 (11%), and 19 (1.0%) were recovered from urine, wound, and blood specimens, respectively. Cultures reported as normal flora, mixed growth, or probable contaminant (355 [17.5%]), and repeat cultures growing the same organisms with identical susceptibility patterns, taken from a single individual within a 1-month period (16 [0.007%]), were excluded. The remaining 1,661 isolates are described in the following analysis.
A total of 824 (49.6%) isolates were identified as gram-negative bacteria, of which 180 (21.8%) met the criteria defined in this study for multidrug resistance. Gram-positive bacteria were isolated from 837 cultures of which 104 (12.4%) isolates were identified as MRSA and 11 (1.3%) isolates were identified as VRE. MRSA was recovered from urine (56.7%) and wound (43.3%) cultures. VRE was recovered from urine (90.9%) and wound (9.1%) cultures. Rates of VRE, MRSA, and MDRGN during the study period are shown in . For the 6-month intervals during the study period, rates of MDRGN were 7.9%, 9.8%, 13.7%, and 14.0%. MRSA rates were 3.0%, 2.0%, 10.4%, and 7.8%, and rates of VRE were 0.0%, 0.7%, 1.0%, and 1.0%. MDRGN were more frequently isolated than MRSA or VRE throughout the study period. The prevalence of MRSA and MDRGN increased significantly over time (p = 0.001 and p = 0.02, respectively). MDRGN were recovered from the following sites (number of specimens [percent]): urine (169 [93.9%]), wound (10 [5.6%]), and blood (1 [0.5%]). The most common MDRGN species were Proteus mirabilis (92 [51.1%] isolates), Escherichia coli (47 [26.1%] isolates), and Providencia stuartii (19 [10.6%] isolates). Other species of MDRGN included Klebsiella pneumoniae (8 [4.4%] isolates), Morganella morganii (5 [2.8%] isolates), Klebsiella oxytoca (3 [1.7%] isolates), Stenotrophomonas maltophilia (2 [1.1%] isolates), and Enterobacter aerogenes (1 [0.6%] isolate). MDRGN isolates were resistant to (percent of isolates) ciprofloxacin (96.7%), ampicillin/sulbactam (92.1%), TMP/SMX (81.5%), gentamicin (79.4%), cefazolin (54.3%) ceftriaxone (13.6%), and piperacillin/tazobactam (5.1%). Susceptibility testing to ceftazidime, cefepime, and impemen was performed on less than 20% of isolates. A total of 13 different coresistance patterns among MDRGN isolates were identified. Among these, resistance to three, four, and five or more antimicrobials were identified among 122 (67.8%), 47 (26.1%), and 11 (6.1%) MDRGN isolates, respectively. The most common coresistant pattern was three-drug resistance to ciprofloxacin, gentamicin, and TMP/SMX present among 79 (43.9%) MDRGN isolates (). Coresistance patterns among the most common MDRGN species, P. mirabilis, E. coli, and P. stuartii, were also analyzed. Among P. mirabilis isolates, the most common coresistance pattern was three-drug resistance to ciprofloxacin, TMP/SMX, and gentamicin present among 50 (61%) of 82 isolates and a four-drug resistance to ciprofloxacin, TMP/SMX, gentamicin, and cefazolin present among 37 (45%) isolates. The most common coresistance pattern among E coli isolates was also ciprofloxacin, TMP/SMX, and gentamicin present among 30 (64%) of 47 isolates. Among P. stuartii isolates, the most common MDR pattern was four-drug resistance to extended-spectrum penicillins, ciprofloxacin, gentamicin, and cefazolin present among 9 (47%) of 19 isolates, and three-drug resistance to extended-spectrum penicillins, cefazolin, and ciprofloxacin present among 8 (42%) isolates.
Rates of Multidrug-Resistant Gram-Negative Bacteria (MDGRN), Vancomycin-Resistant Enterococci (VRE), and Methicillin-Resistant Staphylococcus aureus (MRSA) Recovered From Clinical Cultures for the Study Period.
Coresistance patterns among gram-negative bacteria recovered from clinical cultures.