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41st Interscience Conference on
Antimicrobial Agents and Chemotherapy

16-19 December, 2001, Chicago, USA
Poster # 007/67

Results of Russian Country-wide Surveillance of Antimicrobial Resistance of Nosocomial Gram-negative Bacteria (Ngnb) from 28 Intensive Care Units (ICUs)

L. Stratchounski, G. Reshedko, O. Stetsiouk, O. Kretchikova, E. Riabkova
Institute of Antimicrobial Chemotherapy, Smolensk, Russian Federation

The PDF format poster (297 kb)




ABSTRACT

Objective: To evaluate the prevalence and antimicrobial resistance of NGNB from Russian ICUs.

Methods: Minimal inhibitory concentrations of amoxicillin/clavulanate (XL), piperacillin (PP), piperacillin/tazobactam (PTc), cefuroxime (XM), cefotaxime (CT), ceftazidime (TZ), imipenem (IP), gentamicin (GM), amikacin (AK), ciprofloxacin (CI) were determined by Etest (AB Biodisk, Sweden). Interpretation of results was performed according to NCCLS guidelines, 2000.

Results: A total of 2664 aerobic NGNB were isolated in 28 ICUs in 15 Russian cities during 1997-99. Predominant pathogens were Pseudomonas aeruginosa (30%), Escherichia coli (18%), Klebsiella pneumoniae (15%), Proteus spp. (10%), Enterobacter spp. (8%), Acinetobacter spp. (7%). Other species accounted for 12% in total. Resistance (I+R) rates (%) were:


  P.aeruginosa (n=798) E.coli (n=489) K.pneumoniae (n=389) Proteus spp. (n=263) Enterobacter spp. (n=203) Acinetobacter spp. (n=184)
XL - 36 56 33 90 -
PP 45 41 68 38 45 76
PTc 30 6 30 9 29 58
XM - 19 57 51 63 -
CT - 11 38 21 29 85
TZ 11 8 34 7 25 64
IP 19 0 0 0 0 0
GM 61 21 56 43 24 72
AK 7 2 9 3 3 9
CI 29 8 13 9 6 32

Decreased activity of PP and GM against the majority of NGNB was alarming, as well as high resistance to CI in P.aeruginosa and Acinetobacter spp. Significant differences in prevalence and resistance patterns were revealed among participating centers.

Conclusion: AK, TZ were the most active against P.aeruginosa; AK, IP - against other NGNB in Russian ICUs. Existing geographical differences underline the necessity of obtaining the local data.


INTRODUCTION AND PURPOSE

Nosocomial infections are of great importance in hospitals worldwide. Due to severity they often require the empirical treatment that should be based on the local epidemiological data. In spite of emerging role of gram-positive bacteria and fungi in the etiology of nosocomial infections, gram-negative bacteria still cause about 23-76% of different nosocomial infections in intensive care units (Fridkin et al., 1997). The purpose of our study was to evaluate the prevalence and resistance patterns of nosocomial gram-negative bacteria (NGNB) in Russian intensive care units (ICUs).


MATERIALS AND METHODS

Participating centers collected approximately 100 consecutive aerobic NGNB each from patients with documented nosocomial infection during 1997-1999.

Duplicate isolates were excluded from the study. Isolated strains were identified in local laboratories using standard biochemical tests. Strains were transferred to central laboratory in Smolensk where reidentification of 100% bacteria was performed. Collected strains were stored at 70oC. Minimal inhibitory concentrations (MICs) of piperacillin (PP), piperacillin/ tazobactam (PTc), cefuroxime (XM), cefotaxime (CT), ceftazidime (TZ), imipenem (IP), gentamicin (GM), amikacin (AK), ciprofloxacin (CI) were determined by Etest (AB Biodisk, Sweden). Interpretation of results was performed according to NCCLS guidelines, 2000. Intermediate strains were included into the "resistant" category. E.coli ATCC 25922 and P.aeruginosa ATCC 27853 were used as quality control strains for susceptibility. Data management and statistical analysis were performed with M-lab® software (Institute of Antimicrobial Chemotherapy, Smolensk, Russia).


RESULTS

Twenty eight ICUs from 15 Russian cities took part in the study. Location of participating cities is shown on the Fig 1.

Geographical location of participating cities.

Figure 1. Geographical location of participating cities.



In total 2664 NGNB isolated from 2306 specimens from 2187 patients were included in the study. The studied specimens were skin and soft tissue specimens (760/33.0%), low respiratory tract specimens (575/24.9%), urine (383/16.6%), abdominal samples (305/13.2%), blood (74/3.2%) and others (209/9.1%). The most common pathogens isolated were P.aeruginosa (798/29.9%), E.coli (489/18.3%), K.pneumoniae (389/14.6%), Proteus spp. (263/9.9%), Enterobacter spp. (203/7.6%), Acinetobacter spp. (184/6.9%), while Serratia spp. (108/4.0%), Stenotrophomonas spp. (35/1.3%), Citrobacter spp. (34/1.3%), Flavobacter spp. (22/0.8%), Morganella spp. (20/0.8%) and other NGNB (119/4.6%) were infrequent pathogens. Distribution (%) of species with respect to site of infection is presented in Table 1. Table 2 shows resistance rates (%), Tables 3-4 - MICs50/MICs90 and MIC ranges of predominant pathogens.


Table 1. Pathogens distribution (%) in different infection sites.

Microorganisms (n=2664) Skin and soft tissue Respiratory tract Urinary tract Abdomen Blood Other sites
P.aeruginosa (n=798) 300
(37.6%)
236
(29.6%)
115
(14.4%)
54
(6.7%)
12
(1.5%)
81
(10.2%)
E.coli (n=489) 135
(27.6%)
58
(11.9%)
142
(29.0%)
91
(18.6%)
10
(2.1%)
53
(10.8%)
K.pneumoniae (n=389) 91
(23.4%)
157
(40.3%)
48
(12.3%)
26
(6.7%)
17
(4.4%)
50
(12.9%)
Proteus spp. (n=263) 138
(52.5%)
40
(15.2%)
47
(17.9%)
26
(9.9%)
4
(1.5%)
8
(3.0%)
Enterobacter spp. (n=203) 76
(37.4%)
42
(20.7%)
29
(14.3%)
20
(9.9%)
7
(3.4%)
29
(14.3%)
Acinetobacter spp. (n=184) 54
(29.3%)
45
(24.5%)
12
(6.5%)
33
(17.9%)
9
(4.9%)
31
(16.9%)
Serratia spp. (n=108) 19
(17.7%)
48
(44.4%)
12
(11.1%)
9
(8.3%)
9
(8.3%)
11
(10.2%)
Stenotrophomonas spp. (n=35) 3
(8.5%)
23
(65.7%)
1
(2.9%)
1
(2.9%)
2
(5.7%)
5
(14.3%)
Citrobacter spp. (n=34) 10
(29.4%)
2
(6.0%)
6
(17.6%)
6
(17.6%)
0
(0.0%)
10
(29.4%)
Flavobacter spp. (n=22) 1
(4.5%)
15
(68.2%)
0
(0.0%)
0
(0.0%)
1
(4.5%)
5
(22.8%)
Morganella spp. (n=20) 8
(40.0%)
2
(10.0%)
6
(30.0%)
2
(10.0%)
0
(0.0%)
2
(10.0%)
Other microorganisms (n=119) 32
(26.9%)
31
(26.1%)
16
(13.4%)
14
(11.8%)
6
(5.0%)
20
(16.8%)

Table 2. Resistance (%) of predominant pathogens.

  P.aeruginosa (n=798) E.coli (n=489) K.pneumoniae (n=389) Proteus spp. (n=263) Enterobacter spp. (n=203) Acinetobacter spp. (n=184)
XL - 35.8 56.0 32.7 89.7 -
PP 44.7 40.9 68.4 37.6 44.8 75.5
PTc 29.7 6.3 30.1 8.7 29.1 58.1
XM - 19.2 57.3 51.3 63.1 -
CT - 11.0 37.5 20.9 29.1 84.8
TZ 11.2 7.8 33.7 6.9 24.6 63.6
IP 18.8 0.0 0.0 0.0 0.0 0.0
GM 61.3 20.9 55.8 43.3 24.1 71.7
AK 6.7 2.2 9.0 3.4 2.5 8.7
CI 28.9 8.4 12.9 8.7 5.9 31.5

Table 3. MICs50, MICs90 and MIC ranges of P.aeruginosa, E.coli and K.pneumoniae.

  P.aeruginosa (n=798) E.coli (n=489) K.pneumoniae (n=389)
MIC50 MIC90 MIC range MIC50 MIC90 MIC range MIC50 MIC90 MIC range
XL - - - 6 32 0.75-256 16 64 0.125-256
PP 32 256 0.25-256 3 256 0.19-256 256 256 0.75-256
PTc 16 256 0.25-256 1.5 8 0.25-256 4 256 0.5-256
XM - - - 4 128 0.5-256 16 256 0.75-256
CT - - - 0.094 12 0.016-256 3 256 0.023-256
TZ 3 12 0.094-256 0.38 6 0.025-256 3 128 0.094-256
IP 3 8 0.125-32 0.25 0.38 0.016-3 0.25 0.5 0.064-2
GM 96 256 0.064-256 1 64 0.25-256 16 256 0.25-256
AK 4 12 0.25-256 2 3 0.5-256 2 16 0.38-256
CI 0.38 32 0.023-32 0.016 0.38 0.004-32 0.064 2 0.008-32

Table 4. MICs50, MICs90 and MIC ranges of Proteus spp., Enterobacter spp. and Acinetobacter spp.

  Proteus spp. (n=263) Enterobacter spp. (n=203) Acinetobacter spp. (n=184)
MIC50 MIC90 MIC range MIC50 MIC90 MIC range MIC50 MIC90 MIC range
XL 6 48 0.38-256 192 256 1-256 48 256 0.25-256
PP 1.5 256 0.094-256 3 256 0.5-256 192 256 2-256
PTc 0.5 4 0.094-256 3 256 0.5-256 48 256 0.016-256
XM 12 256 0.25-256 16 256 1.5-256 256 256 1-256
CT 0.032 256 0.016-256 0.38 256 0.032-256 64 256 0.064-256
TZ 0.19 3 0.025-256 0.75 256 0.125-256 24 96 0.25-256
IP 0.5 2 0.023-4 0.38 1 0.125-3 0.38 1 0.064-4
GM 2 256 0.047-256 1 256 0.125-256 24 256 0.023-256
AK 2 6 0.19-256 2 3 0.75-48 2 12 0.125-256
CI 0.032 0.75 0.006-32 0.032 0.5 0.004-32 0.75 32 0.006-32

DISCUSSION

Among b-lactams PP, XL and XM showed low activity against all NGNB. PTc exhibited high acitvity against E.coli and Proteus spp. but about one third of P.aeruginosa, K.pneumoniae and Enterobacter spp. were resistant. CT was active mainly against E.coli while its activity was quite poor against other species. TZ was the most active b-lactam against P.aeruginosa whereas IP possessed decreased activity against this pathogen. No strains of Enterobacteriaceae and Acinetobacter spp. resistant to IP were revealed. Generally AK was much more active than GM against all tested NGNB. CI had quite poor activity against non-fermenting bacteria, showing also decreased activity against Enterobacteriaceae.

We observed significant inter-hospital and inter-regional variations in the resistance rates. The observed resistance rates of P.aeruginosa in different cities were 0-47.5% for IP; 0-69.2% for TZ; 0-41.7% for AK; 0-84.4% for CI. Resistance rates of E.coli to PTc varied between 0-35.7%, to AK - 0-57.1%; to CI - 0-85.7%; of K.pneumoniae to PTc were 0-72.3%; to AK - 0-69%; to CI - 0-61.1%. At the same time in 9 Moscow centers resistance of P.aeruginosa also varied considerably; for IP variations were 0-36.9%; for TZ - 0-31.3%; for AK 0-41.7%; for CI 0-84.4%. The similar situation was observed with antibiotic resistance rates of other pathogens.


CONCLUSIONS

  1. P.aeruginosa, K.pneumoniae, E.coli, Proteus spp., Enterobacter spp. and Acinetobacter spp. were the predominant gram-negative nosocomial pathogens in Russian ICUs.
  2. TZ, AK were the most active against P.aeruginosa; IP and AK - against other NGNB in Russian ICUs.
  3. Due to the high resistance rates of NGNB to PP, XL, XM and GM these drugs should not be recommended for the treatment of nosocomial infections caused by these pathogens.
  4. Significant inter-regional and inter-hospital differences in the prevalence and resistance patterns of NGNB emphasize the vast need for local epidemiology data.

ACKNOWLEDGMENTS

The survey was supported by Merck, Sharp and Dohme Idea, Inc. We also thank all participating laboratories for submitting nosocomial strains.



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