Antimicrobial Resistance


Antimicrobial Resistance in Russia

Publications

References

Previous page Next page Main page E-Mail
Navigation

22th International Congress of Chemotherapy

30 June - 3 July, 2001, Amsterdam, The Netherlands

The Results of IACMAC External Quality Assurance (Eqa) Program for Identification and Antimicrobial Susceptibility Testing (Ast) of Gram-Positive Bacteria In Russia

O.U. STETSIOUK, E.L. RJABKOVA, D.V. GALKIN, M.V. SUKHORUKOVA, L.S. STRATCHOUNSKI
Scientific Center of Ministry of Health of Russian Federation for Monitoring of Antimicrobial Resistance
Interregional Association for Clinical Microbiology and Antimicrobial Chemotherapy (IACMAC), RUSSIA
Institute of Antimicrobial Chemotherapy, Smolensk, RUSSIA



ABSTRACT

Objectives: To assess ability of Russian laboratories to identify and detect clinically significant resistance of gram-positive bacteria.

Methods: 53 laboratories in 28 Russian cities performed the following EQA tests: identification and AST of the 5 control strains of gram-positive bacteria granted by CDC (CDC-103 — CDC-107) to a defined set of antimicrobials.

Results: Correct identification (S.aureus CDC-103, S.aureus CDC-104, S.epidermidis CDC-105, E.faecalis CDC-106 and E.faecalis CDC-107) to the species level was achieved in 86.3 — 88%, to the genus level — in 95.8-98% cases. Laboratories used for AST Russian AGV-medium and Mueller-Hinton agar. Agreement with the CDC AST results was attained in 55.6 (co-trimoxazole) — 100% for CDC-103, 73.9 (oxacillin) — 100% for CDC-104, 32 (oxacillin) — 100% for CDC-105, 17.2 (chloramphenicol) — 100% for CDC-106, and 0 (gentamicin) — 100% for CDC-107. High rate of major errors (25-44.4%) of co-trimoxazole AST can be explained by the use of AGV-medium with improper thimidine content. Unacceptable rate of very major errors was observed for oxacillin in S.epidermidis CDC-105 (64%) and for gentamicin in E.faecalis CDC-107 (88.9%).

Conclusions: The obtained results show the vast need to implement in Russia internationally recognized standards for AST and detection of clinically significant resistance (MRSS, HLAGR) in gram-positive bacteria.


INTRODUCTION AND OBJECTIVES

The impact of AST on effective antibacterial therapy is of increasing importance due to emergence and spread of antimicrobial resistance in bacteria. The results of AST in vitro serve as basis for administration of optimal antibiotic regimen for current patient, for empirical choice of antimicrobials and for creating of hospital formulary.

Strict standardization of the testing procedure and regular performing of quality control tests are essential for achieving of repeatable clinically relevant results.

The objectives of the current study were to assess ability of Russian laboratories to identify and detect clinically significant resistance of gram-positive bacteria.


MATERIALS AND METHODS

Fifty three (53) laboratories in 28 Russian cities performed the following EQA tests:

  • Identification
  • AST to a defined set of antimicrobials

of the 5 control strains of gram-positive bacteria granted by CDC:

  • CDC-103 (S.aureus ATCC 33591 — MRSA, mecA-positive)
  • CDC-104 (S.aureus ATCC 43387 — MSSA with b-lactamase hyperproduction)
  • CDC-105 (S.epidermidis — Vancomycin-Intermediate MRSE strain)
  • CDC-106 (E.faecalis — Vancomycin-Resistant strain, vanA-positive)
  • CDC-107 (E.faecalis ATCC 51299 — vanB-positive, recommended by NCCLS as control strain for vancomycin resistance screening test on BHI agar)

RESULTS AND DISCUSSION

The participating laboratories used different media (Russian AGV-medium and Mueller-Hinton agar) and antimicrobial disks from different producers both domestic and imported.

Interpretation of the results was performed according to the "Methodical Rules" by Ministry of Health of USSR (1983), NCCLS guidelines (1995-98) and disk manufacturers’ recommendations.

Correct identification (S.aureus CDC-103, S.aureus CDC-104, S.epidermidis CDC-105, E.faecalis CDC-106 and E.faecalis CDC-107) to the genus level was achieved in 95.8 — 98.0% cases, to the species level in 86.3 — 88.0%.

Agreement with the CDC AST results was attained in 55.6 — 100% for CDC-103, 73.9 (oxacillin) — 100% for CDC-104, 32 (oxacillin) — 100% for CDC-105, 17.2 (chloramphenicol) — 100% for CDC-106, and 0 (gentamicin) — 100% for CDC-107.

The results are presented in Tables 1—5. Minor errors are marked with green, major errors (false resistance) — in yellow, and very major errors (false susceptibility) — in red color.

High rate of major errors (25 — 44.4%) of trimethoprim/sulfamethoxazole AST can be explained by the use of AGV-medium with improper thimidine content.

Unacceptable rate of very major errors was observed for oxacillin in S.epidermidis CDC-105 (64%) and for gentamicin in E.faecalis CDC-107 (88.9%).


Table 1. The results of identification and AST of CDC-103
(S.aureus ATCC 33591 — MRSA, mecA-positive)

Antimicrobial CDC results Q-ty (%) of Labs reporting the result as
MIC, mg/L Zone, mm S I R
Vancomycin <1 (S) 16 (S) 35 (100) 0 (0) 0 (0)
Gentamicin <4 (S) 17 (S) 38 (92.7) 1 (2.4) 2 (4.9)
Clindamycin >8 (R) 6 (R) 1 (4.5) 1 (4.5) 20 (90.9)
Co-trimoxazole <0.25 (S) 16 (S) 5 (55.6) 0 (0) 4 (44.4)
Oxacillin >16 (R) 6 (R) 2 (7.4) 0 (0) 25 (92.6)
Penicillin >2 (R) 6 (R) 0 (0) 1 (2.9) 33 (97.1)
Rifampicin <0.12 (S) 33 (S) 20 (100) 0 (0) 0 (0)
Tetracyclin >16 (R) 6 (R) 1 (3.6) 0 (0) 27 (96.4)
Chloramphenicol >32 (R) 8 (R) 2 (7.7) 3 (11.5) 21 (80.8)
Ciprofloxacin <0.5 (S) 25 (S) 32 (88.9) 0 (0) 4 (11.1)
Erythromycin >8 (R) 6 (R) 3 (6.7) 0 (0) 42 (93.3)
Identification S.aureus S.aureus — 86.3%,
Staphylococcus spp. — 9.8%

Table 2. The results of identification and AST of CDC-104
(S.aureus ATCC 43387 — MSSA with b-lactamase hyperproduction)

Antimicrobial CDC results Q-ty (%) of Labs reporting the result as
MIC, mg/L Zone, mm S I R
Vancomycin <1 (S) 15 (S) 37 (100) 0 (0) 0 (0)
Gentamicin <1 (S) 18 (S) 39 (100) 0 (0) 0 (0)
Clindamycin 0.25 (S) 22 (S) 22 (100) 0 (0) 0 (0)
Co-trimoxazole <0.25 (S) 25 (S) 6 (75.0) 0 (0) 2 (25.0)
Oxacillin 2 (S) 15 (S) 17 (73.9) 4 (17.4) 2 (8.7)
Penicillin >2 (R) 6 (R) 0 (0) 1 (2.8) 35 (97.2)
Rifampicin <0.12 (S) 29 (S) 32 (100) 0 (0) 0 (0)
Tetracyclin < 0.25 (S) 29 (S) 25 (92.6) 1 (3.7) 1 (3.7)
Chloramphenicol 8 (S) 18 (S) 27 (100) 0 (0) 0 (0)
Ciprofloxacin 0.25 (S) 29 (S) 35 (100) 0 (0) 0 (0)
Erythromycin 0.5 (S) 23 (S) 43 (93.5) 2 (4.3) 1 (2.2)
Identification S.aureus S.aureus — 88.0%,
Staphylococcus spp. — 10.0%

Table 3. The results of identification and AST of CDC-105
(S.epidermidis — MRSE, Vancomycin-Intermediate strain)

Antimicrobial CDC results Q-ty (%) of Labs reporting the result as
MIC, mg/L Zone, mm S I R
Vancomycin 8 (I) 16 (S) 29 (90.6) 2 (6.3) 1 (3.1)
Gentamicin 16 (R) 10 (R) 15 (42.9) 0 (0) 20 (57.1)
Clindamycin 0.25 (S) 25 (S) 19 (100) 0 (0) 0 (0)
Co-trimoxazole 8 (R) 8 (R) 4 (50.0) 0 (0) 4 (50.0)
Oxacillin >16 (R) 6 (R) 16 (64.0) 1 (4.0) 8 (32.0)
Penicillin >2 (R) 10 (R) 2 (5.7) 0 (0) 33 (94.3)
Rifampicin <0.12 (S) 31 (S) 31 (100) 0 (0) 0 (0)
Teicoplanin 16 (I) 14 (S) - - -
Tetracyclin <0.5 (S) 24 (S) 21 (91.3) 1 (4.35) 1 (4.35)
Chloramphenicol 8 (S) 21 (S) 21 (87.5) 0 (0) 3 (12.5)
Ciprofloxacin >8 (R) 6 (R) 4 (13.8) 0 (0) 25 (86.2)
Erythromycin 0.5 (S) 26 (S) 36 (90.0) 1 (2.5) 3 (7.5)
Identification S.epidermidis S.epidermidis — 86.7%, Staphylococcus spp. — 6.7%, S.aureus — 4.4%

Table 4. The results of identification and AST of CDC-106
(E.faecalis — Vancomycin-Resistant strain, vanA-positive)

Antimicrobial CDC results Q-ty (%) of Labs reporting the result as
MIC, mg/L Zone, mm S I R
Ampicillin 1 (S) 25 (S) 36 (76.6) 2 (4.3) 9 (19.1)
Vancomycin 512 (R) 6 (R) 4 (10.5) 0 (0) 34 (89.5)
High Level Gentamicin Resistance S* 19 (S) 8 (88.9) 1 (11.1) 0 (0)
High Level Streptomycin Resistance S* 16 (S) 2 (40.0) - 3 (60.0)
Penicillin 2 (S) 18 (S) 10 (29.4) 7 (20.6) 17 (50.0)
Teicoplanin 128 (R) 10 (R) 0 (0) 0 (0) 2 (100)
Tetracyclin - 6 (R) 0 (0) 0 (0) 27 (100)
Chloramphenicol 16 (I) 11 (R) 20 (69) 4 (13.8) 5 (17.2)
b-lactamase production Negative ND — 41 (82%),
Positive — 5 (10%),
Negative — 4 (8%)
Identification E.faecalis E.faecalis — 88%,
Enterococcus spp. — 8%,
E.faecium — 4%

* Broth microdilution screening test : streptomycin — 1000 mg/L, gentamicin — 500 mg/L


Table 5. The results of identification and AST of CDC-107
(E.faecalis — vanB-positive)

Antimicrobial CDC results Q-ty (%) of Labs reporting the result as
MIC, mg/L Zone, mm S I R
Ampicillin 1 (S) 20 (S) 36 (80.0) 3 (6.7) 6 (13.3)
Vancomycin 16 (I) 16 (I) 16 (44.45) 13 (36.1) 7 (19.45)
High Level Gentamicin Resistance R* 6 (R) 8 (88.9) 1 (11.1) 0 (0)
High Level Streptomycin Resistance R* 6 (R) 0 (0) 0 (0) 4 (100)
Penicillin 4 (S) 17 (S) 6 (18.8) 5 (15.6) 21 (65.6)
Teicoplanin 0.25 (S) 14 (S) 1 (50.0) 0 (0) 1 (50.0)
Tetracyclin <1 (S) 25 (S) 21 (77.8) 2 (7.4) 4 (14.8)
Chloramphenicol >32 (R) 8 (R) 0 (0) 0 (0) 25 (100)
b-lactamase production Negative ND — 46 (92%),
Positive — 1 (2%),
Negative — 3 (6%)
Identification E.faecalis E.faecalis — 88%,
Enterococcus spp. — 10%,
E.faecium — 2%

* Broth microdilution screening test : streptomycin — 1000 mg/L, gentamicin — 500 mg/L

The obtained results of testing of CDC control strains confirm that AST of clinical strains in routine practice in Russian microbiology laboratories produce a lot of errors.

Frequent problems with the AST and clinically significant resistance mechanisms detection in Gram-positive bacteria (MRSS, Vancomycin resistance and HLAGR in enterococci) were revealed.

The main reason of the majority of problems with AST is that the only official document regulating the AST procedure in Russia is the "Methodical Rules" by Ministry of Health of the USSR revised last time in 1983. This document advocates use of Russian AGV-medium for testing, composition of which differs considerably from Muller-Hinton agar and does not meet WHO requirements for cautions and thimidine contents, etc.

These guidelines include only disk-diffusion procedure of 23 "old" antimicrobials for non-fastidious bacteria only. No recommendations have been developed for dilution tests and screening of specific types of resistance (MRSS, Vancomycin resistance and HLAGR in enterococci, etc.)


CONCLUSIONS

  • The above results elucidate the problems with the internal quality control in most Russian laboratories
  • Personnel education and procedures standardization are needed for the improvement of the present situation
  • There is a vast need for National guidelines for AST and detection of clinically significant resistance mechanisms (MRSS, HLAGR) in Gram-positive bacteria in Russia, harmonized with international practices (WHO, NCCLS, SFM, DIN, BSAC, etc.)

ACKNOWLEDGMENTS

  • We are indebted for Dr. Fred C. Tenover (Nosocomial Pathogens Laboratory Branch, CDC), Dr. Herve Richet, Jasmine Mohammed (WHO Collaborating Center) and INSPEAR project team for their kind permission to use the CDC control strains for IACMAC EQA program in Russia
  • We are grateful to our colleagues from Russian microbiology laboratories who participated in IACMAC EQA program


© 2000-2006 IAC SSMA · E-mail: website@antibiotic.ru