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Prevalence of Antimicrobial Resistances in Streptococcus pneumoniae Isolates in
Australia, 2005: Report from the Australian Group on Antimicrobial Resistance (AGAR) South Metropolitan Area
Thomas Gottlieb1, Peter Collignon2, Jennifer Robson3, Julie Pearson4, Jan Bell5, and the Australian Group on Antimicrobial Resistance
1Department of Microbiology and Infectious Diseases, Concord Hospital, New South Wales, 2Infectious Diseases Unit and Microbiology Department, The Canberra Hospital, Woden, ACT, 3Microbiology Department, Sullivan Nicolaides Pathology, Taringa, Queensland,
4Department of Microbiology and Infectious Diseases, Royal Perth Hospital, PathWest Laboratory Medicine, Western Australia, 5Department of Microbiology and Infectious Diseases, Women’s and Children’s Hospital, South Australia.
Introduction
Results continued
Results continued
Streptococcus pneumoniae is a common cause of meningitis and bacteraemia as well as community- Table 1 CLSI (2009) interpretive standards for penicillin Invasive
Non-invasive
pneumonia, sinusitis, and otitis media. Rates of antimicrobials have increased over the past two decades, compromising treatment efficacy particularly The Australian Group on Antimicrobial Resistance antimicrobial resistance. Resistance rates from this Figure 4 Trends in erythromycin resistance 1994-2005 current study were compared to those from previous Invasive
AGAR surveys conducted in 1989 (where only Non-invasive
Invasive
penicillin was tested), 1994, 1999 and 2002.
Non-invasive
Twenty institutions from the 5 mainland states and the Australian Capital Territory (ACT) participated in the S.
pneumoniae AGAR survey. Starting 1st January 2005, each laboratory collected up to 100 consecutive significant clinical MIC (mg/L)
Figure 1 Penicillin MIC distribution 2005 (%S, I and R refer to Identification: Alpha-haemolytic, optochin sensitive, and/or
bile-soluble, Gram-positive cocci were identified as S.
pneumoniae. Any strain with an optochin zone of inhibition of Figure 5 Trends in tetracycline resistance 1994-2005 Penicillin R
between 6 and 14mm in CO was tested for bile solubility.
Penicillin I
Susceptibility testing: Participating laboratories performed
Overall penicillin I+R
laboratory’s routine standardised methodology (CDS, CLSI or BSAC disc diffusion, Vitek2®, agar dilution or MIC testing).
Invasive
Clindamycin and erythromycin discs were placed side by side Non-invasive
to look for clindamycin inducibility. Penicillin and moxifloxacin MICs were determined for all isolates using Etest® strips.
Four hundred and seventy one (95%) of the 497 isolates that were penicillin intermediate or resistant (MIC >0.064 mg/L) were also tested with either a ceftriaxone or cefotaxime Figure 2 Trends in penicillin for non-invasive isolates 1989-2005 Figure 6 Trends in co-trimoxazole resistance 1994-2005 Penicillin R
A total of 1,776 S. pneumoniae isolates were included Penicillin I
Table 2 Multi-resistance in S. pneumoniae, 2005 in the study. 20% of isolates were from invasive Overall penicillin I+R
Penicillin: The new penicillin CLSI breakpoints
(Table 1) were employed for this survey. Overall 497/1,776 (28%) isolates were non-susceptible to oralpenicillin. All of the blood culture isolates were breakpoints. One CSF isolate (MIC 0.25mg/L) was resistant by the parenteral (meningitis) breakpoint.
Figure 3 Trends in penicillin for invasive isolates 1989-2005 Trend data shows that overall penicillin resistance levofloxacin was detected in another four isolates.
continues to increase for invasive and non-invasive Tetracycline: 326/1,775 (18.4%) isolates were
Moxifloxacin resistance was present in two isolates strains however since 2005 high-level resistant tetracycline resistant. There was a significant difference (P<0.001) in tetracycline resistance intermediate strains have declined (Figures 2 and 3).
Multi-resistance: 17.3% of isolates were multi-
among non-invasive (21.3%) and invasive (6.3%) resistant (acquired resistance to >2 drug classes) Ceftriaxone/cefotaxime: Cefotaxime or ceftriaxone
strains. Trend data shows that after an increase in (Table 2). Multi-resistance was significantly higher MICs were determined on 95% of penicillin non- resistance in non-invasive isolates from 1994 to susceptible strains. Fourteen isolates (3.0%) were 1999, overall resistance has remained relatively compared with invasive strains (6.0%).
resistant to either cefotaxime or ceftriaxone.
steady from 1999 to 2005 (Figure 5).
Conclusions
Erythromycin and clindamycin: 404/1,776 (22.7%)
Co-trimoxazole: 550/1,775 (31.0%) isolates were
isolates were erythromycin resistant. Resistance was significantly higher (P<0.001) in non-invasive (24.6%) mainly due to the increase of high-level resistant compared with invasive strains (15.1%). 228/1,462 strains in invasive and non-invasive infections.
(32.2%) compared with invasive (25.6%) strains.
(15.6%) isolates were clindamycin resistant. Of 364 Macrolide resistance continues to increase with Trend data shows decreasing rates of resistance in erythromycin resistant isolates, 222 (61%) had a current rates at 23%. Of concern is the high invasive isolates from 1994 to 2005 and a MLS constitutive resistant phenotype and 6 (1.6%) proportion of multi-resistant strains with almost one decrease for non-invasive strains from 2002 to had inducible resistance. Trend data shows that erythromycin resistance for all strains is increasing Levofloxacin
moxifloxacin:
albeit slowly. A decline in resistance from 19.2% to resistance was detected in only four of 1,775 Acknowledgements
15.1% over the last two surveys was evident for (0.2%) isolates tested. Intermediate resistance to AGAR has been supported by the Department of Health and Ageing www.antimicrobial-resistance.com

Source: http://www.agargroup.org/files/SPNE%202005%20poster%20final.pdf