Summation: beta-lactam resistance surveillance in the Asia-Western Pacific region

Surveillance programmes and antibiotic resistance: worldwide and regional monitoring of antibiotic resistance trends

Since the introduction of the penicillins many decades ago, multiple species of bacteria have responded to the use of antimicrobial agents in their ability to develop and transmit antimicrobial resistance. Increased consumption of antimicrobial agents, their misappropriate use among other factors have further catalysed this resistance phenomenon. As bacterial resistance is a global healthcare issue, appropriate monitoring through governmental, institutional and industry or pharmaceutical led surveillance programmes is essential. This chapter describes the resistance issue, factors affecting this issue and examples of such ongoing resistance surveillance programmes.

Risk-factors for gastrointestinal colonisation with resistant Enterobacteriaceae among hospitalised patients: a prospective study

This study assessed the incidence of gastrointestinal colonisation by resistant Enterobacteriaceae among hospitalised patients, and identified risk-factors for ceftazidime and ofloxacin resistance. A prospective cohort study was performed in five wards in a French teaching hospital during a 2-year period. Patients hospitalised for > 48 h were enrolled between 17 April 2000 and 30 April 2002. A rectal swab was taken at admission, then once-weekly and/or on the day of discharge. In total, 933 patients were investigated and 585 amoxycillin-resistant isolates were obtained. Resistance rates for ceftazidime and ofloxacin were 9.4% and 4.8%, respectively. Multivariate analysis indicated that previous hospitalisation (p < 0.004) and exposure to amoxycillin-clavulanate (p < 0.003) and ceftriaxone (p < 0.002) were associated significantly with ceftazidime resistance. Hospitalisation in the urology ward (p < 0.02) and previous exposure to fluoroquinolones (p < 0.01) were the two independent risk-factors associated with ofloxacin resistance. The results of the study confirmed that antibiotic use selected resistant Enterobacteriaceae from the gut flora. Resistance was observed mostly in patients with previous antibiotic exposure and previous hospitalisation in wards with a high antibiotic selection pressure.

A pragmatic approach to identify extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in Taiwan: in vitro activity of newer and established antimicrobial agents

The activities of 17 antimicrobials were evaluated against 211 clinical extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae isolates from Taiwan. A pragmatic approach by sequential Etest (AB BIODISK, Solna, Sweden) ESBL screen (narrow MIC range) and/or the usual Etest method (broad MIC range) was used. Among 131 isolates with a ceftazidime MIC of > 8 microg/ml, 125 (95.4%) had a reduction of > or =3 log2 dilution steps for ceftazidime (positive test). Among 83 isolates with a ceftriaxone MIC of > 8 microg/ml and ceftazidime MIC at < or =8 microg/ml, 81 (97.5%) had a reduction of > or =3 three log2 dilution steps for ceftriaxone. Among the remaining eight isolates with nondeterminable results, additional Etest MIC method results revealed five ESBL-positive and two ESBL-negative (putative AmpC) determinations. This approach offered a cost-effective strategy to screen for ESBL among large number of isolates. The carbapenems (meropenem and imipenem) were the most active compounds (100% susceptibility) followed by newer fluoroquinolones (levofloxacin, gemifloxacin and gatifloxacin) at approximately 80% susceptible. Co-resistance to gentamicin was 96%, tobramycin 96%, and amikacin 62%. In conclusion, ESBL-producing strains of K. pneumoniae, also resistant to cefepime and aminoglycosides, are now widespread in Taiwan. The carbapenems and newer fluoroquinolones remain quite active against these ESBL strains recognized by this novel diagnostic approach.

Global patterns of susceptibility for 21 commonly utilized antimicrobial agents tested against 48,440 Enterobacteriaceae in the SENTRY Antimicrobial Surveillance Program (1997-2001)

A total of 48,440 Enterobacteriaceae isolates collected consecutively from patients hospitalized in participant SENTRY Antimicrobial Surveillance Program sites in four international regions (Asia-Pacific, Europe, Latin America, and North America) were tested by reference broth microdilution method against the most commonly used antimicrobial agents. The most active compounds could be divided in 3 groups based on their spectrum of activity. The first group included meropenem and imipenem, with 99.9% susceptibilty (S) rates for the Enterobacteriaceae. The second group includes amikacin (97.3% S) and cefepime (97.2% S); and a third active group had a rank order of susceptibility of: gatifloxacin = levofloxacin (91.7% S) > ceftazidime (91.4% S) > ceftriaxone (91.2% S) > aztreonam (91.1% S) > gentamicin (90.6% S) > piperacillin/tazobactam = ciprofloxacin (90.5% susceptibility). These latter antimicrobial agents presented susceptibility rates of approximately 90% (89.8%-91.7%). Continued resistance surveillance by various programs remain necessary to monitor the in vitro effectiveness of antimicrobial agents currently used in clinical practice.

Extended spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae: considerations for diagnosis, prevention and drug treatment

Extended spectrum beta-lactamase (ESBL)-producing organisms pose unique challenges to clinical microbiologists, clinicians, infection control professionals and antibacterial-discovery scientists. ESBLs are enzymes capable of hydrolysing penicillins, broad-spectrum cephalosporins and monobactams, and are generally derived from TEM and SHV-type enzymes. ESBLs are often located on plasmids that are transferable from strain to strain and between bacterial species. Although the prevalence of ESBLs is not known, it is clearly increasing, and in many parts of the world 10-40% of strains of Escherichia coli and Klebsiella pneumoniae express ESBLs. ESBL-producing Enterobacteriaceae have been responsible for numerous outbreaks of infection throughout the world and pose challenging infection control issues. Clinical outcomes data indicate that ESBLs are clinically significant and, when detected, indicate the need for the use of appropriate antibacterial agents. Unfortunately, the laboratory detection of ESBLs can be complex and, at times, misleading. Antibacterial choice is often complicated by multi-resistance. Many ESBL-producing organisms also express AmpC beta-lactamases and may be co-transferred with plasmids mediating aminoglycoside resistance. In addition, there is an increasing association between ESBL production and fluoroquinolone resistance. Although in in vitro tests ESBLs are inhibited by beta-lactamase inhibitors such as clavulanic acid, the activity of beta-lactam/beta-lactamase inhibitor combination agents is influenced by the bacterial inoculum, dose administration regimen and specific type of ESBL present. Currently, carbapenems are regarded as the drugs of choice for treatment of infections caused by ESBL-producing organisms. Unfortunately, use of carbapenems has been associated with the emergence of carbapenem-resistant bacterial species such as Stenotrophomonas sp. or Pseudomonas sp.

Evaluation of the in vitro activity of six broad-spectrum beta-lactam antimicrobial agents tested against recent clinical isolates from India: a survey of ten medical center laboratories

The widespread use of beta-lactam antimicrobial agents as first-line therapy for the treatment of serious infections has led to the development of various resistances that have compromised the use of some agents. In certain countries, the lack of local or national surveillance programs limits the ability to detect these resistant strains and prevent their dissemination. A 10 medical center study in India was initiated to benchmark prevailing resistance rates for a range of bacterial pathogens to beta-lactams, and it found high rates of beta-lactamase-mediated resistance in Escherichia coli and Klebsiella spp. These rates included: cephalosporins (55.6-61.3% resistance), with extended-spectrum beta-lactamase (ESBL) phenotypes noted in over 60% of E. coli isolates and in Salmonella spp. (3.2-8.1%). Imipenem, a carbapenem, was the only antimicrobial agent tested with 100% activity against Enterobacteriaceae. Cefpirome was the most active of the tested cephalosporins, and all were fully active against methicillin-susceptible staphylococci with the exception of ceftazidime. Molecular and susceptibility characterization of 52 selected ESBL-producing strains showed a high level of co-resistance with aminoglycosides and fluoroquinolones, and clonal dissemination of resistant strains within medical centers. Collaborative studies, such as those presented here, can accurately detect changes in resistance patterns, and their continued use may help limit the further development and spread of bacterial resistances in India.

Distribution of extended-spectrum beta-lactamases in clinical isolates of Enterobacteriaceae in Vietnam

Among 730 Escherichia coli, 438 Klebsiella pneumoniae, and 141 Proteus mirabilis isolates obtained between September 2000 and September 2001 in seven hospitals in Ho Chi Minh City, Vietnam, 26.6% were resistant to ceftazidime, 30% were resistant to cefotaxime, 31.5% were resistant to ceftriaxone, 15.9% were resistant to cefoperazone, and 6% were resistant to cefepime. Resistance to imipenem was found in 5.6% of the isolates. In 55 strains producing extended-spectrum beta-lactamases (32 E. coli isolates, 13 K. pneumoniae isolates, and 10 P. mirabilis isolates), structural genes for VEB-1 (25.5%), CTX-M (25.5%), SHV (38.1%), and TEM (76.3%) enzymes were detected alone or in combination. Sequencing of the PCR products obtained from the K. pneumoniae isolates revealed the presence of bla(VEB-1), bla(CTX-M-14), bla(CTX-M-17), bla(SHV-2), and bla(TEM-1). Molecular typing of the strains with a similar resistance phenotype to broad-spectrum cephalosporins indicated polyclonal spread. ISEcp1 was presumably responsible for dissemination of the bla(CTX-M-like) gene.

A comparison of the antimicrobial activity of meropenem and selected broad-spectrum antimicrobials tested against multi-drug resistant Gram-negative bacilli including bacteraemic Salmonella spp.: initial studies for the MYSTIC programme in India

The evolution in India of multi-drug resistant pathogens possessing extended-spectrum beta-lactamases (ESBLs) threatens to compromise the clinical utility of third-generation cephalosporins and monobactams. Using selected resistant strains from a recent Indian 10 centre surveillance study that measured the prevailing incidence of resistance to beta-lactam antibiotics, the potential clinical utility of meropenem was assessed against nine other antimicrobial agents. A total of 212 Gram-negative bacilli were tested, of which 125 were confirmed by reference methods to be ESBL-producers. Meropenem was the most active of the test antimicrobials against these strains and the rank order of susceptibility was meropenem (99.1% susceptible) > piperacillin/tazobactam (76.9%) > ciprofloxacin (42.5%) > aminoglycosides (34.4-39.6%) = other beta-lactams (30.0-39.6%). Of the tested strains only two (Acinetobacter spp. and Pseudomonas putida) showed an intermediate susceptibility (8 mg/l) to meropenem. Of the 57 tested strains of Salmonella spp., three had an ESBL phenotype, confirmed two of the strains. This study confirms the high levels of resistance to beta-lactams agents in India reported elsewhere and also demonstrates, for Escherichia coli and Klebsiella spp., high levels of co-resistance between the tested beta-lactam agents and ciprofloxacin and the aminoglycosides, gentamicin and tobramycin. However, carbapenems such as meropenem, remain a therapeutic option.

Pathogen occurrence and antimicrobial resistance trends among urinary tract infection isolates in the Asia-Western Pacific Region: report from the SENTRY Antimicrobial Surveillance Program, 1998-1999

Worldwide surveillance of antimicrobial resistance among urinary tract pathogens is useful to determine important trends and geographical variation for common Gram-positive and -negative species. The most common causative uropathogens often have intrinsic or acquired resistance mechanisms which include ESBL production among enteric bacilli, multi-drug resistant staphylococci and non-fermentative Gram-negative bacilli such as Pseudomonas aeruginosa and Acinetobacter spp. and vancomycin-resistant Enterococcus spp. This study evaluates pathogen frequency and the resistance rates among urinary tract infection (UTI) pathogens in 14 medical centres in the Asia-Pacific region between 1998 and 1999. The isolates were referred to a central monitor for reference NCCLS broth microdilution testing, identification confirmation and patient demographic analysis. Over 50% of the 958 pathogens were Escherichia coli and Klebsiella spp. followed by P. aeruginosa, Enterococcus spp. and Enterobacter spp. Susceptibility for the three enteric bacilli was high for carbapenems (100%), 'fourth-generation' cephalosporins (cefepime 94.9-98.6%) and amikacin (> or = 93.0%). Beta-lactamase inhibitor compounds were more active against E. coli (piperacillin/tazobactam; > 90% susceptible) than the other two enteric species and all other tested agents had a narrower spectra of activity. The rank order of anti-pseudomonal agents was amikacin (91.5% susceptible)> imipenem > piperacillin/tazobactam > tobramycin > ceftazidime and cefepime (77.4 and 76.4% susceptible, respectively). Susceptibility to quinolones for the P. aeruginosa isolates was only 63.2-67.0%. Only one vancomycin-intermediate Enterococcus spp. (van C phenotype) was detected among the 103 strains tested. Newer fluoroquinolones (gatifloxacin; MIC(50), mg/l) were more potent against enterococci than ciprofloxacin (MIC(50), 2 mg/l) and high-level resistance to aminoglycosides was common (41.7%). The data presented are compared to studies of similar design from other areas which are part of the SENTRY surveillance network.

In vitro evaluation of cefepime and other broad-spectrum beta-lactams in 22 medical centers in Japan: a phase II trial comparing two annual organism samples. The Japan Antimicrobial Resistance Study Group

An antimicrobial resistance surveillance study in Japan is presented representing the second year (Phase II) results from 22 medical centers. Each participant laboratory tested (Etest, AB BIODISK, Solna, Sweden) 100 organisms, 10 strains each from 10 species groups including Escherichia coli, Klebsiella spp., Enterobacter spp., Citrobacter spp., indole-positive Proteae, Serratia spp., Acinetobacter spp., Pseudomonas aeruginosa, and oxacillin-susceptible Staphylococcus aureus and coagulase-negative staphylococci. Generally only modest variations in the activity of the studied broad-spectrum beta-lactams was observed compared to the study a year before. Specifically, extended spectrum beta-lactamase (ESBL) rates in E. coli increased (2.9 to 8.1%), but the ESBL rate in Klebsiella spp. fell (8.6 to 5.0%). Overall the resistance to the beta-lactams varied from a 4.7% decrease (ceftazidime as a consequence of a modified staphylococcal breakpoint criteria) to a 1.0% increase (cefepime, not significant). The rank order of spectrums in 1998 only changed for cefoperazone-sulbactam (6.1% resistance) that was active against more strains than cefpirome (6.8% resistance). The overall spectrum rank order for the 1998 Japan sample (% resistance) was: cefepime (3.2%) > imipenem (4.1%) > cefoperazone-sulbactam (6.1%) > cefpirome (6.8%) > ceftazidime (8.4%) > piperacillin (19.9%). As with a similar study in 1997, imipenem-resistant isolates of P. aeruginosa and Serratia spp. were discovered with metalloenzymes, usually found in the same medical centers. These results demonstrate the continued in vitro activity and potential sustained clinical efficacy of several broad-spectrum beta-lactams in Japan. Rapid emergence of new or novel resistance were not wide spread using a precise quantitative MIC system. Continued surveillance in this nation would be prudent to document the activity of this clinically valuable class of safe, antimicrobial agents.