Henrik Westh - Academia.edu (original) (raw)
Papers by Henrik Westh
Antimicrobial Agents and Chemotherapy, Oct 1, 2006
International Journal of Infectious Diseases, 2010
To elucidate the evolutionary history of Staphylococcus aureus clonal complex (CC) 8, which encom... more To elucidate the evolutionary history of Staphylococcus aureus clonal complex (CC) 8, which encompasses several globally distributed epidemic lineages, including hospital-associated methicillin-resistant S. aureus (MRSA) and the highly prevalent community-associated MRSA clone USA300. Methods: We reconstructed the phylogeny of S. aureus CC8 by mutation discovery at 112 genetic housekeeping loci from each of 174 isolates, sampled on five continents between 1957 and 2008. The distribution of antimicrobial resistance traits and of diverse mobile genetic elements was investigated in relation to the isolates' phylogeny. Results: Our analyses revealed the existence of nine phylogenetic clades within CC8. We identified at least eight independent events of methicillin resistance acquisition in CC8 and dated the origin of a methicillin-resistant progenitor of the notorious USA300 clone to the mid-1970s. Of the S. aureus isolates in our collection, 88% carried plasmidic rep gene sequences, with up to five different rep genes in individual isolates and a total of eight rep families. Mapping the plasmid content onto the isolates' phylogeny illustrated the stable carriage over decades of some plasmids and the more volatile nature of others. Strikingly, we observed trends of increasing antibiotic resistance during the evolution of several lineages, including USA300. Conclusions: We propose a model for the evolution of S. aureus CC8, involving a split into at least nine phylogenetic lineages and a subsequent series of acquisitions and losses of mobile genetic elements that carry diverse virulence and antimicrobial resistance traits. The evolution of MRSA USA300 towards resistance to additional antibiotic classes is of major concern.
BackgroundSeveral viral infections are known to be harmful to the fetus in the first trimester of... more BackgroundSeveral viral infections are known to be harmful to the fetus in the first trimester of pregnancy and can cause increased nuchal translucency thickness and pregnancy loss. Currently, no evidence exists regarding possible effects of SARS-CoV-2 in first trimester pregnancies.MethodsCohort 1 included pregnant women with a double test taken between Feb. 17 and Apr. 23, 2020, during the SARS-CoV-2 epidemic peak in Denmark. The double test was taken as part of the first trimester risk assessment. Cohort 2 included women with a first trimester pregnancy loss before double test. Serum from the double test or from a blood sample, in case of pregnancy loss, was analyzed for SARS-CoV-2 antibodies. The results were correlated to the nuchal translucency thickness and the number of pregnancy losses.ResultsIn total, 1,019 pregnant women with double test and 36 women with pregnancy loss participated in the study. Thirty (2.9%) women had SARS-CoV-2 antibodies in the serum from the double t...
Frontiers in Microbiology, 2018
This study describes a sporadically occurring 4-year outbreak of methicillin-resistant Staphyloco... more This study describes a sporadically occurring 4-year outbreak of methicillin-resistant Staphylococcus aureus (MRSA) originating from a surgical ward. Whole-genome sequencing (WGS) identified the outbreak clone as spa type t267, sequence type ST97, and SCCmec IVa. Prompted by the finding of four patients within 6 months in the same ward with this unusual MRSA type, an outbreak was suspected. Subsequent MRSA screening in the ward in February 2017 identified three-additional patients and two health care workers (HCWs) with t267/ST97-IVa. WGS linked these 9 isolates to 16 previous isolates in our WGS database and the outbreak thus included 23 patients and two HCWs. Twenty-one patients had a connection to the surgery ward during the period 2013-2017, but half of them had MRSA diagnosed in the community long after discharge. The community debut of several patients MRSA infections weeks to months after hospital discharge made the identification of a hospital source difficult and it was the SNP relatedness of the isolates that led us to identify the common denominator of hospitalization. An index patient was not identified, but our hypothesis is that HCWs with unrecognized long-term MRSA colonization could have caused sporadic nosocomial transmission due to intermittent breaches in infection prevention and control practice.
Ugeskrift for Læger, 2016
BackgroundDaptomycin is a cyclic lipopeptide used in the treatment of vancomycin-resistant Entero... more BackgroundDaptomycin is a cyclic lipopeptide used in the treatment of vancomycin-resistant Enterococcus faecium (VREfm). However, the development of daptomycin-resistant VREfm challenges the treatment of nosocomial VREfm infections. Resistance mechanisms of daptomycin are not fully understood. Here we analysed the genomic changes leading to a daptomycin-susceptible VREfm isolate becoming resistant after 40 days of daptomycin and linezolid combination therapy.MethodsThe two isogenic VREfm isolates (daptomycin-susceptible and daptomycin-resistant) were analysed using whole genome sequencing with Illumina and Nanopore.ResultsWhole genome comparative analysis identified the loss of a 46.5 kb fragment and duplication of a 29.7 kb fragment in the daptomycin-resistant isolate, with many implicated genes involved in cell wall synthesis. Two plasmids of the daptomycin-susceptible isolate were also found integrated in the chromosome of the resistant isolate. One nonsynonymous SNP in the rpoC ...
Drug Resistance Updates, 2018
Vancomycin-resistant enterococci (VRE) are important nosocomial pathogens. Invasive VRE infection... more Vancomycin-resistant enterococci (VRE) are important nosocomial pathogens. Invasive VRE infections are difficult to treat since common therapeutic options including ampicillin and glycopeptides often fail. In vitro, most VRE remain susceptible to last-resort antibiotics such as linezolid, tigecycline and daptomycin. However, neither tigecycline nor linezolid act in a bactericidal manner, and daptomycin has proven activity only at high dosages licensed for treating enterococcal endocarditis. Despite these pharmacological and therapeutic limitations, reports on resistance to these last-resort drugs in VRE, and enterococci in general, have increased in recent years. In this review, we briefly recapitulate the current knowledge on the mode of action as well as the known and novel mechanisms of resistance and describe surveillance data on resistance to linezolid, tigecycline and daptomycin in enterococci. In addition, we also suggest a common nomenclature for designating enterococci and VRE with resistances to these important last-resort antibiotics. Enterococcus faecalis have been recognized for decades as major nosocomial pathogens in humans. Moreover, E. faecalis is occasionally implicated in community-associated infections such as urinary tract infections and endocarditis. Members of the genus Enterococcus are known to be versatile
The Lancet, 1995
SiR-Staphylococci, corynebacteria, and propionibacteria are found in the openings of the hair fol... more SiR-Staphylococci, corynebacteria, and propionibacteria are found in the openings of the hair follicles and at the openings of sweat ducts of human skin. After the introduction of ciprofloxacin, resistant S epidermidis and S aureus became a problem in departments which relied heavily upon this new drug.' Antibiotics must reach the skin surface in order to interfere with the skin flora. Possible routes of excretion are the exocrine glands (arms, legs, and most other areas) and the apocrine glands (axilla, inguinal and perineal areas). Little is known about excretion of antibiotics in sweat. We have therefore developed a simple method for measuring the concentration of antibiotics in sweat.
Antimicrobial Agents and Chemotherapy, 2021
Staphylococcus saprophyticus is a common pathogen of the urinary tract, a heavy metal-rich enviro... more Staphylococcus saprophyticus is a common pathogen of the urinary tract, a heavy metal-rich environment, but information regarding its heavy metal resistance is unknown. We investigated 422 S. saprophyticus isolates from human infection and colonization/contamination, animals, and environmental sources for resistance to copper, zinc, arsenic, and cadmium using the agar dilution method.
Hendriksen, Rene S.; Karlsmose Pedersen, Susanne; Larsen, Mette Voldby; Neubert Pedersen, Jamie; ... more Hendriksen, Rene S.; Karlsmose Pedersen, Susanne; Larsen, Mette Voldby; Neubert Pedersen, Jamie; Lukjancenko, Oksana; Kaas, Rolf Sommer; Leekitcharoenphon, Pimlapas; Bergmark, Lasse; Hansen, Inge Marianne; Sintchenko, Vitali; Wolfgang, William J.; Westh, Henrik Torkil; Moran-Gilad, Jacob; Hsiao, William; Cuesta, Isabel; Barrera, Jorge; Zaballos, Angel; Olson, Nathanael David; Beck, Brian; Underwood, Anthony; Aarestrup, Frank Møller; Strain, Errol; Pettengill, James
Consultant, MSc, of the Council on Health and Disease Prevention' s secretariat has been the proj... more Consultant, MSc, of the Council on Health and Disease Prevention' s secretariat has been the project manager and technical editor for the workgroup.
PLoS medicine, 2018
Nucleic Acid Amplification Tests (NAATs) are the recommended test type for diagnosing Chlamydia t... more Nucleic Acid Amplification Tests (NAATs) are the recommended test type for diagnosing Chlamydia trachomatis (chlamydia). However, less sensitive diagnostic methods-including direct immunofluorescence (IF) and enzyme-linked immunoassay (ELISA)-remain in use in lower resourced settings. We estimate the risk of pelvic inflammatory disease (PID) following undiagnosed infection in women tested with non-NAATs and estimate the health gain from using accurate diagnostic tests. We used Denmark's national Chlamydia Study dataset to extract all chlamydia tests performed in women aged 15-34 years (1998-2001). Tests were categorised as non-NAAT (IF/ELISA) or NAAT and limited to each woman's first test in the study period. We linked test data to hospital presentations for PID within 12 months from the Danish National Patient Register. The study included 272,105 women with a chlamydia test, just under half (44.78%, n = 121,857) were tested using NAATs. Overall, 6.38% (n = 17,353) tested po...
Emerging Infectious Diseases, 2017
Journal of Clinical Virology, 2016
Ugeskrift for laeger, Jan 15, 1999
APMIS. Supplementum, 1996
PLoS ONE, 2013
Introduction: The purpose of the study was to describe demographic and clinical characteristics a... more Introduction: The purpose of the study was to describe demographic and clinical characteristics and outbreak handling of a large methicillin-resistant Staphylococcus aureus (MRSA) outbreak in a neonatal intensive care unit (NICU) in Denmark June 25 th-August 8 th 2008, and to identify risk factors for MRSA transmission. Methods: Data were collected retrospectively from medical records and the Danish Neobase database. All MRSA isolates obtained from neonates, relatives and NICU health care workers (HCW) as well as environmental cultures were typed. Results: During the 46 day outbreak period, 102 neonates were admitted to the two neonatal wards. Ninety-nine neonates were subsequently sampled, and 32 neonates (32%) from 25 families were colonized with MRSA (spa-type t127, SCCmec V, PVL negative). Thirteen family members from 11 of those families (44%) and two of 161 HCWs (1%) were colonized with the same MRSA. No one was infected. Five environmental cultures were MRSA positive. In a multiple logistic regression analysis, nasal Continuous Positive Airway Pressure (nCPAP) treatment (p = 0.006) and Caesarean section (p = 0.016) were independent risk factors for MRSA acquisition, whereas days of exposure to MRSA was a risk factors in the unadjusted analysis (p = 0.04). Conclusions: MRSA transmission occurs with high frequency in the NICU during hospitalization with unidentified MRSA neonates. Caesarean section and nCPAP treatment were identified as risk factors for MRSA colonization. The MRSA outbreak was controlled through infection control procedures.
Microbial Drug Resistance, 2004
Antibiotic consumption during 1996 was measured in 15 large hospitals from 14 countries and 3000 ... more Antibiotic consumption during 1996 was measured in 15 large hospitals from 14 countries and 3000 consecutive Staphylococcus aureus samples were collected, allowing calculation of local resistance rates and typing of isolates. Antibiotic consumption data were converted to defined daily doses (DDD), and similar antibiotics were grouped if they belonged to the same therapeutic subgroup. Variations in hospital size were corrected by using DDD per 1000 bed-days. The total antibiotic consumption in the 15 hospitals varied between 296 DDD/1000 bed-days and 1108 DDD/1000 bed-days. Differences in the usage of therapeutical subgroups of antimicrobials varied significantly between hospitals. A positive correlation was found between S. aureus resistance to methicillin (MRSA) and consumption of -lactam combinations, between resistance to quinolones and consumption of -lactam combinations and carbapenems and resistance to aminoglycosides and consumption of -lactam combinations. The consumption of -lactamase-sensitive antibiotics was negatively correlated to resistance to methicillin, quinolones, and aminoglycosides. Usage of the different antimicrobial therapeutical subgroups was also correlated. Consumption of -lactamase-sensitive antibiotics (penicillin) was positively correlated to consumption of -lactamase-resistant penicillins and negatively correlated to consumption of carbapenems, quinolones, and glycopeptides, whereas consumption of cephalosporins was positively correlated to consumption of aminoglycosides, quinolones, and glycopeptides. In this study of hospitals with MRSA prevalence of between 0% and 63%, significant correlations were found between resistance and consumption of antimicrobials. These findings support the importance of antimicrobial consumption on resistance. An accompanying paper addresses the issue of antibiotic resistance and clonality of isolates.
Antimicrobial Agents and Chemotherapy, Oct 1, 2006
International Journal of Infectious Diseases, 2010
To elucidate the evolutionary history of Staphylococcus aureus clonal complex (CC) 8, which encom... more To elucidate the evolutionary history of Staphylococcus aureus clonal complex (CC) 8, which encompasses several globally distributed epidemic lineages, including hospital-associated methicillin-resistant S. aureus (MRSA) and the highly prevalent community-associated MRSA clone USA300. Methods: We reconstructed the phylogeny of S. aureus CC8 by mutation discovery at 112 genetic housekeeping loci from each of 174 isolates, sampled on five continents between 1957 and 2008. The distribution of antimicrobial resistance traits and of diverse mobile genetic elements was investigated in relation to the isolates' phylogeny. Results: Our analyses revealed the existence of nine phylogenetic clades within CC8. We identified at least eight independent events of methicillin resistance acquisition in CC8 and dated the origin of a methicillin-resistant progenitor of the notorious USA300 clone to the mid-1970s. Of the S. aureus isolates in our collection, 88% carried plasmidic rep gene sequences, with up to five different rep genes in individual isolates and a total of eight rep families. Mapping the plasmid content onto the isolates' phylogeny illustrated the stable carriage over decades of some plasmids and the more volatile nature of others. Strikingly, we observed trends of increasing antibiotic resistance during the evolution of several lineages, including USA300. Conclusions: We propose a model for the evolution of S. aureus CC8, involving a split into at least nine phylogenetic lineages and a subsequent series of acquisitions and losses of mobile genetic elements that carry diverse virulence and antimicrobial resistance traits. The evolution of MRSA USA300 towards resistance to additional antibiotic classes is of major concern.
BackgroundSeveral viral infections are known to be harmful to the fetus in the first trimester of... more BackgroundSeveral viral infections are known to be harmful to the fetus in the first trimester of pregnancy and can cause increased nuchal translucency thickness and pregnancy loss. Currently, no evidence exists regarding possible effects of SARS-CoV-2 in first trimester pregnancies.MethodsCohort 1 included pregnant women with a double test taken between Feb. 17 and Apr. 23, 2020, during the SARS-CoV-2 epidemic peak in Denmark. The double test was taken as part of the first trimester risk assessment. Cohort 2 included women with a first trimester pregnancy loss before double test. Serum from the double test or from a blood sample, in case of pregnancy loss, was analyzed for SARS-CoV-2 antibodies. The results were correlated to the nuchal translucency thickness and the number of pregnancy losses.ResultsIn total, 1,019 pregnant women with double test and 36 women with pregnancy loss participated in the study. Thirty (2.9%) women had SARS-CoV-2 antibodies in the serum from the double t...
Frontiers in Microbiology, 2018
This study describes a sporadically occurring 4-year outbreak of methicillin-resistant Staphyloco... more This study describes a sporadically occurring 4-year outbreak of methicillin-resistant Staphylococcus aureus (MRSA) originating from a surgical ward. Whole-genome sequencing (WGS) identified the outbreak clone as spa type t267, sequence type ST97, and SCCmec IVa. Prompted by the finding of four patients within 6 months in the same ward with this unusual MRSA type, an outbreak was suspected. Subsequent MRSA screening in the ward in February 2017 identified three-additional patients and two health care workers (HCWs) with t267/ST97-IVa. WGS linked these 9 isolates to 16 previous isolates in our WGS database and the outbreak thus included 23 patients and two HCWs. Twenty-one patients had a connection to the surgery ward during the period 2013-2017, but half of them had MRSA diagnosed in the community long after discharge. The community debut of several patients MRSA infections weeks to months after hospital discharge made the identification of a hospital source difficult and it was the SNP relatedness of the isolates that led us to identify the common denominator of hospitalization. An index patient was not identified, but our hypothesis is that HCWs with unrecognized long-term MRSA colonization could have caused sporadic nosocomial transmission due to intermittent breaches in infection prevention and control practice.
Ugeskrift for Læger, 2016
BackgroundDaptomycin is a cyclic lipopeptide used in the treatment of vancomycin-resistant Entero... more BackgroundDaptomycin is a cyclic lipopeptide used in the treatment of vancomycin-resistant Enterococcus faecium (VREfm). However, the development of daptomycin-resistant VREfm challenges the treatment of nosocomial VREfm infections. Resistance mechanisms of daptomycin are not fully understood. Here we analysed the genomic changes leading to a daptomycin-susceptible VREfm isolate becoming resistant after 40 days of daptomycin and linezolid combination therapy.MethodsThe two isogenic VREfm isolates (daptomycin-susceptible and daptomycin-resistant) were analysed using whole genome sequencing with Illumina and Nanopore.ResultsWhole genome comparative analysis identified the loss of a 46.5 kb fragment and duplication of a 29.7 kb fragment in the daptomycin-resistant isolate, with many implicated genes involved in cell wall synthesis. Two plasmids of the daptomycin-susceptible isolate were also found integrated in the chromosome of the resistant isolate. One nonsynonymous SNP in the rpoC ...
Drug Resistance Updates, 2018
Vancomycin-resistant enterococci (VRE) are important nosocomial pathogens. Invasive VRE infection... more Vancomycin-resistant enterococci (VRE) are important nosocomial pathogens. Invasive VRE infections are difficult to treat since common therapeutic options including ampicillin and glycopeptides often fail. In vitro, most VRE remain susceptible to last-resort antibiotics such as linezolid, tigecycline and daptomycin. However, neither tigecycline nor linezolid act in a bactericidal manner, and daptomycin has proven activity only at high dosages licensed for treating enterococcal endocarditis. Despite these pharmacological and therapeutic limitations, reports on resistance to these last-resort drugs in VRE, and enterococci in general, have increased in recent years. In this review, we briefly recapitulate the current knowledge on the mode of action as well as the known and novel mechanisms of resistance and describe surveillance data on resistance to linezolid, tigecycline and daptomycin in enterococci. In addition, we also suggest a common nomenclature for designating enterococci and VRE with resistances to these important last-resort antibiotics. Enterococcus faecalis have been recognized for decades as major nosocomial pathogens in humans. Moreover, E. faecalis is occasionally implicated in community-associated infections such as urinary tract infections and endocarditis. Members of the genus Enterococcus are known to be versatile
The Lancet, 1995
SiR-Staphylococci, corynebacteria, and propionibacteria are found in the openings of the hair fol... more SiR-Staphylococci, corynebacteria, and propionibacteria are found in the openings of the hair follicles and at the openings of sweat ducts of human skin. After the introduction of ciprofloxacin, resistant S epidermidis and S aureus became a problem in departments which relied heavily upon this new drug.' Antibiotics must reach the skin surface in order to interfere with the skin flora. Possible routes of excretion are the exocrine glands (arms, legs, and most other areas) and the apocrine glands (axilla, inguinal and perineal areas). Little is known about excretion of antibiotics in sweat. We have therefore developed a simple method for measuring the concentration of antibiotics in sweat.
Antimicrobial Agents and Chemotherapy, 2021
Staphylococcus saprophyticus is a common pathogen of the urinary tract, a heavy metal-rich enviro... more Staphylococcus saprophyticus is a common pathogen of the urinary tract, a heavy metal-rich environment, but information regarding its heavy metal resistance is unknown. We investigated 422 S. saprophyticus isolates from human infection and colonization/contamination, animals, and environmental sources for resistance to copper, zinc, arsenic, and cadmium using the agar dilution method.
Hendriksen, Rene S.; Karlsmose Pedersen, Susanne; Larsen, Mette Voldby; Neubert Pedersen, Jamie; ... more Hendriksen, Rene S.; Karlsmose Pedersen, Susanne; Larsen, Mette Voldby; Neubert Pedersen, Jamie; Lukjancenko, Oksana; Kaas, Rolf Sommer; Leekitcharoenphon, Pimlapas; Bergmark, Lasse; Hansen, Inge Marianne; Sintchenko, Vitali; Wolfgang, William J.; Westh, Henrik Torkil; Moran-Gilad, Jacob; Hsiao, William; Cuesta, Isabel; Barrera, Jorge; Zaballos, Angel; Olson, Nathanael David; Beck, Brian; Underwood, Anthony; Aarestrup, Frank Møller; Strain, Errol; Pettengill, James
Consultant, MSc, of the Council on Health and Disease Prevention' s secretariat has been the proj... more Consultant, MSc, of the Council on Health and Disease Prevention' s secretariat has been the project manager and technical editor for the workgroup.
PLoS medicine, 2018
Nucleic Acid Amplification Tests (NAATs) are the recommended test type for diagnosing Chlamydia t... more Nucleic Acid Amplification Tests (NAATs) are the recommended test type for diagnosing Chlamydia trachomatis (chlamydia). However, less sensitive diagnostic methods-including direct immunofluorescence (IF) and enzyme-linked immunoassay (ELISA)-remain in use in lower resourced settings. We estimate the risk of pelvic inflammatory disease (PID) following undiagnosed infection in women tested with non-NAATs and estimate the health gain from using accurate diagnostic tests. We used Denmark's national Chlamydia Study dataset to extract all chlamydia tests performed in women aged 15-34 years (1998-2001). Tests were categorised as non-NAAT (IF/ELISA) or NAAT and limited to each woman's first test in the study period. We linked test data to hospital presentations for PID within 12 months from the Danish National Patient Register. The study included 272,105 women with a chlamydia test, just under half (44.78%, n = 121,857) were tested using NAATs. Overall, 6.38% (n = 17,353) tested po...
Emerging Infectious Diseases, 2017
Journal of Clinical Virology, 2016
Ugeskrift for laeger, Jan 15, 1999
APMIS. Supplementum, 1996
PLoS ONE, 2013
Introduction: The purpose of the study was to describe demographic and clinical characteristics a... more Introduction: The purpose of the study was to describe demographic and clinical characteristics and outbreak handling of a large methicillin-resistant Staphylococcus aureus (MRSA) outbreak in a neonatal intensive care unit (NICU) in Denmark June 25 th-August 8 th 2008, and to identify risk factors for MRSA transmission. Methods: Data were collected retrospectively from medical records and the Danish Neobase database. All MRSA isolates obtained from neonates, relatives and NICU health care workers (HCW) as well as environmental cultures were typed. Results: During the 46 day outbreak period, 102 neonates were admitted to the two neonatal wards. Ninety-nine neonates were subsequently sampled, and 32 neonates (32%) from 25 families were colonized with MRSA (spa-type t127, SCCmec V, PVL negative). Thirteen family members from 11 of those families (44%) and two of 161 HCWs (1%) were colonized with the same MRSA. No one was infected. Five environmental cultures were MRSA positive. In a multiple logistic regression analysis, nasal Continuous Positive Airway Pressure (nCPAP) treatment (p = 0.006) and Caesarean section (p = 0.016) were independent risk factors for MRSA acquisition, whereas days of exposure to MRSA was a risk factors in the unadjusted analysis (p = 0.04). Conclusions: MRSA transmission occurs with high frequency in the NICU during hospitalization with unidentified MRSA neonates. Caesarean section and nCPAP treatment were identified as risk factors for MRSA colonization. The MRSA outbreak was controlled through infection control procedures.
Microbial Drug Resistance, 2004
Antibiotic consumption during 1996 was measured in 15 large hospitals from 14 countries and 3000 ... more Antibiotic consumption during 1996 was measured in 15 large hospitals from 14 countries and 3000 consecutive Staphylococcus aureus samples were collected, allowing calculation of local resistance rates and typing of isolates. Antibiotic consumption data were converted to defined daily doses (DDD), and similar antibiotics were grouped if they belonged to the same therapeutic subgroup. Variations in hospital size were corrected by using DDD per 1000 bed-days. The total antibiotic consumption in the 15 hospitals varied between 296 DDD/1000 bed-days and 1108 DDD/1000 bed-days. Differences in the usage of therapeutical subgroups of antimicrobials varied significantly between hospitals. A positive correlation was found between S. aureus resistance to methicillin (MRSA) and consumption of -lactam combinations, between resistance to quinolones and consumption of -lactam combinations and carbapenems and resistance to aminoglycosides and consumption of -lactam combinations. The consumption of -lactamase-sensitive antibiotics was negatively correlated to resistance to methicillin, quinolones, and aminoglycosides. Usage of the different antimicrobial therapeutical subgroups was also correlated. Consumption of -lactamase-sensitive antibiotics (penicillin) was positively correlated to consumption of -lactamase-resistant penicillins and negatively correlated to consumption of carbapenems, quinolones, and glycopeptides, whereas consumption of cephalosporins was positively correlated to consumption of aminoglycosides, quinolones, and glycopeptides. In this study of hospitals with MRSA prevalence of between 0% and 63%, significant correlations were found between resistance and consumption of antimicrobials. These findings support the importance of antimicrobial consumption on resistance. An accompanying paper addresses the issue of antibiotic resistance and clonality of isolates.