Susceptibility to beta-lactam antibiotics and gentamicin of gram-negative bacilli isolated from hospitalized patients: a Swedish multicenter study

Antibiotic consumption and antibiotic stewardship in Swedish hospitals

BACKGROUND

The aim of this paper was to describe and analyze the effect of antibiotic policy changes on antibiotic consumption in Swedish hospitals and to review antibiotic stewardship in Swedish hospitals.

RESULTS

The main findings were: 1) Antibiotic consumption has significantly increased in Swedish hospitals over the last decade. The consumption of cephalosporins has decreased, whereas that of most other drugs including piperacillin-tazobactam, carbapenems, and penicillinase-sensitive and -resistant penicillins has increased and replaced cephalosporins. 2) Invasive infections caused by ESBL-producing Escherichia coli and Klebsiella pneumoniae have increased, but the proportion of pathogens resistant to third-generation cephalosporins causing invasive infections is still very low in a European and international perspective. Furthermore, the following gaps in knowledge were identified: 1) lack of national, regional, and local data on the incidence of antibiotic resistance among bacteria causing hospital-acquired infections e.g. bloodstream infections and hospital-acquired pneumonia-data on which standard treatment guidelines should be based; 2) lack of data on the incidence of Clostridium difficile infections and the effect of change of antibiotic policies on the incidence of C. difficile infections and infections caused by antibiotic-resistant pathogens; and 3) lack of prospective surveillance programs regarding appropriate antibiotic treatment, including selection of optimal antimicrobial drug regimens, dosage, duration of therapy, and adverse ecological effects such as increases in C. difficile infections and emergence of antibiotic-resistant pathogens.

CONCLUSIONS

Evidence-based actions to improve antibiotic use and to slow down the problem of antibiotic resistance need to be strengthened. The effect of such actions should be analyzed, and standard treatment guidelines should be continuously updated at national, regional, and local levels.

Versatility of aminoglycosides and prospects for their future

Aminoglycoside antibiotics have had a major impact on our ability to treat bacterial infections for the past half century. Whereas the interest in these versatile antibiotics continues to be high, their clinical utility has been compromised by widespread instances of resistance. The multitude of mechanisms of resistance is disconcerting but also illuminates how nature can manifest resistance when bacteria are confronted by antibiotics. This article reviews the most recent knowledge about the mechanisms of aminoglycoside action and the mechanisms of resistance to these antibiotics.

High incidence of antibiotic resistance among bacteria in 4 intensive care units at a university hospital in Sweden

The frequency of antibiotic resistance among bacteria in 4 intensive care units (ICUs) at a university hospital in Sweden was investigated annually from 1993 to 1996. An increase in ampicillin-resistant enterococci from 1993 to 1995 was seen which was due to a shift from Enterococcus faecalis to Enterococcus faecium. After a special infection control programme was instituted, the rate of ampicillin resistance among enterococci and the number of E. faecium isolates declined during 1996. The oxacillin resistance rates for Staphylococcus aureus were < or = 2%, while most of the coagulase-negative staphylococci (CNS) were oxacillin resistant. No vancomycin-resistant enterococci or staphylococci were seen. The ciprofloxacin resistance rate for CNS and Enterococci spp. were high. Relatively, high levels of resistance to cefotaxime and piperacillin/tazobactam among Enterobacter spp. were also seen. During 1995 and 1996 Pseudomonas aeruginosa showed increasing resistance to ceftazidime, ciprofloxacin and piperacillin/tazobactam. This was due to an outbreak among rather few patients. The overall resistance rates for Gram-negative bacteria were low for aminoglycosides and imipenem. From 1993 to 1996 the total antibiotic consumption decreased by 27% in the whole hospital and 16.5% in the ICUs. However, the reduced antibiotic consumption was paralleled with a 23% decrease in the total number of patients treated in the hospital from 1993 to 1996. In contrast there was an 11.5% increase in the number of ICU patients treated during this period. The conclusion is that all ICUs within a hospital should have a programme for 'on-line' antibiotic resistance surveillance of drugs used in that unit in order to change the empiric treatment when there is an increase in antibiotic resistance. It is also important to survey the antibiotic consumption in the ICUs in order to avoid further selective pressure on bacteria showing increased resistance rates.

High frequency of antibiotic resistance among Gram-negative isolates in intensive care units at 10 Swedish hospitals

OBJECTIVE: To investigate the resistance rates among Gram-negative isolates in Swedish intensive care units (ICUs). METHODS: During 1994-95, members of the Swedish Study Group collected, on clinical indication, 502 consecutive initial isolates of Gram-negative bacteria from patients admitted to ICUs at 10 Swedish hospitals and performed minimal inhibitory concentration (MIC) determinations with the Etest. Breakpoints were defined according to the criteria of the Swedish Reference Group for Antibiotics (SRGA). RESULTS: The distribution of bacterial species was: Escherichia coli > Klebsiella spp. > Enterobacter spp. > Pseudomonas aeruginosa > Haemophilus spp. > Proteus spp. > Stenotrophomonas maltophilia > Citrobacter spp. > Acinetobacter > Pseudomonas spp. > Morganella morganii > Serratia spp. Together these constituted 97% of all isolates. The frequencies of resistance for all the initial Gram-negative isolates were: ceftazidime 6.8%, cefotaxime 14.9%, ceftriaxone 18.5%, cefuroxime 44.1%, ciprofloxacin 4.2%, co-trimoxazole 17.8%, gentamicin 5.8%, imipenem 8.6%, piperacillin 20.2%, piperacillin/tazobactam 12.9% and tobramycin 5.8%. CONCLUSIONS: Among Gram-negative isolates in Swedish ICUs, a very high frequency of resistance was seen to cefuroxime, and rather high frequencies of resistance to cefotaxime, ceftriaxone, piperacillin and piperacillin/tazobactam. These drugs cannot be recommended for further use as empirical monotherapy for severe ICU-acquired Gram-negative infections in ICUs in Sweden.

Gentamicin-resistant Klebsiella spp. and Escherichia coli in a neonatal intensive care unit

A case of septicemia in a 7-day-old infant with a gentamicin-resistant strain of Klebsiella oxytoca prompted an epidemiological survey in a neonatal unit. Within a 3-month period 7 patients presented with symptomatic infection with gentamicin-resistant gram-negative bacilli. Another 3 patients were asymptomatic and only harboured the organisms in the stool. The aminoglycoside modifying enzyme ANT(2")-a was identified with a probe technique in different gram-negative species indicating the spread of a plasmid. After the replacement of gentamicin with amikacin and the adherence to proper barrier precautions the gentamicin-resistant strains disappeared from the ward.