Low antibiotic resistance rates in Staphylococcus aureus, Escherichia coli and Klebsiella spp but not in Enterobacter spp and Pseudomonas aeruginosa: a prospective observational study in 14 Swedish ICUs over a 5-year period

BACKGROUND

Intensive care units (ICUs) are hot zones for emergence and spread of antibiotic resistance because of frequent invasive procedures, antibiotic usage and transmission of bacteria. We report prospective data on antibiotic use and bacterial resistance from 14 academic and non-academic ICUs, participating in the ICU-STRAMA programme 1999-2003.

METHODS

The quantity of antibiotics delivered to each ICU was calculated as defined daily doses per 1,000 occupied bed days (DDD(1,000)). Specimens for culture were taken on clinical indications and only initial isolates were considered. Species-related breakpoints according to the Swedish Reference Group for Antibiotics were used. Antibiotic resistance was defined as the sum of intermediate and resistant strains.

RESULTS

Mean antibiotic use increased from 1,245 DDD(1,000) in 1999 to 1,510 DDD(1,000) in 2003 (P = 0.11 for trend). Of Staphylococcus aureus, 0-1.8% were methicillin resistant (MRSA). A presumptive extended spectrum beta-lactamase (ESBL) phenotype was found in <2.4% of Escherichia coli, based on cefotaxime susceptibility, except a peak in 2002 (4.6%). Cefotaxime resistance was found in 2.6-4.9% of Klebsiella spp. Rates of resistance among Enterobacter spp. to cefotaxime (20-33%) and among Pseudomonas aeruginosa to imipenem (22-33%) and ciprofloxacin (5-21%) showed no time trend.

CONCLUSION

MRSA and cefotaxime-resistant E. coli and Klebsiella spp strains were few despite high total antibiotic consumption. This may be the result of a slow introduction of resistant strains into the ICUs, and good infection control. The cause of imipenem and ciprofloxacin resistance in P. aeruginosa could reflect the increased consumption of these agents plus spread of resistant clones.

Mutations in fusA associated with posttherapy fusidic acid resistance in Clostridium difficile

In silico, we identified fusA (2,067 bp) in Clostridium difficile 630. Sequencing of fusA in posttherapy fusidic acid-resistant C. difficile isolates from 12 patients with C. difficile-associated diarrhea (CDAD) identified fusA mutations, one or two nonsynonymous substitutions, or in one case a deletion of one codon associated with resistance. Five of these mutations have previously been described in fusA of fusidic acid-resistant Staphylococcus aureus, but seven were novel fusA mutations. Fusidic acid monotherapy for CDAD seemed to rapidly select conserved resistant mutants.

Frequent emergence of resistance in Clostridium difficile during treatment of C. difficile-associated diarrhea with fusidic acid

Samples from patients with Clostridium difficile-associated diarrhea (CDAD) that were randomized to fusidic acid (n = 59) or metronidazole (n = 55) therapy for 7 days were cultured for Clostridium difficile in feces on days 1, 8 to 13, and 35 to 40. Of the patients who were culture positive only before treatment, 77% (36/47) were permanently cured (no treatment failure and no clinical recurrence), compared to 54% (22/41) of those with persistence of C. difficile at one or both follow-ups (P = 0.03). A similar association between bacterial persistence and a worse outcome of therapy was seen in both treatment groups. Resistance to fusidic acid was found in 1 of 88 pretherapy isolates available, plus in at least 1 subsequent isolate from 55% (11/20) of patients who remained culture-positive after fusidic acid therapy. In 10 of these 11 patients, the resistant follow-up isolate(s) belonged to the same PCR ribotype as the susceptible day 1 isolate, confirming frequent emergence of resistance to fusidic acid during treatment. Despite this, 5 of these 11 patients were permanently cured with fusidic acid, relative to 5 of 9 patients with susceptible C. difficile at follow-up (P = 1.0). None of the 36 PCR ribotypes of C. difficile identified was associated with any particular clinical outcome or emergence of fusidic acid resistance. In conclusion, culture positivity for C. difficile was common after both fusidic acid and metronidazole therapy and was associated with treatment failure or recurrence of CDAD. Development of resistance in C. difficile was frequent in patients given fusidic acid, but it was without apparent negative impact on therapeutic efficacy in the actual CDAD episode.

Further bacteriological evaluation of the TOUL mobile system delivering ultra-clean air over surgical patients and instruments

Two mobile TOUL-400 units (types 1 and 2) that produce an exponential ultra-clean air flow (EUA) via a mobile screen were evaluated (maximum height from floor to centre of screen: type 1, 1.4m; type 2, 1.6m). Bacterial deposition rates were lowered by >60% (P=0.001) over a table area of 1.7 m (length)x1.0m (width) with the TOUL-400 type 1 unit, and the mean air count at 1.0m from the screen was reduced from 23 to 1.6 colony-forming units (CFU)/m3 in experiments in a room with six air changes/h (ACH). The corresponding reductions were two- to three-fold greater in an operating room (OR) with 16 ACH due to higher bacterial contamination levels in the control experiments. The dramatic but localized reduction of the deposition rate recorded on one 14-cm settle plate (>2376-fold at 0.8m from the screen in the OR) apparently reflected the focus of the EUA. The impact of the TOUL-400 unit was underestimated by almost 100-fold by the air counts of bacteria recorded in parallel at the same sampling point (26.5-fold reduction). During sham coronary angiography and sham hip arthroplasty performed in a room with six ACH, ultra-clean air (<10 CFU/m3) was obtained over the incision area with the TOUL-400 type 2 unit when the EUA was undisturbed (maximum screen-wound distance 1.7 m). In actual coronary angiography (room with six ACH, screen-wound distance 2.0-2.3m) and various surgical procedures in the OR (screen-wound distance 1.4-1.8m), ultra-clean air was obtained at the wound in three of 18 instances, characterized by undisturbed air flow and a maximum distance of 1.8 m. The newly developed TOUL-300 surgical instrument table (1.3-1.7 x 0.6m), equipped at one end with the same EUA unit as the TOUL-400 unit, was evaluated for a room with six ACH and an OR with 16 ACH. It yielded ultra-clean air at 0.8m (1.9 CFU/m3, 96% reduction, P=0.01) and reduced the deposition rate by >60% over most of the table surface. Simplified positioning of the screen or a longer reach, plus a mechanism for precise focusing of the air flow on to the wound area would increase the clinical utility of the TOUL EUA system.

Molecular epidemiology of hospital-associated and community-acquired Clostridium difficile infection in a Swedish county

All episodes of Clostridium difficile associated diarrhea (CDAD) diagnosed in a defined population of 274,000 including one tertiary and two primary hospitals and their catchment areas were studied during 12 months. The annual CDAD incidence in the county was 97 primary episodes per 100,000, and 78% of all episodes were classified as hospital associated with a mean incidence of 5.3 (range, 1.4 to 6.5) primary episodes per 1,000 admissions. The incidence among hospitalized individuals was 1,300-fold higher than that in the community (33,700 versus 25 primary episodes per 100,000 persons per year), reflecting a 37-fold difference in antibiotic consumption (477 versus 13 defined daily doses [DDD]/1,000 persons/day) and other risk factors. Three tertiary hospital wards with the highest incidence (13 to 36 per 1,000) had CDAD patients of high age (median age of 80 years versus 70 years for other wards, P < 0.001), long hospital stay (up to 25 days versus 4 days), or a high antibiotic consumption rate (up to 2,427 versus 421 DDD/1,000 bed days). PCR ribotyping of C. difficile isolates available from 330 of 372 CDAD episodes indicated nosocomial acquisition of the strain in 17 to 27% of hospital-associated cases, depending on the time interval between index and secondary cases allowed (2 months or up to 12 months), and only 10% of recurrences were due to a new strain of C. difficile (apparent reinfection). In other words, most primary and recurring episodes were apparently caused by the patient's endogenous strain rather than by one of hospital origin. Typing also indicated that a majority of C. difficile strains belonged to international serotypes, and the distribution of types was similar within and outside hospitals and in primary and relapsing CDAD. However, type SE17 was an exception, comprising 22% of hospital isolates compared to 6% of community isolates (P = 0.008) and causing many minor clusters and a silent nosocomial outbreak including 36 to 44% of the CDAD episodes in the three high-incidence wards.

Clonality among ampicillin-resistant Enterococcus faecium isolates in Sweden and relationship with ciprofloxacin resistance

OBJECTIVE

To investigate clonal relationships in a nationwide sample of human Enterococcus faecium isolates.

METHODS

Biochemical fingerprinting (PhP (PhenePlate) typing) was used to compare 180 fecal ampicillin-resistant E. faecium (ARE) isolates with 169 matched fecal ampicillin-susceptible E. faecium (ASE) isolates from patients in 23 hospitals, collected in 1998, and to study 39 fecal ARE isolates from non-hospitalized individuals collected in 1998, and five ARE and 29 ASE isolates from the early 1990s. Representative ARE and ASE isolates were subjected to pulsed-field gel electrophoresis (PFGE) analysis of genomic DNA and sequencing of the regions encoding the fluoroquinolone targets of the enzymes GyrA and ParC.

RESULTS

Both PhP and PFGE results showed a higher homogeneity among ARE than among ASE isolates (P < 0.001). One PhP type (FMSE1) comprised 73% of the hospital ARE isolates (53% of ARE isolates from non-hospitalized individuals, and four of five ARE isolates from the early 1990s), but only 1% of the ASE isolates. PFGE of the hospital E. faecium isolates revealed that 23 of the 25 ARE isolates and one of the 22 ASE isolates were of one dominating type. High-level resistance to ciprofloxacin (MIC > 16 mg/L) was present in 91% of ARE isolates, whereas only low-level resistance (MIC 4-16 mg/L; 35% of isolates) was found among ASE isolates. One mutation in parC (codon 80) and one of two mutations in gyrA (codons 83 or 87) were detected in all ARE isolates tested with high-level ciprofloxacin resistance, but were lacking in ARE and ASE isolates with low-level ciprofloxacin resistance.

CONCLUSION

Most ARE isolates in Sweden were clonally related. High-level ciprofloxacin resistance was found in ARE isolates of PhP type FMSE1 as well as in other PhP types, but never in ASE isolates.

Clonal Analysis ofStreptococcus pneumoniaeNonsusceptible to Penicillin at Day-Care Centers with Index Cases, in a Region with Low Incidence of Resistance: Emergence of an Invasive Type 35B Clone among Carriers

The nasopharyngeal carriage rate of potential respiratory pathogens was studied in 36 index children with a pneumococci nonsusceptible to penicillin (PNSP), in 595 healthy children, and in 123 personnel at 16 day-care centers (DCCs) with index cases in the Stockholm area, an urban area with a low incidence of antibiotic resistant pneumococci, during the winter of 1997-1998. The spread and clonality of PNSP, Haemophilus influenzae and Moraxella catarrhalis, were studied by analyzing antibiotic susceptibility and serotype, and for PSNP also by using pulsed-field electrophoresis (PFGE) and multilocus sequence typing (MLST). In contrast to the low carriage rate found among the adult contacts (2%), 40% of the children harbored pneumococci, of which 20% were PNSP. Nasopharyngeal colonization decreased with age. The 49 PNSP isolates consisted of 20 clones, of which 10 could be identified in more than one child attending the same or different DCCs. In five DCCs, we observed a spread of PNSP from the index case. A novel PNSP clone of type 35B, found to cause invasive disease in several states in the United States, was found to emerge among several carriers at two DCCs . A high proportion of PNSP isolates were multiresistant to antibiotics (34%), which has implications for treatment regimens, even in a country like Sweden where the proportion of PNSP currently is low (3-4%). One PNSP clone of type 9V found among the carriers, has been shown to cause invasive disease in Sweden as well as in other countries, suggesting that one reason for the occurrence of invasive PNSP clones may be their ability to colonize and spread among healthy carriers. Other internationally spread antibiotic resistant pneumococcal clones found were of types 9V, 19F, and 23F.

Comparison of AP-PCR typing and PCR-ribotyping for estimation of nosocomial transmission of Clostridium difficile

We recently attempted to clarify an increased incidence of Clostridium difficile-associated diarrhoea (CDAD) in our hospital by arbitrarily primed polymerase chain reaction (AP-PCR) typing of isolates from 147 consecutive patients collected during a 12 month period (Wullt et al. J Hosp Infect 1999;43:265-273). In the present study we compared the results based on previous AP-PCR data with those based on recent PCR ribotyping of the same isolates and re-analysis of a subset of isolates by AP-PCR typing. The pattern of PCR ribotypes was similar among inpatients and outpatients. A cluster of three closely related PCR ribotypes, related to those of the serogroup H and A8 type strains, dominated and comprised 31% of inpatient and 28% of outpatient C. difficile isolates. The apparent nosocomial transmission rate among inpatients with CDAD was only 9% by AP-PCR typing compared with 18 or 36% by PCR ribotyping depending on the definition used (proportion of patients sharing C. difficile type and ward within two or 12 months). Corresponding rates for all CDAD patients were 5% by AP-PCR and 11 or 21% by PCR ribotyping. Thus, most CDAD patients apparently became ill due to their endogenous strain of C. difficile. Because of the low concordance between the two typing methods the proportion of patients fulfilling the criteria for nosocomial transmission by both methods was only 1%. Re-examination of isolates from patients with recurrences revealed a reproducibility problem with AP-PCR typing. We conclude, that of these two PCR-based options for typing of C. difficile PCR ribotyping offers a superior experimental robustness compared with AP-PCR typing.

Antibiotic prescription practices, consumption and bacterial resistance in a cross section of Swedish intensive care units

BACKGROUND

The purpose of this work was to study usage of antibiotics, its possible determinants, and patterns of bacterial resistance in Swedish intensive care units (ICUs).

METHODS

Prospectively collected data on species and antibiotic resistance of clinical isolates and antibiotic consumption specific to each ICU in 1999 were analyzed together with answers to a questionnaire. Antibiotic usage was measured as defined daily doses per 1000 occupied bed days (DDD1000).

RESULTS

Data were obtained for 38 ICUs providing services to a population of approximately 6 million. The median antibiotic consumption was 1257 DDD1000 (range 584-2415) and correlated with the length of stay but not with the illness severity score or the ICU category. Antibiotic consumption was higher in the ICUs lacking bedside devices for hand disinfection (2193 vs. 1214 DDD1000, p=0.05). In the ICUs with a specialist in infectious diseases responsible for antibiotic treatment the consumption pattern was different only for use of glycopeptides (58% lower usage than in other ICUs: 26 vs. 11 DDD1000,P=0.02). Only 21% of the ICUs had a written guideline on the use of antibiotics, 57% received information on antibiotic usage at least every 3 months and 22% received aggregated resistance data annually. Clinically significant antimicrobial resistance was found among Enterbacter spp. to cephalosporins and among Enterococcus spp. to ampicillin.

CONCLUSIONS

Availability of hand disinfection equipment at each bed and a specialist in infectious diseases responsible for antibiotic treatment were factors that correlated with lower antibiotic consumption in Swedish ICUs, whereas patient-related factors were not associated with antibiotic usage.

Surgical area contamination--comparable bacterial counts using disposable head and mask and helmet aspirator system, but dramatic increase upon omission of head-gear: an experimental study in horizontal laminar air-flow

The effect of different head coverings on air-borne transmission of bacteria and particles in the surgical area was studied during 30 strictly standardized sham operations performed in a horizontal laminar air flow (LAF) unit. The operating team members wore disposable gowns plus either a non-sterile head covering consisting of a squire type disposable hood and triple laminar face mask, a sterilized helmet aspirator system or no head cover at all. In the wound area both types of head cover resulted in low and comparable air (means of 8 and 4cfu/m(3)) and surface contamination (means of 69 and 126cfu/m(2)/h) rates. Omission of head-gear resulted in a three- to five-fold increase (P > or = 0.01- 0.001), depending on site sampled air contamination rate (mean of 22cfu/m(3)) whereas the bacterial sedimentation rate in the wound area increased about 60-fold ( P > or = 0.0001). A proper head cover minimized the emission of apparently heavy particles that were not removed by the horizontal LAF and contained mainly streptococci, presumably of respiratory tract origin. Dust particle counts revealed no differences between the three experimental situations. No correlation between air and surface contamination rates or between air contamination and air particle counts was found. We conclude that, from a bacteriological point of view, disposable hoods of squire type and face masks are equally as efficient as a helmet aspirator system and both will efficiently contain the substantial emission of bacteria-carrying droplets from the respiratory tract occurring when head cover is omitted. Finally, the use of bacterial air counts to assess surgical site surface contamination in horizontal LAF units must be seriously questioned.

Toxins, butyric acid, and other short-chain fatty acids are coordinately expressed and down-regulated by cysteine in Clostridium difficile

It was recently found that a mixture of nine amino acids down-regulate Clostridium difficile toxin production when added to peptone yeast extract (PY) cultures of strain VPI 10463 (S. Karlsson, L. G. Burman, and T. Akerlund, Microbiology 145:1683-1693, 1999). In the present study, seven of these amino acids were found to exhibit a moderate suppression of toxin production, whereas proline and particularly cysteine had the greatest impact, on both reference strains (n = 6) and clinical isolates (n = 28) of C. difficile (>99% suppression by cysteine in the highest toxin-producing strain). Also, cysteine derivatives such as acetylcysteine, glutathione, and cystine effectively down-regulated toxin expression. An impact of both cysteine and cystine but not of thioglycolate on toxin yield indicated that toxin expression was not regulated by the oxidation-reduction potential. Several metabolic pathways, including butyric acid and butanol production, were coinduced with the toxins in PY and down-regulated by cysteine. The enzyme 3-hydroxybutyryl coenzyme A dehydrogenase, a key enzyme in solventogenesis in Clostridium acetobutylicum, was among the most up-regulated proteins during high toxin production. The addition of butyric acid to various growth media induced toxin production, whereas the addition of butanol had the opposite effect. The results indicate a coupling between specific metabolic processes and toxin expression in C. difficile and that certain amino acids can alter these pathways coordinately. We speculate that down-regulation of toxin production by the administration of such amino acids to the colon may become a novel approach to prophylaxis and therapy for C. difficile-associated diarrhea.

Angiotensin II type 1 receptor antagonist (losartan) down-regulates transforming growth factor-beta in experimental acute pyelonephritis

PURPOSE

To study the effect of an angiotensin II type 1 receptor antagonist, losartan, on cytokine expression, kidney growth and renal scarring in experimental acute pyelonephritis.

MATERIALS AND METHODS

Female Bki NMRI mice, 8 weeks old were infected with E. coli CFT 073 via the urethra. Mice were divided into four groups; either left untreated; or treated with NaCl 0.9%; or an angiotensin II type 1 receptor antagonist, losartan, in doses of 1 mg. or 40 mg. /kg. body weight. The treatment was given daily i.p. for 48 hours, 3 weeks or 8 weeks respectively. Kidneys were weighed and sectioned for histo-pathology and in situ hybridization for mRNA of IL-1beta, TNF-alpha, IL-4, IL-6, IL-10, IL-12, TGF-beta and IFN-gamma. Homogenized kidneys were used for EIA of TGF-beta and bacterial growth.

RESULTS

The mRNA expression of the studied cytokines generally peaked at 48 hours in all four groups. In animals treated with losartan, kidney TGF-beta, IFN-gamma and IL-6 decreased significantly at 3 and 8 weeks as compared with controls, untreated or those treated with NaCl, (p <0.005 respectively). Infection was associated with a declining kidney weight, also in the presence of losartan. A 50% reduction of the spread of renal scarring was observed in the losartan treated group, but this did however not reach significance. The proportion of kidneys showing bacterial growth was not influenced by losartan although in these kidneys the mean bacterial counts at 3 weeks were significantly higher in the losartan treated mice (p <0.006).

CONCLUSIONS

Losartan is associated with downregulation of TGF-beta, IFN-gamma and IL-6 and may, in combination with antimicrobial therapy, reduce the risk of cortical renal scarring in recurrent acute pyelonephritis in infants.

Epidemiology and ecology of enterococci, with special reference to antibiotic resistant strains, in animals, humans and the environment. Example of an ongoing project within the European research programme

The objectives of the present study are to generate knowledge of the ecology and epidemiology of enterococci in the food chain by studying the following: (1) the population structure (in measures of abundance, number of vancomycin resistant strains, antibiotic resistance patterns, diversity, and stability) among enterococcal populations in different geographical regions and in different links of the food chain (2) possible transmission of strains through the food chain and between hospital environments and the food chain (3) the association between vancomycin resistance and individual strains of enterococci and (4) the diversity of the drug resistance genes in enterococci. So far, 1578 samples have been collected from different countries within the EU (Sweden, Denmark, UK and Spain), and from different habitats (pig farms, carcasses in slaughter houses, soil, manure, water, sewage, and humans). Total and vancomycin resistant enterococcal populations in each sample have been enumerated and more than 12000 isolates have been characterised by phenotyping. Representative isolates are further species identified and characterised by genotyping and MIC determination and from antibiotic resistant isolates the resistance genes are characterised.

Near absence of vancomycin-resistant enterococci but high carriage rates of quinolone-resistant ampicillin-resistant enterococci among hospitalized patients and nonhospitalized individuals in Sweden

Rates of colonization with enterococci with acquired resistance to vancomycin (vancomycin-resistant enterococci [VRE]) and ampicillin (ampicillin-resistant enterococci [ARE]) were determined by using fecal samples from 670 nonhospitalized individuals and 841 patients in 27 major hospitals. Of the hospitalized patients, 181 (21.5%) were carriers of ARE and 9 (1.1%) were carriers of VRE. In univariate analyses, length of hospital stay (odds ratio [OR], 4.6; 95% confidence interval [CI], 2.5 to 8.9) and antimicrobial therapy (OR, 4.7; 95% CI, 3.3 to 6.7) were associated with ARE colonization, as were prior treatment with penicillins (OR, 3.1; 95% CI, 1.8 to 5. 5), cephalosporins (OR, 2.9; 95% CI, 1.7 to 5.0), or quinolones (OR, 2.7; 95% CI, 1.5 to 4.7). In logistic regression analysis, antimicrobial therapy for at least 5 days was independently associated with ARE carriage (adjusted OR, 3.8; 95% CI, 2.6 to 5.4). Over 90% of the ARE isolates were fluoroquinolone resistant, whereas 14% of the ampicillin-susceptible Enterococcus faecium isolates were fluoroquinolone resistant. ARE carriage rates correlated with the use of fluoroquinolones (P = 0.04) but not with the use of ampicillin (P = 0.68) or cephalosporins (P = 0.40). All nine VRE isolates were E. faecium vanB and were found in one hospital. Seven of these isolates were related according to their types as determined by pulsed-field gel electrophoresis. Among the nonhospitalized individuals, the ARE carriage rate was lower (6%; P < 0.05), and only one person, who had recently returned from Africa, harbored VRE (E. faecium vanA). The absence of VRE colonization in nonhospitalized individuals reflects an epidemiological situation in Sweden radically different from that in countries in continental Europe where glycopeptides have been widely used for nonmedical purposes.

Inconsistent correlation between aerobic bacterial surface and air counts in operating rooms with ultra clean laminar air flows: proposal of a new bacteriological standard for surface contamination

The relationship between surface contamination (cfus/m2/h) with particles carrying aerobic bacteria and corresponding air contamination rates (cfus/m3) was evaluated in operating rooms (OR) equipped with ultra clean vertical or horizontal laminar airflow (LAF). For the evaluation we collected data during strictly standardized sham operations using non-woven disposable or cotton clothing. Air contamination in the wound and instrument areas (Casella slit sampler) was related to the surface contamination rate (settle plates) in the same areas and in addition, on the patient chest. Typically, the mean surface counts were 20-70 cfus/m2/h and the air counts 1-2 cfus/m3 in disposable clothing experiments, whilst the use of cotton clothing resulted in higher counts of 100-200 cfus/m2/h (wound P > 0.05, patient P > 0.05, instruments P < 0.01) and 4 cfus/m3 (P < 0.02-0.001). In the vertical LAF, taking both disposable and cotton clothing operations together, the surface and air contamination rates (surface/air ratio SAR) were highly correlated (P = 0.02-0.004) and the ratio varied between 18:1 and 50:1 with a mean for wound air of 36:1. Using only disposable clothing in the vertical LAF, the number of significant correlations was reduced. With cotton clothing experiments in vertical LAF and in the horizontal LAF using disposable clothing, no significant correlation between surface and air contamination was found. The wide variation of SAR values and the inconsistent relationship between surface and air counts indicates that measurement of OR air contamination represents an unhelpful method for assessment of surgical site contamination in LAF units. We propose instead that colony counts on sedimentation plates is a clinically more relevant indicator of bacterial OR contamination in LAF units. In addition to the current bacteriological standard for ultra clean OR air of (< 10 cfus/m3) we suggest a corresponding standard for the surface contamination rate of < 350 cfus/m2/h.

Correlation between surface and air counts of particles carrying aerobic bacteria in operating rooms with turbulent ventilation: an experimental study

Airborne contamination with bacteria-carrying particles (cfu/m3) and their sedimentation rate (cfu/m2/h) was compared in an operating room (OR) equipped with two turbulent ventilation systems. One was a thermally based system with inlet of cool clean air at the floor level and evacuation of the air at the ceiling by convection (17 air changes/h). The other was a conventional plenum pressure system with air supply at the ceiling and evacuation at the floor level (16 air changes/h). The study was made during rigidly standardised sham operations (N = 20) performed in the same OR by the same six member team wearing non-woven disposable or cotton clothing. Airborne contamination in the wound and instrument areas was related to the surface contamination rate in the same areas and in addition, on the patient chest and in the periphery of the OR. With the exception of the periphery of the OR, the surface and air contamination rates were highly correlated in both ventilation systems (P = 0.02-0.0006, r2 = 0.52-0.79). This was also true particularly when disposable clothing was used while the correlation was weaker in cotton clothing experiments. An equation describing the relation between surface and air counts is given. Typically, the surface counts were numerically 16-fold the air counts, i.e., the number of colonies sedimenting on four 14 cm-diameter agar plates during 1 h will almost equal the number of airborne cfu per m3. We propose, that sedimentation plates represent not only a technically easier method than air sampling but when correctly used, are also the most realistic indicator of airborne bacterial OR contamination in areas critical for surgery.

Control of an outbreak of a highly beta-lactam-resistant Enterobacter cloacae strain in a neonatal special care unit

Two successive outbreaks of colonization and infection with Enterobacter cloacae resistant to third generation cephalosporins (cephalosporin-resistant E. cloacae, CREC) and involving 15 infants occurred within 12 months in a neonatal special care unit. Isolates of clinical significance were obtained from four infants (urine 2 cases, blood, pleural drainage). According to epidemiological typing using computerized biochemical fingerprinting and pulsed-field gel electrophoresis (PFGE) the same CREC strain was found in both outbreaks. The origin of the strain and its reservoir between the two outbreaks remained unknown. Emphasizing strict barrier nursing of the infants had little or no impact on the presence and transmission of the strain in the unit. In contrast, replacing ampicillin plus cefotaxime as standard empiric therapy with penicillin G plus netilmicin plus consequent cohorting of newborns and staff promptly halted both the outbreaks. During a 5-y follow-up after the last episode, the choice of antibiotics for empirical treatment has varied, and no further outbreaks of CREC have been seen, with the exception of two sporadic cases.

Zoned exponential, vertical and horizontal ultra-clean laminar airflows. No differences in bacteriological efficiency

We compared the novel zoned exponential ultra-clean operating room ventilation, needing no extra side-walls with the traditionally used ultra-clean air systems having vertical or horizontal laminar airflow, but requiring extra side-walls. The three units were evaluated with regard to elimination of particles with focus on airborne and sedimenting bacteria-carrying particles (colony forming units, cfu) during rigidly standardized sham operations. Although minor differences were recorded inside the ultra-clean airflows, the three systems were comparable with regard to bacteriological efficiency and ensured a low air and surface contamination (0.05-4 cfu/m3 and 7-72 cfu/m2/h, depending on the site of sampling). We conclude that all three systems fulfilled well the criteria for ultra-clean air (< 10 cfu/m3), but that exponential airflow is the most versatile alternative, as additional side-walls around the operating area can be omitted.

A prospective nationwide study of Clostridium difficile-associated diarrhea in Sweden. The Swedish C. difficile Study Group

Clostridium difficile-associated diarrhea (CDAD) is regarded as an emerging nosocomial infection. All patients positive for C. difficile in Sweden were recorded during 1995, including primary care patients. Those positive for toxin in feces were defined as CDAD cases. A total of 5,133 CDAD cases were recorded (58 per 100,000 inhabitants per year), as compared with 86 cases diagnosed in 1978 and 553 in 1983. CDAD was almost twice as prevalent as all (combined) diagnosed domestic cases of reportable bacterial and protozoal diarrhea. The age-specific incidence was little affected by gender but increased > 10-fold over the age range of 60-98 years. The differences in overall CDAD incidence were sixfold between counties and threefold between major hospitals. Among hospitalized patients the incidences were highest in geriatric/rehabilitation wards, followed by infectious diseases and internal medicine wards; 28% of all cases involved no recent hospitalization and were defined as community-acquired CDAD.

An allelic variant of the chromosomal gene for class A beta-lactamase K2, specific for Klebsiella pneumoniae, is the ancestor of SHV-1

Fecal Klebsiella isolates from neonates in 22 Swedish special care units were examined by a PCR we developed for detection of the SHV-1 beta-lactamase gene. All 105 K. pneumoniae isolates and all 11 K. pneumoniae reference strains (including the K. pneumoniae subsp. pneumoniae, ozaenae, and rhinoscleromatis type strains) tested were positive, whereas all 67 K. oxytoca isolates and the K. oxytoca, K. planticola, and K. terrigena type strains tested were negative. Resistance to beta-lactams in K. pneumoniae was not transferable by conjugation, and the beta-lactamase gene was never found on a plasmid. Southern blot analysis showed that the gene had a defined chromosomal location. Isoelectric focusing and sequencing of 231-bp PCR amplicons from different isolates revealed many variants of the enzyme, with the two main groups being SHV-1 like (pI 7.6; 68 isolates) and LEN-1 like (pI 7.1; 14 isolates). Clavulanic acid markedly reduced the MICs of ampicillin for all the K. pneumoniae isolates tested. This fact, MIC profiles (penicillin rather than cephalosporin resistance), pIs, and sequence data showed that the chromosomal beta-lactamase of K. pneumoniae is a class A, group 2 enzyme distinct from the chromosomal AmpC enzymes found in several other gram-negative bacteria and from the chromosomal beta-lactamase K1 of K. oxytoca. We propose that the chromosomal beta-lactamase of K. pneumoniae be designated K2 and suggest that an allelic pI 7.6 variant of this enzyme is the ancestor of the SHV family of plasmid-mediated beta-lactamases.

Cytokine gene expression during experimental Escherichia coli pyelonephritis in mice

PURPOSE

We studied nine inflammatory and immunoregulatory cytokines in acute pyelonephritis and urethral obstruction in mice to better understand the processes underlying kidney inflammation and scarring.

MATERIALS AND METHODS

Experimental acute pyelonephritis was established in Bki NMRI outbred mice by bladder inoculation of Escherichia coli, followed by 6 h urethral obstruction. The numbers of cytokine mRNA expressing cells for interleukin-1 (IL-1), IL-4, IL-6, IL-10, IL-12, tumor necrosis factor alpha (TNF-alpha), TNF-beta, transforming growth factor beta (TGF-beta) and interferon gamma (IFN-gamma) were determined in the kidneys and spleens from the infected, non-infected but obstructed and untouched mice using in situ hybridization with radio-labelled oligonucleotide probes at 12 h, 48 h and 6 d after release of the urethral obstruction.

RESULTS

Kidney cell expression of IL-1, IL-6 and TNF-alpha mRNA was observed already at 12 h and persisted on day 6 in the infected animals. A significant proinflammatory cytokine response occurred also in the non-infected obstructed animals, albeit later and at lower levels. A marked increase of IL-4, IL-10, TGF-beta and IFN-gamma mRNA producing cells was also found in the kidneys of these two groups again with higher levels in the infected animals. Very high numbers of splenocytes expressing mRNA for IL-1 were observed especially in the infected animals. A high proportion of splenocytes further expressed mRNA for IL-6, TNF-alpha, IL-4, IL-10, IFN-gamma and TGF-beta, again with highest numbers in the infected group of animals.

CONCLUSIONS

The present study extends previous knowledge about the local and systemic cytokine expression profiles during acute pyelonephritis and after urethral obstruction. Of particular interest was the marked kidney cell expression of mRNA for TGF-beta, presumed to be important both for obstructive and post-infectious renal scarring.

Transmission of urinary bacterial strains between patients with indwelling catheters--nursing in the same room and in separate rooms compared

Despite lack of supporting scientific data it has been suggested that patients with an indwelling urinary catheter (IUC) should be nursed in separate rooms to reduce the risk of cross-infection. We conducted a one-month case-control study of nursing home patients with an IUC and bacteriuria, 20 nursed together pairwise and 20 in separate rooms, by weekly urine cultures and typing of the bacterial isolates. The transmission rate of urinary strains between patients was three times higher within rooms (5/9 possible transmissions) than between rooms (9/53 possible transmissions, P = 0.02). The study thus supported nursing IUC patients in separate rooms.

Zoned vertical ultraclean operating room ventilation. A novel concept making long side walls unnecessary

We evaluated a novel concept of High Efficiency Particulate Air (HEPA)-filtered vertical Laminar Air Flow (LAF) for operating room ventilation, designed to be used without side-walls. The LAF-unit has a central zone with an airflow of 0.4 m/s and a peripheral zone with an airflow of 0.2 m/s. The design provides an exponential downflow of air resembling an upside-down trumpet mouth and it was claimed to prevent entrainment of peripheral contaminated air. The unit was evaluated with regard to elimination of particles with focus on bacteria-carrying particles (colony-forming units = cfu) during rigidly standardized sham operations. Three different lengths of walls/enclosures (short-ending 2.0 m, medium 1.0 m and long 0.2 m above the floor) were tested. It provided a high degree of bacteriological cleanliness (0.05-4 cfu/m3 of air and 7-64 cfu/m2/h surface contamination) and its efficiency was proved to be independent of the length of the enclosures. We conclude that the novel zoned ultraclean vertical LAF unit is versatile, as it allows for omitting long side-walls, without compromising bacteriological safety.

Inefficiency of upward displacement operating theatre ventilation

A new thermally based ventilation system ('Floormaster') with inlet of cool clean air at floor level, and evacuation at the ceiling of the air warmed by activity in the room (upward displacement ventilation, 17 air changes/h) was compared with a standard positive pressure (plenum) ventilation system with air supply through an inclined perforated screen along one wall at the ceiling and evacuation at floor level (conventional turbulent or mixing system, 16 air changes/h). The study was made during rigidly standardized sham operations (N = 20) performed in the same operating room by a six-member team wearing non-woven disposable or cotton clothing. In general the upward displacement system removed dust particles too small to carry bacteria (0.16-<0.3 microm, 0.001<P<0.01) more efficiently than the conventional system. However, the displacement system also yielded two to threefold higher air and surface bacterial counts in areas important for surgical asepsis (wound area, instrument table) especially with regard to bacterial sedimentation (0.001<P<0.05). The major shortcoming of the displacement system was insufficient elimination of the larger bacteria-carrying particles. The type of clothing worn by the members of the team did not influence the overall results. We conclude that an upward displacement system will lead to increased counts of airborne and sedimenting bacteria and thus increase the risk of postoperative infection in comparison with conventional operating room ventilation systems.

Interleukin-1 alpha and interleukin-6 in the urine, kidney, and bladder of mice inoculated with Escherichia coli

After bladder inoculation of mice using the pyelonephritogenic Escherichia coli strain DS17, urinary interleukin-1 alpha (IL-1 alpha) peaked at 0.5 h post infection (mean 233 pg/ml), interleukin-6 (IL-6) at 2 h (mean 572 pg/ml), and leukocyturia at 4 h, all three persisting for more than 24 h. In the kidneys IL-1 alpha peaked at 2 h, persisted over 24 h (mean 900-1,000 pg/ml), and decreased over 2-6 days post inoculation to a mean value of 208 pg/ml. Control kidneys showed low IL-1 alpha values. IL-6 in the kidneys peaked at 5 h (mean 9,999 pg/ml) but normalized, i.e., similar to control kidneys, by 48 h (mean 105 pg/ml). A similar cytokine response, but with tenfold lower levels, was found in the bladder tissue. The isogenic P-negative E. coli mutant DS178 elicited lower IL-6 in the kidneys at 5 h, but persisted in higher numbers in the kidneys at 6 days. Bacterial counts and cytokine levels correlated both in the kidneys and in bladder tissue, (r = 0.50-0.76, P < 0.001). Characterization of the immune response gives a better understanding of the relative importance of different bacterial characteristics for the local inflammatory process and is needed for studies of its pharmacological down-regulation.

Elevated cytokine levels in tracheobronchial aspirate fluids from ventilator treated neonates with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease often occurring in ventilator-treated very low birth weight infants. The aetiology of BPD is multifactorial and pulmonary immaturity, high oxygen concentrations, peak inspiratory pressure levels and large tidal volumes during prolonged mechanical ventilation are important factors. We measured in tracheobronchial aspirate fluid (TAF) the concentrations of the pro-inflammatory cytokines tumour necrosis factor alpha, interleukin-1 beta (IL-1 beta), IL-6, IL-8, and IL-1 receptor antagonist in infants requiring artificial ventilation for BPD (n = 17) or respiratory distress syndrome (RDS) (n = 15) or postoperatively after surgery (n = 15). The median levels of all studied cytokines in TAF were higher in infants with BPD without local or systemic corticosteroid treatment compared to the median TAF levels of BPD neonates treated with corticosteroids (P = 0.06-P < 0.01). The neonates with BPD not treated with corticosteroids also showed higher levels of the five studied cytokines in TAF compared to infants on short-time ventilator treatment (P < 0.01-P < 0.001) and compared to neonates with RDS (P = 0.07-P < 0.001). The corticosteroid treated neonates with BPD had TAF cytokine levels approaching those of the control neonates.

CONCLUSION

Tumour necrosis factors alpha, IL-1 beta, IL6, IL8 and IL1ra were markedly elevated in tracheobronchial aspirate fluids from neonates with bronchopulmonary dysplasia. Corticoid treatment seemed to reduce these levels.

Interleukin-1 alpha and interleukin-1 receptor antagonist in the urine of children with acute pyelonephritis and relation to renal scarring

Urinary concentrations of interleukin-1 alpha (IL-1 alpha) and interleukin-1 receptor antagonist (IL-lra) standardized to urinary creatinine concentrations were studied. The median standardized IL-1 alpha creatinine quotient in children with first-time acute pyelonephritis was 3.6 pg/mumol, but was nondetectable in children with recurrent pyelonephritis, children with non-renal febrile conditions and children convalescent after acute pyelonephritis (p < 0.05-0.01). IL-lra levels were also significantly higher in children with acute first-time pyelonephritis (median of 239 pg/mumol) compared to these three groups of children (p < 0.01-0.001). The highest urinary IL-lra levels, however, were found in the healthy controls (median value 1.019; p < 0.001). Both cytokines were higher among children younger than one year compared to older children. The acute IL-1 alpha creatinine quotients were lowest in children with uptake defects on 99mTC-dimercaptosuccinic acid (DMSA) scintigraphy both during the acute infection (reflecting the acute inflammation) (p < 0.001) and 1 year after the acute infection (reflecting permanent kidney scarring) (p < 0.001). In conclusion, persisting high urinary levels of IL-1 alpha were associated with less renal inflammation and scarring.

A hospital outbreak of high-level beta-lactam-resistant Enterobacter spp.: association more with ampicillin and cephalosporin therapy than with nosocomial transmission

We studied an 8 month outbreak of a 7-fold increased isolation rate of high-level beta-lactam-resistant Enterobacter spp. from clinical infections (20 patients, 22 isolates: 20 E. cloacae, 2 E. aerogenes). In a case-control analysis the occurrence of resistant Enterobacter spp. was found to be associated with treatment with multiple antibiotics (p = 0.03), broad-spectrum beta-lactam agents (p = 0.0001) including ampicillin (p = 0.04), and cephalosporins (cefuroxime and cefotaxime, p = 0.004). Biochemical fingerprinting and pulsed-field gel electrophoresis (PFGE) typing showed no identity between the resistant isolates, indicating that neither cross-infection nor nosocomial transmission from a common source was the immediate cause of the problem. The outbreak was not paralleled by the overall Enterobacter spp. isolation rate or the antibiotic usage pattern in the hospital. Thus, the underlying cause of the outbreak remained obscure.

Biochemical fingerprinting compared with ribotyping and pulsed-field gel electrophoresis of DNA for epidemiological typing of enterococci

The Phene Plate (PhP) biochemical fingerprinting system for bacteria is based on measurements of the kinetics of bacterial biochemical reactions. This system was modified for typing of enterococci and was compared with DNA typing by pulsed-field gel electrophoresis and with ribotyping by using 45 Enterococcus faecalis isolates from international collections. It was also used to study 170 fecal enterococcal isolates from healthy individuals and 28 isolates of E. faecalis from the blood of neonates. The PhP system showed a high degree of discriminatory power for unrelated enterococcal isolates. Among the 170 unrelated fecal isolates, 107 isolates from international collections, PhP typing discriminated 19 types, and ribotyping discriminated 5 types. In most cases, when isolates were of the same DNA type, they were also of the same PhP type, and the level of agreement between these two methods was high (96%). A combination of PhP typing and DNA typing identified 34 different types, but ribotyping did not yield any further discrimination. PhP typing of E. faecalis isolates from healthy individuals (n = 89) and from the blood of neonates with septicemia (n = 28) yielded a diversity of 0.93 for both populations and similar major PhP types in both populations. Thus, the isolates from blood seemed to consist of a normal E. faecalis population, without a dominance of certain strains associated with virulence. We conclude that the PhP system is useful for epidemiological studies of enterococcal isolates, yielding results similar to those obtained with DNA typing by pulsed-field gel electrophoresis. Since PhP typing is a method that is simple and rapid and that is based on automatic evaluation of the data, it is suitable for analyzing large numbers of isolates and can be used alone or in combination with DNA typing or epidemiological and ecological studies of enterococci.

Epidemiology and attack index of gram-negative bacteria causing invasive infection in three special-care neonatal units and risk factors for infection

Of 13 consecutive episodes of gram-negative septicemia (Escherichia coli eight, Klebsiella oxytoca four, Klebsiella pneumoniae one) among 113 infants in three special-care neonatal units studied, five episodes were epidemiologically related according to a novel fingerprinting method for enterobacteria. In ten episodes the invasive phenotype was found in the fecal flora of up to 54% of the fellow infants in the same ward and for periods of up to 70 days. Two units exchanged patients, which further promoted the transmission of invasive strains. The attack index was highest for certain E. coli strains, generally low for K. oxytoca strains, but lowest for other E. coli strains. The infants contracting septicemia had lower birth weight (p = 0.04) or were more often classified as high-risk infants than matched non-infected fecal carriers of the invasive strains (p = 0.04). In summary, gram-negative neonatal septicemia was either due to an apparently high-virulent strain capable of attacking the single full-term infant carrier or a high-colonizing phenotype of lower apparent virulence, which occasionally attacked a high-risk infant among a large number of infants colonized.

Survival on skin and surfaces of epidemic and non-epidemic strains of enterobacteria from neonatal special care units

It has been suggested that increased ability to survive on the hands of hospital staff contributes to transmission of certain strains of Gram-negative bacteria. We tested this hypothesis by comparing the survival on fingertips, glass slides and membrane filters of epidemic (M, major) and matched non-epidemic (S, sporadic) faecal strains of Escherichia coli (n = 13 vs. 13) and Klebsiella spp. (n = 19 vs. 19) found among 1066 neonates in 25 special care units (SCUs). The time to 50% killing at 22 degrees C in air was longer for E. coli than for Klebsiella spp. both on human skin (median 6 vs. 2 min P < 0.001) and glass surfaces (15 vs. 8 min P < 0.001). On the other hand, Klebsiella spp. were superior to E. coli in long-term survival tests on membrane filters expressed as the minimum inoculum still yielding growth after 10 days exposure at 22 degrees C in air (10(5) vs. 10(8) bacteria P < 0.001). Despite a large variation in survival times between individual strains no differences between M strains and S strains were observed in any of the three tests. This indicates that bacterial properties other than survival on surfaces contribute to the increased capacity for transmission of certain strains of enterobacteria in SCUs.

Correlation between susceptibility of infants to infections and interaction with neutrophils of Escherichia coli strains causing neonatal and infantile septicemia

The ability of Escherichia coli strains causing invasive infections to associate to human neutrophils and induce oxygen radicals was studied in three groups of blood isolates from neonates and infants: low-virulence septicemia strains (LVS), normal septicemia strains (NS), and meningitis strains (M). Infants were classified by susceptibility to infection as low- (LR) or high-risk (HR). All LVS strains were isolated from HR infants and showed higher association to neutrophils (P < .05) and induced a higher oxidative response (P < .05) compared with that of NS and M strains from LR infants. Three LVS strains caused the cells to release oxidative metabolites extracellularly. Thus, impaired interaction with neutrophils is characteristic of virulent clones of E. coli capable of causing invasive infection in healthy full-term neonates. Furthermore, increased extracellular release of oxygen metabolites could harm the surrounding tissue and potentiate the inflammatory process.

Interleukin-6 and interleukin-8 in the urine of children with acute pyelonephritis

Interleukin-6 (IL-6) and interleukin-8 (IL-8) are important mediators of the inflammatory response in serious bacterial infections. We studied the levels of these two cytokines (standardised for urinary creatinine) in the urine of infants and children during and 6 weeks after acute pyelonephritis and in non-renal febrile controls and healthy children without apparent infection. IL-6 was detected in the urine of 52% of children with pyelonephritis compared with 15% of other children (P < 0.001). The median urinary IL-6 level in acute pyelonephritis was 4 pg/mumol compared with undetectable levels in the control group (P < 0.001). IL-8 was detected in 98% of children with pyelonephritis and 42% of other children (P < 0.001). The median concentration of IL-8 was 188 pg/mumol in pyelonephritis; it was undetectable in controls (P < 0.001). IL-8 levels were higher in children less than 1 year of age (P < 0.001).

Urine interleukin-6 and interleukin-8 in children with acute pyelonephritis, in relation to DMSA scintigraphy in the acute phase and at 1-year follow-up

The relationship between urine interleukin-6 (IL-6) and interleukin-8 (IL-8)/creatinine quotients and 99mTc-dimercaptosuccinic acid (DMSA) scintigraphy, performed within 10 days of acute first-time pyelonephritis and after 1 year, was studied in 41 children. The urine IL-6 and IL-8/creatinine quotients were also related to the urine N-acetyl-beta-D-glucosaminidase (NAG) and albumin/creatinine quotients. Presence of DMSA uptake defects, reflecting local inflammation, in children in the acute phase of pyelonephritis, were associated with elevated urine IL-6/creatinine quotients (median 27 pg/mumol); in children without DMSA changes there was no increase in quotients (median non-detectable) (P < 0.05). Persistent DMSA changes at the 1-year follow-up, probably reflecting renal scarring, were only seen in children with increased urine IL-6/creatinine quotients in the acute phase (P < 0.01). No correlation was found between urine IL-8 and DMSA uptake defects. Vesicoureteral reflux (VUR) at 6-8 weeks did not correlate with the urine cytokine levels in the acute phase. The urine excretion of NAG and albumin, reflecting renal dysfunction, was associated with values of both urine IL-6 and IL-8/creatinine quotients, but not with DMSA defects or VUR. Thus, the initial urine IL-6/creatinine quotients might be used as an indicator of risk for persistent renal damage in acute pyelonephritis.

Association between climate and Enterobacter colonization in Swedish neonatal units

OBJECTIVE

To study risk factors for the highly variable local colonization rates with unrelated Enterobacter species strains previously found in 22 Swedish neonatal units (0% to 32.4% of the infants).

PATIENTS AND SETTING

The fecal Enterobacter species carriage rates among 953 infants in the 22 special-care neonatal units were correlated with variables related to the ward (size, crowding, staffing, work load, antibiotic usage, level of care, hygienic precautions), and the hospital (temperature of water supplied, geographical location).

RESULTS

The average Enterobacter species carriage rate was highest at seven days of age (17% of the infants) and then declined to 3%. Only location of the hospital in an area with warmer climate according to horticultural zone showed an association with Enterobacter species carriage in multivariate analysis (P = 0.005).

CONCLUSION

Although Enterobacter species mainly cause nosocomially acquired infections, the occurrence of the organism in special-care neonatal units seemed to be determined more by extrahospital than by intrahospital factors.

The use of colonization rate and epidemic index as tools to illustrate the epidemiology of faecal Enterobacteriaceae strains in Swedish neonatal wards

The epidemiology of faecal Gram-negative bacteria was studied in 953 infants from 22 neonatal special care wards in Swedish hospitals. Two complementary methods to measure presumed nosocomial transmission of bacterial strains were used: the prevalence rate of major (M) phenotypes (strains that had colonized at least 10% of the infants in a particular ward) and the epidemic index (Ei) (which measures the probability of isolating identical strains from different infants in a ward). About 1500 strains of the most common species (Klebsiella spp., Escherichia coli and Enterobacter cloacae) were typed by the Phene Plate (PhP) biochemical fingerprinting system, and selected Klebsiella isolates were also typed by K antigen serotyping. Klebsiella spp. showed a high propensity to spread (median Ei 0.034, max 0.234), whereas E. coli (median Ei 0.006, max 0.140) and E. cloacae (median Ei 0.0, max 0.012) were more seldom involved in outbreaks. High total Eis in the wards were correlated with high cephalosporin usage (Rs = -0.56, P < 0.05). A total of about 600 biochemical phenotypes of Enterobacteriaceae strains were isolated from the 953 infants. Most of these were found in only one or a few infants, but 24 M phenotypes belonging to Klebsiella spp. (N = 19), E. coli (N = 4) and E. cloacae (N = 1) had colonized altogether 239 (25%) infants. Klebsiella M phenotypes similar or identical to each other and carrying K antigen 55 were isolated from 108 (11%) infants in eight wards, and were thus responsible for 45% of the M phenotype carrier rate in all studied infants. It is suggested that they represent a clone of Klebsiella with a high ability to multiply and spread in hospital environments.

Relation between nursing procedures, other local characteristics and transmission of enteric bacteria in neonatal wards

Faecal colonization patterns were studied in 22 neonatal special care units (N = 953 babies) using a novel method for typing of Escherichia coli, Klebsiella spp. and Enterobacter spp. isolates. Sporadic strains of E. coli (found in only one infant in a ward) were taken to indicate natural colonization, whereas local spread of E. coli strains or colonization with sporadic or spreading strains of Klebsiella spp. and Enterobacter spp. was regarded as abnormal (non-maternal) colonization. All apparent risk factors for abnormal neonatal colonization with enteric bacteria identified were modifiable (ward size, staff work load, antibiotic policy, hygienic precautions). Another encouraging finding was that variables harder to modify (crowding, intensity of care) appeared to be unimportant in influencing neonatal colonization patterns with such bacteria.

Introducing fosfomycin for surgical prophylaxis--emergence of resistance in aerobic faecal gram-negative bacteria of in-patients, but not among strains causing infection after elective colorectal procedures

Fosfomycin was introduced for prophylaxis of surgical infection at 6 centres in a randomized study of elective colorectal operations (fosfomycin/metronidazole, n = 251 vs doxycycline/metronidazole, n = 237). Preoperative faecal specimens from the patients showed a relatively high prevalence rate of doxycycline-resistant bacteria (aerobic Gram-negative isolates 38%, enterococci 24%, overall 35%) with constant rates over time during the 15-month study period. The resistance rates for fosfomycin were lower (overall 12%), and remained constant for enterococci (average 10%), but increased for aerobic Gram-negative isolates from 9% during the initial part to 17% during the final part of the study (p = 0.007). Most aerobic strains in wound secretions from infected patients (20/26) could not be recovered from a preoperative faecal swab of the same patient. Isolates from infection after doxycycline prophylaxis had twice as high doxycycline resistance rates (overall 63%, 82% for Gram-negative isolates) as wound isolates from infection after fosfomycin prophylaxis (30%) and preoperative faecal flora isolates (35%, p = 0.02), indicating that bacterial resistance contributed to failure of doxycycline prophylaxis. In contrast, no increase in fosfomycin resistance rates was found among aerobic isolates from infection after fosfomycin prophylaxis (10%). This suggested that the emerging fosfomycin resistance was associated with reduced bacterial virulence and thus was of less clinical significance than doxycycline resistance.

Effect of ampicillin versus cefuroxime on the emergence of beta-lactam resistance in faecal Enterobacter cloacae isolates from neonates

Enterobacter cloacae strains dominated the aerobic faecal flora of 8.3% of 953 infants discharged from 32 Swedish neonatal intensive care units and the susceptibility of these strains to seven beta-lactam antibiotics was determined. Isolates from infants treated with cefuroxime showed slightly increased MICs only to ampicillin, cephalexin and cephalothin as compared to isolates from untreated infants matched for ward and time of sampling (P = 0.02). In contrast, E. cloacae isolates from ampicillin treated infants showed markedly elevated MICs of all agents tested including piperacillin, cefuroxime, cefotaxime and ceftazidime as compared to those from control neonates (P values between 0.001 for ampicillin and 0.017 for cefotaxime). Thus, E. cloacae with cefotaxime MICs as high as 512 mg/L were isolated only after ampicillin therapy. The resistant strains were negative in a colony DNA hybridization assay using gene probes for the plasmid beta-lactamases TEM-1, OXA-1 and SHV-1. The resistant strains also showed only one beta-lactamase band when crude cell sonicates were analysed by isoelectric focusing, and were not found in other infants in the same ward. The results indicate that the selection of chromosomal E. cloacae mutants, presumably with stably derepressed beta-lactamase production, in the faecal flora of neonates is rare during treatment with cefuroxime and more common during ampicillin therapy.

Novel coagglutination method for serotyping group B streptococci

A group G streptococcal strain was coated with antibody against six different serotypes (Ia, Ib, II, III, IV, and V) of group B streptococci. The coagglutination patterns of 114 strains of group B streptococci were compared with the serotypes determined after immunoprecipitation. The specificity of the method was 100% and the sensitivity 97%. It was used for the typing of 89 invasive and 101 colonizing isolates. The new method is swift, specific, and highly sensitive. It consumes only minute amounts of antibody.

Nationwide spread of Klebsiella oxytoca K55 in Swedish neonatal special care wards

In a nationwide survey of invasive bacterial infections in Swedish neonates, 36% of Klebsiella spp. were Klebsiella oxytoca serotype K55. This unexpectedly high proportion of K55 infections was due to clusters of infection in neonatal special care wards, and at first seemed attributable to nosocomial spread of a K. oxytoca strain of high virulence. Factors predisposing infants to infection were, however, found irrespective of whether the infecting strain was of serotype K55 or not. Additionally, the prevalence rates of a potential virulence factor, siderophore production, were similar among the two groups of strains. During the same period of time a K. oxytoca K55 with similar biochemical phenotype and drug resistance pattern was found to be spread among the neonates in 12 of 22 neonatal wards in Sweden. The increased proportion of invasive neonatal K. oxytoca K55 infections thus seemed to reflect a high rate of colonization rather than an increased virulence of the K55 strain.