An electronic surveillance network for monitoring antibiotic resistance in The Netherlands has been in operation since 1989. Seven public health laboratories participate and the system covers about 25% of all bacteriological determinations in The Netherlands. This paper reports the results of staphylococci isolated in the period 1989-1995. About 0.3% of the Staphylococcus aureus isolates in the study period were resistant to methicillin. This low percentage may be due to the restrictive use of antibiotics and to strict isolation measures aimed at eradicating methicillin-resistant S. aureus. Low frequencies of resistance among methicillin-resistant S. aureus were found for vancomycin (0%), chloramphenicol (11%), cotrimoxazole (11%), mupirocin (3% low-level resistance) and fusidic acid (7%). Twenty-one percent of the coagulase-negative staphylococci were resistant to methicillin. Low frequencies of resistance among these methicillin-resistant coagulase-negative staphylococci were those to vancomycin (0.4%), nitrofurantoin (2%), doxycycline (20%) and amikacin (20%). Coagulase-negative staphylococci from cerebrospinal fluid, blood and skin were less often resistant to quinolones than isolates from respiratory tract, faeces and urine. A significant increase in resistance of coagulase-negative staphylococci to methicillin, erythromycin, gentamicin and ciprofloxacin was observed in the investigated period but the resistance to doxycycline and co-trimoxazole decreased in the last few years. To confirm the determination of methicillin resistance and coagulase production, a PCR method was developed which detects both the mecA and the coagulase gene. The results of the PCR method correlated well with the methicillin MIC as determined by an agar-dilution method.

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IgM and IgG antibodies to Mycoplasma pneumoniae were measured in 147 sera from four groups of patients by means of an indirect enzyme-linked immunosorbent assay (ELISA) and the results compared with those obtained by other methods. A good correlation was demonstrated between the complement fixation test and ELISA-IgM and to a lesser extent ELISA-IgG; for the metabolic inhibition test the reverse was the case. The indirect haemagglutination test appeared to detect mainly IgM antibodies. Low levels of IgM antibodies were detected by ELISA in 60 sera of children not suffering from pneumonia. However, if only high titres (greater than 800) were regarded as indicative of Mycoplasma pneumoniae infection, a presumptive diagnosis could have been made in 42 of 73 single acute phase sera from patients. Comparable results were obtained with IHA. The diagnostic level of IgM antibodies. was reached during the second week of the disease. It is concluded that examination of a single serum sample by either ELISA-IgM or IHA may assist in early diagnosis of Mycoplasma pneumoniae infection.

In this open, non-comparative study 45 lower respiratory tract infections were treated with the new 4-quinolone, enoxacin. Special attention was paid to infections caused by Pseudomonas aeruginosa. Pseudomonas infections were treated with 600 mg bd. whereas infections caused by other bacteria were treated with 400 mg enoxacin bd. In 43 cases efficacy could be assessed. In six out of 23 cases Pseudomonas spp. were eradicated from the sputum. In 12 of the remaining 17 cases a clear reduction in bacterial numbers and a decrease of sputum volume and purulence were obtained. Clinical improvement or cure was obtained in 20 out of the 23 cases. Most of the causative microorganisms in the other infections were eradicated. In two patients Staphylococcus aureus persisted. Overgrowth with streptococci occurred in three patients. Adverse reactions were frequent and occurred in 29 out of 45 treatment periods. They were mainly related to the gastrointestinal tract and the central nervous system. In 25 out of 30 patients on concomitant treatment with theophylline an elevation of plasma theophylline concentrations occurred. Twelve of these patients developed signs and symptoms possibly related to theophylline toxicity. After treatment with enoxacin the MICs of most persisting Pseudomonas strains were two to four times higher than pre-treatment values.

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Oral norfloxacin prevented Gram-negative bacilluria in female patients with hip fractures, who needed medium-term transurethral catheterization. This was shown in a placebo-controlled double-blind study of 34 patients. Seventeen of these received a suspension containing 200 mg norfloxacin and 500 mg amphotericin B, twice daily. In the placebo group, six cases of Gram-negative bacilluria had occurred by day 7, as compared with no cases during a median time of catheterization of 23 days in the group on medication. Bacteriuria, either by Gram-positive cocci or by Gram-negative bacilli, was observed in 50% of patients on placebo by day 7; in the treatment group this was the case by day 17 (P less than 0.001). Subsequent bacteriuria with Gram-positive cocci was eliminated by nitrofurantoin (50 mg qid) within four days. Norfloxacin is very suitable for the prevention of Gram-negative bacilluria, because it decontaminates Gram-negative bacilli from the bowel, reaches high concentrations in urine and rarely produces resistant variants.

We investigated the influence of oral administration of amoxycillin, erythromycin and roxithromycin on colonization resistance in healthy volunteers. Antibiotics were administered in a randomized cross-over design. No effect on the colonization resistance of the oropharynx could be demonstrated. Amoxycillin decreased the colonization resistance of the bowel against Enterobacteriaceae and yeasts, whose median concentration in faeces increased 100-fold and 30-fold respectively. Roxithromycin and erythromycin decreased the concentration of Enterobacteriaceae in faeces. Secondary colonization with Enterobacteriaceae was detected as often following roxithromycin as following amoxycillin, but the level of colonization with these bacteria was much higher following amoxycillin. Following roxithromycin and erythromycin the level of secondary colonization did not exceed the original concentration of Enterobacteriaceae, showing that these antibiotics did not decrease the colonization resistance against Enterobacteriaceae. The appearance of secondary colonization in faeces at levels equal to or lower than the concentration of Enterobacteriaceae before administration of antibiotics, should not be regarded as proof of disturbance of colonization resistance.

The influence of oral administration of cefaclor, phenethicillin, co-trimoxazole and doxycycline on colonization resistance (CR) of the oropharynx and colon in healthy volunteers was studied. Antimicrobial agents were administered in a randomized cross-over design. No effect on CR of the oropharynx could be demonstrated. Phenethicillin decreased CR of the colon against Enterobacteriaceae (P = 0.001). Co-trimoxazole significantly decreased the concentration of Enterobacteriaceae in faeces (P = 0.03) but the decrease caused by cefaclor and doxycycline did not reach statistical significance. Administration of antimicrobial agents increased the appearance of secondary colonization by Enterobacteriaceae in faeces, especially when Escherichia coli was eliminated. During administration of phenethicillin, secondary colonization occurred at a concentration exceeding 10(7)/g in some volunteers. Following administration of cefaclor, co-trimoxazole and doxycycline, elimination of E. coli may result in the substitution by resistant Gram-negative bacilli in low concentrations.