Effects of subinhibitory concentrations of chlorhexidine and mupirocin on biofilm formation in clinical meticillin-resistant Staphylococcus aureus.

BACKGROUND: The effects of subinhibitory concentrations (sub-MICs) of antibacterial agents on the biofilm-forming ability of Staphylococcus aureus require further study. AIM: To investigate the effects of sub-MICs of chlorhexidine and mupirocin on biofilm formation in clinical meticillin-resistant Staphylococcus aureus (MRSA) isolates. METHODS: MRSA isolates were collected from patients with bloodstream infections at a tertiary care hospital. The basal level of biofilm formation and biofilm induction by sub-MICs of chlorhexidine and mupirocin were evaluated by measuring biofilm mass stained with Crystal Violet. FINDINGS: Of the 112 MRSA isolates tested, 63 (56.3%) and 44 (39.3%) belonged to sequence type (ST)5 and ST72 lineages, respectively, which are the predominant healthcare- and community-associated clones in South Korea. ST5 isolates were more likely to have chlorhexidine MIC ≥4 (73.0% vs 29.5%), resistance to mupirocin (23.8% vs 0%), agr dysfunction (73.0% vs 9.1%), and qacA/B gene (58.7% vs 2.3%) compared to ST72 isolates. The basal level of biofilm formation ability was frequently stronger in ST72 isolates compared to ST5 isolates (77.3% vs 12.7%). Sub-MICs of chlorhexidine and mupirocin promoted biofilm formation in 56.3% and 53.6%, respectively, of all isolates. Biofilm induction was more prevalent in ST5 isolates (85.7% for chlorhexidine, 69.8% for mupirocin) than in ST72 isolates (15.9% for chlorhexidine, 27.3% for mupirocin). CONCLUSION: Sub-MICs of chlorhexidine and mupirocin promoted biofilm formation in half of the clinical MRSA isolates. Our results suggest that ST5 MRSA biofilm can be induced together with some other bacterial virulent factors following exposure to chlorhexidine, which might confer a survival advantage to this clone in the healthcare environment.

Clinical implication of extended-spectrum cephalosporin nonsusceptibility in Streptococcus pneumoniae meningitis.

The clinical implication of extended-spectrum cephalosporin (ESC) resistance has been unclear in patients with Streptococcus pneumoniae meningitis (SPM). We collected the clinical data of 120 patients with SPM in 12 hospitals of the Republic of Korea. The clinical characteristics and outcomes of 23 ESC-nonsusceptible SPM episodes were compared to those of 97 ESC-susceptible episodes. Hospital acquisition, presence of other foci of pneumococcal infection, septic shock at initial presentation, or concomitant bacteremia were more commonly observed in ESC-nonsusceptible than ESC-susceptible SPM. Empiric antimicrobial therapy with vancomycin and ESC combination was very common in both groups. Although there was a tendency towards higher early fatality in ESC-nonsusceptible SPM (3-day mortality; 17.4 % vs. 4.4 %, p = 0.05), in-hospital mortality (26.1 % vs. 20.9 %, p = 0.59) and median length of hospital stay (20 days vs. 24 days, p = 0.34) did not differ between ESC-nonsusceptible and ESC-susceptible SPM.

2009 H1N1 influenza infection in Korean healthcare personnel.

Healthcare personnel (HCP) can acquire influenza and transmit it to patients and other hospital staff. The aim of this study was to evaluate the attack rate of HCP by the 2009 H1N1 influenza virus during the 2009 pandemic influenza season in Korea. HCP infected with H1N1 virus were asked to fill out a questionnaire, which included job type, method of diagnosis, facility type, history of contact with patients infected by H1N1 virus, vaccination status, and use of personal protective equipment. A total of 328 HCP (female 68.6%, 225/328) were infected with H1N1 virus at the nine study centers. The highest attack rate was in physicians, followed by nurses and nurses' aides. Transmission occurred primarily after contact with outpatients (27.8%), followed by contact with inpatients (21.6%). Most (77.3%) of the infected HCP never used an N95 mask during contact with patients. Surgical masks were always used by 29.4% of the subjects and usually or intermittent used by 46.9%. The peak incidence of the H1N1 infection among HCP preceded that among the general population. Among HCPs, physicians, nurses, and nurses' aides were at the greatest risk of H1N1 infection. HCP should be more vigilant and protect themselves with appropriate personal protective equipment during the influenza season.

Hospital outbreak of Burkholderia stabilis bacteraemia related to contaminated chlorhexidine in haematological malignancy patients with indwelling catheters.

Burkholderia cepacia complex (BCC) is an opportunistic pathogen that occasionally causes hospital outbreaks. This paper describes an outbreak of BCC bacteraemia in haematological malignancy patients related to a contaminated chlorhexidine gluconate solution. Eight BCC isolates were obtained from patients hospitalised in the same ward of a cancer centre in a Korean hospital. A further three BCC isolates were obtained from 0.5% chlorhexidine gluconate used in the same ward. The isolates were identified as B. stabilis and exhibited identical pulsed-field gel electrophoresis profiles. All patients with B. stabilis bacteraemia had indwelling intravenous catheters, which were treated with chlorhexidine to disinfect the catheters. Following identification of the source of contamination, strict controls regarding surveillance cultures for disinfectants have been enforced. No further B. stabilis infections have been found in the hospital.

Phylogenetic analysis of reverse transcriptase in antiretroviral drug-naive Korean HIV type 1 patients.

To study whether genotypic antiretroviral resistance testing (GART) is needed to guide initial antiretroviral therapy in Korea, we determined partial pol sequences in peripheral blood mononuclear cells (PBMCs) obtained from 29 antiretroviral drug-naive HIV-1 patients. Phylogenetic analysis revealed four subtypes: B (23 patients), D (1 patient), recombinant strain (2 patients), and "untyped" (3 patients). Eighteen (78.3%) of the 23 subtype B isolates formed a distinct monophyletic cluster. The average genetic distances of 23 subtype B compared with reference strain HXB2 were 2.7% (range, 1.5-4.6%). Only one patient harbored variant virus containing a V179D mutation causing resistance to efavirenz. These data derived from therapy-naive patients suggest that potential use of primary resistance testing to guide initial antiretroviral therapy should be considered in Korea. This is the first report on the molecular nature of HIV-1 RT in Korea.

Group B streptococcal bacteremia in nonpregnant adults with hepatic disease in Korea.

Sixty-seven cases of group B streptococcal bacteremia in adults were retrospectively reviewed during the period 1991-2000. Not one case occurred in pregnant women. The mean age of the patients was 57 years, and 67.2% were men. Of the 67 cases of illness, 25.4% were hospital acquired and 11.9% were polymicrobial. Common predisposing diseases included hepatic disease (55.2%), diabetes mellitus (28.4%), malignancy (20.9%), and cardiovascular diseases (17.9%). Primary bacteremia, peritonitis, bone and joint infections, and skin and soft tissue infections accounted for most presentations. Peritonitis was a more common presentation in patients with hepatic disease (P<0.001), whereas skin and soft tissue infection was more common in patients with non-hepatic disease (P=0.008). More patients with hepatic disease had polymicrobial bacteremia than did patients with nonhepatic disease (P=0.018). Death occurred in 9.8% of cases, and mortality did not differ between patients with hepatic disease and those with nonhepatic disease. Hepatic disease was found to be an important predisposing condition in adults with group B streptococcal bacteremia. However, mortality for patients with hepatic disease was similar to that for patients with nonhepatic disease.