Coagulase-negative staphylococci: update on the molecular epidemiology and clinical presentation, with a focus on Staphylococcus epidermidis and Staphylococcus saprophyticus.

Coagulase-negative staphylococci (CoNS), originally described as ubiquitous commensals of the healthy human skin and mucosa, have emerged as important opportunistic pathogens primarily causing healthcare-associated infections in patients with indwelling medical devices. Recent studies, utilizing new molecular typing methods, particularly on Staphylococcus epidermidis, have increased our understanding of the mechanisms that contribute to the evolutionary success of these extremely versatile microorganisms. In the following mini-review, we summarize recent research in this area focusing on the molecular methods and epidemiology of S. epidermidis and S. saprophyticus.

Molecular epidemiology of meticillin-resistant coagulase-negative staphylococci in a Swedish county hospital: evidence of intra- and interhospital clonal spread.

During a 10-month period in 2003, consecutive routine clinical cultures from patients treated in 15 different ward units in a Swedish county hospital were screened for the presence of meticillin-resistant coagulase-negative staphylococci (CNS). Genetic similarity between isolates was analysed using pulsed-field gel electrophoresis (PFGE). The results were compared with multi-drug-resistant Staphylococcus epidermidis isolated previously at the tertiary referral hospital. In total, 428 isolates of CNS were identified, of which 188 (44%) were meticillin resistant. Three clusters (Groups A, B and C) of S. epidermidis, each consisting of more than 10 isolates, with a PFGE-DNA similarity of >90% were identified. The strains in Groups A and B (N=15 and N=13, respectively), which were generally resistant to gentamicin, co-trimoxazole and clindamycin, originated from 24 patients, of whom 21 had been treated in the intensive care unit (ICU) before sampling. The third cluster, Group C, involved 14 isolates from 14 patients. Only two of these patients had stayed at the ICU, and all for less than one day. Isolates in Group C were less resistant than those in Groups A and B. Isolates belonging to Group A showed an identical PFGE profile compared with multi-drug-resistant S. epidermidis isolated from patients at the referral hospital. This study demonstrated the persistence and spread of meticillin-resistant clones of CNS within the county hospital, especially in the ICU, and possible interhospital spread of a multi-drug-resistant clone between the county and referral hospitals.

A preliminary evaluation of a new selective agar supplemented with desferrioxamine for detection of methicillin-resistant Staphylococcus aureus.

The aim of the present study was to evaluate the performance of two new selective screening agars, Colombia agar supplemented with 1000 mg/L desferrioxamine, 5 mg/L amphotericin B, 16 mg/L polymyxin B, and 2 mg/L methicillin (CMDAP agar) or 0.5 mg/L oxacillin (CODAP agar), for detection of methicillin-resistant Staphylococcus aureus (MRSA). Both the CMDAP and the CODAP agar effectively inhibited growth of 151 isolates of coagulase-negative staphylococci (CoNS), 45 of Enterobacteriaceae and six Candida spp. examined. The sensitivity and specificity of the CMDAP and CODAP agars for detection of MRSA was calculated by comparing the growth of 52 MRSA with the inhibition of 74 mecA negative S. aureus and of 151 CoNS. The performance of the new agars was compared with four previously described MRSA screening agars. The sensitivity and specificity for detection of MRSA after incubation at 35 degrees C for 24 h was 0.94 and 0.91, respectively, for the CMDAP agar, 0.60 and 0.90 for the CODAP agar, 0.98 and 0.57 for methicillin aztreonam mannitol salt agar (MAMSA), 0.23 and 0.84 for oxacillin mannitol salt agar (OMSA), 0.48 and 0.76 for oxacillin Mueller-Hinton agar (OMHA) and 0.75 and 0.77 for lithium oxacillin mannitol salt agar (LOMSA). Agars supplemented with desferrioxamine, CMDAP and CODAP, were more specific for detecting MRSA compared with agars not supplemented with desferrioxamine. The detection rate was higher for agars supplemented with methicillin than for agars supplemented with oxacillin.

Mueller-Hinton agar is superior to PDM blood agar for detection of methicillin-resistant Staphylococcus aureus.

The aim of this study was to compare the expression of oxacillin resistance in methicillin-resistant Staphylococcus aureus (MRSA) on Paper Disc Method agar supplemented with 5% defibrinated blood (PDM blood agar) and Mueller-Hinton agar supplemented with 2% NaCl (MH NaCl agar) using different susceptibility tests. Fifty mecA-containing isolates of S. aureus, exhibiting 46 different pulsed-field gel electrophoresis patterns, were comparatively tested using the E test, the single disk diffusion test, and the multipoint inoculation technique, under various culture conditions. The E test incubated at 35 degrees C for 24 h (breakpoint of resistance > or = 2.0 mg/L) detected 94% of the isolates on MH NaCl agar, compared with 28% for PDM blood agar (P < 0.05). The disk diffusion test (breakpoint < 10 mm in diameter) under these incubation conditions detected resistance in 100% of the isolates on MH NaCl agar and in 80% of the isolates on PDM blood agar (P < 0.05). The multipoint technique (breakpoint > or = 1 mg/L), applied at 35 degrees C for 24 h, detected 100% on MH NaCl agar and 46% on PDM blood agar (P < 0.05). Irrespective of the method of susceptibility testing evaluated, MH NaCl agar was superior to PDM blood agar for the detection of oxacillin resistance in mecA-containing S. aureus.

Frequency of antibiotic-associated diarrhoea in 2462 antibiotic-treated hospitalized patients: a prospective study.

The frequency of antibiotic-associated diarrhoea (AAD) and Clostridium difficile-associated diarrhoea (CdAD) was prospectively determined in a population of 2462 patients recruited from five Swedish hospitals, including divisions for infectious diseases, orthopaedics, surgery, geriatrics, nephrology and internal medicine. AAD developed in 4.9% of the treated patients. Faecal samples were obtained from 69% of patients with AAD and 55.4% were positive for C. difficile cytotoxin B. The frequency of AAD varied from 1.8 to 6.9% at the participating centres (P < 0.001). The frequency of AAD also varied considerably between medical disciplines and wards within different hospitals and was highest in the nephrology and geriatric units (6.7 and 7.1%, respectively). There was no difference in frequency of AAD when analysed with respect to gender or age. Medical interventions (laxative treatment, endoscopy and abdominal surgery) or presence of one concomitant disease (diabetes, malignancy, chronic renal disease and inflammatory bowel disease) did not significantly affect the frequency of AAD, whereas patients suffering from two or more of these illnesses had significantly (P = 0.001) higher frequencies of AAD. Patients treated with antibiotics for 3 days had a significantly (P = 0.009) lower frequency of AAD than those treated for longer periods. Treatment with cephalosporins, clindamycin or broad-spectrum penicillins was associated with an increased risk of AAD. With specimens from one centre, 62.5% of tested patients with AAD and 33.8% of asymptomatic patients were positive for cytotoxin B. Although C. difficile cytotoxin B in stool samples was significantly associated with AAD (P = 0.003), the causal relationship with diarrhoea is not always evident.

Bactericidal effect of pulsed 1,064 nm Nd:YAG laser light on Staphylococcus epidermidis is of photothermal origin: an in vitro study.

BACKGROUND AND OBJECTIVE: The aim was to investigate the bactericidal effect of the 1,064 nm Nd:YAG laser on Staphylococcus epidermidis. MATERIAL AND METHODS: S. epidermidis was inoculated on agar plates and then exposed to pulsed laser light in three different modes: with an uninterrupted train of pulses, or with two different repeated cycles of fractionated trains of pulses. The agar temperature was measured directly after uninterrupted radiation. RESULTS: A bacterial growth inhibition area of 0.3 cm(2) and maximum temperature of approximately 80 degrees C was observed after uninterrupted radiation at 2,000 J cm(-2). The corresponding figures after an exposure of 5,000 J cm(-2) were 0.9 cm(2) and 100 degrees C, respectively. No bacterial inhibition was observed after exposure to repeated cycles of 20 seconds of radiation followed by 60 seconds of rest. CONCLUSION: The antimicrobial effect of the 1,064 nm Nd:YAG laser light is caused by a photothermal rather than a photochemical effect.

Clonal spread of staphylococci among patients with peritonitis associated with continuous ambulatory peritoneal dialysis.

BACKGROUND: Peritonitis is the most important complication of continuous ambulatory peritoneal dialysis (CAPD). Coagulase-negative staphylococci (CNS) are the most common causes of peritonitis, only limited information is available regarding the distribution and epidemiology of different CNS species associated with CAPD peritonitis. METHODS: CNS isolated from dialysis effluent from CAPD patients with peritonitis was identified by species and further analyzed with pulsed-field gel electrophoresis (PFGE). RESULTS: A total of 216 microorganisms (206 bacteria and 10 Candida species) were isolated from 196 consecutive culture-positive CAPD samples obtained from 75 patients. One hundred and twenty-one (56%) isolates represented staphylococci. The four most frequently isolated staphylococcal species were Staphylococcus epidermidis (70 isolates), Staphylococcus aureus (31 isolates), Staphylococcus hemolyticus (10 isolates), and Staphylococcus hominis (4 isolates). PFGE analysis revealed the clonal spread among patients of three different clones of S. epidermidis and one clone of S. aureus among the investigated patients. Indistinguishable isolates of either S. epidermidis, S. hominis, or S. aureus were also isolated in repeated samples from several patients. CONCLUSION: PFGE is a useful method for the epidemiological evaluation of staphylococci-associated CAPD infections and should replace older and less accurate methods, such as antibiotic sensitivity patterns. We recommend that CNS isolates from patients with CAPD-associated peritonitis should be saved for future investigations and typing, which would aid in the management of this patient category.

Antibiotic susceptibility of staphylococci isolated in blood cultures in relation to antibiotic consumption in hospital wards.

A total of 510 isolates of Micrococcaceae, 500 of staphylococci and 10 micrococci, detected in 485 (3.3%) of 14,860 consecutive blood cultures obtained from patients at a Swedish university hospital and 2 local hospitals were identified to species level and investigated for antibiotic susceptibility. The 5 most frequently isolated species were Staphylococcus epidermidis (54.8%), S. aureus (28.0%), S. hominis (3.4%), S. warneri (3.2%) and S. haemolyticus (2.8%). All isolates of S. aureus were oxacillin sensitive. Great diversity in antibiotic resistance among coagulase negative staphylococci between hospitals and different ward units in the university hospital was observed. The frequency of antimicrobial resistance among S. epidermidis correlated with the antibiotic consumption at different ward units, in particular for ciprofloxacin (p < 0.001) and co-trimoxazole (p < 0.004). The study emphasizes the importance of monitoring antibiotic consumption and resistance patterns of nosocomial staphylococci in order to avoid emergence and spread of multi-resistant bacteria within the hospital environment.

Booster vaccination with recombinant hepatitis B vaccine four years after priming with one single dose.

We here studied the antibody response to a booster dose four years after the administration of one single dose of recombinant HB vaccine. Before receiving the booster dose, levels of protective antibodies (anti-HBs) were generally low and 24/41 (59%) individuals lacked detectable antibodies (< 1 IU/L). Within 14 d of booster vaccination, 36/38 (95%) vaccinees showed levels of antibodies > 100 IU/L. Notably, these levels were at least as high as those of a reference group 12 months after initiation of vaccination according to the standard three-dose vaccination at intervals of 0, 1 and 6 months. In conclusion, one single dose of HB vaccine seemed to confer on young healthy individuals a well preserved B cell memory, disclosed as a rapid and strong antibody response to a second dose four years later.

[Infections and treatment of chronic leg ulcers: the use of antibiotics is too excessive, restrictive prescription is recommended]. / Infektioner och behandling vid kroniska bensår: antibiotikaförbrukningen alltför hög, restriktivitet förordas.

Chronic venous leg ulcers are contaminated or colonised with bacteria that seldom affects ulcer healing. Signs of clinical infection appear in only a minority of chronic ulcers. In spite of this, data show a high consumption of antibiotics in this group of patients. Treatment with antibiotics is indicated only when clinical signs of infection or obvious risk factors are present or when Streptococcus pyogenes is isolated from the ulcer. In these cases an oral antistaphylococcal agent (semisynthetic penicillinase-resistant penicillin or first generation oral cephalosporin) is recommended as the first choice. Enterococci, anaerobic bacteria and gram-negative bacteria including pseudomonas spp. often colonise chronic ulcers, but do not usually cause antibiotic requiring infection.

An inexpensive and reliable method for routine identification of staphylococcal species.

The aim of this study was to develop a simple, reliable, and inexpensive in-house system for routine species identification of staphylococci in clinical practice. The system combines 15 key tests (including carbohydrate fermentation) performed in micro-well strips and antimicrobial disk diffusion susceptibility tests performed on standardised paper disk method antibiotic sensitivity medium agar. Twenty-eight staphylococcal reference strains belonging to 18 different species were correctly identified using this in-house system. A total of 291 clinical staphylococci isolates were evaluated with the in-house system and a conventional identification scheme. The in-house system identified 281 (96.6%) of these 291 isolates. Eleven different species were recognised. The five species most frequently identified were Staphylococcus epidermidis (48.6%), Staphylococcus aureus (27.8%), Staphylococcus haemolyticus (8.2%), Staphylococcus hominis (5.7%), and Staphylococcus warneri (5.3%). There was an agreement of 86.3% between the species identification obtained with the in-house system and the conventional identification scheme. All coagulase-negative isolates initially identified as species other than Staphylococcus epidermidis as well as indistinctly identified isolates were also evaluated with a commercial identification system. The agreement between species identification obtained with the in-house system and the commercial system for 101 identified isolates was 73%. Several isolates that were difficult to distinguish with the conventional scheme and/or the commercial system were identified with the aid of the antimicrobial susceptibility test included in the in-house system. The described test scheme should be of value for identification of clinically significant staphylococci species.

Virological, biochemical and histological effects of human lymphoblastoid interferon in Swedish patients with chronic hepatitis C.

Thirty-eight Swedish patients with chronic hepatitis C were randomly assigned to receive either 3 million units (MU) or 5 MU of human lymphoblastoid interferon-alpha-n1 (Wellferon) three times per week for either 6 or 12 months. The patients were monitored biochemically, histologically and by quantitative polymerase chain reaction for circulating HCV RNA, during therapy and for the following year. Overall, 22 (58%) of the patients lost detectable hepatitis C virus (HCV) viraemia during therapy but eight of these patients relapsed during follow-up, leaving 14 (37%) sustained responders. Patients infected with HCV non-type 1 genotypes were significantly more likely to achieve a sustained response than were those infected with HCV type 1 (63% vs 10.5%, P = 0.001). Sustained virological responses were also associated with lower pretreatment viraemia level, younger age, absence of cirrhosis and the higher interferon dosage regimens but these associations failed to reach statistical significance. In 97% of patients there was concordance between virological and biochemical responses, and a statistically significant (P = 0.005) improvement in the Knodell histological activity index was observed in the virological sustained responders.

A case of Plesiomonas shigelloides cellulitis and bacteraemia from northern Europe.

Bacteremia caused by Plesiomonas shigelloides is a rare event, often associated with consumption of seafood and fresh or estuarine water in temperate or tropical climates. Most patients have showed underlying health disorders. Here we present a case of P. shigelloides septicaemia and cellulitis of the left hand associated with fish handling in Northern Sweden (65 degrees latitude north). The patient, who suffered from multiple myeloma, recovered uneventfully after initial treatment with intravenous cefuroxime followed by a course of oral ciprofloxacin. P. shigelloides seems to be ubiquitous in freshwater world-wide and may cause invasive infections also in cold climate areas.

Fluoroquinolones and bacterial enteritis, when and for whom?

During the last decade quinolones such as norfloxacin, ciprofloxacin, ofloxacin and fleroxacin have emerged as drugs of choice for treatment of various bacterial enteric infections. Controlled studies have shown that quinolones, administered in varying regimens ranging from a single dose to 5 days treatment, significantly reduce the intensity and severity of travellers' diarrhoea as well as shigellosis. They have also been found to be highly effective in the treatment of invasive non-typhoid salmonellosis as well as typhoid fever. Results from trials evaluating quinolone treatment of uncomplicated salmonella and campylobacter enteritis have generally been disappointing. We studied norfloxacin for the empirical treatment of suspected bacterial enteritis of less than 6 days duration in a large placebo controlled trial. Although statistical differences in clinical outcome favouring norfloxacin were found among 259 culture positive patients, the differences were not striking and of doubtful clinical importance. However, a clear beneficial effect of norfloxacin, resembling that observed in early treatment of travellers' diarrhoae was found among the severely ill patients who initiated treatment within 48 h of onset of symptoms to start of treatment seemed to be of major importance in relation to therapeutic efficacy. Quinolone treatment of bacterial enteritis is furthermore limited by the rapid development of resistance seen in Campylobacter spp. and the failure of these compounds to eradicate Salmonella spp. Presently quinolones can be recommended in treatment of travellers' diarrhoea and shigellosis as well as enteric fever. They have limited usefulness for the routine empirical treatment of bacterial enteritis caused by Salmonella spp and Campylobacter spp. Treatment should be restricted to early empirical treatment of the severely ill and vulnerable patients with an underlying health problem.

Health problems and self-medication among Swedish travellers.

500 consecutive travellers seeking pre-travel health advice were issued a questionnaire before leaving Sweden to continuously record health problems and use of medication during travel. Of 442 subjects who turned in assessable questionnaires (232 male and 210 female, mean age 37 years), 81% travelled to areas at high risk for the acquisition of diarrhea. The mean duration of travel was 4 weeks. During travel 218 (49% at 95% CI 44.3 to 53.7%) of the travellers experienced some illness and 61 (14%) had symptoms of more than one illness. The mean duration of illness was 4.5 days, and 65 subjects (30% of ill travellers) were confined to bed for a mean duration of 2 days. The incidence of illness was significantly (p < 0.01) higher among travellers to high risk than to low risk areas (55% vs 26%), among young travellers than among elderly (65% vs 33%), and among those going on adventure tours compared with recreational tourists (74% vs 41%). Diarrhea was reported by 36% (95% CI 31.6 to 40.5%), and respiratory tract infection by 21% (95% CI 17.2 to 24.8%). Self-medication with one or several drugs was initiated by 163 (75%) travellers experiencing illness during travel. Thus, every second Swedish traveller to tropical and subtropical areas experienced some kind of travel-related, often incapacitating, health problem.

Ecological effects of short-term ciprofloxacin treatment of travellers' diarrhoea.

Forty-two subjects travelling to Mexico for 11 days were enrolled in a randomized, double-blind, placebo-controlled trial comparing ciprofloxacin 250 mg twice daily for three days or placebo for treatment of travellers' diarrhoea. Seventeen (41%) subjects were randomized to treatment. By the last treatment day, all seven evaluable subjects in the ciprofloxacin group, and three of eight evaluable subjects in the placebo group were cured (P = 0.04). The mean time to cure was 26 h for ciprofloxacin and 60 h for placebo-treated patients (P = 0.03). Faecal specimen were collected pre-travel, after four days in Mexico, 48 h post-travel and four weeks post-travel. Potentially pathogenic Escherichia coli strains carrying diarrhoeagenic virulence genes were detected by DNA hybridization tests, during or after travel, in 41% of treated and 31% of asymptomatic travellers. Travel, irrespective of diarrhoea and type of treatment, had a minor impact on the aerobic and anaerobic microflora. In travellers with ongoing diarrhoea, a suppression of the numbers of anaerobic bacteria was found, but the microflora was otherwise virtually unaffected. Significantly increased frequencies of E. coli resistant to ampicillin, doxycycline, chloramphenicol and co-trimoxazole were found during and after travel in all categories of travellers, though more frequently in subjects who experienced diarrhoea. The susceptibility of Bacteroides spp. remained unchanged. The sensitivity of E. coli to ciprofloxacin was not affected by travel, except in four ciprofloxacin-treated subjects who acquired multiresistant E. coli with ciprofloxacin MICs of > or = 0.125 mg/L post-travel. Bacteroides strains with MICs of > or = 64 mg/L were isolated post-travel from four ciprofloxacin-treated patients, and from one of the other 34 travellers not treated with ciprofloxacin.