Comparison of Staphylococcus aureus carriage and skin infection rates in hospital and office employees

Nasal and Hand Carriage ofStaphylococcus aureusin Staff at a Department for Thoracic and Cardiovascular Surgery: Endogenous or Exogenous Source?

Objective:

To investigate the rates ofStaphylococcus aureuscarriage on the hands and in the noses of healthcare workers (HCWs) and the relatedness ofS. aureusisolates found in the two sites.

Design:

Point-prevalence study.

Setting:

Department for Thoracic and Cardiovascular Surgery at the University Hospital of Uppsala, Uppsala, Sweden.

Subjects and Methods:

Samples were obtained from 133 individuals, 18 men and 115 women, using imprints of each hand on blood agar and a swab from the nose.S. aureusisolates were identified by standard methods and typed by pulsed-field gel electrophoresis.

Results:

S. aureuswas found on the hands of 16.7% of the men and 9.6% of the women, and in the noses of 33.3% of the men and 17.4% of the women. The risk ratio forS. aureuscarriage on the hands with nasal carriage was 7.4 (95% confidence interval, 2.7 to 20.2;P< .001). Among the 14 HCWs carryingS. aureuson their hands, strain likeness to the nasal isolate was documented for 7 (50%).

Conclusions:

Half of the HCWs acquiredS. aureuson the hands from patients or the environment and half did so by apparent self-inoculation from the nose. Regardless of the source of contamination, good compliance with hand hygiene is needed from all HCWs to protect patients from nosocomial infections. The moderate rate ofS. aureuscarriage on hands in this setting could be the result of the routine use of alcoholic hand antisepsis.

Carriage of Staphylococcus aureus among 104 healthy persons during a 19-month period

The present study was undertaken to investigate the frequency of the nasal carrier rate of Staphylococcus aureus. The investigation was performed on 104 healthy persons. The total number of swabs performed was 1498 and this resulted in isolation of 522 S. aureus strains. All strains have been identified, tested for antibiotic susceptibility, and phage-typed. The carrier-index (number of positive swabs/number of total swabs for each individual person) was compared with different sampling and culturing methods, phage type, age, and resistance to antibiotics. There was statistical difference in carrier rate according to sex (P < 0.05). Among the 104 persons 15 (14.4%) were persistent carriers, 17 (16.3%) intermittent carriers, 55 (52.9%) occasional carriers and 17 (16.3%) non-carriers. Among intermittent and occasional carriers the phage-type distribution was different from the S. aureus strains isolated from Danish hospitalized patients in 1992, while the persistent carriers had similar phage-type distribution.

Staphylococcus aureus isolated from nostril anteriors and subungual spaces of the hand: comparative study of medical staff, patients, and normal controls

An epidemiologic investigation of methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus aureus (S. aureus) colonization was conducted at Kansai Medical University Hospital between 1990 and 1991. The incidence of nasal and subungual positivity for S. aureus was examined in a total of 156 subjects including inpatients, physicians, and nurses at a ward for dermatology, plastic surgery, and emergency patients, outpatients with atopic dermatitis and other skin diseases, and normal controls. Inpatients were most heavily colonized with MRSA (40.8%), but S. aureus colonization was most frequent in outpatients with atopic dermatitis (95.5%). Not only nostrils, which have been much discussed as a reservoir of S. aureus, but also subungual spaces seemed to be havens of S. aureus. Twelve out of 22 atopic dermatitis patients were positive for S. aureus on skin regions, and coagulase and phage testing showed a correlation between the nasal and skin-colonizing S. aureus. Coagulase type II and phase type NT (not typable) were the predominant types of S. aureus, including MRSA.

Nasal, axillary, and perineal carriage of Staphylococcus aureus among women: identification of strains producing epidermolytic toxin

Following two outbreaks of staphylococcal scalded skin syndrome in a maternity unit, 500 pregnant women attending an antenatal clinic were screened for carriage of epidermolytic toxin producing Staphylococcus aureus. Nasal, axillary, and perineal swabs were collected from women whose gestational ages ranged from 12-40 weeks. Isolates of S aureus were purified, phage typed, and tested for methicillin sensitivity and production of epidermolytic toxin. The results showed that 164 (33%) women carried S aureus; of these, 100 (61%) were from the nose and three (2%) from axillae, but 41 (25%) strains were isolated from the perineum alone. Screening for nasal carriage alone will therefore miss 25% of carriers. More than one strain of S aureus was identified in seven of 20 women with multiple site carriage. Three (2%) methicillin resistant strains were isolated during the survey, and five (3%) isolates produced epidermolytic toxin. Phage typing identified 63 (34%) strains as non-typable, but 50% of isolates typed either groups I, II or III, and a further 10% represented varying combinations of these and other phage groups. These results provide baseline information on S aureus in the community, and identification of methicillin resistant and toxin producing strains shows a reservoir of outbreak potential which could become relevant on hospital admission of such a carrier.

Staphylococcus aureus in Antarctica: carriage and attempted eradication

The carriage of Staphylococcus aureus was studied in a group of 28 men living in a totally isolated environment for a year. Initially, nasal, axillary and perineal swabs were taken at weekly intervals, but from week 24 throat swabs were taken from known nasal carriers. Several attempts were made during the study to eradicate S. aureus. Eight subjects consistently carried their own phage type throughout the study, despite the application of antibacterial agents. In three subjects strains were isolated late in the study of a phage type which had either not been isolated before in this study, or had not been found for a prolonged period. Nine of the 12 nasal carriers also yielded S. aureus from the throat. It is apparent that following attempted eradication, S. aureus may seem to disappear, only to reappear some time later; 'eradication' in this case would be an erroneous appellation.

Colonization of hospitalized patients by Staphylococcus aureus, Staphylococcus epidermidis and enterococci

Patients admitted to a medical intensive care unit (29), a surgical intensive care unit (29) and a general medical ward (34) were studied to determine the frequency of colonization by Staphylococcus aureus, Staph. epidermidis and enterococci. Cultures of anterior nares, pharynx, axilla, periurethral tissues, and rectum were done within 24 h of admission and every 48-72 h thereafter for the duration of hospitalization. We found Staph. aureus colonization of pharynx, axilla, periurethral tissues and rectum to be equally frequent in patients with and without nasal colonization. Staphylococcus epidermidis was commonly recovered from all sites except the pharynx. The 49 strains of this organism acquired in the hospital were significantly more often resistant to nafcillin, cephalothin, chloramphenicol, trimethoprim-sulfamethoxazole and gentamicin than were 199 isolates recovered from patients at the time of admission. Enterococci were commonly isolated from rectal swabs and, less often, from other sites. Acquisition of enterococcal colonization during hospitalization was correlated significantly with antibiotic administration.

Influence on oropharyngeal and nasal carriage of Staphylococcus aureus by dicloxacillin therapy in patients undergoing oral surgery

71 healthy oral, throat and nasal carriers of Staphylococcus aureus undergoing surgical removal of impacted mandibular third molars were assigned to the following regimens. 40 patients received dicloxacillin 500 mg orally 60 min before the operation and then 500 mg dicloxacillin 3 times daily for 7 days and 31 patients no antibiotic. Oropharyngeal and nasal cultures were obtained from each patient before, during and after the operation. Dicloxacillin reduced the carrier rates significantly. No increase in in vitro antibiotic resistance was observed in the staphylococcal isolates obtained after therapy. Dicloxacillin was well tolerated and toxicity was not encountered in any patient.

Nasal carrier rates and antibiotic resistance of Staphylococcus aureus isolates from hospital and non-hospital populations, Addis Ababa

Surgical staff of five different hospitals and university biology students were screened for nasal carriage of Staphylococcus aureus: 32.4% of the surgical staff and 21.6% of the students were carriers. The rate for the hospital staff was significantly higher (chi 2 = 9.2, P less than 0.01). The carrier rates among the surgical staff varied between 59.1% for surgeons and 22.7% for other surgical staff. 195 S. aureus strains were isolated: 109 from surgical staff and 86 from students. All were tested for their resistance to antibiotics. Resistance to penicillin was 86.2% and 74.4%, respectively, for hospital and non-hospital isolates. Resistance to erythromycin, gentamicin, kanamycin or co-trimoxazole was not detected among the non-hospital isolates. All isolates were sensitive to vancomycin, cephalothin and clindamycin. Over 96% and 88% of hospital and non-hospital isolates, respectively, were resistant to at least one antibiotic. About 45% of the hospital isolates and 2.3% of the non-hospital isolates showed multiple resistance. The rate of multiple resistance among the hospital staff isolates was considered high and indicative of still higher rates among clinical isolates. Further studies are suggested in order to take appropriate measures against bacterial resistance to antibiotics.

Coagulase-negative staphylococci and cloxacillin prophylaxis in pacemaker surgery

In a prospective study of cloxacillin prophylaxis at pacemaker surgery per- and post-operative cultures were made. The most commonly isolated organisms from the wound were coagulase-negative staphylococci. These were typed by the scheme devised by Kloos and Schleifer. The routinely performed per-operative culture was of very little prognostic value. However, the typing was found to be useful in cases with suspected infection, as repeated isolation of the same species of coagulase-negative staphylococci with the same antibiotic susceptibility pattern may indicate pathogenicity. Incubation in enrichment medium for 2-4 days was needed in one patient who received antibiotic therapy when the specimen for culture was taken. The antibiotic prophylaxis did not eradicate even susceptible bacteria from the wound, but the infection rate was significantly lower in the prophylaxis group.

Staphylococcal nasal carriage in medical students with varying clinical exposure

Nasal carriage and antibiotic sensitivities of coagulase-positive and coagulase-negative staphylococci were assessed among medical students of three different years. Although carriage rates did not change, there was a trend towards multiple resistance with increasing hospital exposure. Gentamicin resistance in Staphylococcus albus showed a similar trend. The relevance of these findings to current views on the origin of gentamicin resistance is discussed.