Methicillin-resistant Staphylococcus aureus (MRSA) isolated in clinics and hospitals in the Fukuoka city area

A prospective study on bacteriological profile and antibiogram of postoperative wound infections in a tertiary care hospital in Western Rajasthan

BACKGROUND

Surgical site infections (SSI) are one of the most common hospital-acquired infections worldwide. SSI are known to increase morbidity, mortality, length of stay in hospital as well as the cost of treatment to the patients. The incidence varies from 1% to 20% among developed countries to as high as 40% in developing world.

AIMS

To find the incidence and risk factors, bacteriological profile, and antibiogram for SSI in General Surgery department of a tertiary care hospital in Western Rajasthan.

METHODS

Culture and sensitivity of wounds of all the clinically suspected cases of SSI were taken. Bacterial identification and antimicrobial susceptibility were performed according to standard CLSI guidelines. Statistical analysis was done using Microsoft Excel, SPSS 13 software.

RESULTS

Among total 609 patients, 102 were clinically suspected SSI and 88 were culture positive. Incidence of SSI was 14.45%. The most common organism was Staphylococcus aureus followed by Klebsiella pneumoniae. Most of the Gram-positive isolates were resistant to penicillin and cephalosporin antibiotics and were moderately susceptible to fluoroquinolones and aminoglycosides. Gram-negative isolates were resistant to beta-lactam and beta-lactam/beta-lactamase inhibitor combination also but were susceptible to fluoroquinolones, aminoglycosides, and carbapenems.

RESULTS

Among total 609 patients, 102 were clinically suspected SSI and 88 were culture positive. Incidence of SSI was 14.45%. The most common organism was Staphylococcus aureus followed by Klebsiella pneumoniae. Most of the Gram-positive isolates were resistant to penicillin and cephalosporin antibiotics and were moderately susceptible to fluoroquinolones and aminoglycosides. Gram-negative isolates were resistant to beta-lactam and beta-lactam/beta-lactamase inhibitor combination also but were susceptible to fluoroquinolones, aminoglycosides, and carbapenems.

CONCLUSION

High incidence rate of SSI in our setup emphasizes the need of quality surgical care which takes into consideration all the three important factors, i.e. host, environmental, and microorganism characteristics before doing any surgery. Increasing resistance to commonly used antibiotics warrants the judicious use of antibiotics and establishment of antibiotic policy in the hospital.

Bench-to-bedside review: Therapeutic options and issues in the management of ventilator-associated bacterial pneumonia

Despite progress in the diagnosis, prevention and therapy for hospital-acquired infections, ventilator-associated pneumonia (VAP) continues to complicate the course of a significant proportion of patients receiving mechanical ventilation. Mortality rates among patients with VAP have been reported to be as high as 72%, and the morbidity associated with VAP is also considerable, adding days to the hospital stay and increasing health care costs. Appropriate initial antimicrobial therapy for patients with VAP has been shown to reduce mortality rates and improve outcomes; therefore, rapid identification of infected patients and timely, accurate selection of effective antimicrobial agents are important clinical goals. The primary organisms responsible for VAP include Enterobacteriaceae, Pseudomonas aeruginosa and Staphylococcus aureus. However, aetiologies differ considerably between intensive care units, and the increase in antibiotic resistance and nosocomial outbreaks worldwide have presented clinicians with a serious dilemma with respect to selecting appropriate empirical therapy. To date, no optimal antimicrobial regimen for the treatment of VAP has been identified, largely because none of the currently marketed antibiotics has a sufficiently extended spectrum of activity to cover all of the potential key pathogens. More active, less toxic antibacterial agents are still needed, in particular to combat problematic pathogens such as multiresistant Gram-negative bacilli and resistant Gram-positive organisms (e.g. methicillin-resistant S aureus).

Epidemiological study of methicillin-resistant Staphylococcus aureus at Fukuoka University Hospital

To clarify what types of methicillin-resistant Staphylococcus aureus (MRSA) strains were easily transmitted and colonized in the inpatients of the emergency center and the neonatal intensive-care unit (NICU) at Fukuoka University Hospital, 70 MRSA isolates obtained from February to November 1995 (the first survey) and from November 1996 to March 1997 (the second survey) were investigated biologically and genetically. Pulsed-field gel electrophoresis (PFGE) showed 12 types (PFGE types A-L) of DNA patterns for the MRSA isolates. At the emergency center, the PFGE types A and B strains were isolated from 40.9% and 27.2% of the MRSA-excreting patients in the first survey, respectively, while type E was isolated from 66.7% in the second survey. At the NICU, type A and J strains were isolated from 33.3% and 55.6% of the MRSA-excreting patients in the first survey, while the types A and B were isolated from 25% and 50%, respectively, in the second survey. Type A-D strains were isolated in both wards, while other epidemic types strains were isolated in only one ward. These results suggest that the type A and B strains have been colonized in the two wards for a long time and these strains might spread and colonize easily in the patients. Type C and D strains have also been colonized, but only in a small population over the two wards.

Methicillin-resistant Staphylococcus aureus (MRSA) isolated at Fukuoka University Hospital and hospitals and clinics in the Fukuoka city area

Bacteriological and epidemiological studies were carried out on 106 isolates of methicillin-resistant Staphylococcus aureus (MRSA) isolated at our hospital (56 isolates) and from 15 other hospitals and clinics (50 isolates) in the Fukuoka city area. Strains were studied regarding coagulase-type, beta-lactamase production, and antimicrobial susceptibility; genotype studies used pulsed-field gel electrophoresis (PFGE) with cluster analysis. The majority of isolates produced coagulase type II (75.5%) and beta-lactamase (72. 6%); there was high susceptibility to arbekacin (84.9%) but no resistance to vancomycin. Dendrogram analysis of PFGE patterns identified five major clusters that generally correlated with coagulase-type and beta-lactamase production. Though isolates of two clusters were both coagulase type II and beta-lactamase producing, which was the most common circulating strain both in our hospital and other hospitals and clinics, dendrogram analysis of PFGE patterns showed that they were heterogeneous. Four genetically identical isolates from the same hospital suggested the existence of hospital-specific strains. Nine genetically identical isolates from intensive care units (ICU) in our hospital suggested that a unique strain of MRSA was found there. It had not been transmitted from another area. PFGE with cluster analysis seemed to be an essential tool to detect area-specific or hospital-specific strains undifferentiated by phenotyping. These findings confirmed that a combination of PFGE, including cluster analysis along with coagulase-type and beta-lactamase production may provide more detailed information for the epidemiological study of MRSA.

Methicillin-resistant Staphylococcus aureus: a questionnaire and microbiological survey of nursing and residential homes in Barking, Havering and Brentwood

The study determined the policies and procedures for the control and prevention of methicillin-resistant Staphylococcus aureus (MRSA) and its prevalence among nursing and residential homes, and evaluated whether certain home characteristics such as bed size, staffing level, and type of home are related to the prevalence of MRSA. A 21-questionnaire survey, with primarily categorical responses, was mailed to the home managers of all the 121 nursing and residential homes in the district, following which a simple, stratified random sample of 28 (23.14%) homes was taken and all agreeing residents screened from multiple sites for MRSA. Seventy-seven (63.6%) homes returned a completed questionnaire, 13 (46.4%) of whom agreed to participate in the microbiological study. The response rates for returning questionnaires and agreeing to participate in the microbiological study were similar for nursing and residential homes (65% vs. 60%; 67% vs. 40%; P = 0.12; P = 0.62), respectively. Nursing homes had a mean bed size of 30 (95% Confidence Interval (CI) 17-43), not significantly different from residential homes of 23 (95% CI 18-27; P = 0.26). The nursing homes employed a mean of 8.6 (95% CI 4.7-12.5) staff nurses per home; significantly higher than residential homes with a mean of 1.6 (95% CI 0.3-2.8; P = 0.006). No significant differences in mean number of home care assistants employed per home (22.8; 95% CI 12.4-33.13; and 14.4; 95% CI 11.83-16.90; P = 0.098, for nursing and residential homes, respectively) were observed. None of the homes had employed infection control practitioners. Only four (6.8%) of the responding homes stated that MRSA was a problem. Nursing homes were not significantly more likely to have admission policies for colonized person than residential homes (10/13 vs. 40/55, P = 1.00). Of the fifty-five (71.4%) homes who had admission policies, 40 (72.7%) stated that persons colonized/infected with MRSA would not be accepted, while 12 (21.8%) would accept such persons in single-room isolation and/or barrier nursing. Greater proportions of residential homes than nursing homes would not accept admission of persons with documented MRSA colonization (30/35 vs. 4/10, P = 0.007). Four (9.1%) homes (three nursing) had identified a total of five residents colonized/infected with MRSA in 5 years prior to the survey. Two hundred and forty-six residents were screened (552 sites), two (0.81%) of whom were found to be colonized in the nose (one resident) and in the groin (two residents) with MRSA, giving a 2-month weighted point prevalence rate of 0.14% (95% CI 0.01-0.26%). We conclude that in our district the nursing staffing levels and control measures vary widely within these homes, while the prevalence of residents who are colonized/infected with MRSA is lower than in other areas. We suggest that the exclusion admission policy for MRSA positive patients should be abandoned and targeted infection control programmes be instituted.

Investigation of nosocomial infection caused by arbekacin-resistant, methicillin-resistant Staphylococcus aureus

An outbreak of coagulase VII-producing, arbekacin (ABK)-resistant, methicillin-resistant Staphylococcus aureus (MRSA) occurred between September 1994 and December 1995, involving five different wards. Twenty-one patients developed skin, wound, drainage, or respiratory tract colonization with coagulase VII-producing, (ABK)-resistant MRSA. Phenotypic characteristics (production of enterotoxin and TSST-1, antimicrobial susceptibility) and molecular-typing procedure (plasmid DNA profile, pulsed-field gel electrophoresis [PFGE] and arbitrarily primed polymerase chain reaction [AP-PCR] of chromosomal DNA) in isolated strains were compared. Plasmid analysis identified four different profiles and 19 of 22 strains recovered had identical patterns. PFGE of chromosomal DNA identified three different subtypes and 18 (81.8%) isolates shared the same subtype. AP-PCR also demonstrated that most strains had the same phenotypic characteristics. Although traditional epidemiological methods; for example, coagulase typing, plays a central role in hospital infection control, combination of plasmid DNA profile, AP-PCR, and PFGE may prove to be a particularly informative means of tracking the nosocomial spread of MRSA.

Comparison of screening methods to identify methicillin-resistant Staphylococcus aureus

Screening methods to identify methicillin-resistant Staphylococcus aureus (MRSA) were compared using 96 isolates representing 17 distinct clones. The sensitivity of four commercial agglutination tests was determined in comparison to the tube coagulation test, and the results related to the presence of the coagulase gene. The broth screening test, agar dilution test and disc diffusion test were carried out, and the results related to the presence of the mecA gene. Mannitol salt agar and Iso-Sensitest agar with varying salt supplements were used. All agglutination tests had high rates of detection of Staphylococcus aureus (95.8-99.0%). Resistance in mecA gene-positive Staphylococcus aureus isolates was correctly detected by the oxacillin broth test, the agar dilution test and the disc diffusion test on mannitol salt agar, whereas on Iso-Sensitest agar detection rates were lower (between 68.5% and 94.4%, depending on the salt supplement). Incubation of the Iso-Sensitest plates for 48 hours significantly improved the rate of detection of resistance, but increased the major error rate up to 71.4%. MecA gene-positive Staphylococcus aureus isolates not detected by the disc diffusion test on Iso-Sensitest agar had significantly lower oxacillin minimal inhibitory concentration values and were significantly less resistant to a variety of antibiotics. Thus, mannitol salt agar might be a suitable medium for use in the disc diffusion and agar dilution test to detect resistance to oxacillin in Staphylococcus aureus.

Multidrug resistance among methicillin-resistant Staphylococcus aureus in Greece

A total of 472 strains of Staphylococcus aureus isolated in a university hospital in Thessaloniki, Greece during 1993-1994 were studied; 202 (42.8%) of them were characterized as methicillin-resistant (MRSA) and were mainly recovered from respiratory materials. The minimal inhibitory concentrations (MICs) of methicillin-susceptible (MSSA) and methicillin-resistant strains to 10 alternative antibiotics were also compared. All MRSA isolates were resistant to penicillin and most of them, in contrast to MSSA, exhibited resistance to gentamicin, tobramycin, tetracycline, erythromycin and ciprofloxacin with resistance rates ranging from 89.6% to 59.4%. Also, considerable proportions of MRSA were found resistant to co-trimoxazole (47.0%) and rifampicin (27.7%). All isolates were sensitive to vancomycin while susceptibility to chloramphenicol was of equal incidence among the examined populations. Overall, MRSA vs. MSSA exhibited a significantly (chi 2; P < 10-8) higher incidence of resistance to 8 out of the 10 antibiotics examined.