Strain relatedness of endemic MRSA isolates in a burns unit in South India--a five year study

Molecular characterisation of methicillin-resistant Staphylococcus aureus isolated from patients at a tertiary care hospital in Hyderabad, South India

Context

Infections with methicillin-resistant Staphylococcus aureus (MRSA) greatly influence clinical outcome. Molecular characterisation of MRSA can help to predict their spread and to institute treatment and hospital protocols.

Aim

The aim of this study is to understand the diversity of MRSA in a tertiary care hospital in Hyderabad, India.

Settings and Design

Samples collected at Gandhi Medical College, Hyderabad, and designed to assess hospital-or community-associated MRSA (HA-MRSA or CA-MRSA).

Subjects and Methods

MRSA were subjected to antibiotic susceptibility testing, pulsed-field gel electrophoresis (PFGE), spa typing, multi-locus sequence typing and staphylococcal cassette chromosome-mec (SCCmec) typing.

Statistical Analysis Used

Discriminatory index and 95% confidence interval.

Results

Of the 30 MRSA, (a) 18 and 12 were HA-MRSA and CA-MRSA, respectively, and (b) 23.3% and 6.6% displayed induced clindamycin and intermediate vancomycin resistance, respectively. Genetic diversity was evident from the presence of (a) 20 pulsotypes, (b) eight spa types, with the predominance of t064 (n = 9) and (c) seven sequence types (ST), with the preponderance of ST22 and ST8 (9 each). ST22 and ST8 were the most prevalent among HA-MRSA and CA-MRSA, respectively. SCCmec type IV was the most frequent (n = 8). 44.4% of HA-MRSA belonged to SCCmec IV and V, whereas 33.3% of CA-MRSA belonged to SCCmec I and III; 33.3% (5/15) of the isolates harbouring the pvl gene belonged to SCCmec IVC/H.

Conclusions

ST8 was a dominant type along with other previously reported types ST22, ST239, and ST772 from India. The observations highlight the prevalence of genetically diverse clonal populations of MRSA, suggesting potential multiple origins.

Bacteriophage types of methicillin-resistant Staphylococcus aureus in a tertiary care hospital

BACKGROUND

Phage typing had been utilised extensively to characterise methicillin-resistant Staphylococcus aureus (MRSA) outbreak strains in the past. It is an invaluable tool even today to monitor emergence and dissemination of MRSA strains.

AIMS

The aim of this study was to determine the prevalent phage types of MRSA in south India and the association between phage types, antibiotic resistance pattern and risk factors.

METHOD

A total of 48 non-duplicate MRSA strains recovered from various clinical samples during January to December, 2010 were tested against a panel of anti-staphylococcal antibiotics. Phage typing was carried out at the National Staphylococcal Phage Typing Centre, New Delhi. Out of 48, 32 hospitalised patients were followed up for risk factors and response to empirical and post sensitivity antibiotic therapy. The risk factors were compared with a control group of 30 patients with methicillin sensitive Staphylococcus aureus (MSSA) infection.

RESULTS

Amongst the five prevalent phage types, 42E was most common (52%), followed by a non-typable variant (22.9%), 42E/47/54/75 (16.6%), 42E/47 (6.2%) and 47 (2%). Phage type 42E was the predominant strain in all wards and OPDs except in the ICU where 42E/47/54/75 was most common. Although not statistically significant, strain 42E/47/54/75 (n=8) showed higher resistance to all drugs, except ciprofloxacin and amikacin, and were mostly D-test positive (87.5%) compared to the 42E strain (32%). Duration of hospital stay, intravenous catheterisation and breach in skin were the most significant risk factors for MRSA infection.

CONCLUSION

We found MRSA strain diversity in hospital wards with differences in their antibiotic susceptibility pattern. The findings may impact infection control and antibiotic policy significantly.

Antibacterial resistance and molecular typing of methicillin-resistant Staphylococcus aureus in a Kuwaiti general hospital

OBJECTIVE

To investigate antibiotic resistance and genetic relatedness of methicillin-resistant Staphylococcus aureus (MRSA) isolated in a general hospital in Kuwait over a period from 1996 to 1998 and 2001.

MATERIAL AND METHODS

The isolates were characterized by antibacterial susceptibility testing, coagulase serotyping, coagulase gene polymorphism (coag-RFLP) and pulsed-field gel electrophoresis (PFGE).

RESULTS

The MRSA isolates were highly resistant to gentamicin, kanamycin, ciprofloxacin, tetracycline, fusidic acid and mupirocin. The prevalence of gentamicin, kanamycin, streptomycin, tetracycline and erythromycin resistance remained high (80-96%) throughout the study period, but the prevalence of resistance to ciprofloxacin, fusidic acid and mupirocin steadily increased. The already high mupirocin resistance level increased from 12.5 in 1996, to 85.7% in 2001, and the fusidic acid resistance varied between 70.8 and 85.7%. In contrast, chloramphenicol and trimethoprim resistance declined from 25 and 29% in 1996 to 4.7 and 14.2% in 2001, respectively. The majority (91.5%) of the isolates were coagulase serotype 4. AluI restriction endonuclease analysis of amplified coagulase gene generated four coag-RFLP patterns: 92% of them were coag-RFLP type 1, while types 2, 3 and 4 were 3.5, 4.6 and 1.1% respectively. PFGE differentiated them into seven pulsotypes (PFGE types 1-7). The PFGE type 1 pulsotype constituted 90.2% of the isolates. Isolates with the type A coag-RFLP also had the type1 PFGE pulsotypes.

CONCLUSION

The concordant results of PFGE and coag-RFLP demonstrated the presence of a persistent MRSA clone in the hospital during the study period.