Use of antibiotics in animal agriculture & emergence of methicillin-resistant Staphylococcus aureus (MRSA) clones: need to assess the impact on public health.

Widespread use of antibiotics in human, veterinary medicine and agricultural settings has played a significant role in the emergence of resistant MRSA clones due to selection pressure. MRSA has now become established in human population as well as in various animal species. An animal associated clone, MRSA ST 398 has been reported from animal foods and also from human infections in the community as well as from the health care associated infections. Clonal relationship between strains of animal and human origins are indicators of interspecies transmission of clones. Spread of these organisms may pose a great impact on public health if animal associated strains enter into the community and health care settings. Surveillance is important to correlate the genetic changes associated with their epidemiological shift and expansion to predict its impact on public health. Strict regulations on the use of antibiotics in humans as well as in animal food production are required to control the emergence of drug resistant clones. this article reviews the information available on the role of antibiotics in emergence of MRSA strains, their epidemiological shift between humans and animals and its impact on the public health.

Typing of Methicillin resistant Staphylococcus aureus: A technical review.

Increasing prevalence of Methicillin-resistant Staphylococcus aureus (MRSA) worldwide is a growing public health concern. MRSA typing is an essential component of an effective surveillance system to describe epidemiological trends and infection control strategies. Current challenges for MRSA typing are focused on selecting the most appropriate technique in terms of efficiency, reliability, ease of performance and cost involved. This review summarises the available information on application, potential and problems of various typing techniques in discriminating the strains and understanding the epidemiology of MRSA strains. The phenotypic methods in general are easier to perform, easier to interpret, cost effective and are widely available, however less discriminatory. The genotypic methods are expensive and technically demanding, however more discriminatory. Newer technologies involving sequencing of various genes are coming up as broadly applicable and high throughput typing systems. Still there is no consensus regarding the single best method for typing of MRSA strains. Phage typing is recommended as first line approach in epidemiological investigation of MRSA strains. PFGE remains the gold standard for characterisation of outbreak strains. DNA sequencing methods including MLST, spa typing, SCCmec typing and toxin gene profile typing are more practical methods for detecting evolutionary changes and transmission events. The choice of typing technique further depends on the purpose of the study, the facilities available and the utility of data generated to answer a desirable research question. A need for harmonisation of typing techniques by following standard protocols is emphasised to establish surveillance networks and facilitate global MRSA control.

Staphylococcus aureus phage types and their correlation to antibiotic resistance.

Context: Staphylococcus aureus is one of the most devastating human pathogen. The organism has a differential ability to spread and cause outbreak of infections. Characterization of these strains is important to control the spread of infection in the hospitals as well as in the community. Aim: To identify the currently existing phage groups of Staphylococcus aureus, their prevalence and resistance to antibiotics. Materials and Methods: Study was undertaken on 252 Staphylococcus aureus strains isolated from clinical samples. Strains were phage typed and their resistance to antibiotics was determined following standard microbiological procedures. Statistical Analysis: Chi square test was used to compare the antibiotic susceptibility between methicillin resistant Staph. aureus (MRSA) and methicillin sensitive S. aureus (MSSA) strains. Results: Prevalence of MRSA and MSSA strains was found to be 29.36% and 70.65% respectively. Of these 17.56% of MRSA and 40.44% of MSSA strains were community acquired. All the MSSA strains belonging to phage type 81 from the community were sensitive to all the antibiotics tested including clindamycin and were resistant to penicillin. Forty five percent strains of phage group III and 39% of non-typable MRSA strains from the hospital were resistant to multiple antibiotics. Conclusion: The study revealed that predominant phage group amongst MRSA strains was phage group III and amongst MSSA from the community was phage group NA (phage type 81). MSSA strains isolated from the community differed significantly from hospital strains in their phage type and antibiotic susceptibility. A good correlation was observed between community acquired strains of phage type 81 and sensitivity to gentamycin and clindamycin.

Molecular typing of methicillin-resistant Staphylococcus aureus strains by PCR-RFLP of SPA gene: a reference laboratory perspective.

PURPOSE: To characterize methicillin-resistant Staphylococcus aureus (MRSA) strains by molecular typing based on polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of spa gene and to assess the utility of spa genotyping over bacteriophage typing in the discrimination of the strains. MATERIALS AND METHODS: Studies were undertaken on 125 MRSA strains representing the most predominant phage types and the non phage typeable strains. Strains were typed by bacteriophage typing and PCR-RFLP of spa gene. DNA sequence analysis of the amplified spa gene fragment of the representative RFLP patterns was performed using standard protocols. RESULTS: All the strains resistant to oxacillin were found to contain mec A gene. Fifty-two per cent of these strains were typeable by the international basic set of 23 phages. Five different PCR-RFLP patterns were observed among 125 MRSA strains. Non phage typeable strains were differentiated into four PCR-RFLP patterns. Sequencing of the spa gene from the representative strains of each RFLP pattern confirmed the length of these restriction fragments due to variation in the 24 bp and the 174 bp tandem repeats. It also revealed the presence of three new spa repeat patterns. CONCLUSION: The study demonstrates the importance of spa genotyping in the discrimination of MRSA strains, which were otherwise indistinguishable by bacteriophage typing. spa genotyping allowed differentiation of strains within a particular phage type. Nucleotide sequencing of isolates of different PCR-RFLP patterns indicated a correlation between the RFLP patterns of a variable number of tandem repeats and the phage type. The study provides valuable information on the epidemiological characterization of MRSA strains.

Carbimazole induced ANCA positive vasculitis.

Anti-thyroid drugs, like carbimazole and propylthiouracil (PTU) are commonly prescribed for the treatment of hyperthyroidism. One should be aware of the side effects of antithyroid medications. Antineutrophil cytoplasmic antibody (ANCA)--associated vasculitis is a potentially life-threatening adverse effect of antithyroidmedications. We report a patient with Graves' disease who developed ANCA positive carbimazole induced vasculitis. The episode was characterized by a vasculitic skin rash associated with large joint arthritis, pyrexia and parotiditis but no renal or pulmonary involvement. He was referred to us for neurological evaluation because he had difficulty in getting up from squatting position and was suspected to have myositis. Carbimazole and methimazole have a lower incidence of reported ANCA positive side effects than PUT. To the best of our knowledge this is the first ANCA positive carbimazole induced vasculitis case reported from India.

Methicillin resistant Staphylococcus aureus (MRSA): the associated risk factors.

Methicillin Resistant Staphylococcus Aureus (MRSA) infections are common among hospitalized patients in whom surgical/medical therapy provides easy and ample opportunity for infection. The present study was conducted to examine the incidence of MRSA amongst patients from burns and orthopaedic units which are high risk units, and to see the correlation of the risk factors associated with these infections. Four hundred and fifty patients from the above two units were included with complete clinical details. Pus samples/swabs were transported in glucose broth and subsequent identification of MRSA was based on standard techniques. The incidence of MRSA infection was found to be 17.5% while the nasal carriage of this pathogen was seen in 2.9% patients. The risk factors which were found to be significantly associated with these infections were prolonged hospital stay, (16.95+6.7d) previous history of hospitalization during the last three months (38%), intake of broad spectrum antibiotics within the last two weeks (39.2%), prior history of intake of any intravenous drug (6.3%) and carriage of Staphylococcus aureus (30.3%) particularly MRSA (61.5%) in nose. Since these risk factors were found to be significant, it is therefore essential to control and prevent these factors to minimize the spread of these multi drug resistant MRSA infections.

Bacteriophage therapy: an alternative to conventional antibiotics.

Bacteriophage therapy is an important alternative to antibiotics in the current era of multidrug resistant pathogens. We reviewed the studies that dealt with the therapeutic use of phages from 1966-1996 and few latest ongoing phage therapy projects via internet. Phages were used topically, orally or systemically in Polish and Soviet studies. The success rate found in these studies was 80-95% with few gastrointeslinal or allergic side effects. British studies also demonstrated significant efficacy of phages against Escherichia coli, Acinetobacter spp., Pseudomonas spp and Staphylococcus aureus. US studies dealt with improving the bioavailability of phage. Problems faced in these studies have also been discussed. In conclusion, phage therapy may prove as an important alternative to antibiotics for treating multidrug resistant pathogens.

A study on Staphylococcus aureus strains submitted to a reference laboratory.

BACKGROUND & OBJECTIVES: Staphylococcus aureus is regarded as one of the most devastating human pathogens. Recently there have been reports of increasing incidence of S. aureus strains resistant to methicillin (MRSA). A surveillance study was undertaken to record the occurrence of MRSA and to study the prevalence of various phage groups in India. METHODS: A total of 7574 strains of S. aureus received during 1992-98 at the National Staphylococcal Phage Typing Centre, New Delhi were tested for methicillin resistance and susceptibility to phages of the International basic set. The occurrence of various phage groups between MRSA and MSSA (methicillin sensitive S. aureus) was compared. Results were analyzed according to the geographical origin and source of isolation of the strains. RESULTS: The dominant phage group from different parts of the country was phage group III. Prevalence of phage group III among the MRSA and MSSA isolates was 62.32 and 33.95 per cent respectively. The highest isolation of phage group III strains was from nasal carriers (45.94%), phage group II strains from skin (8.74%), phage group I strains from blood (19.44%) and nontypable strains from the environment (80.68%). An increase in the occurrence of MRSA has been noticed from 9.83 per cent in 1992 to 45.44 per cent in 1998. INTERPRETATION & CONCLUSION: S. aureus strains of phage group III are prevalent in India. The increase in occurrence of MRSA indicates an alarming spread of these organisms. A constant monitoring is important to take appropriate and timely measures to control their spread.

Study of methicillin resistant S. aureus (MRSA) isolates from high risk patients.

MRSA is an important hospital pathogen, the incidence of which is increasing every year especially in high risk groups. The present study was performed in high risk patients admitted in burns and orthopaedic units of LN hospital to study the infection rate of MRSA from these units. The proportion of MRSA amongst S. aureus isolates was found to be 51.6% and these isolates were multidrug resistant. Phage typing of these isolates gave a typeability of 41.8% using the MRSA set of phages. Biotyping of these isolates could divide them into four groups. The study shows a high incidence of MRSA from burns and orthopaedic units with a high level of antibiotic resistance amongst these isolates.

Characterization of methicillin resistant Staphylococcus aureus strains by a set of MRSA phages.

A recently developed international set of phages for typing methicillin resistant Staphylococcus aureus (MRSA) was used to characterize 300 strains of MRSA. The results were compared to that of phage typing with conventional phages and reverse phage typing. The use of MRSA phages increased the percentage typability from 17.6 per cent with the conventional set to 45.6 per cent with MRSA set and the strains were recognised as five distinct phage pattern viz., 622, M3/M5, MR8/MR12/MR25, 30/33/38 and mixed group. Phage type 622 was the most prevalent. On reverse phage typing 73 per cent strains could be typed with most strains belonging to one pattern i.e., 83A complex with limited discrimination. These 83A strains were highly resistant to erythromycin (98%) and tetracycline (93%). Our results show that MRSA phages are more useful in increasing typability and discrimination between the strains as compared to the conventional phages, reverse phage typing, and antibiogramtyping.

Community acquired methicillin resistant Staphylococcsus aureus: a new threat for hospital outbreaks?

Methicillin resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen. Recently, there have been reports of increasing prevalence of MRSA in the community. We here report an outbreak of post operative wound sepsis by MRSA in the surgical ward of LN hospital. A surveillance study for MRSA was undertaken in the corresponding surgical ward, operation theater and OPD and the source of this outbreak was traced to an outdoor patient with community acquired MRSA infection. A total of 320 clinical and environmental samples were screened for MRSA. Seventy (21.8%) S. aureus were obtained, of which 12.8% were resistant to methicillin. 14% of the MRSA infections were from the community. Nasal carriage rates of MRSA in the screened hospital staff and admitted patients were 5.8% and 4.3% respectively. None of the environmental sites sampled yielded MRSA. A study of antibiogram revealed that all the MRSA were uniformly resistant to penicillin, erythromycin, gentamicin, tobramycin and tetracycline and sensitive to vancomycin. All isolates belonged to the same biotype and were nontypable by the standard set of phages.