Prevalence of MLSB Resistance and Observation of

erm A & erm C Genes At A Tertiary Care Hospital

Ameer Abbas, Preeti Srivastava, PremSingh Nirwan

Jose Daniel Villegas Mesa Tercer semestreMedicina UPB

Introduction:

Staphylococcus aureus is the reason of greatest apprehension as a pathogen becauseof its intrinsic virulence that it has ability to quickly adjust itself into environmentalconditions. Severity and diversity of disease caused by S. aureus is the main reason ofarrival of multi- drug resistance. One of the most common sorts of resistance isMethicillin resistance which has been threat to human wall fare for past 50 years.

A few options are available for the treatment of methicillin resistant (MRSA)staphylococcal infections, such as macrolides, lincosamides and streptogramin B(MLSB) with clindamycin being one of the good alternatives, particularly for skin andsoft tissue infections and work as an alternative in penicillin allergic patients.However, excess and inappropriate use of MLSB agents has led to an increase innumber of S. aureus strains which are resistant to MLSB as well.

There are two primary mechanisms provides resistance to macrolide antibioticsAmong S. aureus the gene msr A encodes efflux pump which is a primarymechanism of defense and quite common in some geographical areas. Thesecond mechanism includes modification of drug binding sites on theribosomes that also enhances resistance to macrolides. These twomechanisms promotes resistance to macrolides, lincosamides andstreptogramins B group of antibiotics and termed as MLSB resistance. An ermgene usually erm A or erm C encodes methylation of 23S rRNA- binding whichis shared commonly by these three drug classes.

In a previous study we had reported the prevalence of hospital andcommunity associated MRSA along with antibiogram. Now we undertookmolecular studies for detection of erm A and erm C genes among inducibleclindamycin resistant isolates, also illustrating the prevalence of MLSBresistance and antibiogram of inducible clindamycin resistance (MLSBi) andconstitutive resistance (MLSBc) isolates

MLSB: Macrolides, lincosamide and streptogramin B

MLSB

MLSBc

MLSBi

(It is constitutive) resistant

Inducible resistance

Geneserm A

erm C

Are genes coding for themethylase, these modified 23 SRNAr generating resistance tothe antibiotics

Staphylococcus aureus

Generalities and shape: It is a gram positive coccus, are purple in clusters, catalase and coagulase positive

Coloration process:

Diseases

Staphylococcus usually causes disease in skin and soft tissue, septic arthritis and impetigo

General purpose:

This study was aimed to detect the prevalence of MLSBi and MLSBc resistance and observation of erm A and erm C genes among MLSBi isolates

Materiales y métodos

Este estudio se llevó a cabo durante un período de 18 meses. Duranteeste tiempo fueron aisladas un total de 500 S. aureus de diferentesmuestras clínicas tales como pus, esputo, hisopo oído, orina, sangre,hisopos de diferentes sitios, etc.

Detección de MRSA

Se determina con la prueba de difusión en disco con Cefoxitin 30µg, la cualpredice la expresión del gen mecA, y de esta manera, la sensibilidad o resistencia;si estos aislamientos muestran zona de inhibición de menos de 21 mm seconsideran como MRSA.

PCR :

El fundamento de esta prueba es replicar una secuencia especifica de ADN en estecaso se busco replicar los genes erm A y erm C, para ellos se usaron unos primersespecíficos que solo son funcionales en caso de estar presente la secuencia de losgenes de interés, luego de aisladas las secuencias se realizan varios ciclos paramultiplicar las cadenas de DNA a través de la enzima Taq la cual es una polimerasa.

Resultados :

Resultados

Discussion

Overall prevalence of Inducible clindamycin resistance was 54 (10.8%)

In our study 46 (22.68%) MLSBi isolates were MRSA and only 8(2.67%) wereMSSA

We observed overall prevalence of constitute resistant isolates was 58 (11.6%)which is almost similar to the prevalence of inducible clindamycin resistantisolates

In our study prevalence of constitutive resistant isolates among MRSA andMSSA was 32 (15.92%) and 26 (8.69%) respectively which is in accordancewith K Prabhu

Conclusions :

Staphylococcus aureus has great ability to adjust to the adverseenvironment and generates resistance to antibiotics quickly.

There are several mechanisms by which Staphylococcus can becomeresistant to treatment, each mechanism modifies something different.

There is great variety of erm genes, and despite this are not in a strain atrandom, most of them are in a specific strain and code for somethingspecial.

The erm genes are carried by plasmids and transposons that are able to beself-transferable and which are of great importance when it comes totransmitting genetic information coding for resistance to antibiotics.

Gracias !