This study investigated the prevalence of resistance to macrolides, lincosamides, and streptogramin B (MLSB) in Staphylococcus aureus isolates from a tertiary care hospital in India. The study detected the erm A and erm C genes in isolates that showed inducible clindamycin resistance (MLSB i). The overall prevalence of MLSB i resistance was found to be 10.8% and the prevalence of constitutive resistance (MLSB c) was 11.6%. The erm A and erm C genes were detected in MLSB i isolates, demonstrating that methylation of the 23S rRNA is a mechanism of MLSB resistance in these clinical S. aureus strains.

1. 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 semestre
Medicina UPB

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

3. 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 and
soft tissue infections and work as an alternative in penicillin allergic patients.
However, excess and inappropriate use of MLSB agents has led to an increase in
number of S. aureus strains which are resistant to MLSB as well.

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

5. In a previous study we had reported the prevalence of hospital and
community associated MRSA along with antibiogram. Now we undertook
molecular studies for detection of erm A and erm C genes among inducible
clindamycin resistant isolates, also illustrating the prevalence of MLSB
resistance and antibiogram of inducible clindamycin resistance (MLSBi) and
constitutive resistance (MLSBc) isolates

6. MLSB: Macrolides, lincosamide and streptogramin B
MLSB
MLSBc
MLSBi
(It is constitutive) resistant
Inducible resistance

7. Genes
erm A
erm C
Are genes coding for the
methylase, these modified 23 S
RNAr generating resistance to
the antibiotics

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

9. Coloration process:

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

11. 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

12. Materiales y métodos
Este estudio se llevó a cabo durante un período de 18 meses. Durante
este tiempo fueron aisladas un total de 500 S. aureus de diferentes
muestras clínicas tales como pus, esputo, hisopo oído, orina, sangre,
hisopos de diferentes sitios, etc.

13. Detección de MRSA
Se determina con la prueba de difusión en disco con Cefoxitin 30µg, la cual
predice 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 se
consideran como MRSA.

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

15. Resultados :

16. Resultados

17. 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%) were
MSSA
We observed overall prevalence of constitute resistant isolates was 58 (11.6%)
which is almost similar to the prevalence of inducible clindamycin resistant
isolates
In our study prevalence of constitutive resistant isolates among MRSA and
MSSA was 32 (15.92%) and 26 (8.69%) respectively which is in accordance
with K Prabhu

18. Conclusions :
 Staphylococcus aureus has great ability to adjust to the adverse
environment and generates resistance to antibiotics quickly.
 There are several mechanisms by which Staphylococcus can become
resistant to treatment, each mechanism modifies something different.
 There is great variety of erm genes, and despite this are not in a strain at
random, most of them are in a specific strain and code for something
special.
 The erm genes are carried by plasmids and transposons that are able to be
self-transferable and which are of great importance when it comes to
transmitting genetic information coding for resistance to antibiotics.

21. Gracias !