Staphylococcal Infection in California : Strain Dominancy and Trends , a Good Day Against

In California, an average of 41,900 patients are diagnosed annually with Staphylococcus bacterial infection; out of these, 24,090 patients have methicillin-resistant Staphylococcus aureus (MRSA) infection and 17,810 patients have methicillin-sensitive Staphylococcus aureus (MSSA) infection. The aim of this paper is to find out whether there is a significant difference in strain dominancy and in what direction. The paper gathered and analyzed data for period of five years of infection rate due to Staphylococcus aureus. This study indicates that a significant difference in dominancy exists, the MRSA infection rate (an average of five years period) is 1.35 times higher than the MSSA infection rate (P-value < 0.05, CI: 95%), but the gap between the two infection rates is decreasing. The infection rate of both MRSA and MSSA is in a path of decline.


Introduction
There is considerable evidence to indicate that Staphylococcus infection has been increasing over the past 40 years, with the main cause of the increase being antibiotics overuse and the main contraction route being through healthcare workers [1,2].The antibiotic resistance of S. aureus attributed to its the ability, via genetic mutation, to escape drug action [1,2].In this study, we examined the type of Staphylococcus that is dominant and its trend.We hypothesized that MRSA infection is more common than methicillin-sensitive Staphylococcus aureus (MSSA) infection.Although evidence indicates that healthcare workers have a greater risk of contracting Staphylococcus infection (Datta et al., 2008) [3], other frontiers are emerging as potential areas of exposure risk to both MRSA and MSSA infections.Some recent studies have explored the existence of Staphylococcus in beach areas (Goodwin et al., 2012) [4], whereas others have explored the role of antibiotics and zinc in increasing resistance of Staphylococcus infections in animals processing facilities (Hatcher et al., 2017;Huijsdens et al., 2006) [5,6].In addition, the carrier status of Staphylococcus in veterinary personnel has been studied (Hanselman et al., 2006;Rosenkranz et al., 2014) [7,8].In this study, Staphylococcus aureus infection data (of five years period) were gathered and analyzed.Statistical analysis used to find out whether there is a significant difference.

Materials and Methodology
We collected data the hospital discharge data obtained from the Hospital Inpatient -Diagnosis Code Frequency dataset published by the California Health and Human Services Agency (from 2012 to 2016) [9].The data were tested by performing an independent t-test and were plotted to demonstrate the significance of the analyzed data.For the Staphylococcus infection rate hypothesis, the independent variables were the methicillin resistance states (sensitivity or resistance of S. aureus to methicillin) and the dependent variables were the means of the annual infection incident rate due to MRSA or MSSA.An independent t-test was statistically significant with a P-value of 0.05 and a CI of 95%.

Results
An average of (41,900) patients are diagnosed annually with Staphylococcus bacterial infection in California; out of these, (24,090) patients have MRSA infection and (17,810) patients have MSSA infection.The admission rate for MRSA infection has been reported to be higher than that for MSSA infection, in a ratio of (1.35) of MRSA to MSSA.The gap in the ratio between the admission rates for the MRSA to MSSA infections narrowed to (1.1) in 2016 from 2012 (1.5).Both MRSA and MSSA infection rates are decreasing.The incident rate decreased by (34.5%) for MRSA, and lowered by (7.3%) for MSSA between 2012 and 2016.

Discussion
The gap between MRSA and MSSA is substantial, and the current strategy of focusing on the healthcare worker factor should be revised and other variables should be considered.
Although the healthcare worker factor was explored and targeted, a probable reason for the significant decrease in MRSA infection rate might be attributed to the focus on prevention of MRSA infection (decrease of 34.5%) but not on MSSA infection (average decrease of 7.3%).
The emerging discovery of different sources of exposure, such as slaughterhouses, veterinarian facilities, and sand beaches, may help to elucidate the different ways in which the disease is contracted [4,5,6,7].Hormonal factors have been investigated from the perspective of disease treatment and have been found to play a significant role in the treatment of infectious diseases; however, the molecular and cellular mechanisms have not been fully elucidated.Araneo et al. (1993) showed that dehydroepiandrosterone (DHEA) enhances the immune system and prevents the growth of Listeria monocytogenes [10].Nathan et al. (1999) suggested that both DHEA, which may inhibit TNF-α, and androstenediol (AED), whose mechanism is independent of TNF, regulate the neuroendocrine system and protect it from lethal bacterial infection [11].
Contraceptive use extends the carrier status in females, which in turn increases the risk of exposure to Staphylococcus infection [12].

Conclusions
This paper explored the dominancy of S. aureus.MRSA infection is dominant over MSSA infection in the period 2012-2016.There is a significant decrement in the incident of infection rate of S. aureus.This marks a turning point in antibiotic resistance era.The healthcare worker factor has already been explored; however, increasing evidence of other potential areas of exposure risk (Figure 2) to Staphylococcus infection has emerged.Hormonal factors may play a major role in providing more immunity against the infection.Further research is warranted to investigate the association of exposure risks with clinical infection and carrier status.In addition, further research is warranted to explore the immunological mechanism that provides females more immunity and protection against higher mortality rates.

Preprints
(www.preprints.org)| NOT PEER-REVIEWED | Posted: 5 April 2019 doi:10.20944/preprints201904.0059.v1 Further research is warranted to explore the role of hormones in Staphylococcus infection.There is a lack of research on the routes of acquiring the clinical infection in California apart from the healthcare worker route.Recent research in different countries has explored the role of animal slaughterhouses and the effect of disposing potentially infected waste in rivers and oceans.Further research is warranted to investigate the route of transmission in California and the reason behind male patients being more vulnerable to death due to S. aureus infection than female patients.

Figure 1
Figure 1 Dominance of MRSA infection incident rate over MSSA infection incident rate

Figure 2
Figure 2 Areas of potential exposure for both MRSA and MSSA infections

Table 1
Absolute numbers and incident rates for MRSA and MSSA infections.

Table 3
Two-sample t-test and CI method for MRSA and MSSA infection rates.Variances are not assumed to be equal for this analysis.