A retrospective analysis of cases of Spontaneous Bacterial Peritonitis in cirrhosis patients.

BACKGROUND & AIMS: Spontaneous Bacterial Peritonitis (SBP) is an infection in patients with cirrhosis and carries significant mortality. The management of SBP is evolving with the rise of multidrug resistant organisms. Our aim was to perform a retrospective analysis to determine if identification of bacteria in culture could aid in prognosis and provide information regarding optimal treatment.
METHODS: We analyzed our 10-year experience of SBP in a single academic center (Northwestern Memorial Hospital). We obtained information regarding SBP prophylaxis, culture data and resistance patterns of bacteria, choice/duration of inpatient antibiotics, and key laboratory measurements and determined outcomes including mortality, hospital duration, and ICU stay.
RESULTS: Patients with SBP had a 17.8% mortality and had culture positive SBP 34.4% of the time. Antimicrobial resistance was seen in 21.3% of cases and trended towards worsening mortality, with worsened mortality associated with first line use of piperacillin-tazobactam (p = 0.0001). Patients on SBP prophylaxis who developed SBP had improved mortality (p<0.0001) unless there was a positive culture, in which case patients had worsened mortality (p = 0.019). Patient with a higher PMN counts after repeat paracentesis had higher mortality (p = 0.02).
CONCLUSIONS: Our results show that SBP continues to be a morbid and deadly condition and identification of an organism is key in treatment. The standard initial antibiotic for SBP may need to be modified to reflect emerging resistant pathogens and gram-positive organisms. Further, antibiotic prophylaxis should be utilized only in select cases to prevent development of resistance.

Introduction

Spontaneous Bacterial Peritonitis (SBP) is an infection in the peritoneum that develops in patients with ascites related to cirrhosis. SBP remains an important complication in persons with cirrhosis and is a significant cause of mortality, with rates between 20–40% in decompensated cirrhosis [1] and as high as 75% in some cohorts [2-4]. The mechanism of SBP is poorly understood and is thought to be secondary to bacterial translocation from the gut, reduced gut motility leading to bacterial overgrowth, and/or altered intestinal defenses and immune responses [5, 6]. The most common organisms causing SBP arise from the gastrointestinal tract and include Escherichia coli, Klebsiella pneumoniae, Streptococcus species (spp.) and Enterococcus spp. [7].

The incidence of SBP has been estimated to be between 10 and 30% in chronic liver disease patients [8], with up to 3% occurring in the outpatient setting [6, 9]. Laboratory diagnosis of SBP is established by identifying an elevated ascitic fluid polymorphonuclear cell (PMN) count greater than or equal to 250 cells/ul and a positive culture of the ascitic fluid. Without a positive culture, the diagnosis is referred to as Culture Negative Neutrocytic Ascites (CNNA) and SBP with a positive culture and a PMN threshold less than 250 is referred to as Non-Neutrocytic Bacteria-Ascites (NNBA). SBP, CNNA and NNBA are often used interchangeably. A recent retrospective review demonstrated no difference in mortality in patients with SBP vs. NNBA [10]. With proper technique, up to 60% of peritoneal fluid samples will be positive for a bacterial pathogen [11-14].

SBP prevention is recommended for higher risk cirrhotic patients, such as those with low ascitic fluid protein, risk factors for hepatorenal syndrome, and a prior history of SBP. Oral fluoroquinolones are currently the prophylactic antibacterial of choice [15, 16] Empiric therapy for SBP typically relies on the use of third-generation cephalosporins and when possible therapy should be targeted for the cultured organism [17, 18]. Treatment is often modified or continued based on a follow-up paracentesis done on day 3 of treatment [19], although there is limited data on repeating paracentesis and this strategy may not improve mortality [20]. Resistance to standard first line agents and prophylaxis is high, ranging from 33–49% [7, 11, 21] of cases, and continues to increase [22-25]. Infection with a resistant bacteria portends a poor prognosis [26].

Our project is a single center review on the causative agents of SBP in patients with cirrhosis. We reviewed data among patients with cirrhosis and SBP from a single academic center and identify a sub-set of risk factors that could potentially change standard treatment and management of SBP. Our aim was to determine the incidence, mortality and morbidity of SBP, the percentage of patients with positive bacterial cultures, the types of bacteria grown from those cultures and the morbidity/mortality of each individual bacteria, the change in Day 1 and Day 3 paracentesis results, and the resistance rates to standard treatment and prophylaxis. We hypothesized that identification of bacteria in culture could aid in prognosis and provide targeted treatment given resistance patterns to first line agents.

Patients and methods

We performed a chart review using the Northwestern Enterprise Data Warehouse(EDW) with the approval of the Northwestern Biomedical IRB (STU00204726). Consent: Consent order was waived by approved IRB. Rationale: The study was retrospective and involves collection of data elements, which have already been obtained as part of clinical care. We queried the database to report all patients who underwent paracenteses at Northwestern Memorial Hospital in the inpatient and outpatient settings from January 1st, 2006 to December 31st, 2016.

Inclusion criteria for review were patients with a diagnosis of SBP, cirrhosis (identified by ICD-9, ICD-10 and CPT codes) and adults between the ages of 18 and 88 years old. We excluded patients <18 years old and >88 years old, individuals undergoing post-surgical paracentesis, individuals with HIV infection, patient who received a stem cell transplant, and those without cirrhosis at the time of the procedure. We reviewed the Epic Electronic Medical Record system to verify information from EDW queries in all cases (Fig 1).

Fig 1

Stepwise process of data mining starting with EDW patient data.

Demographic information including age, gender, and ethnicity, date of paracentesis, and etiology of cirrhosis diagnosis was extracted from each chart. Information regarding the details of the diagnosis of SBP from the paracentesis were obtained via chart review and included PMN count, culture data and species/resistance patterns. Data related to agent used for SBP prophylaxis, the choice/duration of inpatient antibiotics for treatment of SBP, whether changes were made in antibiotic choice, and key laboratory measurements at the time of diagnosis were analyzed from the subjects’ chart. Outcomes of patient stay were determined including hospital duration, all-cause mortality, ICU stay, in- hospital and recurrence of SBP.

Descriptive statistics were produced using frequencies to describe the SBP cohort. To assess the differences in demographics and other hospitalization factors between those with positive SBP cultures and negative SBP cultures, Student’s t-tests and Chi-square tests were performed. Other univariate testing was done to assess types of bacteria in positive cultures, drug resistance, and prophylactic antibiotics. Statistical significance was set at p<0.05. Statistical analyses were performed using Statistical Analysis System (SAS) version 9.4 (SAS Institute Inc., Cary, North Carolina, USA) and Microsoft Excel 2019.

Results

In total, 2159 patients were identified as having cirrhosis and undergoing a paracentesis over the 10-year study period. Of these subjects, 314 patients were diagnosed and treated for SBP at Northwestern Memorial Hospital for a rate of 14.5% (Table 1).

Table 1

Descriptive statistics of patients in the SBP cohort.

	Culture Positive	Culture Negative
	n = 108	n = 206	P
Average Age at SBP diagnosis (Years, Range 20–87)	57.8	56.1	0.177
Gender	62.4% Male, 37.6% Female	63.4% Male, 36.6% Female	0.857
Etiology of Cirrhosis	75.2% Non-Alcoholic Cirrhosis	67.3% Non-Alcoholic Cirrhosis	0.169
Race	65% Caucasian, 10% Hispanic, 8% African-Amer, 3% Asian, 14% Other	54% Caucasian, 18% Hispanic, 7% African-Amer, 2% Asian, 19% Other	0.203
Average Hospital Length of Stay (Days)	13.1	11	0.107
Mortality during Hospitalization	25.7%	13.7%	0.008*
Transfer to ICU during Hospitalization	52.3%	36.1%	0.007*
Average MELD-Na	28.5	25.9	0.009*
Percentage on prophylactic antibiotics	27.5%	19.0%	0.083

Bacterial culture data

Among all episodes of SBP, 34.4% were culture positive and yielded 27 unique organisms, with 50.4% being gram negative organisms (Table 2). There were no significant differences in culture positive and culture negative patients in terms of age, gender, etiology of cirrhosis, race, length of stay and percentage of patients on prophylactic antibiotics; there were significant differences in mortality (25.7% vs. 13.7%, p = 0.008), ICU Transfer rates (52.3% vs. 36.1%, p = 0.007) and MELD-Na score (28.5 vs. 25.9, p = 0.009) (Table 1).

Table 2

Details on positive culture including bacteria, mortality and susceptibility to ceftriaxone or piperacillin-tazobactam.

Bacteria	Frequency of Positive Culture	Mortality	ICU Stay	MELD-Na	Susceptibility to Ceftriaxone	Susceptibility to Piperacillin-Tazobactam
Gram-negative bacteria
Escherichia coli	28	36%	50%	30	25/28	26/27
Klebsiella pneumonia	18	17%	56%	28	15/18	11/12
Klebsiella oxytoca	4	25%	25%	25	4/4	3/3
Citrobacter spp.	4	0%	75%	26	4/4	ND
Corynebacterium spp.	3	33%	67%	30	ND	ND
Pseudomonas aeruginosa	2	0%	100%	43	0/2	1/1
Enterobacter cloacae	2	0%	100%	20	1/2	1/2
Serratia marcescens	1	100%	100%	20	1/1	ND
Acinetobacter spp.	1	0%	0%	23	1/1	ND
Proteus mirabilis	1	0%	0%	17	1/1	1/1
Gram-positive bacteria
Streptococcus spp.	21	10%	14%	27	14/16	ND
Enterococcus spp.	15	33%	73%	27	0/15	7/7
Other Staph spp.	9	22%	56%	28	ND	2/2
Staphylococcus aureus	3	0%	67%	30	0/1	2/3
Total/Average	112	22%	56%	28.2	66/93 (71%)	52/59 (88%)

Note not all isolates were tested against ceftriaxone and/or piperacillin-tazobactam. Of note, susceptibility of Enterococcus spp. to piperacillin-tazobactam were extrapolated from ampicillin susceptibilities.

The four most common organisms include Escherichia coli n = 28, Klebsiella pneumoniae n = 18, Enterococcus faecium or faecalis. n = 15, and viridans group Streptococcus n = 9. Of note, one patient grew Clostridium perfringens and two grew Candida spp. which were not included in the overall analysis. These organisms were included in analysis to determine mortality and morbidity (Table 3). There was no statistically significant difference in mortality between Gram Positives vs. Gram Negatives or between specific organism, although common organisms trended towards significantly worse mortality (p = 0.08, Table 3). The three most common organisms were associated with increased ICU transfer (p = 0.01) and increased length of stay (p<0.001). Infection with a gram-negative organism was associated with an increased length of stay (p = 0.002). The MELD-Na score was not statistically different between Gram Positive vs. Gram Negative organisms or between specific organisms.

Table 3

Mortality and ICU stay comparisons for gram type among the most common organisms (E. coli, K. pneumoniae and Enterococcus spp).

Death	Gram		Total
	Positive	Negative
Yes	6	13	19
No	18	33	51
Total	24	46	70

Chi-Square = 0.08 p-value = 0.77

Note that there was no statistical difference in mortality for Gram Type but the most three most common bacteria trended towards worsened mortality (p = 0.08) but were significantly more likely to lead to ICU transfer (data not shown) (p = 0.01).

Antimicrobial resistance

Among the bacteria isolated, 27 (21.3%) were resistant to at least one first line antibacterial agent for the treatment of SBP. Of the 27 resistant bacteria isolated 15 were identified as Enterococcus spp. (bacteria inherently resistant to ceftriaxone), 9 were gram negative bacteria and two were Streptococcus species. Of those with a gram negative isolate resistant to ceftriaxone, 3 also had resistance to piperacillin-tazobactam. Patients with drug resistant bacteria had a mortality rate of 25.9% compared to 22.3% mortality rate for any positive culture (Table 4). Patient with positive cultures and drug resistant bacteria were more likely to be transferred to the ICU (p = 0.026) compared to the main cohort.

Table 4

Comparison of all patient with SBP, patients with positive cultures and patient with resistant organisms.

Patient Characteristics	All SBP Patients	Culture Positive SBP	Cultures with Drug Resistant Bacteria	P
Number of Patients	314	108	27
Age (years)	56.7	57.8	58.6	0.33
MELD-Na	26.7	28.5	28.5	0.393
Mortality	17.8%	25.7%	25.9%	0.298
ICU Transfer	41.4%	52.3%	66.7%	0.028

Of note, drug resistant bacteria implies drug resistance to either ceftriaxone or piperacillin-tazobactam.

First-line antibiotic treatment

Ceftriaxone and piperacillin-tazobactam were the most frequently used empiric antibiotics. Empiric antimicrobials were changed in 47.8% of cases and broadening of antibiotics was not associated with a change in mortality (p = 0.16). Use of piperacillin-tazobactam was associated with higher mortality (29.1% compared to 10.4%, p = 0.0001, Fig 2), transfer to an ICU (62.0% compared to 29.7%, p<0.001) and longer length of stay (p<0.001) without any statistically significant difference in MELD-Na (p = 0.056).

Fig 2

First line antibiotic choice.

Using Piperacillin/Tazobactam as the first line agent leads to statistically worsened mortality (p = 0.0001).

SBP prophylaxis

In our cohort of patients, 22% of patients (69 total) were on SBP prophylaxis (most commonly ciprofloxacin) prior to diagnosis of SBP. Among these 69 patients, 30 were culture positive, with 16 out of 30 (53%) being resistant to the prophylaxis used (Table 5).

Table 5

Analysis of patients on prophylactic antibiotics.

	Number of Patients	MELD-Na	Age (years)	Mortality	P	ICU Transfer	p
Patients not on Prophylaxis	245	26.6	57.6	18.3%	n/a	40.8%	n/a
Patients on Prophylaxis	69	27.2	53.6	15.9%	< .00001*	43.5%	0.692
Culture Positive	30	26.6	53.4	36.7%	0.019*	50.0%	0.336
Resistant Bacteria to Prophylaxis	11	29.1	59.8	18.2%	0.988	45.5%	0.76
Sensitive Bacteria to Prophylaxis	8	28.3	46.1	25.0%	0.635	62.5%	0.221

Mortality and ICU transfer rate were compared between patients not on prophylaxis and subsets of groups of patients on prophylaxis.

Overall, patients who developed SBP while on prophylaxis had improvement in overall mortality (p<0.0001) compared with patients not on prophylaxis. However, the development of culture positive peritonitis while on prophylaxis was associated with higher mortality when compared to all patients not on prophylaxis (p = 0.019).

Repeat paracentesis data

Most patients (77.1%) underwent a repeat paracentesis at Day 3 to determine a repeat PMN count. A decrease in the PMN count was seen in most patients, however 42 patients (17.4%) had a higher Day 3 PMN count. Therapy was changed in 72% of patients regardless of the repeat peritoneal fluid PMN count. A majority of patients started on ceftriaxone (84%) had their antibacterial changed, compared to 53.6% of patients empirically started on piperacillin-tazobactam (p = 0.045). Patients with a higher day 3 PMN count in the peritoneal fluid had higher mortality rates compared to those that had a decrease in the PMN count (17.3% compared to 13.7%, p = 0.02). There was no statistically significant difference in ICU transfer (p = 0.38), length of stay (p = 0.39), and MELD-Na (p = 0.75) in patients with higher compared to lower day 3 paracentesis counts. Patients who did not undergo a repeat paracentesis had a mortality of 27.8%, significantly higher than patients who had repeat paracenteses.

Discussion

Our results indicate SBP continues to be a very challenging infection to treat and carries with it a high mortality rate (17.8% in our review). Culture positive peritonitis was seen in 34.4% of patients, with an equal distribution between Gram Positive and Gram-Negative organisms. Culture positive peritonitis was associated with higher MELD-Na score, rate of ICU transfer and mortality.

Antimicrobial resistance was seen in 27 cases of peritonitis, to either ceftriaxone or piperacillin-tazobactam. Antimicrobial resistance was associated with ICU transfer and a trend towards worsening mortality. First line use of piperacillin-tazobactam was associated with significantly worsened mortality. Worse mortality was also seen in patients who had a higher PMN count on repeat paracentesis or whom never had a repeat paracentesis.

A majority of episodes of SBP in our study were culture negative. The most common pathogens identified in our study were Escherichia coli and Klebsiella pneumonia, in agreement with the bacteriology of SBP seen in the literature [7, 27], although recent studies demonstrate a trend toward more Gram Positive organisms [28, 29]. In our study, patients who had positive bacterial cultures had significantly worse morbidity and mortality. A potential explanation for this finding is that patients who have positive cultures are more ill due to worsened gut translocation, poorer immune defenses, or lack of antibiotic prophylaxis. Further research into improved diagnostics for SBP, namely use of multiplex polymerase chain reaction (PCR) bacterial panels, should be undertaken to help identify pathogens and potential resistance patterns quicker which should lead to earlier targeted therapy.

Patients receiving prophylaxis for SBP had overall improved mortality compared to patients not on prophylaxis. However, those with a positive bacterial culture on prophylaxis had worsened mortality. A likely explanation for this finding is selecting for more resistant bacteria, as multi-drug resistant organisms are on the rise in SBP [27, 30]. Rostkowska et al. presents data that long term use of fluoroquinolones as prophylaxis may increase the risk of ESBL producing Enterobacter spp. by 4 fold [30]. Further research will be needed to determine if prophylaxis leads to enough resistance to warrant cessation of this practice.

Of the patients with a positive bacterial culture, 21% had antimicrobial resistance to first line SBP treatment, similar to what has been found in the literature [11, 20, 28, 31, 32]; these patients tended to be sicker and had a trend towards worsened mortality. Lutz et al. describes a series of 86 patients with SBP in which resistance to initial antibiotic treatment worsened 30 day mortality from 18% to 68% [32]. Oliveira et al. performed a retrospective study of 113 patients with SBP which found 46.9% with multidrug resistant bacteria, including 39% resistance to third generation cephalosporins [31]. Our data as well as the literature demonstrate the value of culture data in management of SBP by allowing for targeted therapy based on bacterial sensitivities and potentially affecting outcomes. Clinicians managing patients who have cultures that grow resistant bacteria should modify therapy and be mindful of the worsened prognosis seen in these individuals.

Performing a repeat paracentesis is still a valuable tool in the management of SBP. Patients found to have worsening PMN values on repeat paracentesis, as well as those that did not have a repeat paracentesis, have a higher mortality than patients with improving PMN numbers. The latter of these findings is unclear but may indicate patients who may have been too unstable to get a repeat procedure or may have already been clinically worsening. Repeat paracentesis often led to significant management changes, either based off of culture data or PMN values. Thus, we recommend continuing to perform a repeat paracentesis on day 3 of patient care in agreement with recent recommendations [20].

In our cohort broader initial therapy was not better therapy. Patients who received piperacillin-tazobactam as first line therapy had worsened mortality compared with patients receiving ceftriaxone. One obvious reason for this would be that the patients receiving piperacillin-tazobactam were sicker, thus warranting broader initial treatment. However, there was no difference in patients receiving either antibiotic in terms of MELD-Na, meaning that the overall illness level of these patients was relatively similar. Further, all of these patients were suitably stable for management on a general medicine or hepatology floor on admission, which suggests a similar level of illness throughout the cohort, although we did not chart blood pressure or lactate in our analysis.

Our data bring into question the use of standard first line regimens in SBP and whether the first line antibiotic should account for multi-drug resistant organisms not covered by ceftriaxone or piperacillin-tazobactam. Although these agents are still effective for the majority of patients, two factors drive the ineffectiveness of these medications: 1). The emergence of gram-positive bacteria not covered by these agents and 2). multi-drug resistant pathogens that are on the rise. Our results support the growing literature in SBP [32, 33] that indicate that the empiric antibiotic therapy for SBP likely needs to be changed [27, 31, 34]. Further research needs to be conducted in order to determine if extended spectrum antibiotics, e.g. carabapenems, or the addition of resistant gram-positive therapy, e.g. daptomycin, should be used as first line therapy.

Our research was limited to a single center study and may not necessarily be generalizable. Further, the study was retrospective and occurred over a period of 10 years, of which there have been many changes in SBP and cirrhosis management (more prevalent antibiotic prophylaxis, improvements in cirrhosis treatment, recent emergence of more resistant pathogens, etc.) which may have affected the result of the work.

Conclusions

Our study demonstrates the importance of choice of initial therapy, identification of a causative organism and the impact of prophylaxis on the outcomes of SBP. Further, our results demonstrate that while prophylaxis is beneficial for patients with cirrhosis who are at higher risk for SBP, it may impact morbidity if patients develop SBP.

Antimicrobial resistant pathogens, as demonstrates by our results as well as others, are playing a more important role in SBP and outcomes from SBP. Choice of antibiotics should consider local antibiotic resistance patterns to ceftriaxone or piperacillin-tazobactam. Perhaps the use of more modern pathogen identification (rapid, multiplex polymerase chain reaction searching for the most common SBP bacteria for instance) would help to aid in targeted therapy for patients.

(XLSX)

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21 Jul 2020

PONE-D-20-15175

A Retrospective Analysis of cases of Spontaneous Bacterial Peritonitis in Cirrhosis patients

PLOS ONE

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Reviewer #1: 1. The details of all laboratory investigations done on these patients should have been included. Was ascitic total protein concentration measured ?

2. The complete antibiogram of the isolates has not been provided. Results of susceptibility to two antibiotics (Ceftriaxone and piperacillin-tazobactam) alone are given. Majority of the patients were treated with these two antibiotics. What about the remaining patients ? What antibiotics were they treated with and what was the susceptibility profile ?

3. What was the daily dose of Ceftriaxone ?

4. How many patients had a PMN count of more than 500 ?

5. What could be the reason for increased mortality in patients who were treated with piperacillin-tazobactam.

Why did piperacillin-tazobactam continue to be used as empiric therapy in spite of the fact that it increased mortality rates ?

Is piperacillin-tazobactam recommended according to the practice guidelines ?

6. Did practice guidelines for SBP change during the course of 10 years of study duration ?

7. The hypothesis that identification of bacteria in culture could aid in prognosis and provide targeted treatment is already known and proven.

Reviewer #2: Dear Authors

The paper describes a retrospective analysis for 10 years of spontaneous bacterial peritonitis in cirrhosis in a single center.

The paper shows data on a sizable population.However, the following needs to be addressed

1. The authors mention mortality but do not mention time frame. Is this 30 day mortality data that is limited to the hospitalized patients?

2. The authors mention the changes in the guidelines during the 10 year period. But what changes were made in the department policy in line with the newer guidelines?

3. What is the inference of this study? Do you recommend that the policy needs to be institutional or regional as antibiograms and organism profiles vary between different hospitals

4. The recommendation of use of cefotaxime/ ceftriaxone needs addressal here with such a large number of isolates of Emterococcus seen

5. What were the other parameters looked at? Albumin?

6. Culture technique for these cases also needs to be mentioned.

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Reviewer #1: Yes: Thangam Menon

Reviewer #2: No

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25 Aug 2020

Comments

We note that you have included the phrase “data not shown” in your manuscript. Unfortunately, this does not meet our data sharing requirements. PLOS does not permit references to inaccessible data. We require that authors provide all relevant data within the paper, Supporting Information files, or in an acceptable, public repository. Please add a citation to support this phrase or upload the data that corresponds with these findings to a stable repository (such as Figshare or Dryad) and provide and URLs, DOIs, or accession numbers that may be used to access these data. Or, if the data are not a core part of the research being presented in your study, we ask that you remove the phrase that refers to these data.

Thank you for your response. We have removed the phrase that refers to these data.

We have included all of our data in an excel file which we can upload.

Reviewer #1:

1. The details of all laboratory investigations done on these patients should have been included. Was ascitic total protein concentration measured?

Thank you for your comment. Yes, in addition to PMN count, culture data and species/resistance patterns, we obtained ascites total protein and albumin on almost all patients. Further, we obtained a number of basic lab values including blood counts, creatinine, liver function tests, etc. that were used to determine MELD score. We have updated our manuscript to include the fact that we determined ascites protein and albumin levels, and also included the data set where this information was obtained:

“Information regarding the details of the diagnosis of SBP from the paracentesis were obtained via chart review and included PMN count, ascites protein and albumin levels, culture data and species/resistance patterns.”

2. The complete antibiogram of the isolates has not been provided. Results of susceptibility to two antibiotics (Ceftriaxone and piperacillin-tazobactam) alone are given. Majority of the patients were treated with these two antibiotics. What about the remaining patients ? What antibiotics were they treated with and what was the susceptibility profile ?

This is a great point and we appreciate your response. The focus on our article was on the two primary drugs used to treat SBP, Ceftriaxone and Piperacillin-tazobactam. Most patients, unfortunately, did not have culture positive results. Most patients, due to the nature of the way the data was obtained as well as the fact not all patients had full susceptibility testing, do not have a full report on susceptibility on every bacteria.

In our review, we did not focus on the patients who received alternative to standard of care antibiotics; these include patients that had allergies to first line agents, prior resistant pathogens, or when clinicians decided to trial other antimicrobials. We do not report when other antibiotics were used because there were very few cases, please see attached dataset for further review. .

3. What was the daily dose of Ceftriaxone ?

At our institution, usually, standard dosing is 2 grams IV daily. Some providers choose 1 gram IV daily.

4. How many patients had a PMN count of more than 500 ?

I think this is a very interesting comment. Per the definition of SBP, we use a cutoff of 250 to make the diagnosis. In reviewing the data, it appears most patients (around 85%) of patients with SBP had a PMN count of more than 500. We decided to follow the guideline definition of SBP for our analysis.

5. What could be the reason for increased mortality in patients who were treated with piperacillin-tazobactam. Why did piperacillin-tazobactam continue to be used as empiric therapy in spite of the fact that it increased mortality rates ? Is piperacillin-tazobactam recommended according to the practice guidelines ?

Thank you for your questions. Our reasons for increased mortality are discussed in the discussion section; but mainly we are unclear as to the exact reason (see expanded response below).

To answer your second question, this was a retrospective study and so it was unknown that piperacillin-tazobactam led to higher mortality.

See next question for answer to your third part question.

“Unfortunately, we do not have a logical explanation for why a more broad initial regimen was inferior to a narrower antibiotic.”

6. Did practice guidelines for SBP change during the course of 10 years of study duration ?

Thank you for your question, as this is an excellent question that we struggled with.

The practice guidelines have not drastically changed over the last 10 years on SBP. There has been an increase in the use of prophylactic antibiotics, but in general, first line therapy remains 3rd generation cephalosporins. With emerging data, including that from our study, we argue that empiric therapy likely needs to be changed given more resistant pathogens and likely clinicians will need to start broader in patients who are more likely to have resistant pathogens. We discuss this in the second to last paragraph of our discussion.

We have added a few sentences in the discussion on this question with citations.

“Unfortunately, practice guidelines for empiric coverage for SBP have not drastically changed over the last 10 years. (along with the most recent guideline citation). “

7. The hypothesis that identification of bacteria in culture could aid in prognosis and provide targeted treatment is already known and proven.

It is true that having advanced diagnostics in terms of culture data is valuable; what was not known was how having positive cultures could change outcomes (better or worse, would this lead to changes in antibiotics, etc.) which is what we addressed in our paper.

Reviewer #2:

1. The authors mention mortality but do not mention time frame. Is this 30 day mortality data that is limited to the hospitalized patients?

Sorry this was not clear. We studied mortality during hospitalization. All of the patients were hospitalized so this is only if they had mortality during their hospital stay; we have clarified this in the text

2. The authors mention the changes in the guidelines during the 10 year period. But what changes were made in the department policy in line with the newer guidelines?

This is a great point. The practice guidelines have not drastically changed over the last 10 years on SBP. There has been an increase in the use of prophylactic antibiotics, but in general, first line therapy remains 3rd generation cephalosporins. With emerging data, including that from our study, we argue that empiric therapy likely needs to be changed given more resistant pathogens and likely clinicians will need to start broader in patients who are more likely to have resistant pathogens. We discuss this in the second to last paragraph of our discussion.

We have made changes in our department as a result of our data.

We have added a few sentences in the discussion on this question along with guideline citation.

“Unfortunately, practice guidelines for empiric coverage for SBP have not drastically changed over the last 10 years. (along with the most recent guideline citation). “

3. What is the inference of this study? Do you recommend that the policy needs to be institutional or regional as antibiograms and organism profiles vary between different hospitals

That is a great question and point. Yes, especially for hospitalized patients, we believe that policy needs to be institutional (especially given the wide difference in antibiograms from all around the world), but need to encompass more broad treatment at the onset. We have added a sentence in the discussion to that very point.

“We recommend that a policy be established for treatment of SBP on an institutional basis, especially for hospitalized patients, based on the hospitals antibiogram to encompass emerging resistance patterns. Perhaps, if patients are on prophylaxis, are clinically unstable, or have increased risk for resistant pathogens (i.e. frequent antibiotic courses, previously positive cultures with resistant bacteria), that they are started on a carbapenem as first line therapy. “

4. The recommendation of use of cefotaxime/ ceftriaxone needs addressal here with such a large number of isolates of Enterococcus seen.

This is an excellent point. We agree that treatment of ceftriaxone is likely too narrow for SBP given the fact that enterococcus is a somewhat common pathogen in our cohort. Again, practices likely need to change as addressed in your third point.

5. What were the other parameters looked at? Albumin?

Yes, in addition to PMN count, culture data and species/resistance patterns, we obtained ascites total protein and albumin on almost all patients. Further, we obtained a number of basic lab values including blood counts, creatinine, liver function tests, etc. that were used to determine MELD score. The details on all of these lab values are in the supplemental data file. We have updated our manuscript to include the fact that we determined ascites protein and albumin levels.

“Information regarding the details of the diagnosis of SBP from the paracentesis were obtained via chart review and included PMN count, ascites protein and albumin levels, culture data and species/resistance patterns.”

6. Culture technique for these cases also needs to be mentioned.

I agree, this is a great point. Certainly, we can add this statement to our methods section.

“Patients who underwent paracentesis undergo sterile bedside procedure technique; aerobic and anaerobic culture bottles are inoculated at bedside and sent to the microbiology lab where the fluid is plated on culture media plates. “

Submitted filename: Response to Reviewers.docx

Click here for additional data file.

8 Sep 2020

A Retrospective Analysis of cases of Spontaneous Bacterial Peritonitis in Cirrhosis patients

PONE-D-20-15175R1

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Reviewer #2: Dear Authors

All comments seem to be addressed adequately. However, I would appreciate it if the authors brought out the issue of the use of Ceftriaxone/ cefotaxime use not being appropriate in their cohort that had a large number of Enterococci more explicitly. This would raise awareness in the reader when developing institutional guidelines.

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Reviewer #2: Yes: Anusha Rohit

14 Sep 2020

PONE-D-20-15175R1

A Retrospective Analysis of cases of Spontaneous Bacterial Peritonitis in Cirrhosis patients

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