Ventilator-associated pneumonia due to carbapenem-resistant Providencia rettgeri

Abstract

Ventilator-associated pneumonia (VAP) is one of the leading cause of mortality and morbidity in critically ill patients on mechanical ventilation. We report a case of VAP caused by Providencia rettgeri in a postoperative 58-year-old man with prepyloric perforation. The patient’s ICU stay was complicated by VAP. As the organism was carbapenem resistant, high-dose extended infusion of meropenem along with cefepime was started. Early identification and treatment helped in successful weaning of the patient from the ventilator. Providencia is an emerging nosocomial pathogen with an increase in resistance pattern. This case highlights the rarity and importance of Providencia as a cause of VAP.

Background

Ventilator-associated pneumonia (VAP) is defined as pneumonia that occurs 48 hours or more after endotracheal intubation. The incidence of VAP is 9%–27% with a mortality rate of 9%–13%.¹ Common pathogens known to cause VAP are Pseudomonas (24.4%), Staphylococcus aureus (20.4%), Enterobacteriaceae (14.1% includes Klebsiella spp, Escherichia coli, Proteus spp, Enterobacter spp, Serratia spp and Citrobacter spp), Streptococcus sp (12.1%), Haemophilus sp (9.8%), Acinetobacter sp (7.9%), Neisseria sp (2.6%), Stenotrophomonas maltophilia (1.7%), coagulase-negative Staphylococcus (1.4%), others (4.7% includes Corynebacterium, Moraxella, Enterococcus and fungi).¹ Providencia rettgeri, a gram negative bacillus, is a rare cause of VAP. To the best of our knowledge, this is the first reported case of VAP in India due to carbapenem-resistant P. rettgeri.

Case presentation

A 58-year-old man presented to the emergency department with abdominal pain and vomiting for 3 days. The pain was sudden in onset, initially localised to the umbilicus and then spread to the entire abdomen. He had received analgesic (tablet paracetamol) and antiemetic (tablet ondansetron) from a primary care physician. But his symptoms were not relieved and for the past 24 hours, he had severe abdominal distension with non-passage of stool or flatus for which he came to the hospital. He did not have any previous surgical history or any comorbidities. On examination, he was dehydrated, tachycardic (122 breaths/min) and tachypnoeic (34 breaths/min). Abdomen was distended with generalised and rebound tenderness. Guarding and rigidity were present and bowel sounds were diminished.

An abdominal X-ray was done, which showed air under the diaphragm with dilated bowels. A diagnosis of hollow viscous perforation was made and he was immediately taken for emergency laparotomy. He was intubated using rapid sequence induction with continuous cricoid pressure to prevent aspiration. He had prepyloric perforation, which was repaired by an omental patch. During the surgery, patient developed hypotension for which fluid boluses were given and low-dose norepinephrine was started. Arterial blood gas (ABG) was suggestive of metabolic acidosis. Postoperatively, he was transferred to the intensive care unit (ICU) in view of septic shock. On arrival to the ICU, he had a heart rate of 112 beats/min, blood pressure of 132/76 mm Hg with norepinephrine 20 μg/min and saturation of 98% with endotracheal tube in situ. He was put on invasive mechanical ventilator synchronised intermittent mandatory ventilation mode with tidal volume of 400 mL, pressure support (PS) of 12 cm H₂O, PEEP (Positive end expiratory pressure) of 6 cm H₂O, respiratory rate of 18 breaths/min and fractional inspired oxygen (FiO₂) of 40%.

Investigations

In the ICU baseline ABG, chest X-ray and routine blood investigations were done (table 1). ABG showed metabolic acidosis with a pH of 7.21, partial pressure of oxygen of 112 mmHg, partial pressure of carbon dioxide of 30 mmHg, bicarbonate of 15 mEq and base deficit of −12 mEq. Initial chest X-ray (figure 1A) was normal. He was empirically started on injection (intravenous) ceftriaxone 1 g two times per day and metronidazole 500 mg three times per day after taking blood cultures. Fluid boluses were administered as he was fluid responsive. Gradually, he was tapered off the vasopressors on postoperative day 2 and was planned for weaning. The next day, he developed fever (101 F), tachypnoea (28 breaths/min) and tachycardia (132 breaths/min) with an increase in ventilatory requirements (FiO₂: 60%, PS: 15 cm H₂O and PEEP: 10 cm H₂O). He had purulent endotracheal secretions. Repeat chest X-ray was done on postoperative day 3, which showed right lower zone consolidation (figure 1B). Blood investigations showed an increase in white blood cell count with elevated procalcitonin (table 1). A diagnosis of VAP was made. Blood, urine and tracheal cultures were taken. Antibiotic was broadened to intravenous meropenem 1 g three times per day. Tracheal culture revealed 1 000 000 CFU/mL non-haemolytic gram-negative bacilli. The organism was a non-lactose fermenter, positive for mannitol, citrate, urease, rhamnose and inositol, and negative for sucrose. It was identified as P. rettgeri by VITEK 2 automated system.

Table 1.

Laboratory data at admission and during hospitalisation

Variable	ICU admission	Postoperative day 3 (VAP onset)	Day 5	Day 7	Day 10	Day 12
Haemoglobin (g/dL)	10.6	8.7	9	10.8	899	10.1
White cell count (×109/L)	7000	16 600	17 200	9080	8520	6400
Platelets (/μL)	250 000	170 000	267 900	396 000	288 000	286 000
Neutrophils (%)	74	88	84	72	68	71
Creatinine (mg/dL)	1.2	1.4	1.42	0.88	1.1	0.92
Procalcitonin (mg/L)	2	15			3

ICU, intensive care unit; VAP, ventilator-associated pneumonia.

Figure 1.

Chest X-ray on intensive care unit admission (A) and on postoperative day 3 (1B).

Treatment

As the organism was carbapenem resistant (figure 2), high-dose extended infusion of meropenem (2 g) over 3 hours three times per day was given along with high-dose intravenous cefepime 2 g three times per day. Urine and blood cultures did not reveal any bacterial growth. Gradually, the patient was weaned off the ventilator on postoperative day 10. He was shifted to the surgery ward on postoperative day 12.

Figure 2.

Antibiogram of endotracheal secretion.

Outcome and follow-up

Antibiotics were continued for a total duration of 14 days. He was discharged on postoperative day 16 and was asked to follow-up in surgery outpatient clinics after 1 month.

Discussion

Providencia is a urease producing gram-negative bacillus ubiquitously found in the environment. Providencia can naturally be found in the gastrointestinal tract. It belongs to the family Morganellaceae consisting of five common species, that is, Providencia alcalifaciens, Providencia rustigianii, P. rettgeri, Providencia stuartii and Providencia heimbachae.² It seldom causes human infection. P. stuartii and P. rettgeri are reported as pathogens in some immunocompromised patients. P. stuartii can cause complicated urinary tract infections in patients with long standing urinary catheters.³ P. alcalifaciens and P. rettgeri are associated with gastroenteritis and Traveler’s diarrhoea.⁴ There are reports of community-acquired pneumonia, meningitis, surgical site infection, ocular infection, meningitis, intra-abdominal infection and septicaemia caused by Providencia.⁵ Providencia is not commonly found in tracheal aspirates but, when it is, it is usually deemed to be colonisation (ie, not a source of infection). But in our patient, the colony-forming unit count and sensitivity pattern were in favour of its pathogenicity. Also, there was clinical and radiological improvement after antibiotics were broadened and the patient was gradually weaned off the ventilator.

Providencia sp are generally resistant to polymyxin, tetracyclines, older generation cephalosporins and ampicillin but susceptible to newer cephalosporins, imipenem, meropenem and aztreonam. They have variable susceptibilities to aminoglycosides, trimethoprim–sulfamethoxazole and fluoroquinolones.⁶ In our case, the organism was carbapenem resistant, so we had limited antibiotic options. High-dose extended meropenem infusion was proven effective against some enterobacteria.⁷ Hence, we decided to start high-dose extended meropenem infusion along with high-dose cefepime for our patient.

Learning points.

• Ventilator-associated pneumonia (VAP) is associated with an increase in morbidity and mortality.

• Providencia is an emerging nosocomial pathogen with an increase in resistance pattern.

• This case highlights the rarity and importance of Providencia as a cause of VAP.

• However, more information is required to clarify the pathogenicity.

Ethics statements

Patient consent for publication

Next of kin consent obtained.