Ventura County Public Health Puts Resistant Bacteria to the Test 

Story Highlights

Originally published: January 2026

Testing for antibiotic resistant bacteria is a high priority for Ventura County's Public Health (VCPH) Laboratory and the work they're doing has been both revealing and rewarding in terms of improving public health. The credit goes to a visionary staff and Future of Public Health (FoPH) funding.

Jared Hoffman, VCPH's Assistant Laboratory Director, was hired in 2021 and is now supported by FoPH. He quickly saw a need to implement a testing program for genotypic antibiotic resistance. This is a “next level" type of testing that helps determine which bacteria strains are most resistant to antibiotics. 

Hoffman and his FoPH-funded team, a lab technician and medical office assistant, began carbapenemase gene detection testing in 2023.

This testing identifies particular genes that a bacteria may possess that allows it to be resistant to carbapenem antibiotics, better known as “last resort" antibiotics. Doctors turn to them when a patient fails to respond to more common antibiotic drugs.

"FoPH funding gives us the staff we need to continue this operation. And we want to be able to continue to expand our antibiotic resistance testing. That's not something that public health labs do, but we want to be able to offer that. One of our Future of Public Health goals is to bring on even more types of testing."

– Jared Hoffman, Ventura County Public Health Assistant Laboratory Director

Phenotypic vs. Genotypic Testing​

Phenotypic testing is typically done in hospitals and examines how bacteria function in everyday settings, such as a patient's body or in a lab culture dish. It helps determine which antibiotic a doctor should use to treat a patient. Genotypic testing parallels and supports phenotypic testing but from the perspective of testing the cell itself. 

“So, hospitals take the bacteria, they put it in the presence of an antibiotic and say, well, can it grow or not?" said Hoffman. “We do genotypic carbapenemase gene testing because we want to know is how is the bacteria resistant? And is it this one patient that's experiencing resistance or are there other bacteria in that location, such as a skilled nursing facility, that are resistant?"

Hoffman explained that some bacteria have different mechanisms of resistance, including genes that make them more resistant. Some have developed abilities to evade antibiotics while others can actually pump antibiotics out of the cell. Others produce protein products that allow them to become more resistant, including carbapenemases. It basically makes the antibiotic inactive so bacteria can survive no matter how much of the drug is in the patient's system. In addition, some bacteria are able to transfer their antibiotic resistance genes to other bacteria, which can result in the increasing spread of antibiotic resistance.​

Phenotypic Testing

• Tests the Whole System: overall effect of a treatment on a whole cell or organism.
• Allows Observation: researchers add a potential medicine to the system to see what happens. Does the organism get better or do cells die?
• Real-Time Relevance: can capture complex biological interactions that might be missed in simpler lab tests.

Genotypic Testing:

• Identifies Risks: shows if patient has genes that increase the chance of a certain illness.
  
• Guides Treatment: helps doctors choose the best drug because it reveals how patient's DNA might affect the medicine's effectiveness.
• Inherited Conditions: can see if patient carries a gene for a disorder that can be passed to children.
  

Initial Findings

Carbapenemase testing helps doctors treat their patients with the right antibiotic. And it's instrumental in identifying bacterial infection outbreaks, particularly in medical facilities and institutions such as skilled nursing facilities. When Hoffman and his team were first thinking of initiating the testing, they checked with lab managers in the area to get an idea of what they were finding in terms of volume and impact. ​

The managers reported finding very little presence of the bacteria, but the more the VCPH team tested, the more they found. Hoffman says VCPH's genotypic testing program has become a critical part of their role in public health.